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230 terms

AP Bio semester 1

STUDY
PLAY
-Made up of cells
-all use some sort of energy
-all contain genetic information
-all replicate either sexually or asexually
-all have the capacity to evolve
Five fundamental characteristics of living things
Atoms are little bubbles of space with mass concentrated at the center of the bubble (c)
Atom's physical structure:
a) An atom is a solid mass of material
b) the particles that form an atom are equidistant from each other
c) Atoms are little bubbles of space with mass concentrated at the center of the bubble
d) Atoms are little bubbles of space with mass concentrated on the outside surface of the bubble
A nonpolar covalent bond (c)
When the atoms involved in a covalent bond have the same electronegativity, what type of bond results?
a) an ionic bond
b) a hydrogen bond
c) a nonpolar covalent bond
d) a polar covalent bond
Hydrogen bond formed between the hydrogen of one water molecule and the oxygen of another water molecule (c)
Water has a high specific heat because of the...
a) polar covalent bond formed between the oxygen and a hydrogen of a single water molecule
b) ionic bonds formed between the hydrogen of one water molecule and the oxygen of another water molecule
c) Hydrogen bond formed between the hydrogen of one water molecule and the oxygen of another water molecule
d) covalent bond formed between the hydrogen of one water molecule and the oxygen of another water molecule
Energy in the form of sunlight or heat was transformed into chemical energy (a)
Which statement best summarizes the essence of chemical evolution?
a) Energy in the form of sunlight or heat was transformed into chemical energy
b) instead of being radiated back to space, energy in the form of sunlight or heat was retained in the oceans and atmosphere because of water's high specific heat
c) entropy increased
d) an increasing number of exothermic reactions occurred
Higher temperature and concentration tend to increase the rate of chemical reactions.
Higher __________ and ____________ tend to increase the rate of chemical reactions.
Nucleus
-Eukaryotic Animals and plants
-Info storage and DNA
-chromosomes coiled, tightly wound
-proteins from the genes (usually)
Ribosome
-Eukaryotic A/P and Prokaryotic
-Protein synthesis
Rough ER
-Eukaryotic A/P
-Protein synthesis and processing to golgi apparatus
-bumpy ribosomes
-glycosylation inside
Smooth ER
-Eukaryotic A/P
-Lipid synthesis or breakdown
-Ca+ storage
Golgi apparatus
Eukaryotic A/P
-protein processing and glycosylation
-Cis first then trans next
-stacks
Lysosome
Eukaryotic Animals and possibly plants
-digestion and recycling
-hydrolysis site
-golgi provides the enzymes
Peroxisome
Eukaryotic A/P
-oxidation reactions produce H2O2, then catalase breaks it further
Vacuole
Eukaryotic A/P
-storage space, especially in plants
-turgor pressure high
-osmosis makes it happen, with pigments and toxins
mitochondria
Eukaryotic A/P
-site of aerobic respiration
-ATP produced
Chloroplasts
Eukaryotic plants
-site of photosynthesis
cytoskeleton
Eukaryotic A/P
-Structural: actin, intermediate filaments and microtubules
-3 types of filaments: shape movement, support, divide
plasma membrane
Eukaryotic A/P
-controls entry/exit, attachment, and communication
-fluid mosaic
-homeostasis maintained
cell wall
Eukaryotic plants and prokaryotes
-structure and support
Cells would have appeared in both flasks (B)
Recall Pasteur's experiment on spontaneous generation. If he had just warmed the nutrient-rich broth, rather than boiled it, what would have been the likely outcome of his experiment?
a) cells would not have appeared in either flask
b) cells would have appeared in both flasks
c) cells would have appeared in the swan-neck, but not the straight-neck flask
d) cells would have appeared in the straight-neck, but not the swan-neck flask
Includes a large number of replicates, a control, and alters only one condition between the controls and the experimental condition (d)
The best experimental design...
a) includes a large number of replicates/trials for each condition
b) includes a control
c) alters only one condition between the controls and the experimental condition
d) Includes a large number of replicates, a control, and alters only one condition between the controls and the experimental condition
Lance Armstrong, because he has reproduced (d)
Lance Armstrong just finished third in the 2009 Tour de France cycling race. This was an incredible feat for the 37-year-old father of 4. First and second-place winners, Alberto Contador (27) and Andy Schleck (24), respectively, have no children. Which of these three men shows the greatest evolutionary fitness?
a) Alberto Contador, because he won the race
b) Lance Armstrong, because he came in third at the advanced age of 37
c) Andy Schleck, because he beat the highly experienced Lance Armstrong
d) Lance Armstrong, because he has reproduced
A reaction that is slightly exothermic and leads to a huge increase in entropy (d)
Which reaction is most spontaneous?
a) a reaction that is slightly exothermic and leads to a slight increase in entropy
b) a reaction that is slightly endothermic and leads to a huge decrease in entropy
c) a reaction that is highly exothermic and leads to a huge decrease in entropy
d) a reaction that is slightly exothermic and leads to a huge increase in entropy
It is included in almost every reaction of life. Because it has 4 valence electrons, it can form a wide variety of molecules. Also, it forms strong bonds with other atoms, thus helping to make it a solid backbone.
Why is carbon so well suited to forming the types of molecules found in living things?
R group-basic shape and structure-->function
functional group-bonding
Explain the relationship of the "R" group and the functional group found on the same molecule.
Carbohydrates
-Function: structure, energy storage, and ID
-Building blocks/monomers: monosaccharides
-Ex. lactose
Lipids
-Function: energy storage, membrane
-monomers: glycerol/fatty acids
-Ex. steroids
proteins
-Function: enzymes
-monomers: amino acids
-Ex. Amylase
Nucleic acids
-Function: genetic information/storage
-monomers: nucleotides
-Ex. DNA, RNA
A phosphorus atom (A)
Which one of the following is not a component of each monomer used to make proteins?
a) a phosphorus atom, P
b) an amino functional group, NH2
c) a side chain, R
d) a carboxyl group, COOH
e) a central carbon atom
The components of the R-group (C)
What aspects of amino acid structure vary among different amino acids?
a) the long carbon-hydrogen tails of the molecule
b) the presence of a central C atom
c) the components of the R-group
d) the glycerol molecule that forms the backbone of the amino acid
The presence of carboxyl and amino groups gives it the ability to form peptide bonds, and its side chain gives it unique chemical properties (c)
How does structure of an amino acid enable it to play its most important roles in cells?
a) it can serve a wide variety of functions in a cell because it contains the atoms most commonly found in organisms (C, H, N, O)
b) Because both carboxyl and amino groups are present, polymerization is exergonic. In addition, the presence of a side chain makes the molecule water soluble
c) The presence of carboxyl and amino groups gives it the ability to form peptide bonds, and its side chain gives it unique chemical properties
d) because each amino acid contains a variety of functional groups, they can participate in a wide variety of chemical reactions
Hydrogen bonds, covalent bonds, glycosylation
Three types of interactions that stabilize the tertiary structure of a protein
Primary structure (a)
You disrupt all hydrogen bonds in a protein. What level of structure will be preserved?
a) primary structure
b) secondary structure
c) tertiary structure
d) quaternary structure
Allosteric Regulation
a substance enters the site of the enzyme, changing the shape of the enzyme, not allowing certain substances to be catalyzed
Competitive inhibition
Every enzyme has an active site. A molecule enters and blocks others from getting in
-carries information
-acts as an enzyme, catalyzing information
For what two reasons is RNA thought to be the most likely molecule to have been the first life form to have evolved on Earth?
The strands of the double helix are complementary (c)
In the context of chemical evolution, DNA's structure is interesting because it suggests a possible copying mechanism. What about DNA's structure facilitates copying?
a) it has the same number of adenines and cytosines
b) the nitrogenous bases are located on the inside of the double helix
c) the strands of the double helix are complementary
d) DNA always goes from 5' to 3'
glycogen-long-term energy storage in animals; starch-long-term energy storage in plants; cellulose-cell walls in plants
Examples of polysaccharides and their functions
breaks bacteria apart in humans
Lysozyme, an enzyme found in human saliva and tears, catalyzes the hydrolysis of the glycosidic linkages in pepditoglycan. What effect does this enzyme have on bacteria?
The polar heads interact with water; the nonpolar tails do not (c)
How do phospholipids interact with water molecules?
a) the polar heads avoid water; the nonpolar tails attract water
b) phospholipids don't interact with water because water is polar and lipids are nonpolar
c) the polar heads interact with water; the nonpolar tails do not
d) phospholipids dissolve in water
Ions cannot cross planar lipid bilayers (d)
In an experiment involving planar lipid bilayers, a solution of table salt is added on the left side of the membrane while pure water is added on the right side. After 30 minutes the researchers test for the presence of ions on each side of the membrane. The right side tests negative for ions. What can you conclude?
a) the experiment failed
b) the water somehow blocked the movement of ions across the membrane
c) the left side would probably also test negative for ions
d) ions cannot cross planar lipid bilayers
The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC (d)
What will happen to a red blood cell (RBC), which has an internal ion concentration of about 0.9 percent, if it is placed into a beaker of pure water?
a) nothing
b) the cell would shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC
c) the cell would shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC
d) the cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC
Transmembrane (a)
Rhodopsins are light-sensitive molecules composed of a protein (opsin) and retinal. Opsin is a membrane protein with several helical segments tha loop back and forth through the plasma membrane. Which of the following best describes this particular protein?
a) transmembrane
b) peripheral
c) external
d) internal
Tertiary (c)
Proteorhodopsin consists of a single polypeptide chain. What is the highest level of structure found in this protein?
The sodium-potassium pump is an example of active transport because it moves ions from regions of low concentration to regions of high concentration, requiring the use of ATP, a common energy carrying molecule in all cells.
The sodium-potassium pump is an example of ______ transport because it moves ions from regions of ___ concentration to regions of ____ concentration, requiring the use of ___, a common energy carrying molecule in all cells.
The 20 amino acids serve as a signal sequence that directs the forming polypeptide to the endoplasmic reticulum, where they are cleaved off during processing (b)
Scientists have found that polypeptides that are normally synthesized in the endoplasmic reticulum are about 20 amino acids longer when they are synthesized by ribosomes not attached to the ER. What is the hypothesized explanation for the greater length of these polypeptides?
a) the ribosomes that function as free ribosomes function differently than the ribosomes that are attached to the ER
b) the 20 amino acids serve as a signal sequence that directs the forming polypeptide to the ER, where they are cleaved off during processing
c) the 20-amino-acid sequence helps the ER package these proteins for shipping to the golgi
d) the protein has a different function in the cytosol than in the ER
abnormally shaped RBCs (a)
Spherocytosis is a human blood disorder associated with a defective cytoskeletal protein in the red blood cells (RBCs). What do you suspect is the consequence of such a defect?
a) abnormally shaped RBCs
b) an insufficient energy supply in the RBCs
c) an insufficient supply of oxygen-transporting proteins in the RBCs
d) adherence of RBCs to blood vessel walls causing plaque formation
6 CO2 + 6 H2O + light energy--> C6H12O6 +6 O2
Photosynthesis equation
Light reactions
-Thylokoid membrane
-Sunlight, ADP+P, H20, NADP+H+-->ATP, NADPH, O2
-turns light energy into chemical energy in the form of ATP and NADPH
Calvin Cycle
-Stroma
-3 RuBP, 3 CO2, ATP, NADPH-->6 3-phosphoglycerate, CH2O, G3P (sugars), 3 RuBP, H2O, ADP+P, NAD++H+
-Carbon dioxide fixation-->reduction to G3P-->Regeneration of RuBP
C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + 38 ATP
Cellular Respiration equation
Glycolysis
-Cytosol
-glucose-->2 pyruvate, 2 NADH, 2 ATP
-breaks glucose in half and extracts a little energy from glucose
Acetyl CoA formation
-mitochondrial matrix
-pyruvic acid-->2 CO2, 2NADH, 2 Acetyl CoA
-pyruvate enters the krebs cycle after being modified and combining with Acetyl CoA
Citric Acid Cycle
-mitochondrial matrix
-2 Acetyl CoA--> Electron carriers (NADH and FADH2), CO2, ATP
-series of reactions that continues oxidation of C6H12O6 to create e- carrier molecules
Electron transport
-Mitochondrial membranes
-NADH, FADH2, O2-->ATP, H2O
-Electrons are passed through a chain of electron carriers, resulting in a charge gradient... chemiosmosis-->spins ATP synthase
Most of the CO2 from the catabolism of clucose is released during the Krebs cycle (d)
Most of the CO2 from the catabolism of glucose is released during...
a) glycolysis
b) electron transport
c) chemiosmosis
d) the Krebs cycle
NADH (d)
Following glycolysis and the Krebs cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of...
a) acetyl-CoA
b) glucose
c) pyruvate
d) NADH
In the energy-yielding phase of glycolysis, energy is extracted in the form of ATP and NADH (D)
In the energy-yielding phase of glycolysis, energy is extracted in the form of...
a) pyruvate
b) ATP
c) NADH
d) ATP and NADH
NADH and FADH2 (d)
Which electron carrier(s) function in the Krebs cycle?
a) NAD+ only
b) both NAD+ and FAD
c) the ETC
d) NADH and FADH2
The rates of ATP production and carbon dioxide production would both increase (b)
If you were to add one or more of the eight Krebs cycle intermediates to the culture medium of yeast growing in the laboratory, what do you think would happen to their rates of ATP and carbon dioxide production?
a) There would be no change in ATP production, but we would observe an increased rate of carbon dioxide production
b) the rates of ATP production and carbon dioxide production would both increase
c) the rate of ATP production would decrease, but the rate of carbon dioxide production would increase
d) rates of ATP and carbon dioxide production would probably both decrease
The krebs cycle is an unregulated reaction cycle (b)
Which of the following statements about cellular respiration is false?
a) glycolysis is inhibited when cellular energy levels are abundant
b) the Krebs cycle is an unregulated reaction cycle
c) in the ETC, electrons decrease in energy level as they are transferred from one electron carrier to the next
d) reactions of the Krebs cycle take place in the mitochondrial matrix
The first CO2 that is released during aerobic cellular respiration is between glycolysis and the Krebs cycle (b)
The first CO2 that is released during aerobic cellular respiration is...
a) during glycolysis
b) between glycolysis and the Krebs cycle
c) during the Krebs cycle
d) just after the Krebs cycle
The extraction of energy from high-energy electrons remaining from glycolysis and the Krebs cycle (C)
Which of the following events takes place in the electron transport chain?
a) breakdown of glucose into two pyruvate molecules
b) the breakdown of an acetyl group to carbon dioxide
c) the extration of energy from high-energy electrons remaining from glycolysis and the krebs cycle
d) substrate-level phosphorylation
In the electron transport chain (d)
glucose + 6 O2-->6 carbon dioxide + 6 H2O: where is most of the water in this reaction produced?
a) during glycolysis
b) in the Krebs cycle
c) during fermentation
d) in the electron transport chain
The electron transport chain is a series of redox reactions (a)
The electron transport chain...
a) is a series of redox reactions
b) is a series of substitution reactions
c) is driven by ATP consumption
d) takes place in the cytoplasm of eukaryotic cells
The translocation of protons sets up the electrochemical gradient that drives ATP synthesis in mitochondria (B)
The energy of electron transport serves to move (translocate) protons to the outer mitochondrial compartment. How does this help the mitochondrion to produce energy?
a) the hydrogen ions (protons) are transferred to oxygen in an energy-releasing reaction
b) the translocation of protons sets up the electrochemical gradient that drives ATP synthesis in the mitochondria
c) the protons pick up electrons from the electron transport chain on their way through the inner mitochondrial membrane
d) the protons receive electrons from the NAD+ and FAD that are accepted by electrons in glycolysis and the Krebs cycle
They allow the cell to conserve oxygen for the Krebs cycle (C)
Why are fermentation reactions important for cells?
a) they produce alcohol which enhances the permeability of their mitochondrial membranes to proton translocation
b) they regenerate NAD+ so that glycolysis can continue to operate
c) they allow the cell to conserve oxygen for the Krebs cycle
d) they generate oxygen
They directly enter the Krebs cycle (d)
Fatty acids usually have an even number of carbons in their structures. They are catabolized by a process called beta-oxidation. The end products of this metabolic pathway are acetyl groups of acetyl CoA molecules. What is the most likely fate of the acetyl groups?
a) they directly enter the electron transport chain
b) they directly enter the energy-yielding stages of glycolysis
c) they are directly decarboxylated by pyruvate dehydrogenase
d) they directly enter the Krebs cycle
Ubiquinone is lipid soluble and so can move through the inner mitochondrial membrane while carrying electrons and shuttling protons across the membrane (d)
The constituents of the electron transport chain have similar capabilities, with the exception of ubiquinone (coenzyme Q). What is different about ubiquinone?
a) Ubiquinone is a protein that begins the electron transport chain, so it accepts the highest-energy electrons
b) Ubiquinone is a protein that serves as a regulator of the rate of redox reactions in the ETC
c) Ubiquinone is a protein that is a constituent of all cells, prokaryotic or eukaryotic; hence its name originating from ubiquitous
d) Ubiquinone is lipid soluble and so can move through the inner mitochondrial membrane while carrying electrons and shuttling protons across the membrane
Chemiosmosis is an important concept in our understanding of cellular metabolism in general because it explains how ATP is synthesized by a proton motive force (a)
Chemiosmosis is an important concept in our understanding of cellular metabolism in general because...
a) it explains how ATP is synthesized by a proton motive force
b) it explains how electron transport can fuel substrate-level phosphorylation
c) it explains the sequence of the electron transport chain molecules
d) it explains the reduction of oxygen to water in the final steps of oxidative metabolism
They contain a fluid-filled space called stomata (a)
Which of the following statements concerning chloroplasts is false?
a) they contain a fluid-filled space called stomata
b) they have both outer and inner membranes
c) they have their own DNA
d) they have an internal membrane system known as the thylakoid
Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide. In fact, it comes from glucose (b)
Early investigators thought the oxygen produced by photosynthetic plants came from carbon dioxide. In fact, it comes from...
a) water
b) glucose
c) air
d) electrons from NADPH
Blue and red (b)
Chlorophylls absorb light in which colors of the visible range?
a) green and blue
b) blue and red
c) green and red
d) violet and red
In addition to proteins, thylakoid membranes must contain a large number of pigment molecules in the reaction centers in order to harvest light energy (C)
In addition to proteins, thylakoid membranes must contain a large number of _______ molecules in the reaction centers in order to harvest light energy.
a) phospholipid
b) water
c) pigment
d) electron carrier
Chlorophyll a and b absorb light energy at slightly different wavelengths (d)
Which of the following is a difference between chlorophyll a and chlorophyll b?
a) chlorophyll a is a pigment, and chlorophyll b is the enzyme that transfers excited electrons from chlorophyll a to electron carriers of the thylakoid membrane
b) chlorophyll a absorbs yellow light, and chlorophyll b absorbs green
c) chlorophyll a contains a Mg in its ring structure, whereas chlorophyll b contains iron
d) chlorophyll a and b absorb light energy at slightly different wavelengths
This setup enables the plant to absorb light energy of a variety of wavelengths (b)
Why are there several structurally different pigments in the reaction centers of photosystems?
a) excited electrons must pass through several pigments before they can be transferred to electron acceptors of the electron transport chain
b) this setup enables the plant to absorb light energy from a variety of wavelengths
c) they enable the plant to absorb more photons from light energy, all of which are at the same wavelength
d) they enable the reaction center to excite electrons to a higher energy level
the carotenoids and other pigments are still visible in the leaves (a)
In autumn, the leaves of deciduous trees change colors. This is because the chlorophyll is degraded, and...
a) the carotenoids and other pigments are still visible in the leaves
b) degraded chlorophyll changes color
c) water supply to the leaves has been reduced
d) the cells of the leaves begin to die
Carotenoids probably have a protective function in the cell (b)
Energy from sunlight can excite electrons, kicking them out of their orbitals and creating free radicals. Free radicals are highly reactive atoms or molecules that have unpaired electrons and degrade and destroy other compounds in their vicinity. Carotenoids, one of the pigments present in most chloroplasts, can stabilize these free radicals. This suggests that...
a) once chloroplasts are destroyed, the free radicals will destroy the cell
b) carotenoids probably have a protective function in the cell
c) free radicals induce the synthesis of carotenoids in chloroplasts
d) carotenoids communicate directly with the immune system of plants
An electron is excited (d)
What event occurs just after energy absorption by chlorophyll (or other pigment molecules of the antenna complex)?
a) ATP is synthesized from the energy absorbed
b) a carboxylation reaction of the Calvin Cycle occurs
c) Electrons are stripped from NADPH
d) An electron is excited
It is used to establish and maintain a proton gradient (c)
As electrons are passed through the system of electron carriers associated with photosystem II, they lose energy. What happens to this energy?
a) it excites electrons of the reaction center of P1
b) It is lost forever
c) it is used to establish and maintain a proton gradient
d) it is used to phosphorylate NAD+ to NADPH, the molecule that accepts electrons from p1
Water (C)
The electrons of p2 are excited and transferred to electron carriers. From which molecule or structure do the p2 replacement electrons come?
a) the electron carrier, plastocyanin
b) p1
c) water
d) oxygen
The products of light-dependent reactions are used in light-independent reactions (b)
How are the light-dependent and light-independent reactions of photosynthesis related?
a) The products of the light-independent reactions are used in the light-dependent reactions
b) the products of light-dependent reactions are used in light-independent reactions
c) The products of light-independent reactions must be present for light dependent reactions to take place
d) they are not related
To produce NADPH and ATP (c)
What is the main purpose of the light-dependent reactions of photosynthesis?
a) to generate oxygen by splitting H2O
b) to produce NADPH for use in respiration
c) to produce NADPH and ATP
d) to use ATP to make glucose
Rubisco is a very slow enzyme; what it lacks in speed, it makes up in quantity (b)
Data suggest that rubisco makes up 10% of the total protein found in spinach leaves. Research elucidating the structure of rubisco shows that it has 4 active sites. Why, with four active sites, might there be such a large concentration of rubisco in plant matter?
a) all heterotrophic organisms depend on plants, either directly or indirectly, for their food supply
b) Rubisco is a very slow; what it lacks in speed, it makes up in quantity
c) rubisco catalyzes four of the six reactions found in the Calvin Cycle
d) three of the four active sites bind carbon dioxide; only one binds ribulose-1, 5-biphosphate
Photosynthesis stores energy in complex organic molecules; respiration releases the energy stored in complex organic molecules (d)
Which of the following statements most accurately compares photosynthesis and respiration?
a) ATP generated during photosynthesis is a fundamentally different process than ATP generated during respiration
b) photosynthesis is just respiration in reverse
c) photosynthesis requires ATP, but respiration does not
d) Photosynthesis stores energy in complex organic molecules; respiration releases the energy stored in complex organic molecules
A single antibody gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally (d)
Which of the following contradicts the "one-gene, one-enzyme hypothesis"?
a) a mutation in a single gene can result in a defective protein
b) alkaptonuria results when individuals lack a single enzyme involved in the catalysis of homogentistic acid
c) sickle-cell anemia results in defective hemoglobin
d) a single antibody gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally
At lease in some cases, a single gene must code for more than one protein (c)
The proteome is all the proteins produced by an organism. The genome is the totality of all genes of an organism. If the proteome is much larger than the genome, which of the following statements would be accurate?
a) this finding lends support to the one-gene, one-enzyme hypothesis
b) the number of monomeric subunits found in proteins is fewer than the number of monomeric subunits found in genes
c) at least in some cases, a single gene must code for more than one protein
d) noncoding DNA is important in determining the proteome
The three-base sequence of mRNA (c)
Which of the following is directly related to a single amino acid?
a) the base sequence of the tRNA
b) the amino acetyl tRNA synthase
c) the three-base sequence of mRNA
d) the complementarity of DNA and RNA
Genotype is to DNA base sequence as phenotype is to amino acid sequence (a)
Genotype is to ______ as phenotype is to _____
a) DNA base sequence; amino acid sequence
b) heredity; DNA base sequence
c) gene regulation; translation
d) transcription; amino acid sequence
mRNA because it transfers information from DNA (c)
According to the central dogma, what molecule should go in the blank? DNA-->____-->proteins
a) mRNA because it makes proteins directly
b) rRNA because it makes proteins directly
c) mRNA because it transfers information from DNA
d) tRNA because it transfers information from DNA
To determine the role of proteins coded for by those genes that are knocked out (b)
Knockout mice have been genetically altered to knock out specific genes. How are these mice most often used in research?
a) to study DNA replication in the defective genes (those that have been altered)
b) to determine the role of proteins coded for by those genes that are knocked out
c) to examine defects in DNA structure in those regions that have been altered
d) to study the effect of radiation on DNA
RNA is synthesized (b)
In the process of transcription:
a) DNA is replicated
b) RNA is synthesized
c) proteins are synthesized
d) mRNA attaches to ribosomes
A-A-A-A-A; nucleus
Given the DNA template T-T-T-T-T, which of the following bases would you find in a complementary RNA strand and where would they be synthesized?
a) A-A-A-A-A; nucleus
b) U-U-U-U-U; nucleus
c) A-A-A-A-A; ribosome
d) U-U-U-U-U; ribosome
mRNA (b)
Codons, the three base sequences that code for specific amino acids, are part of...
a) protein
b) mRNA
c) tRNA
d) rRNA
Only a single amino acid could change, because the reading frame is unaffected (a)
How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?
a) only a single amino acid could change, because the reading frame is unaffected
b) the amino acid sequence would be substantially altered, because the reading frame would change with a single base substitution
c) all amino acids following the substitution would be affected, because the reading frame would be shifted
d) it is not possible for a single base substitution to affect protein structure, because each codon is three bases long
If RNA polymerase is missing sigma then transcription initiation would not occur (c)
If RNA polymerase is missing _____ then transcription initiation would not occur
a) amino acids
b) tRNA
c) sigma
d) the holoenzyme
Promoters (d)
Which of the following is part of a DNA molecule?
a) sigma
b) the holoenzyme
c) initiation factors
d) promoters
They bind the sigma subunit that is associated with RNA polymerase (b)
David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the -10 box and the -35 box). What is the function of these two regions of the promoter?
a) they signal the initiation site
b) they bind the sigma subunit that is associated with RNA polymerase
c) they attach the correct nucleotide triphosphate to the template DNA strand
d) they separate the two DNA strands
binding of sigma to the promoter region (a)
Which of the following processes is central to the initiation of transcription?
a) binding of sigma to the promoter region
b) formation of a phosphodiester bond in the elongating RNA strand
c) binding of DNA polymerase to the promoter region
d) formation of a DNA primer
A primary mRNA transcript in the nucleus of a eukaryotic cell is longer than the functional mRNA, while a primary transcript in a prokaryotic cell is the same size as the functional mRNA (b)
A primary mRNA transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is ___ the functional mRNA?
a) the same size as; the same size as
b) longer than; the same size as
c) longer than; smaller than
d) the same size as; longer than
Post-transcriptional modification removes the introns (b)
mRNA is smaller than the length of the DNA that codes for it because...
a) the regulatory regions (introns) of the gene are not transcribed
b) post-transcriptional modification removes the introns
c) post-transcriptional modification removes the exons
d) bases are added to the tail of the primary transcript
RNA polymerase termination (d)
Which of the following does not occur in post-transcriptional modifications occurring in eukaryotic mRNAs?
a) addition of poly A tail
b) addition of methyl-guanosine cap
c) removal of introns
d) RNA polymerase termination
Codons are a nearly universal language among all organisms (d)
Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?
a) Prokaryotic codons usually contain different bases than those of eukaryotes
b) Prokaryotic codons usually specify different amino acids than those of eukaryotes
c) the translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes
d) Codons are a nearly universal language among all organisms
Concurrent transcription and translation (b)
Which of the following occurs in prokaryotes, but not eukaryotes?
a) post-transcriptional splicing
b) concurrent transcription and translation
c) translation in the absence of a ribosome
d) gene regulation
An anticodon forms hydrogen bonds with the codon; it must match the first two bases of the codon, but is less specific with respect to the third base (b)
There are 61 codons that each specify the addition of a specific amino acid, and three stop codons for which there is no corresponding amino acid. However, there are only about 40 tRNA molecules, representing 40 anticodons. How is that possible?
a) only about 40 of the recognized 61 codons are present in mRNA
b) an anticodon forms hydrogen bonds with the codon; it must match the first two bases of the codon, but is less specific with respect to the third base
c) there are tRNAs that can bind one of two related amino acids
Formation of a peptide bond (d)
Which of the following is not one of the steps in initiation of prokaryotic translation?
a) binding of the large ribosomal subunit to the small ribosomal subunit
b) binding of tRNA carrying formyl methionine to the start codon and small ribosomal subunit
c) recognition and binding of mRNA by the small ribosomal subunit
d) formation of a peptide bond
Termination
Step 3 in transcription and translation
Poly A tail
added to 3' end of mRNA
Initiation
Step 1 in transcription and translation
tRNA
carries amino acid to ribosome
Ribozyme
supports RNA world hypothesis
ribosome
site of translation
cap
added to 5' end of mRNA
Crick
proposed wobble hypothesis and existence of tRNA
exons
expressed regions of DNA
RNA polymerase
synthesizes mRNA
elongation
step 2 in transcription and translation
introns
intervening regions of DNA
holoenzyme
sigma plus RNA polymerase
anticodon
portion of tRNA that binds with mRNA
template strand
read by RNA polymerase
snRNPs
proteins and RNA involved in splicing
A P E
three ribosome sites
sigma
binds to promoter region on DNA
Molecular chaperones
assist in post translational folding
The parent cell must first replicate its entire genome (b)
A parent cell divides to form two genetically identical daughter cells in the process of mitosis. For mitosis to take place...
a) the parent cell must maintain its nuclear membrane
b) the parent cell must first replicate its entire genome
c) the parent cell must first undergo cytokinesis
d) the parent cell must divide its DNA in half so that each daughter cell gets only the genes it needs
DNA and proteins (c)
In eukaryotic cells, chromosomes are composed of...
a) DNA and RNA
b) DNA only
c) DNA and proteins
d) DNA and phospholipids
In the S phase of the cell cycle (d)
Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1.5 times more DNA than do G1 phase cells. The cells of this group are...
a) between the G1 and S phases in the cell cycle
b) in the G2 phase of the cell cycle
c) in the M phase of the cell cycle
d) in the S phase of the cell cycle
Normal growth and cell function (a)
The first gap in the cell cycle (G1) corresponds to...
a) normal growth and function
b) the phase in which DNA is being replicated
c) the beginning of mitosis
d) the phase between DNA replication and the M phase
Separation of sister chromatids (d)
The mitotic spindle is a microtubular structure that is involved in...
a) splitting of the cell (cytokinesis) following mitosis
b) triggering the compaction and condensation of chromosomes
c) dissolving the nuclear membrane
d) separation of sister chromatids
Cytokinesis (b)
Mitosis is the process of chromosome separation. Cytoplasm is divided between the two daughter cells in a process known as...
a) cloning
b) cytokinesis
c) binary fission
d) G1 phase
Plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow (b)
How is plant cell cytokinesis different from animal cell cytokinesis?
a) the cleavage furrow in animal cells is composed of protein contractile filaments; the contractile filaments found in plant cells are structures composed of carbohydrates
b) plant cells deposit vesicles containing cell-wall building blocks on the metaphase plate; animal cells form a cleavage furrow
c) the structural carbohydrates of the plant cells separate the two cells, whereas in animal cells, a cell membrane separates the two daughter cells
d) Animal cells have centrosome that are involved in this process, but plant cells have microtubule-organizing centers that are not detectable during most of the cell cycle
The cleavage furrow of eukaryotic animal cells (a)
FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in bacterial cytokinesis. Its function is analogous to...
a) the cleavage furrow of eukaryotic animal cells
b) the cell plate of eukaryotic plant cells
c) the mitotic spindle of eukaryotic cells
d) the microtubule-organizing center of eukaryotic cells
The microtubules elongate and shorten at their kinetochore end (c)
As chromosomes move toward the poles of the daughter cells, the microtubules remained stationary. This result suggests that...
a) the microtubules elongate and shorten at the centrosome end
b) the microtubules overlap, and slide with respect to one another, effectively shortening the microtubules without depolymerizing the actual fiber
c) the microtubules elongate and shorten at their kinetochore end
d) the microtubules are of constant length; centrosomes move farther apart to separate chromosomes
The cells enter mitosis (c)
What happens when MPF (mitosis-promoting factor) is introduced into immature frog oocytes that are arrested in G2?
a) nothing happens
b) the cells undergo meiosis
c) the cells undergo mitosis
d) cell differentiation is triggered
Tumor suppressors (d)
Regulatory proteins that serve to prevent a cell from entering the S phase under conditions of DNA damage are also known as...
a) cyclins
b) cyclin-dependent kinases
c) antibodies
d) tumor suppressors
They are involved in the disassembly of the nuclear envelope (c)
Exposure of zebrafish nuclei to mitotic cytosol resulted in phosphorylation of NEP55 and L68 proteins by cyclin-dependent kinase 2. NEP55 is a protein of the inner nuclear membrane, and L68 is a protein of the nuclear lamina. What is the most likely role of phosphorylation of these proteins in the process of mitosis?
a) they enable the attachment of the spindle microtubules to kinetochore regions of the centromere
b) they are involved in the disassembly and dispersal of the nucleolus
c) they are involved in the disassembly of the nuclear envelope
d) they assist in the movement of the centrosomes to opposite sides of the nucleus
p53 (a)
For cells to divide more rapidly, increased production would likely be required of each of the following proteins except...
a) p53
b) cyclins
c) activated MPF
d) PDGF
Meiosis (c)
Which of the following processes contributes directly to genetic variation?
a) binary fission
b) mitosis
c) meiosis
d) DNA replication
Two (b)
Somatic cells of roundworms have four chromosomes. How many chromosomes would you find in an ovum from a roundworm?
a) four
b) two
c) eight
d) a diploid number
Anaphase I (d)
Homologous chromosomes are separated during...
a) anaphase II
b) prophase I
c) mitosis
d) anaphase I
Sister chromatids separate in mitosis, and homologues separate in meiosis I (a)
What is a major difference between mitosis and meiosis I?
a) Sister chromatids separate in mitosis, and homologues separate in meiosis I
b) DNA replication takes place prior to mitosis, but not before meiosis I
c) Sister chromatids separate in mitosis, and homologues separate in meiosis II
d) only meiosis I results in daughter cells that contain identical genetic information
Prophase I
Crossover, the exchange of segments of homologous chromosomes, takes place during which of the following phases?
a) prophase II
b) metaphase I
c) anaphase I
d) prophase I
Carry information for the same traits (b)
Homologous chromosomes...
a) are identical
b) carry information for the same traits
c) carry the same alleles
d) align on the metaphase plate in meiosis II
8 (c)
The egg of a fruit fly has 4 chromosomes. How many chromosomes are in a somatic cell of a fruit fly?
a) 4
b) 2
c) 8
d) 16
None. DNA replication occurs before meiosis I begins (d)
At what stage of meiosis does DNA replication take place?
a) DNA replication does not take place in cells destined to undergo meiosis
b) prophase I
c) between meiosis I and meiosis II
d) none. DNA replication occurs before meiosis I begins
19 (c)
Quaking aspen can send out underground stems for asexual reproduction. Sexual reproduction is not as common but when it does happen the haploid gametes have 19 chromosomes. How many chromosomes are in the cells of the underground stems?
a) 9
b) 10
c) 19
d) 38
16 (c)
The diploid number of a roundworm species is 4. You have a male and a female roundworm that are planning a family. Assuming there is no crossover, and random segregation of homologues during meiosis, how many possible combinations of chromosomes might there be in the offspring?
a) 4
b) 8
c) 16
d) 64
Crossing over (c)
Genetic recombination takes place in which of the following processes?
a) prophase II of meiosis
b) alignment of tetrads in metaphase I
c) crossing over
d) random alignment of homologous chromosomes in meiosis I
Fertilization (d)
If meiosis produces haploid cells, how is the diploid number restored for those organisms that spend most of their life cycle in the diploid state?
a) DNA replication
b) reverse transcription
c) synapsis
d) fertilization
Sexual reproduction (c)
Adaptation to a changing environment occurs most efficiently through which of the following processes?
a) mutation
b) asexual reproduction and genetic recombination
c) sexual reproduction
Turner's syndrome (a)
Which of the following is an example of monosomy?
a) Turner's syndrome
b) Klinefelter's syndrome
c) Down's syndrome
d) trisomy X
Genetically identical 2n somatic cells (a)
What is the final result of mitosis?
a) genetically identical 2n somatic cells
b) genetically different 2n somatic cells
c) genetically identical 1n somatic cells
d) genetically identical 2n gamete cells
Aligning of chromosomes on the equator (a)
Metaphase occurs prior to the splitting of centromeres. It is characterized by...
a) aligning of chromosomes on the equator
b) splitting of the centromeres
c) cytokinesis
d) separation of sister chromatids
Cytokinesis (b)
Mitosis is the process of chromosome separation. Cytoplasm is divided between the two daughter cells in a process known as...
a) cloning
b) cytokinesis
c) binary fission
d) G1 phase
The cleavage furrow deepens (c)
Myosin is a motor protein involved in animal cell cytokinesis. It binds to ATP or ADP, causing the myosin to move with respect to actin. What is the effect of the interaction between myosin and actin?
a) Vesicles containing plasma membrane constituents are transported to the metaphase plate, where cytokinesis takes place
b) Excess cytoplasm is removed
c) The cleavage furrow deepens
d) It triggers the re-formation of the daughter nuclei
G0 (a)
Nerve cells lose their ability to undergo mitosis. Instead, they are permanently stuck in...
a) G0
b) G2
c) S of interphase
d) metaphase
Cyclin is degraded; the concentration of cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed (c)
Once a cell completes mitosis, molecular division triggers must be turned off. What happens to MPF during mitosis?
a) it is completely degraded
b) it is exported from the cell
c) cyclin is degraded; the concentration of cyclin-dependent kinase remains unchanged, but without cyclin, MPF is not formed
d) cyclin-dependent kinase is degraded; cyclin concentration remains constant, but without cyclin-dependent kinase, MPF is not formed
Homologous chromosomes separate (a)
Meiosis involves the creation of haploid cells from diploid cells. The haploid chromosome number is created when...
a) homologous chromosomes separate
b) the S phase of the cell cycle is bypassed during meiotic interphase
c) sister chromatids separate
d) ova and sperm go through their respective maturation processes
Meiosis II takes place in a haploid cell, while mitosis takes place in diploid cells (c)
What is a major difference between meiosis II and mitosis?
a) homologues align on the metaphase plate in meiosis II
b) sister chromatids separate in mitosis, and homologues separate in meiosis II
c) meiosis II takes place in a haploid cell, while mitosis takes place in diploid cells
d) crossover takes place in meiosis II
Two sister chromatids joined by a centromere (b)
For the duration of meiosis I, each chromosome is...
a) in the form of a tetrad
b) two sister chromatids joined by a centromere
c) a chromosome and its homologue
d) undergoing synapsis
More than two; homologues can cross over (c)
The bulldog ant has a diploid number of two chromosomes. Therefore, following meiosis, each daughter cell will have a single chromosome. There is/are ______ different possible combinations of genes in the daughter cells of meiosis because...
a) one; there is only one chromosome per cell
b) two; there are two homologous chromosomes per cell prior to meiosis
c) more than 2; homologues can cross over
Recessive (c)
Mendel crossed yellow-seeded and green-seeded pea plants and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6022 yellow and 2001 green. The allele for green seeds has what relationship to the allele for yellow seeds?
a) dominant
b) incomplete dominant
c) recessive
d) codominant
1/4
A man and a woman are both of normal pigmentation, but both have one parent who is albino. Albinism is an autosomal recessive trait. What is the probability that their first child will be an albino?
1/2
A man has extra digits. His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits?
3/8
Phenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl?
1/8
Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc x AaBbCc, will produce an AaBbCc offspring?
25 (%)
In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotype BB produces plack fur, Bb brown fur, and bb white fur. If a cross is made between brown rabbits with deformed legs and white rabits with deformed legs, what percentage of the offspring would be expected to have deformed legs and white fur?
Recessive, sex-linked (c)
Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex-linked or autosomal?
a) dominant, sex-linked
b) recessive, autosomal
c) recessive, sex-linked
d) incomplete dominant, sex-linked
1/4
Hemophilia is caused by several genetic factors; one, a recessive allele of an X-linked gene, is the subject of this problem. Assume that a man with hemophilia marries a normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia?
All of his daughters (a)
A man who carries an allele of an X-linked gene will pass it on to...
a) all of his daughters
b) half of his daughters
c) all of his sons
d) half of his sons
e) all of his children
DNA (d)
Hershey and Chase set out to determine what molecule served as the unit of inheritance. They completed a series of experiments in which E. coli was infected by a T2 virus. Which molecular component of the T2 virus actually ended up inside the cell?
a) protein
b) RNA
c) ribosome
d) DNA
The base sequence of DNA carries all the information needed to code for proteins (b)
How does the simple primary and secondary structure of DNA hold the information needed to code for the many features of multicellular organisms?
a) The hydrogen bonding among backbone constituents carries coded information
b) the base sequence of DNA carries all the information needed to code for proteins
c) the width of the double helix changes at each gene due to differences in hydrogen bonds
d) the amino acids that make up the DNA molecule contain the information needed to make cellular proteins
One strand of the DNA molecule (c)
Semiconservative replication involves a template. What is the template?
a) single-stranded binding proteins
b) DNA polymerase contains the template needed
c) one strand of the DNA molecule
d) an RNA molecule
Semiconservative replication (a)
DNA is synthesized through a process known as...
a) semiconservative replication
b) conservative replication
c) translation
d) transcription
The 3' OH (c)
In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and _____ of the last nucleotide in the polymer.
a) the 5' phosphate
b) C6
c) the 3' OH
d) a nitrogen from the nitrogen-containing base
DNA polymerase (b)
DNA contains the template needed to copy itself, but it has no catalytic activity. What catalyzes the formation of phosphodiester bonds between adjacent nucleotides in the DNA polymer being formed?
a) ribozymes
b) DNA polymerase
c) ATP
d) deoxyribonucleotide triphosphates
The leading strand is synthesized continuously in the 5'->3' direction, while the lagging strand is synthesized discontinuously in the 5'->3' direction (c)
What is the difference between the leading strand and the lagging strand in DNA replication?
a) the leading strand is synthesized in the 3'->5' direction in a discontinuous fashion, while the lagging strand is synthesized in the 5'->3' direction in a continuous fashion
b) the leading strand requires an RNA primer, whereas the lagging strand does not
c) the leading strand is synthesized continuously in the 5'->3' direction, while the lagging strand is synthesized discontinuously in the 5'->3' direction
d) there are different DNA polymerases involved in elongation of the leading strand and the lagging strand
The ends of linear chromosomes (d)
What is a telomere?
a) the mechanism that holds two sister chromatids together
b) DNA replication during telophase
c) the site of origin of DNA replication
d) the ends of linear chromosomes
The proofreading mechanism of DNA polymerase was not working properly (c)
Researchers found E. coli that had mutation rates 100 times higher than normal. What is a possible explanation for these results?
a) the single-stranded binding proteins were malfunctioning
b) there were one or more mismatches in the RNA primer
c) the proofreading mechanism of DNA polymerase was not working properly
d) the DNA polymerase was unable to add bases to the 3' end of the growing nucleic acid chain
Thymine dimers (d)
In humans, xeroderma pigmentosum is a disorder of the nucleotide excision repair mechanism. These individuals are unable to repair DNA dapage caused by ultra violet light. Which of the following are the most prominent types of mutations in individuals suffering from xeroderma pigmentosum?
a) mismatch errors
b) telomere shortening
c) methylation of purines
d) thymine dimers
mitosis
-Function: asexual cell division/regeneration of new cells
-location in body: all through somatic cells
-number of daughter cells: 2
-change in chromosome number: 46:46 (2n:2n)
-number of phases: 4 or 5
-number of cell divisions: 1
-difference in DNA between parent and daughter cells: none usually, unless mutation
meiosis
-function: sexual cell division/gamete formation-production of sperm & egg
-location in body: reproductive organs
-number of daughter cells: 4 sperm or 1 usable egg
-change in chromosome number 46:23 (2n:1n)
-number of phases: 8
-number of cell divisions: 2
-difference in DNA between parent and daughter cells: homologous chromosomes assort independently, so each gamete has a unique combination of alleles
Interphase (mitosis)
after chromosome replication, each chromosome is composed of two sister chromatids. Centrosomes have replicated.
Prophase (mitosis)
chromosomes condense, and spindle apparatus begins to form
prometaphase
nuclear envelope breaks down, and kinetochore microtubules contact chromosomes at kinetochore
metaphase (mitosis)
chromosomes complete migration to middle of cell
anaphase
sister chromatids separate, and chromosomes are pulled to opposite poles of the cell
telophase
the nuclear envelope re-forms, and the spindle apparatus disintegrates
Cytokinesis
actinmyosin ring causes the plamsa membrane to begin pinching in and two daughter cells form
G1 checkpoint
in order to pass:
-cell size must be adequate
-nutrients must be sufficient
-social signals are present
-DNA is undamaged
G2 checkpoint
in order to pass:
-chromosomes have replicated successfully
-DNA is undamaged
-activated MPF (mitosis-promoting factor) is present
S phase
DNA synthesis
Prophase I (meiosis)
-chromosomes condense, and nuclear envelope breaks up, spindle apparatus forms. Synapsis of homologous chromosomes
-crossing over of non-sister chromatids
Metaphase I (meiosis)
tetrads migrate to metaphase plate
Anaphase I (meiosis)
homologous chromosomes split and migrate to opposite sides of the cell
Telophase I/cytokinesis
chromosomes move to opposite sides of cell, then cell divides
prophase II (meiosis)
spindle apparatus forms
Metaphase II (meiosis)
duplicated chromosomes line up across equator of cell
anaphase II (meiosis)
duplicated chromosomes/sister chromatids split and migrate
Telophase II and cytokinesis
-cell divides
-males: 4 haploid sperm
-females: 3 "polar bodies" and 1 haploid usable egg
Bunce's children
Jonah Carl and Claire Margaret
photosynthesis
-the process by which autotrophs (plants, some bacteria, algae and some other protists) convert sunlight into chemical energy
-6 CO2 + 6 H2O + light-->C6H12O6 + 6 O2
two reactions of photosynthesis
-light-dependent rxns that generate oxygen from water
-Calvin cycle that generates sugar from carbon dioxide
light dependent reactions
-split water
-make ATP
-reduce the electron carrier NADPH
-occurs in thylakoid membrane
Calvin cycle
-uses energy in ATP and NADPH to reduce CO2 to carbohydrates (CH2O)
-occurs in stroma
chloroplasts
-two membranes
-inside is filled with membrane sacs called thylakoids
--stack of thylakoids is called a granum
--fluid-filled space around the grana is the stroma
--thylakoids have a considerable amount of blue-green absorbing pigment chlorophyll in their membranes
chlorophyll captures light energy
-photosynthetic pigments absorb specific wavelengths of light
when a photon of light hits a pigment:
photon absorbed, transmitted, or reflected
-wavelengths not absorbed by pigment are transmitted or reflected, giving the pigment its color
wavelengths that drive photosynthesis
blue and red are most effective
carotenoids
-accessory pigments found in chloroplasts
-responsible for leaf color in autumn when chlorophyll begins to degenerate
-absorb photons belonging to the blue and green part of the spectrum and pass the energy to the chlorophyll
--extends range of wavelengths that can drive photosynthesis
-protect chlorophyll from free radical damage
flavonoids
accessory pigment that protects plants from high-energy UV radiation
structure of chlorophyll
-long isoprene tail anchors molecule in the thylakoid membrane
-head with a large ring structure has a magnesium atom in the middle
photosystem II
electron in a P680 molecule excited by light-->pheophytin takes electron from chlorophyll (functions as an electron acceptor)-->electron passed through on ETC-->plastoquinone pumps protons into interior of thylakoid, creating proton gradient-->protons diffuse out of thylakoid through ATP synthase-->ATP synthase uses proton-motive force to synthesize ATP (photophosphorylation)
origin of electrons
-photosystem II obtains by oxidizing water
--original chlorophyll oxidized after its excited electron taken away
-water split by PII and the electrons from water used to reduce chlorophyll P680
-highly endergonic and only possible with energy from the sun
photosystem I
-when reaction center of PII absorbs a photon of light, excited electron is eventually passed to ferredoxin, which transfers electron and a proton to NADP+ to form NADPH, which is an electron carrier
Z scheme pathway
-PII-->a small protein (plastocyanin) accepts the electron from ETC and transfers it to a chlorophyll P700 molecule in PI-->PI occurs
cyclic photophosphorylation
-produces additional ATP
-intermittently, P! donates electron to ETC of PII
--results in additional ATP (no NADPH)
-occurs when extra ATP needed
photosystems
distributed differentially and occur in separate regions of thylakoid membranes within individual grana
Rubisco
-in all photosynthetic cells
-slow, inefficient enzyme
--catalyzes 3 reactions per active site per second
-plants synthesize large amounts to make up for the lack of speed
Rubisco can catalyze 2 reactions
1. when high CO2 concentrations, combines CO2 and RuBP to produce G3P
2. when high oxygen concentrations, adds oxygen to RuBP-consumes ATP and releases CO2
--called photorespiration, and effectively reverses photosynthesis
Stomata
-pathway through which CO2 enters the air spaces of a leaf
guard cells
-pairs of specialized cells on leaf surface
-between each is a pore
-when change shape, pore opens and CO2 enters leaf
-CO2 diffuses down its concentration gradient to chloroplasts
C4 plants
-CO2 combined with small organic molecules by an enzyme called PEP carboxylase in meophyll cells that are adjacent to the bundle-sheath cells where rubisco is active
-when low level of CO2 in b-s cells, organic acids transported into those cells, liberating CO2
-reduces photorespiration by keeping CO2 levels high in rubisco-active areas
CAM plants
-combination of CO2 and small organic acids takes place in rubisco-active cells
-initial reaction takes place at night when cells can open their stomata and not risk excessive water transpiration
-CO2 stored during the night, can be used during the day for photosynthesis, whereas C4 plants store CO2 in one cell for use in another
photosynthesis regulation
-presence of light triggers the production of proteins required for photosynthesis
-when sugar abundant, production of proteins required for photosynthesis is inhibited
-Rubisco activated by regulatory molecules produced when light available but inhibited in conditions of low CO2
-low levels of phosphate stimulate the production of calvin cycle proteins
sugars from photosynthesis
-G3P-->sucrose and starch, which acts as a temporary storage product
-glucose used for cell respiration
starch
-not water soluble--> cannot be transported from photosynthetic cells to other areas of the pant
-at night, temporarily stored starch broken down to make sucrose
sucrose
-used by photosynthetic cell in respiration or transported to other parts of the plant