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185 terms

Bio Test 2

STUDY
PLAY
morphology
the shape and appearance of an organisms body and its component parts
phylogeny
Evolutionary history of a group of organisms
chromosome
A single piece of coiled DNA and associated proteins found in linear forms in the nucleus of eukaryotic cells and circular forms in the cytoplasm of prokaryotic cells; contains genes that encode traits. Each species has a characteristic number of chromosomes.
genes
a section of DNA (or RNA, for some viruses) that encodes information for building one or more related polypeptides or functional RNA molecules along with the regulatory sequences required for its transcription
nucleoid
Area in prokaryotic cells in which DNA is concentrated, though not bounded by a membrane
plasmids
a small, usually circular, supercoiled DNA molecule independent of the cells' main chromosome(s) in prokaryotes and some eukaryotes
ribosomes
a large macromolecular machine that synthesizes proteins by suing the generic information encoded in messenger RNA. Consists of two subunits, each composed of ribosomal RNA and proteins
organelles
A membrane-enclosed structure with a specialized function within a cell.
cytoskeleton
A network of microtubules, microfilaments, and intermediate filaments that branch throughout the cytoplasm and serve a variety of mechanical and transport functions.
cell wall
A rigid structure that surrounds the cell membrane and provides support to the cell
cytoplasm
Contents (formation) of the cell (apart from the nucleus and cell membrane).
glycolipids
any lipid molecule that is covalently bonded to a carbohydrate group
flagella
a long, cellular projection that undulates (in eukaryotes) or rotates (in prokaryotes) to move the cell through an aqueous environment
fimbriae
a long needlelike projection from the cell membrane of prokaryotes that is involved in attachment to nonliving surfaces or other cells
cytosol
fluid portion of the cytoplasm, excluding the contents of membrane-enclosed organelles
Compartmentalization also offers two key advantages:
1. incompatible chemical reactions can be separated
2. Chemical reactions become more efficient
Eukaryotic cells vs prokaryotic
1. Eukaryotic chromosoms are found inside a membrane-bound compartment calle dthe nucleus.
2. eukartyotic cells are often much larger than prokaryotes
3. eurkaryotic cells contain extensive amounts of internal membrane
4. eukaryotic cells feature a particularly diverse and dynamic cytoskelteon
nucleus
1) the center of the atom containing protons and neutrons
2) in eukaryotic cells, the large organelle containing the chromosomes and surrounded by a double membrane
3)a discrete clump of neuron cell bodies in the brain, usually sharing a distinct function
nuclear envelope
A double membrane that surrounds the nucleus in the cell
nuclear lamina
a lattice-like sheet of fibrous nuclear laminas, which are one type of intermediate filament. lines the inner membrane of the nuclear envelope, stiffening the envelope and helping to organize the chromosomes
endoplasmic reticulum
a network of interconnected membrane sacs and tubules found inside eukaryotic cells
rough endoplasmic reticulum RER
the portion of the endoplasmic reticulum that is dotted with ribosomes. involved in synthesis of plasma membrane proteins, secreted proteins, and proteins localized to the ER, Golgi apparatus, and lysosomes.
lumen
the interior space of any hollow structure or organ
Smooth endoplasmic reticulum SER
the portion of the ER that does not have ribosomes attached to it. involved in synthesis and secretion of lipids
Golgi apparatus
a eukaryotic organelle, consisting of stacks of flattened membranous sacs (cisternae), that function in processing and sorting proteins and lipids destined to be secreted or directed to other organelles.
cisternae
flattened, membrane-bound compartments that make up the Golgi apparatus
lysosomes
a small, acidified organelle in an animal cell containing enzymes that catalyze hydrolysis reactions and can digest large molecules
endomembrane system
a system of organelles in eukaryotic cells that synthesizes, processes, transports, and recycles proteins and lipids. Includes the endoplasmic reticulum (ER), Golgi apparatus, and lysosomes
peroxisomes
an organelle found in most eukaryotic cells that contains enzymes for oxidizing fatty acids and other compounds, including many toxins, rendering them harmless
glyoxysomes
specialized type of peroxisome found in plant cells and packed with enzymes for processing the products of photosynthesis
mitochondria
a eukaryotic organelle that is bounded by a double membrane and is the site of aerobic respiration and ATP synthesis
thylakoids
a membrane-bound network of flattened sac-like structures inside a plant chloroplast that function in converting light energy to chemical energy. a stack of thylakoid discs is a granum
grana
in chloroplasts, a stack of flattened, membrane-bound thylakoid discs where the light reactions of photosynthesis occur
stroma
the fluid matrix of a chloroplast in which the thylakoids are embedded. site where the Calvin cycle reactions occur
endosymbiosis theory
the theory that mitochondria and chloroplast evolved from prokaryotes that were engulfed by host cells and took up a symbiotic existence within those cells, a process termed primary endosymbiosis. In some eukaryotes, chloroplasts may have originated by secondary endosymbiosis; that is, when a cell engulfed a chloroplast-containing protist and retained its chloroplasts
differential centrifugation
procedure for separating cellular componenets according to their size and density by spinning a cell homogenate in a series of centrifuge runs. After each run, the supernatant is removed from the deposited material (pellet0 and spun again at progressively higher speeds
nuclear pores
an opening in the nuclear envelope that connects the inside of the nucleus with the cytoplasm and through which molecules such as mRNA and some proteins can pass
nuclear pore complex
a large complex of dozens of proteins lining a nuclear pore, defining its shape and regulating transport through the pore
ribosomal RNAs
RNA molecules that, together with proteins, make up ribosomes; the most abundant type of RNA.
messenger RNAs (mRNA)
an RNA molecule transcribed from DNA that carries information (in codons) that specifies the amino acid sequence of a polypeptide
nuclear localization signal (NLS)
a short amino acid sequence that marks a protein for delivery to the nucleus
pulse-chase experiment
A type of experiment in which a population of cells or molecules at a particular moment in time is marked by means of a labeled molecule and then their fate is followed over time.
culture
in cell biology, a collection of cells or a tissue growing under controlled conditions, usually in suspension or on the surface of a dish of solid growth medium
ER singal sequence
a short amino acid sequence that marks a polypeptide for transport to the endoplasmic reticulum, where synthesis of the polypeptide chain is completed and the signal sequence removed
signal recognition particle (SRP)
A RNA protein complex that binds to the ER signal sequence in polypeptide as it emerges from a ribosome and transports the ribosome-polypeptide complex to the ER membrane where synthesis of the polypeptide is completed. The ribosome + signal sequence + SRP complex then attaches to an SRP receptor in the ER membrane itself
cisternal maturation
the process of cargo movement through the Golgi apparatus by residing in cisternae that mature from cis to trans via the import and export of different Golgi enzymes
endocytosis
general term for any pinching off of the plasma membrane that results in the uptake of material from outside the cell. Includes phagocytosis, pinocytosis, and receptor-mediated endocytosis
receptor-mediated endocytosis
uptake by a cell of certain extracellular macromolecules, bound to specific receptors in the plasma membrane, by pinching of the membrane to form small membrane-bound vesicles
early endosome
a small transient organelle that is formed by the accumulation of vesicles from receptor-mediated endocytosis and is an early stage in the formation of a lysosome
late endosome
a membrane-bound vesicle that arises from an early endosome, accepts lysosomal enzymes from the Golgi, and matures into a lysosome
autopahgy
the process by which damaged organelles are surrounded by a membrane and delivered to a lysosome to be recycled
phagocytosis
uptake by a cell of small particles or cells by invagination and pinching off of the plasma membrane to form small, membrane-bound vesicles; one type of endocytosis
bulk-phase endocytosis
nonspecific uptake of extracellular fluid by pinching off the plasma membrane to form small membrane-bound vesicles; considered to be a means of retrieving membranes from the surface following exocytosis
actin filaments
a long fiber, about 7nm in diameter, composed of two intertwined strands of polymerized actin protein; one of the three types of cytoskeletal fibers. Involved in cell movement. Also called microfilament
motor protein
a class of proteins whose major function is to convert the chemical energy of ATP into motion. Includes dynein, kinesin, and mysoin
cytokinesis
division of the cytoplasm to form two daughter cells. Typically occurs immediately after division of the nucleus by mitosis or meiosis
cytoplasmic streaming
the directed flow of cytosol and organelles that facilitates distribution of materials within some large plant and fungal cells. Occurs along actin filaments and is powered by myosin
cell crawling
a form of cellular movement involving actin filaments in which the cell produces bulges (pseudopodia) that stick to the substrate and pull the cell forward
intermediate filament
a long fiber, about 10nm in diameter, composed of one of various proteins; one of the three types of cytoskeletal fibers. Used to form networks that help maintain cell shape and hold the nucleus in place
nuclear lamins
intermediate filaments that make up the nuclear lamina layer--a lattice-like layer inside the nuclear envelope and helping to organize the chromosomes
mircotubules
a long, tubular fiber 25 nm in diameter, formed by polymerization of tubulin protein dimers; one of the three types of cytoskeletal fibers. Involved in cell movement and transport of material within the cell
dimers
an association of two molecules that may be identical (homodimer) or different (heterodimer)
microtubule organizing cener MTOC
General term for any structure that organizes microtubules in cells
centrosome
Structure in animal and fungal cells, containing two centrioles, that serves as a microtubule organizing center for the cells' cytoskeleton and for the spindle apparatus during cell division
centrioles
one of two small cylindrical structures found together within the centrosome near the nucleus of a eukaryotic cell (not found in plants). consist of microtubule triplets and is structurally identical with a basal body
kinesin
a class of motor proteins that uses the chemical energy of ATP to "walk" toward the plus end of a microtubule. Used to transport vesicles, particles, organelles and chromosomes
cilia
One of many short, filamentous projections of some eukaryotic cells, containing a core of microtubules. used to move the cell as well as to circulate fluid or particles around the surface of a stationary cell
axoneme
a structure found in eukaryotic cilla and flagella and responsible for their motion; composed of two central microtubules surrounded by nine doublet microtubules (9+2 arrangement)
basal body
the microtubule organizing center for cilia and flagella in eukaryotic cells. Consists of nine triplets of microtubules arranged in a circle and establishes the structure of axonemes. structurally identical with a centriole
dynein
a class of motor proteins that uses the chemical energy of ATP to "walk" toward the minus end of a microtubule. dyneins are responsible for bend of cilia and flagella, play a role in chromosome movement during mitosis, and can transport vesicles and organelles
free energy
the energy of a system that can be converted into work. It may be measured only through the change in free energy in a reaction
kinetic energy
the energy of motion
potential energy
energy stored in matter as a result of its position or molecular arrangement
first law of thermodynamics
the principle of physics that energy is conserved in any process. Energy can be transferred and converted into different forms, but I cannot be created or destroyed
enthalpy
(H) a quantitative measure of the amount of potential energy, or heat content, of a system plus the pressure and volume it exerts on its surroundings
exothermic
referring to a chemical reaction that releases heat
endothermic
referring to a chemical reaction that absorbs heat
entropy
(S) a quantitative measure of the amount of disorder of any system, such as a group of molecules
second law of thermodynamics
the principle of physics that the entropy of the universe or any closed system always increases
Gibbs free-energy change
a measure of the change in enthalpy and entropy that occurs in a given chemical reaction. Delta G is less than 0 for spontaneous reactions and greater than 0 for nonspontaneous reactions
exergonic
referring to a chemical reaction that can occur spontaneously, releasing heat and/or increasing entropy, and for which the Gibb free-energy change (Delta G) is less than 0
endergonic
referring to a chemical reaction that requires an input of energy to occur and for which the Gibbs free energy change (Delta G) is greater than 0
energetic coupling
in cellular metabolism, the mechanism by which energy released from an exergonic reaction (commonly, hydrolysis of ATP) is used to drive an endergonic reaction
reduction-oxidation reactions (redox reactions)
any chemical reaction that involves either the complete transfer of one or more electrons from one reactant to another, or a reciprocal shift in the position of shared electrons within one or more of the covalent bonds of two reactants
oxidation
the loss of electrons from an atom or molecule during a redox reaction, either by donation of an electron to another atom or molecule, or by the shared electrons in covalent bonds moving farther from the atomic nucleus
reduction
the gain of electrons by an atom or molecule during a redox reaction, either by acceptance of an electron form another atom or molecule, or by the shared electrons in covalent bonds moving closer to the atomic nucleus
flavin adenine dinucleotide (FAD/FADH2)
Oxidized and reduced forms, respectively, of flavin adenine dinucleotide. A nonprotein electron carries that function in the citric acid cycle and oxidative phosphorylation
electron carrier
any molecule that readily accepts electrons from and donates electrons to other molecules. Protons may be transferred with the electrons in the form of hydrogen atoms
nicotinaminde adenine dinucleotide (NAD+)
a non protein carrier that is reduced during the light-dependent reaction in photosynthesis and extensively used in biosynthetic reactions
NADH
a non protein carrier that is reduced during the light-dependent reaction in photosynthesis and extensively used in biosynthetic reactions
adenosine triphosphate (ATP)
a molecule consisting of an adenine base, a sugar, and three phosphate groups that can be hydrolyzed to release energy. Universally used by cells to store and transfer energy
kilocalorie
a unit of energy often used to measure the energy content of food. a kcal of energy raises 1 kg of water 1 degree C
substrate
1) a reactant that interacts with a catalyst, such as an enzyme or ribozyme, in a chemical reaction
2) a surface on which a cell or organism sits
phosphorylation
Addition of a phosphate group.
catalysts
any substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change
active site
the location in an enzyme molecule where substrates (reactant molecules) bind and react
transition state
a high-energy intermediate state of the reactants during a chemical reaction that must be achieved for the reaction to proceed
Enzyme catalysis can be analyzed as a three step process:
Initiation
Transition state Facilitation
Termination
Initiation
1) in an enzyme-catalyzed reaction, the stage during which enzymes orient reactant precisely as the bind at specific location within the enzyme's active site
2) In DNA transcription, the stage suring which RNA polymerase and other proteins assemble at the promoter sequence and open the strands of DNA to start transcription
3) In translation, the stage during which a complex consisting of initiation factor proteins, a ribosome, and mRNA and an aminoacyl tRNA corresponding to the start codon is formed
Transition state facilitation
the second stage (after initiation) in enzyme-catalyzed reactions, in which the enzyme enables formation of the transition state
termination
1) in enzyme-catalyzed reactions, the final stage in which the enzyme returns to its original conformation and products are released.
2) in transcription, the dissociation of RNA polymerase from DNA
3) in translation, the dissociation of a ribosome from mRNA when it reaches a stop codon
Cofactors
an inorganic ion, such as a metal ion, that is required for an enzyme to function normally. May be bound tightly to an enzyme or associate with it transiently during catalysis
Coenzymes
a small organic molecule that is a required cofactor for an enzyme-catalyzed reaction. often donates or receives electrons or function groups during the reaction
prosthetic groups
a non-amino acid atom or molecule that is permanently attached to an enzyme or other protein and is required for its function
competitive inhibition
inhibition of an enzyme's ability to catalyze a chemical reaction via binding of a nonreactant molecule that competes with the substrate(s) for access to the active site
allosteric regulation
regulation of a protein's function by binding of regulatory molecule, usually to a specific site distinct from the active site, that causes a change in the protein's shape
feedback inhibition
a type of control in which high concentrations of the product of a metabolic pathway inhibit one of the enzymes early in the pathway. A form of negative feedback
bioremediation
the sue of living organisms, usually bacteria or archaea, to degrade environmental pollutants
catablic pathways
any set of chemical reaction that breaks down large, complex molecules into smaller ones, releasing energy in the process
anablic pathways
any set of chemical reaction that synthesizes large molecules form smaller ones. Generally requires an input of energy
glucose
six-carbon monosaccharide whose oxidation in cellular respiration is the major source of ATP in animal cells
glycolysis
a series of 10 chemical reactions that oxidize glucose to produce pyruvate, NADH, and ATP. used by organisms as part of fermentation or cellular respiration
oxidative phosphorylation
production of ATP molecules by ATP synthase using the proton gradient established via redox reactions of an electron transport chain
cellular respiration
a common pathway for production of ATP, involving transfer of electrons from compounds with high potential energy through an electron transport chain and ultimately to an electron acceptor (often oxygen)
homeostasis
the array of relatively stable chemical and physical conditions in an animals' cells, tissues, and organ. May be achieved by the body's passively matching the conditions of a stable external environment or by active physiological processes triggered by variation in the external or internal environments
substrate-level phosphorylation
production of ATP or GTP by the transfer of a phosphate group from an intermediate substrate directly to ADP or GDP. Occurs in glycolysis and in the citric acid cycle
phoshofructokinase
enzyme that catalyzes synthesis of fructose-1,6-biphosphate from fructose-6-phosphate, a key reaction in glycolysis
cristae
sac-like invaginations of the inner membrane of a mitochondrion. Location of the electron transport chain and ATP synthase
mitochondiral matrix
central compartment of a mitochondrion, which is lined by the inner membrane; contain mitochondrial SNA, ribosomes, and the enzymes for pyruvate processing and the citric acid cylce
coenzyme A (CoA)
a molecule that is required for many cellular reactions and that is often transiently linked to other molecules, such as acetyl groups
acetyl CoA
a molecule produced by oxidation of pyruvate (the final product of glycolysis) in a reaction catalyzed by pyruvate dehydrogenase. can enter the citric acid cycle and is used as a carbon source in the synthesis of fatty acids, steroids, and other compounds
pyruvate dehydrogenase
a large enzyme complex, located in the mitochondrial matix, that is responsible for converting pyruvate to acetyl CoA during cellular respiration
citric acid cycle
a series of eight chemical reactions that start with citrate (deprotonated citric acid) and ends with oxaloacetate, which reacts with acetyl CoA to form citrate--forming a cycle that is part of the pathway that oxidizes glucose to CO2. Also known as the Krebs cycle or tricarboxylic acid (TCA) cycle
guanosine triphoshpate (GTP)
a nucleotide consisting of guanine, a ribose sugar, and three phosphate groups. Can be hydrolyzed to release free energy. Commonly used in RNA synthesis and also function in signal transduction is association with G proteins
electron transport chain (ETC)
any set of membrane-bound protein complexes and mobile electron carries involved in a coordinated series of redox reactions in which the potential energy of electrons is successively decreased and used to pump protons from one side of the membrane to the other
ubiquinone/co enzyme q
a nonprotien molecule that shuttles electrons between membrane-bound complexes in the mitochondrial electron transport chain
cytochrome c
a soluble protein that shuttles electrons between membrane-bound complexes in the mitochondrial electron transport chain
chemiosmosis
an energetic coupling mechanism whereby energy stored in an electrochemical proton gradient is used to drive an energy-requiring process such as production of ATP
proton-motive force
the combined effect of a proton gradient and an electric potential gradient across a membrane, which can drive protons across the membrane. used by mitochondria and chloroplasts to power ATP synthesis via the mechanism of chemiosmosis
aerobic
referring to any metabolic process, cell or organism that uses oxygen as an electron acceptor
anaerobic
referring to any metabolic process, cell, or organism that uses an electron acceptor other than oxygen, including fermentation or anaerobic respiration
Fermentation
any of several metabolic pathways that regenerate oxidizing agents, such as NAD+, by transferring electrons to a final electron acceptor in the absence of an electron transport chain. Allows pathways such as glycolysis to continue to make ATP
lactic acid fermentation
catabolic pathway in which pyruvate produced by glycolysis is converted to lactic acid in the absence of oxygen
alchohol fermentation
catabolic pathway in which pyruvate produced by glycolysis is converted to ethanol in the absence of oxygen
facultative anaerobes
any organism that can survive and reproduce by performing aerobic respiration when oxygen is available or fermentation when it is not
photosynthesis
the complex biological process that converts the energy of light into chemical energy stored in glucose and other organic molecules. Occurs in most plants, algae, and some bacteria
autotrophs
any organism that can synthesize reduced organic compounds from simple inorganic sources such as CO2 or CH2.l Most plants and some bacteria and archaea are autotrophs.
heterotrophs
any organism that cannot synthesize reduced organic compounds from inorganic sources and that must obtain them from other organisms. Some bacteria, some archaea, and virtually all fungi and animals are heterotrophs
Calvin cycle
in photosynthesis, the set of reaction s that use NADPH and ATP formed in the light-depended reaction to drive the fixation of CO2 reduction of the fixed carbon to produce sugar, and the regeneration of the substrate used to fix CO2. Also called light-independent reactions
NADP+ (nicotinamide adenine dinucleotide phosphate)
Oxidized and reduced forms, respectively, of nicotinamids adenine dinucleotide phosphate. A nonprotein electron carrier that is reduced during the light-dependent reaction in photosynthesis and extensively used in biosynthetic reactions
chloroplasts
a chlorophyll-containing organelle, bounded by a double membrane, in which photosynthesis occurs; found in plants and photosynthetic protists. also the location of starch, amino acid, fatty acid, purine, and pyrimidine synthesis
thylakoids
a membrane-bound network of flattened sac-like structures inside a plant chloroplast that function in converting light energy to chemical energy. a stack of thylakoid discs is a granum
grana
in chloroplasts, a stack of flattened, membrane-bound thylakoid discs where the light reactions of photosynthesis occur
stroma
the fluid matrix of a chloroplast in which the thylakoids are embedded. site where the Calvin cycle reactions occur
pigments
any molecule that absorbs certain wavelengths of visible light and reflects or transmits other wavelengths
wavelenth
the distance between two successive crests in any regular wave, such as light waves, sound waves, or waves in water
elecrtomagnetic spectrum
the entire range of wavelengths of radiation extending from short wavelengths (high energy) to long wavelengths (low energy). Includes gamma rays, X-rays, ultraviolet, visible light, infrared...
visible light
the range of wavelengths of electromagnetic radiation that humans can see, from about 400 to 700 nm
photons
a discrete packet of light energy; a particle of light
chlorophylls
any of several closely related green pigments, found in chloroplasts, that absorb light during photosynthesis
carotenoids
any of a class of accessory pigments, found in chloroplasts, that absorb wavelengths of light not absorbed by chlorophyll; typically appear yellow, orange, or red. included carotenes and xanthophyll
absorption spectrum
the amount of light of different wavelengths absorbed by a pigment. usually depicted as a graph of light absorbed versus wavelength
action spectrum
the relative effectiveness of different wavelengths of light in driving a light-dependent process such as photosynthesis. Usually depicted as a graph of some measure of the process versus wavelength
fluorescence
the spontaneous emission of light from an excited electron falling back to its normal (ground) state
antenna complex
part of a photosystem, contain an array of chlorophyll molecules and accessory pigments, that receives energy from light and directs the energy to a central reaction center during photosynthesis
photosystem
one of two types of units, consisting of a central reaction center surrounded by antenna complexes, that is responsible for the light-dependent reactions of photosynthesis
reaction center
centrally located component of a photosystem containing proteins and a pair of specialized chlorophyll molecules. It is surrounded by antenna complexes that transmit resonance energy to excite the reaction center pigments
photosystem II
A photosystem that contains a pair of P680 chlorophyll molecules and uses absorbed light energy to produce a proton-motive force for the synthesis of ATP. Oxygen is produced as a by-product when water is split to obtain electrons
photosystem I
a photosystem that contains a pair of P700 chlorophyll molecules and uses absorbed light energy to reduce NADP+ to NADPH
pheophytin
the molecule in photosystem II that accepts excited electrons from the reaction center chlorophyll and passes them to an electron transport chain
plastoquinone (PQ)
a nonprotein electron carries in the chloroplast electron transport chain. Receives excited electrons from photosystem II (noncyclic) or photosystem I (cyclic) and passes them to more electronegative molecules in the chain. Also transports protons from the stroma to the thylakoid lumen, generating a proton-motive force
photopohoshporylation
production of ATP molecules by ATP synthase using the proton-motive force generated as light-excited electrons flow through an electron transport chain during photosynthesis
oxygenic
referring to any process or reaction that produces oxygen. Photosynthesis in plants, algae, and cyanobacteria, which involves photosystem II, is oxygenic
anoxygenic
referring to any process or reaction that does not produce oxygen. Photosynthesis in purple sulfur and purple nonsulfur bacteria, which does not involve photosystem II, is anoxygenic.
z-scheme
model for changes in the potential energy of electrons as they pass from photosystem II to photosystem I and ultimately to NADP+ during the light-dependent reactions of photosynthesis
plastocyanin
a small protein that shuttles electrons originating from photosystem II to the reaction center of photosystem I during photosynthesis
noncyclic electron flow
path of election flow in which electron pass from photosystem II, through an electron transport chain, to photosystem I, and ultimately to NADP+ during the light-dependent reactions of photosynthesis
cyclic electron flow
path of electrons in which excited electrons of photosystem 1 are transferred back to plastoquinon (PQ), the start of the electron transport chain normally associated with photosystem II. Instead of reducing NADP+ to make NADPH, the electron energy is used to make ATP via photophosphorylation
carbon fixation
the process of converting gaseous carbon dioxide into an organic molecule, often associated with photosynthesis.
ribulose bisphosphate (RuBP)
a five-carbon compound that combines with CO2 in the first step of the Calvin cycle during photosynthesis
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glyceraldehyde-3-phosphate (G3P)
The phosphorylated three-carbon compound formed as the result of carbon fixation in the first step of the Calvin cycle
rubisco
the enzyme that catalyzes the first step of the Calvin cycle during photosynthesis; the addition of a molecules of CO2 to ribulose bisphosphate
maladaptive
describing a trait that lowers fitness
photorespiration
a series of light-driven chemical reactions that consumes oxygen and releases carbon dioxide, basically undergoing photosynthesis. Usually occurs when there are high O2 and low CO2 concentrations inside plant cells; often occurs when stomata must be kept closed to prevent dehydration
guard cells
one of two specialized, crescent-shaped cells forming the border of a plant stoma. Guard cells can change shape to open or close the stoma
stoma
Generally, a pore or opening. In plants, a microscopic pore, surrounded by specialized cells that open the pore, on the surface of a leaf or stem through which gas exchange occurs
C4 pathway
a variant type of photosynthesis in which atmospheric CO2 is first fixed by PEP carboxylase into four-carbon acids, rather than the three-carbon molecules of the classic C3 pathway. Used to concentrate CO2 to reduce photorespiration in the Calvin cycle white stomata are closed
C3 pathway
the most common form of photosynthesis in which atmospheric CO2 is fixed by rubisco to form 3-phosphoglecerate, a three carbon molecule. used in the first phase of the Calvin cycle
PEP carboxylase
an enzyme that catalyzes addition of CO2 to phosphoendolpyruvate, a 3-carbon compound, forming a 4-carbon organic acid
mesophyll cells
a type of cell, found near the surfaces of plant leaves, that is specialized for the light-dependent reactions of photosynthesis
bundle-sheath cells
a type of cell found around the vascular tissue (veins) of plant leaves
crassulacean acid metabolism
(CAM) a variant type of photosynthesis in which CO2 is fixed and stored in organic acids at night when stomata are open and then released to feed the Calvin cycle during the day when stomata are closed. helps reduce water loss and CO2 loss by photorespiration
gluconeogenesis
synthesis of glucose, often form non-carbohydrate sources. In plants, used to produce glucose form produces of the Calvin cycle. In animals, occurs in the liver in response to low insulin levels and high glucagon levels
sucrose
A disaccharide made of glucose + fructose. one of the two main products of photosynthesis