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UT Bio 311C
Exam 2 Flashcards--Cellular Respiration and Photosynthesis
112
Biology
04/03/2007

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Term
If an enzyme is added to a solution where its substrate and products are in equilibrium, what would occur?
Definition
Nothing; the reaction would stay at equilibrium
Term
Some bacteria are metabolically active in hot springs because?
Definition
their enzymes have high optimal temperatures
Term
What does it mean when we say that organisms are thermodynamically open systems?
Definition
Organisms acquire energy from their surroundings.
Term
Which of the following has the most free energy per molecule?
Definition
Starch.
Term
Which compound could most easily be modified to form ATP?
Definition
The RNA nucleotide Adenosine.

Adenosine has a ribose sugar attached, one phosphate group, and the nitrogenous base adenine.
Term
Why are the bonds between phosphate groups in ATP unstable?
Definition
The negatively charged phosphate groups repel one another and the terminal phosphate group is more stable in water than it is in ATP.
Term
The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?
Definition
The hydrolysis of ATP.

(first hydrolyze ATP, then use the energy released to transfer a phosphate group to glucose)
Term
What does the speed of an enzymatic reaction depend on?
Definition
The speed of a reaction is determined by the activation energy barrier of the reaction and the temperature (which determines how many reactants have the energy to overcome the barrier).
Term
Does increasing the concentration of substrate increase the rate of the reaction?
Definition
Until the enzyme becomes saturated with substrate, increasing the substrate concentration increases the rate of the reaction.
Term
How is enzyme activity affected by PH?
Definition
High or low PH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site.
Term
What are the roles of heat and temperature in biological reactions?
Definition
1. Heat from the environment is necessary for substrates to get over the activation energy barrier.

2. Increasing temperature increases increases the kinetic energy of the substrates.
Term
In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?
Definition
2 net ATP gained.

(4 produced - 2 consumed)
Term
In most cells, not all of the carbon that enters glycolysis is converted to carbon dioxide by cellular respiration. What happens to this carbon that does not end up as CO2?
Definition
The carbon atoms are removed from these processes to serve as building blocks for other complex molecules.
Term
How many net molecules of ATP does the citric acid cycle produce?
Definition
2 net molecules of ATP
Term
How many molecules of ATP are formed by the electron transport chain (oxidative phosphorylation)?
Definition
About 34
Term
What is the end result of glycolysis?
Definition
For every glucose molecule that enters glycolysis, a net of 2 ATP and a net of 2 NADH are formed.
Term
Why don't cells do not catabolize carbon dioxide?
Definition
Carbon Dioxide is already completely oxidized.
Term
In glycolysis, what starts the process of glucose oxidation?
Definition
ATP
Term
For each glucose that enters glycolysis, ____ NADH and H+ are produced by the citric acid cycle.
Definition
6
Term
In fermentation, ____________ is reduced and _______________ is oxidized.
Definition
pyruvate...NADH
Term
Which molecule from the glycolytic pathway has the most chemical energy?
Definition
fructose-1,6-biphosphate
Term
In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and in a few minutes radioactive oxygen atoms showed up in which compound?
Definition
Carbon Dioxide
Term
For each glucose molecule that enters glycolysis, how many ATP, NADH, and FADH2 are produced in the citric acid cycle?
Definition
2 ATP, 6 NADH, 2 FADH2
Term
How many ATP, NADH, and FADH2 are produced for each pyruvate molecule that enters the citric acid cycle?
Definition
In the citric acid cycle, for each pyruvate that enters the cycle, 1 ATP, 3 NADH, and 1 FADH2 are produced.
Term
Which of the following represents the major (but not the only) energy accomplishment of the citric acid cycle?
Definition
formation of NADH and FADH2
Term
How many molecules of ATP are gained by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen?
Definition
4
Term
After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of _____.
Definition
NADH
Term
Which of the following accompanies the conversion of pyruvate to acetyl CoA before the citric acid cycle?
Definition
formation of CO2 and NADH
Term
When a poison such as cyanide blocks the electron transport chain, glycolysis and the citric acid cycle soon grind to a halt as well. Which of the following is the best explanation for this?
Definition
NAD+ and FAD are not available for glycolysis and the citric acid cycle to continue.

Unless the electron transport molecules (NADH and FADH2) can recycle back to their oxidized states (NAD+ and FAD), they will be unable to receive electrons in the other steps of cellular respiration.
Term
In glycolysis in the absence of oxygen, cells need a way to regenerate which compound?
Definition
NAD+
Term
If muscle cells in the human body consume O2 faster than it can be supplied, which of the following is likely to result?
Definition
Muscle cells would not be able to produce enough ATP to meet demands, oxidative phosphorylation would stop, and muscle cells would consume glucose at an increased rate.
Term
Of the metabolic pathways listed below, which is the only pathway found in all organisms?
Definition
Glycolysis.
Term
When protein molecules are used as fuel for cellular respiration, _____ are produced as waste.
Definition
amino groups
Term
A gram of fat oxidized by respiration produces approximately twice as much ATP as a gram of carbohydrate. Which of the following best explains this observation?
Definition
Fats are better electron donors to oxygen than are sugars.
Term
If significant amounts of materials are removed from the citric acid cycle to produce amino acids for protein synthesis, which of the following will result?
Definition
Less ATP will be produced by the cell; Less CO2 will be produced by the cell; The four-carbon compound that combines with acetyl CoA will have to be made by some other process.
Term
.
Definition
Term
Which of the following is produced by the light reactions of photosynthesis and consumed by the Calvin cycle?
Definition
NADPH
Term
he overall function of the Calvin cycle is _____
Definition
making sugar
Term
C4 plants occur more commonly in desert conditions because _____.
Definition
they can fix carbon at the lower CO2 concentrations that develop when the stomata are closed
Term
What is the end product of the Calvin Cycle?
Definition
To summarize, so far the Calvin cycle has used the energy of the light reactions to reduce three molecules of carbon dioxide and produce one molecule of G3P. The cell can combine two G3Ps to make glucose, which stores the energy that chlorophyll originally captured from the sun.
Term
How much ATP and NADPH is used to make one GP3 molecule?
Definition
To make each G3P, the Calvin Cycle consumes 9 ATP molecules and 6 NADPH molecules.
Term
The light reactions of photosynthesis supply the Calvin cycle with _________.
Definition
ATP and NADPH
Term
Cooperation of the two photosystems is required for _____________.
Definition
reduction of NADP+
Term
In what respect are the photosynthetic adaptations of C4 plants and CAM plants similar?
Definition
In both cases, an enzyme other than rubisco carries out the first step in carbon fixation.
Term
Which of the following processes is most directly driven by light energy?
Definition
removal of electrons from chlorophyll molecules
Term
Which of the following statements is a correct distinction between cyclic and noncyclic electron flow?
Definition
Only cyclic electron flow can operate in the absence of photosystem II.
Term
Plants are photoautotrophs. What does this mean?
Definition
1. They make their own food from inorganic materials.
2. They are among the producers of the biosphere.
3. They are in the same category as algae and cyanobacteria.
4. They use light energy to drive the synthesis of organic molecules.
Term
The light reactions of photosynthesis use _____ and produce _____.
Definition
water ... NADPH
Term
Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+.
Definition
Photosystem I
Term
_____ splits water into 1/2 O2, H+, and e-.
Definition
Photosystem II
Term
Carbon fixation involves the addition of carbon dioxide to _____.
Definition
RuBP
Term
After 3-PGA is phosphorylated, it is reduced by _____.
Definition
NADPH
Term
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
Definition
6. Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.
Term
In the Calvin cycle, how many ATP molecules are required to regenerate RuBP from five G3P molecules?
Definition
3
Term
In C4 and CAM plants carbon dioxide is fixed in the _____ of mesophyll cells.
Definition
cytoplasm

(In C3 plants, carbon fixation occurs in the stroma of the thylakoid)
Term
C4 plants differ from C3 and CAM plants in that C4 plants _____.
Definition
transfer fixed carbon dioxide to cells in which the Calvin cycle occurs
Term
In photosynthesis, what is the fate of the oxygen atoms present in CO2? They end up ______.
Definition
in sugar molecules and in water
Term
What are the components of a photosystem?
Definition
1. reaction center
2. light harvesting complexes
3. primary electron acceptors
Term
During photosynthesis, an electron transport chain is used to _____.
Definition
transport electrons from photosystem II to photosystem I

Correct. Each photoexcited electron passes from the primary electron acceptor of photosystem II to photosystem I via an electron transport chain.
Term
Which one of the following is cycled in the cyclic part of light reactions?
Definition
electrons
Term
Light reactions do all of the following except _____.
Definition
reduce CO2
Term
Rubisco is _____.
Definition
the enzyme in plants that first captures CO2 to begin the Calvin cycle
Term
In the Calvin cycle, CO2 is combined _____.
Definition
with a 5-carbon compound to form an unstable 6-carbon compound, which decomposes into two 3-carbon compounds
Term
Glyceraldehyde-3-phosphate is produced in the stroma of chloroplasts. Which of the following statements is true about this compound?
Definition
It is produced from glucose during glycolysis.