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Gen Bio Exam 2
Terms in this set (179)
In terms of the important types of chemical reactions that take place, cellular respiration can be summarized as the _______________ of fuel such as glucose, and the _____________ of O2.
In the familiar figure above, what is the name of the complex polypeptide structure located at the far right, which we described as a molecular mill, and acts like an inverse ion pump?
Which of the following statements describes the first law of thermodynamics?
Energy cannot be created or destroyed.
Which of the following statements is an important consequence of the first law of thermodynamics for a living organism?
An organism ultimately must obtain all of the necessary energy for life from its environment.
Which of the following statements describes what happens to a molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction?
It loses electrons and loses potential energy.
What happens when electrons are passed from one atom to a more electronegative atom?
The more electronegative atom is reduced, and energy is released.
There are a number of genetic diseases associated with mitochondria, which negatively impact metabolism, reminding us of the important role of mitochondria in eukaryotic cells, which is:
They produce energy in the form of ATP.
When a molecule is reduced, it ____.
What is the ultimate fate of the oxygen atoms (O2) in cellular respiration?
They are incorporated into water.
The oxidation of which macromolecule yields the most energy by weight?
What is the type of chemical reaction that must occur, where electrons flow from one molecule to the next and supply the energy for metabolism?
reduction/oxidation, or redox
The final product of glycolysis is ____.
How are NADH and FADH2 similar?
They both act as high energy electron shuttles
Where are the enzymes that hydrolyze glucose - glyceraldehyde-3-phosphate (G3P) found in cells?
We learned that the efficiency of cellular respiration can be assessed by comparing the heat energy released by burning glucose (686 kcal/mol) to the energy content in 32 ATP molecules (224 kcal/mol), giving a value of about:
In higher plants, thylakoids are arranged into stacks called ____.
The molecule of chlorophyll a in photosystem II's reaction center is known as P680 because ____.
it absorbs photons with a wavelength of 680 nm
Where in a plant cell does the Calvin cycle take place?
stroma of the chloroplast
Which two plant types that have evolved a special mechanisms to deal with excessive photorespiration?
CAM and C4
In the light-dependent reactions of photosynthesis, an excited electron from photosystem II is passed along an electron transport chain to ____.
Substance A is synthesized in the liver, travels through the circulatory system bound to a carrier protein, and causes a change in gene expression in a target cell. This is an example of ____.
Substance B is synthesized in neurons, travels through gap junctions, and triggers the transduction of an electrochemical signal. This is an example of ____.
List 2 light absorbing pigments in plants. Circle one of the pigments and list a color of light that it absorbs and one that it reflects?
Chlorophyll A and B, Cartenoids
Chlorophyll A and B reflect green light, absorb reference graph in book. Carotenoids reflect orange and red absorb violet and blue.
______________________plants physically separate rubisco and oxygen ____________________plants temporally separate rubisco and oxygen .
Give an example of a CAM plant:
Succulents, cacti, pineapples
What are the 3 stages of the Calvin Cycle? What is the name of the enzyme that performs stage 1?
1) Carbon Fixation, Reduction, Regeneration
Using the below image, which reactions of photosynthesis happens at A. ____________________________________ and B. _________________________________________. Write the reactant at C. ____________________
and the product at D. ______________________________
A. Light dependent reactions
B. Light independent reactions.
Generally, which phase of the cell cycle varies the most in length?
The cells produced by mitotic divisions are considered to be ____ the original cell.
G1 is associated with which of the following cellular events?
normal growth and cell function
Metaphase is characterized by ________.
alignment of chromosomes on the equator of the cell
One difference between cancer cells and normal cells is that cancer cells
continue to divide regardless of cell signals.
Which statement best describes the difference between cell division in plant and animal cells?
Cytokinesis occurs by formation of a cleavage furrow in animal cells, but not plant cells.
Replication of DNA occurs during ____.
Chromosomes are in a condensed form at which stage(s) of the cell cycle?
throughout mitosis until late telophase
Where is the centromere found?
central region of a chromosome where the spindle microtubules attach
Neurotransmitters are molecules released by ____.
is the totality of an organism's chemical reactions
begins with a specific molecule and ends with a product
a specific catalytic protein
release energy by breaking down complex molecules into simpler compounds
E.g. Cellular respiration, the breakdown of glucosein the presence of oxygen
consume energy to build complex molecules from simpler ones
E.g. the synthesis of protein from amino acids
the study of how energy flows through living organisms
the capacity to cause change and exists in various forms
energy associated with motion
the kinetic energy associated with random movement of atoms or molecules
thermal energy in transfer between objects
energy that matter possesses because of its location or structure
potential energy available for release in a chemical reaction
the study of energy transformations
First law of thermodynamics
Also called the principle of conservation of energy
Energy can be transferred and transformed, but it cannot be created or destroyed
Second law of thermodynamics
every energy transfer or transformation increases the entropy of the universe
a measure of molecular disorder
organisms reduce ordered forms of matter & energy into less ordered forms (↑ entropy)
organisms create ordered forms from less organized forms of energy & matter (↓ entropy)
Change in Free Energy (deltaG)
is related to the change in enthalpy (change in total energy (ΔH)), change in entropy (ΔS), and temperature in Kelvin units (T)
occur without energy input and can happen quickly or slowly
proceeds with a net release of free energy and is spontaneous
absorbs free energy from its surroundings and is nonspontaneous
the use of an exergonic process to drive an endergonic one
the cell's energy shuttle and is composed of ribose (a sugar), adenine (a nitrogenous base), and three phosphate groups
The bonds between the phosphate groups of ATP's tail can be broken
the transfer of a phosphate group to another molecule
an endergonic reaction
Activation energy (Ea)
The initial energy needed to start a chemical reaction
a chemical agent that speeds up a reaction without being consumed by the reaction
the reactant that an enzyme acts on
the region on the enzyme where the substrate binds, so an enzyme is very specific
brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction
non-protein enzyme chemical helpers frequently binding in part of the active site
can be inorganic and organic
switching on or off coding genes
removing a polypeptide "cap"
non-binding site binding / cooperativity
binding site binding
chain of enzymes
occurs when a regulatory molecule binds to a protein at one site and affects the protein's function at another site
a form of allosteric regulation that can amplify enzyme activity
One substrate molecule primes an enzyme to act on additional substrate molecules more readily
It is allosteric because binding by a substrate to one active site affects catalysis in a different active site
bind to the active site of an enzyme, competing with the substrate
bind to enzyme and change its shape, making the active site less effective
the end product of a metabolic pathway shuts down the pathway
a simple process of partial degradation of sugars that occurs without O2
consumes organic molecules and O2 and yields ATP
similar to aerobic respiration but consumes compounds other than O2
includes both aerobic and anaerobic respiration but is often used to refer to just aerobic respiration
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)
Chemical reactions that transfer electrons
Also called redox reactions
a substance loses electrons, or is oxidized, so energy is released (exergonic)
a substance gains electrons, or is reduced, so energy is absorbed (endergonic)
The Stages of Cellular Respiration
2) Citric acid cycle
3) Oxidative phosphorylation
break down of one glucose into two molecules of pyruvate
splits 1 glucose into 2 pyruvates
Citric acid cycle
(aka krebs cycle)
extracts electrons from acetyl-CoA (product of pyruvate reaction)
oxidizes organic fuel derived from pyruvate
generates 2 CO2, 1 ATP, 3 NADH, & 1 FADH2
uses electrons from 1. & 2. to generate most of the ATP
Multi-enzyme complex that catalyzes 3 reactions:
1.Oxidation of pyruvate and release of CO2
2.Reduction of NAD+ to NADH
3.Combination of the remaining two-carbon fragment and coenzyme A to form acetyl CoA
During cellular respiration, most energy flows in this sequence:
glucose → NADH → electron transport chain → proton-motive force → ATP
For each molecule of glucose degraded to CO2 and water by respiration,
the cell makes up to 32 molecules of ATP
pyruvate is converted to ethanol in two steps:
1)The first step releases CO2 from pyruvate
2)The second step produces NAD+ and ethanol
Lactic acid fermentation
pyruvate is reduced by NADH, forming NAD+ and lactate as end products, with no release of CO2
carry out fermentation or anaerobic respiration and cannot survive in O2
they can survive using either fermentation or cellular respiration
e.g. yeast and many bacteria
the process that converts solar energy into chemical energy within chloroplasts
6 CO2 + 6 H2O + Light energy → C6H12O6 + 6 O2
the producers of the biosphere, sustaining themselves by producing organic molecules from CO2 and other inorganic molecules
use photosynthesis to produce the organic compounds, e.g. plants, algae, certain other unicellular eukaryotes, and some prokaryotes
oxidize inorganic compounds, e.g. hydrogen sulfide at hydrothermal vents, to obtain the energy to make organic molecules
the consumers of the biosphere obtain organic material from other organisms
CO2 enters and O2 exits the leaf through microscopic pores called
A chloroplast has an envelope of two membranes surrounding a dense fluid called
connected sacs in the chloroplast that compose a third membrane system
Thylakoids may be stacked in columns called
the pigment that gives leaves their green color, resides in the thylakoid membranes
Two Stages of Photosynthesis
Light reactions (the photo part) & Calvin cycle (the synthesis part)
The light reactions (in the thylakoids):
-Reduce NADP+ to NADPH
-Generate ATP from ADP by photophosphorylation
the distance between wave crests
substances that absorb visible light
wavelengths reflected or transmitted
An absorption spectrum
a graph plotting a pigment's light absorption versus wavelength
An action spectrum
profiles the relative effectiveness of different wavelengths of radiation in driving a process, such as photosynthesis
Three Types of Pigments in Chloroplasts:
the key light-capturing pigment
broadens the action spectrum
broaden the spectrum, but can provide photoprotection - absorb excessive light that would damage chlorophyll or react with oxygen
consist of a reaction-center complex surrounded by light-harvesting complexes
consists of pigment molecules bound to proteins & transfer the energy of photons to the chlorophyll a molecules in the reaction-center complex
an association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor
Two Types of Photosystems in the Thylakoid:
(PS II) functions first (the numbers reflect order of discovery)
The reaction-center chlorophyll a of PS II is called P680 as is best at absorbing wavelength of 680 nm
(PS I) functions second
The reaction-center chlorophyll a of PS I is called P700 as is best at absorbing a wavelength of 700 nm
Linear electron flow
the primary pathway, involves both photosystems and produces ATP & NADPH using light energy
Cyclic electron flow
uses only photosystem I and produces ATP, but not NADPH
generates surplus ATP to satisfy the high Calvin cycle demand for energy
There are nine steps in linear electron flow:
1.A photon hits a pigment in a light-harvesting complex of PS II, and its energy is passed among pigment molecules until it excites P680
2.An excited electron from P680 is transferred to the primary electron acceptor (we now call it P680+)
3.H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it to P680 (i.e. regenerating chlorophyll a)
4.Electrons "fall" down an electron transport chain from the primary electron acceptor of PS II to PS I. Energy released further drives the creation of a proton gradient across the thylakoid membrane
5.Potential energy stored in the proton gradient drives production of ATP by chemiosmosis
6.In PS I transferred light energy excites P700, which loses an electron to the primary electron acceptor
7.P700+ accepts an electron from Pc which was passed down from PS II via the electron transport chain (i.e. regenerating chlorophyll a)
8.Electrons "fall" down an electron transport chain from the primary electron acceptor of PS I to the protein ferredoxin (Fd)
9.NADP+ reductase catalyzes the transfer of electrons to NADP+, reducing it to NADPH
The Calvin Cycle has three phases:
1.Carbon fixation (catalyzed by rubisco)
3. Regeneration of the CO2 acceptor (RuBP)
minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds
There are two distinct types of cells in the leaves of C4 plants:
arranged in tightly packed sheaths around the veins of the leaf
loosely packed between the bundle sheath and the leaf surface
open their stomata at night, incorporating CO2 into organic acids that are stored in the vacuoles
Three Types of Communication Pathways:
Three Steps in Process Signaling Target Cells:
§directly connect the cytoplasm of adjacent cells
between adjacent cells by surface protein receptors
involves exocytosis of signal molecules that diffuse in the extracellular fluid
target is nearby cell
target is same cell
binding of signal molecule to receptor
activation of relay molecule pathway
alteration of protein action or gene regulation
Receptor tyrosine kinase (RTK)
§the most common type of receptor enzyme
Ligand-gated ion channel
a membrane receptor
proteins are found in the cytoplasm or nucleus of target cells
usually a multistep pathway that can greatly amplify a signal
transfer phosphates from ATP to proteins, a process called phosphorylation
rapidly remove the phosphates from proteins, a process called dephosphorylation
acts as a molecular switch, turning protein activities on and off or up or down, as required
small hydrophilic molecules or ions that diffuse throughout the cytosol
e.g. Cyclic AMP (cAMP) and Calcium ions (Ca2+)
There are four aspects of signal regulation:
1. Amplification of the signal by 2nd messengers
2. Specificity of the response
3. Efficiency of the response
4. Termination of the signal
"programmed cell death"
Components of the cell are lysed and packaged into vesicles that are digested by scavenger cells
Prevents enzymes from leaking out of a dying cell and damaging neighboring cells
Can be triggered by signals from outside the cell or inside it
Most cell division yields two daughter cells with identical DNA, found in somatic (body) cells
Same number of chromosomes (ploidy) as parent cell
Humans have 2 chromosome sets (diploid = 2n = 46)
Special type of division producing gamete (sex) cells
Yields four daughter cells with non-identical DNA
Half as many chromosomes as parent cell
Human gametes (sperm/ovum) have (haploid = n = 23)
packages of DNA molecules
the narrow "waist" of the duplicated chromosome, where the two chromatids are most closely attached
Phases of the Cell Cycle:
Mitotic (M) phase (mitosis & cytokinesis)
Interphase (cell growth & copying chromosomes)
G1 phase ("first gap")
S phase ("synthesis")
G2 phase ("second gap")
Cell grows during all three phases, but chromosomes are duplicated only during the S phase
Mitosis is broken down into 5 stages (PPMAT):
the microtubule-organizing center
a short microtubule array
-Chromosomes condense to sister chromatids
-Centrosome is the microtubule-organizing center
-Centriole pairs replicate during interphase
-Mitotic spindle migrating centrioles to opposite ends of the cell
-Nuclear envelope breaks down
-Centrioles complete migration to opposite poles
-Kinetochore forms on each sister chromatid at the centromere
-Microtubules bind to kinetochores
-The mitotic spindle moves sister chromatids into alignment at cell midpoint (metaphase plate)
-Enzyme called separase hydrolyzes cohesins, separating sister chromatids
-Mitotic spindle shortens by depolymerization and pulls the daughter chromosomes to each pole
-The mitotic spindle completely disassembles
-Nuclear envelope reforms
-Produces 2 separate daughter cells
-In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow
-In plant cells, a cell plate forms during cytokinesis
2 types of proteins are involved in cell cycle control:
cyclins and cyclin-dependent kinases (Cdks)
-For many cells, the G1 checkpoint seems to be the most important
-If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and divide
-If a cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G0 phase
-Do not respond normally to the body's control mechanisms
-They exhibit neither contact-dependent nor anchorage dependent regulation of their division
-They do not need growth factors to grow and divide:
-They may make their own growth factor
-They may activate the transduction pathway without the presence of the growth factor
-They may have an abnormal cell cycle control system
masses of abnormal cells
If abnormal cells remain only at the original site, the lump is called
invade surrounding tissues and can undergo metastasis, the spread of cancer cells to other parts of the body, where they may form additional tumors
is promoted by changes that block contact inhibition and alter cell-surface molecules that link cells together
-how prokaryotes reproduce
-chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apart
-plasma membrane pinches inward, dividing the cell
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