Bio Exam 2- Chapters 8-10

a solution of starch at room temperature does not readily decompose to form a solution of simple sugars because

the activation energy barrier for this reaction cannot be surmounted

ATP generally energizes a cellular process by

coupling free energy released by ATP hydrolysis to free energy needed by other reactions

when glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are

\+G, +H, -S

what is true for all exergonic reactions?

the reaction proceeds with a net release of free energy

how can one increase the rate of a chemical reaction?

add a catalyst

the active site of an enzyme is the region that

is involved in the catalytic reaction of the enzyme

how many molecules of carbon dioxide would be produced by five turns of the citric acid cycle?

10

during glycolysis, when glucose is catabolized to pyruvate, most of the energy of glucose is

retained in the pyruvate

which statement is not correct with regard to redox reactions?

\-an electron acceptor is called an oxidizing agent

\-oxidation and reduction always go together

\-a molecule is oxidized if it loses electrons

\-a molecule is reduced if it loses electrons

\-an electron donor is called a reducing agent

a molecule is reduced if it loses electrons

which of the following statements concerning the metabolic degradation of glucose to carbon dioxide and water is (are) true?

\-the breakdown of glucose to carbon dioxide and water involves redox reactions

\-the breakdown of glucose to carbon dioxide and water is exergonic

\-the breakdown of glucose to carbon dioxide and water has a free energy change of -686 kcal/mol

all of the above

where does oxidative phosphorylation take place?

mitochondrial inner membrane

the light reactions supply the Calvin cycle with

ATP and NADPH

one way in which photosynthesis in a typical C4 plant differs from that in a C3 plants is that the C4 plant

carries out the Calvin cycle only in the chloroplasts of bundle-sheath cells

in mechanism, photophosphorylation is more similar to

oxidative phosphorylation in cellular respiration

which of the following occurs during the Calvin cycle>

\-carbon fixation

\-reduction of NADP+

\-release of O2

\-generation of CO2

\-all of the above

carbon fixiation

one reason for carrying out the production of oxygen gas in the space surrounded by the thylakoid membranes, and not the stroma of the chloroplasts is

that the hydrogen ions released can contribute to the H+ electrochemical gradient being generated

which process is most directly driven by light energy?

transfer of energy from pigment molecule to pigment molecule

which of the following statements is true concerning catabolic pathways?

\-they combine molecules into more energy-rich molecules

\-they are usually coupled with anabolic pathways to which they supply energy in the from of ATP

\-they build up complex molecules such as protein from simpler compounds

\-they are endergonic

\-they are spontaneous and do not need enzyme catalysis

they are usually coupled with anabolic pathways to which they supply energy in the form of ATP

Phosphofructokinase is an allosteric enzyme that catalyzes the conversion of frutose-6-phosphate to fructore-1,6-biphosphate, an early step of glycolysis. In the presence of oxygen, an increase in the amount of ATP in a cell would be expected to

inhibit the enzyme and thus slow the rates of glycolysis and critic acid cycle

if an enzyme is added to a solution where its substrates and products are in equilibrium, what would occur?

nothing; the reaction would stay at equilibrium

in mitochondria, chemiosmosis moves protons from the intermembrane space into matric, whereas in chloroplasts, chemiosmosis moves protons from the

thylakoid space to the stroma

what is the sequence that describes the path by which electrons travel downhill energetically in aerobic respiration?

glucose → NADH → electron transport chain → oxygen

photosystems I and II work together to use light energy to generate what?

NADPH and ATP

the oxygen consumed during cellular respiration is involved directly in which process or event?

the making of water

In CAM plants, CO2 is

temporarily fixed at night and later permanently fixed during the day

if a cell contained a radioactive version of rubisco, where would the radioactivity be located?

stroma

newborn mammals have a specialized tissue called ‘brown fat’, where cells burn fat to CO2 without capturing the energy to reduce electron carriers or drive ATP formation. How might this energy be used instead?

to generate heat

during intense exercise, muscles lack sufficient oxygen, so which process will these muscles mainly use?

lactic acid fermentation

the primary role of oxygen in cellular respiration is to

act as an acceptor for electrons and hydrogen forming water

molecules that can potentially be converted to intermediates of glycolysis and/or the citric acid cycle include

\-amino acids and proteins

\-glycerol and fatty acids

\-glucose and sucrose

\-starch and glycogen

all of the above

fatty acids usually have an even number of carbons in their structures. catabolism of fatty acids produces two-carbon fragments that are converted to acetyl CoA molecules. what is the most likely way in which these acetyl CoA molecule would be metabolized in aerobic cellular respiration?

they would directly enter the citric acid cycle

which of the following occurs in the cytosol of the cell?

\-citric acid cycle

\-oxidation of pyruvate to acetyl CoA

\-chemiosmosis

\-oxidative phosphorylation

none of the above

a series of enzymes catalyze the reaction X → Y → Z → A. product A binds to the enzyme that converts X to Y at a position remote from its active site. this binding decreases the activity of the enzyme. substance A functions as

an allosteric inhibitor

a force driving simple diffusion is _______,__ while the energy source for active transport is _____.

a concentration gradient; ATP hydrolysis

approximately what percentage of the energy of glucose is transferred to storage in ATP as a result of the complete oxidation of glucose to CO2 and water in cellular respiration?

40%

cells do not catabolize carbon dioxide because

CO2 is already completely oxidized

most CO2 from catabolism is released during

the citric acid cycle

carbon dioxide is released during which stage of cellular respiration?

oxidative of pyruvate to acetyl CoA and the citric acid cycle

energy released by the electron transport chain is used to pump H+ ions into which location in eukaryotic cells?

mitochondrial intermembrane space

which of the following is not a net product of the typical mitochondrial electron transport chain?

\-ATP

\-water

\-NAD+

\-FAD

\-NADPH

NADPH

if you removed the inner membrane of the mitochondrion, could the cell produce any ATP from glucose?

yes, by glycolysis and fermentation

the direct energy source that drives ATP synthesis during respiratory oxidation phosphorylation is

the difference in H+ concentrations on opposite sides of the inner mitochondrial membrane

zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. the zinc most likely functions as a

cofactor necessary for enzyme activity

which electron carriers(s) function in the citric acid cycle?

\-NADH and FADH2

\-ADP and ATP

\-NAD+

\-the electron transport chain

\-NADPH

NADH and FADH2

in glycolysis, for each molecules of glucose oxidized to 2 pyruvates,

2 molecule of ATP are used and 4 molecules of ATP are produced

how does a non-competitive inhibitor decrease the rate of an enzyme reaction?

by changing the structure of the enzyme

according to the induced fit hypothesis of enzyme catalysis, which of the following is correct?

\-the active site creates a microenvironment ideal for the reaction

\-a competitive inhibitor can outcompete the substrate for the active site

\-some enzymes change their structure when activators bind to the enzyme

\-the binding of the substrate changes the shape of the enzyme’s active site

\-the binding of the substrate depends on the shape of the active site

the binding of the substrate changes the shape of the enzyme’s active site

in the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of

ATP, CO2, and ethanol

which of the following types of reactions would decrease the entropy within a cell?

\-hydrolysis

\-anabolic reactions

\-catabolic reactions

\-digestion

\-diffusion

anabolic reactions

all of the following membrane activities require energy from ATO hydrolysis except

\-Na+ ions moving out of the cell’

\-proton pumps

\-active transport

\-translocation of K+ into a cell

\-facilitated diffusion

facilitated diffusion

which of the following statements and NAD+ is false?

\-NAD+ is reduced to NADH during both glycolysis and the citric acid cycle

NAD+ is reduced by the action of dehydrogenases

\-NAD+ has more chemical energy than NADH

\-NAD+ can receive electrons for use in oxidative phosphorylation

\-in the absence of NAD+, glycolysis cannot function

NAD+ has more chemical energy than NADH

what is the first law of thermodynamics?

energy cannot be created for destroyed

which of the following reactions is most likely to be coupled to the reaction ATP + H2O → ADP + Pi (G= -7.3 kcal/mol)?

\-E + Pi → EP (G = 5 kcal/mol)

\-A + Pi → AP (G=10 kcal/mol)

\-B + Pi → BP (G=8 kcal/mol)

\-DP → D + P (G= -10 kcal/mol)

\-CP → C + Pi (G= -4 kcal/mol)

E + Pi → EP (G = 5 kcal/mol)

the relationship between catabolism and anabolism is most similar to the relationship between

exergonic and endergonic

which incorrectly matches process to location?

\-oxygen gas is produced : the thylakoid space

\-activated chlorophyll donates an electrons : the thylakoid membranes

\-ATP is produced : the intermembrane space

\-NADPH is oxidized to NADP+ : stroma

\-rubisco catalyzes carbon fixation : the stroma

ATP is produced : the intermembrane space

when donating its activated electron, the chlorophyll is photosystem II is a very powerful oxidizing agent. this is best shown by its ability to

force the oxidation of oxygen in water to oxygen gas

how are photosynthesis and cellular respiration connected?

the first produces glucose, and the second extracts that energy

which of the following events is most immediately associated with the absorption of energy by a pair of chlorophyll molecules of the reaction-center complex?

an electron is exicted

during photosynthesis the electron transport chain acidifies which of the following cellular compartments?

\-thylakoid space

\-cytosol

\-mitochondrial matrix

\-stroma

\-intermembrane space

thylakoid space

Ture or false, an exergonic reaction releases energy?

true

a chemical reaction that has a positive G is best described as

endergonic

what is true about anabolic pathways?

they consume energy to build up polymers from monomers

which of the following molecules is a part of ATP?

\-adenosine

\-uracil

\-guanine

\-cytosine

adenosine

when chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?

it is lost to the environment

why is ATP an important molecules in metabolism?

it provides energy coupling between exergonic and endergonic reactions

what do enzymes do?

enzymes increase the rate of chemical reactions by lowering activation energy barriers

The ATP made during glycolysis is generated by

substrate-level phsphorylation

the mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as

feedback inhibition

when a molecule of NAD+ gains a hydrogen atom, the molecule becomes

reduced

what happens to a molecule that function as the reducing agent in a redox or oxidation-reduction reaction?

it loses electrons and loses potential energy

Following glycolysis and the citric acid 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 stored in the form of

NADH

how many molecules of carbon dioxide would be produced by five turns of the citric acid cycle?

10

the oxygen consumed during cellular respiration is involved directly in which process or event?

accepting electrons at the end of the electron transport chain

during oxidative phosphorylation, water is formed. where does the oxygen for the synthesis of the water come from?

carbon dioxide

when hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the

creation of a proton gradient

in which reactions of the cellular respiration and fermentation does substrate-level phosphorylation occur?

in both glycolysis and the citric acid cycle

what describes NAD+?

NAD+ is reduced to NADH during glycolysis, pyruvate oxidation and the citric acid cycle

what produces the most ATP when glucose is completely oxidized to carbon dioxide and water?

oxidative phosphorylation (chemiosmosis)

energy released by the electron transport chain is used to pump H+ into what part of eukaryotic cells

mitochondrial intermembrane space

of these events from the light reactions, which occurs first?

\-light-induced reduction of the primary electron acceptor in the reaction center of PSII'

\-while being split, electrons are taken out of water

\-donation of electrons from reduced plastoquinone to the cytochrome complex

\-acceptance of electrons from plastocyanin from the cytochrome complex

\-plastoquinone gets electrons from the reduced primary electron acceptor of PSII

light-induced reduction of the primary electron acceptor in the reaction center of PSII

in the light reaction of photosynthesis, electrons passed along two photosystems are initially extracted from ___. In aerobic cellular respiration, electrons passed along the electron transport chain are initially extracted from ___.

water … glucose

suppose you were preparing to visit a space station that uses photosynthesis to provide you with oxygen. what color light bulbs should you take with you?

red and blue

which pigments funnel energy from other wavelengths to chlorophyll a and participate in photoprotection against excessive light?

carotenoids

what sequence correctly represents the flow of electrons during phototsynthesis?

H2O → NADPH → Calvin cycle

where do the Calvin cycle enzymes in a plant cell reside?

chloroplast stroma

the enzyme rubisco catalyzes the fixation of carbon. considering all the carbons involved, is the production of 3-PGA a net oxidation, reduction, or neither? Why?

neither. there is no change in the total C-O and C-H bonds between the products and reactants.

in which process or event is the enzyme rubisco involved?

fixing CO2 into an organic molecule

which of the following statements is NOT true about the Calvin cycle?

\-the Calvin cycle fixes CO2

NADPH is oxidized during the Calvin cycle

\-the CO2 acceptor is regenerated as part of the Calvin cycle phases

\-the Calvin cycle synthesizes ATP

\-Enzyme rubisco is involved in the Calvin cycle

the Calvin cycle synthesizes ATP

which of the following is not one of the three phases of the Calvin cycle?

\-carbon fixation

\-reduction

\-regeneration

\-oxidation

oxidation

what best describes a similarity between photosynthesis and cellular respiration?

chemiosmosis

why are CAM plants able to photosynthesize with not apparent photorespiration?

they use PEP carboxylase to initially fix CO2

what is true about C3, C4, and CAM plants?

glucose molecules synthesized by all C3, C4, and CAM plants all have gone through the Calvin cycle

CAM plants keep stomata closed in the daytime, thus reducing loss of water. They can do this because they

fix CO2 into organic acids during the night

are most chemical reactions in living cells at equilibrium?

no

the oxidation of glucose to CO2 and H2O is highly exergonic: G = -686 kcal/mol. this is spontaneous, but why is it very slow?

few glucose and oxygen molecules have the activation energy at room temperature

how does the flow of energy through life differ from the flow of matter through life?

matter can be recycled, while some energy is always converted to unusable forms like heat

the form of energy that is most often least useful to life is energy in

the form of heat

some enzymes can couple the hydrolysis of ATP to ion transport by having

changes during ATP hydrolysis alter the enzyme’s shape, forcing ionic transport to occur

how are effects of feedback inhibition and allosteric factors similar to how enzymes often couple reactions?

all often involved inducing structural changes in their enzymes, influencing its activities

What would happen to cytoplasmic enzyme activity inside a cell with a normal cytoplasmic pH of 7.2 is you injected a chemical that would change the pH of 4.0?

enzymes would probably denature and activity would decline