Biology Test 4

When an electron returns to its ground state, energy will be released as heat or as an emission of light, known as

fluorescence.

The direction of an exergonic reaction can best be described as moving

from higher to lower free energy.

Why are enzymes considered important biological catalysts?

Enzymes lower the activation energy of a biochemical reaction.

Which of the following is a hydrogen ion acceptor?

FAD

A reversible inhibitor forms weak chemical bonds with the enzym

False

A reversible inhibitor forms weak chemical bonds with the enzyme.

False

ATP is generated when protons flow through the cytochrome complex in the thylakoid membrane.

False

According to the Second Law of Thermodynamics, energy cannot be created nor destroyed.

False

An absorption spectrum indicates the relative effectiveness of different wavelengths of light in powering photosynthesis.

False

An enzyme raises the activation energy of the reaction it catalyzes.

False

An example of a(n) anabolic reaction is the splitting of a polysaccharide into monosaccharides.

False

At a constant temperature and pH, the rate of an enzymatically catalyzed reaction is inversely proportional to the enzyme concentration.

False

At a plant's light compensation point the rate of photosynthesis is greater than the rate of respiration.

False

Chemical energy is a form of kinetic energy.

False

The photolysis of water occurs in conjunction with photosystem I.

False

The stage of cellular respiration in which most of the ATP is produced is the citric acid cycle.

False

In which of the following reactions is pyruvate degraded and combined with coenzyme A to form acetyl CoA?

Formation of acetyl CoA

After the conversion of pyruvate molecules to acetyl CoA molecules, how many NADH molecules have been produced from one glucose molecule?

Four

What refers to the alteration of an enzyme's shape due to binding of substrate?

Induced fit

Which class of enzyme can catalyze the conversion of a molecule from one isomeric form to another?

Isomerases

ATP is formed when ____ the thylakoid lumen.

hydrogen ions leave

Many bacterial infections are treated with drugs, such as penicillin and sulpha drugs, that ____ the bacteria's enzyme activity.

inhibit

The unit of measurement for energy that most biologists today prefer is ____________.

kilojoules

Energy that is usable and organized is classified as having ____.

low entropy

An electron absorbs a photon of light energy and becomes energized; the electron shifts from a ____ atomic orbital to a __________ atomic orbital.

lower energy; higher energy

A chlorophyll molecule has a porphyrin ring containing a single atom of

magnesium.

Which best describes a catabolic reaction?

It involves the breakdown of large organic molecules to simple building blocks.

What unit is used to measure thermal energy that flows from an object of higher temperature to an object of lower temperature?

Kilocalories

As you climb a flight of stairs, what type of energy are your legs in motion using?

Kinetic Energy

During which phase of photosynthesis is ATP and NADPH synthesized?

Light-dependent phase

What are the two phases of photosynthesis?

Light-dependent reactions and carbon fixation reactions

Which of the following is the common cofactor for enzymes?

Magnesium

Select the hydrogen acceptor molecule that stores electrons in the process of photosynthesis.

Nicotinamide adenine dinucleotide phosphate (NADP+)

Which organism would be classified as a chemoautotroph?

Nitrogen-fixing bacteria

Which of the following would be classified as a CAM plant?

Orchid

Which process not only yields electrons that replenish photosystems I and II, but also is the source of almost all the oxygen in Earth's atmosphere?

Photolysis

What is the process by which light energy is converted into the stored chemical energy of organic molecules?

Photosynthesis

Which photosynthetic unit consists of a pair of chlorophyll a molecules with an absorption peak of 700 nm?

Photosystem I

Which part of the chlorophyll molecule is responsible for absorbing light?

Porphyrin ring

What form of energy is stored within the molecules of ATP?

Potential

You are out cycling and start to climb a hill. As you crest the hill, just before cycling down, what kind of energy have you stored?

Potential energy

Where is the electron transport chain of photosynthesis located?

Thylakoid membrane

A cell must expend energy to produce a concentration gradient.

True

A closed system does not exchange energy with its surroundings.

True

CAM plants open their stomata at night, admitting CO2 while minimizing water loss.

True

Fermentation is an anaerobic process that does not use an electron transport chain.

True

For each acetyl CoA molecule that enters the citric acid cycle, two CO2 molecules are produced.

True

In the tricarboxylic acid cycle, oxaloacetate reacts with acetyl CoA forming citrate.

True

Some enzymes can only function if an additional chemical component, called a cofactor, is present.

True

The downhill flow of protons through the ATP synthase complex powers the production of ATP.

True

The part of a chlorophyll molecule that absorbs light energy is the porphyrin ring.

True

What is the ultimate source of electrons for noncyclic electron transport, and thus photosynthesis?

Water

Which of the following statements is contrary to the first law of thermodynamics? Correct Answer

When energy is used, it is irreplaceable.

Refer to the accompanying figure. The line on the graph labeled B represents the ____.

activation energy with an enzyme

The region of the enzyme molecule that interacts with a substrate is called the ______.

active site

Some enzymes have a receptor site that is other than the active site. This is also referred to as a(n) ____ site.

allosteric

Respiration which does not use oxygen as the final electron acceptor and is performed by some prokaryotes that live in anaerobic environments, such as waterlogged soil, stagnant ponds, and animal intestines is called ______.

anaerobic respiration

Saturated fatty acids store more energy than unsaturated fatty acids. Based on your knowledge of aerobic respiration, you draw this conclusion because saturated fatty acids

are more highly reduced

During fermentation, the immediate fate of the electrons in NADH is that they

are transferred to an organic molecule.

The equation, G = H − TS, predicts that

as entropy increases, the amount of free energy decreases.

Because enzymes affect the speed of chemical reactions without being consumed, they are referred to as

catalysts

What is the function of the oxidoreductases?

catalyze oxidation-reduction reactions

Refer to the accompanying figure. The line on the graph labeled C represents the ____.

change in free energy

Animals, fungi, and most prokaryotes are known as ________.

chemoheterotrophs

The action spectrum of photosynthesis best matches the absorption spectrum of

chlorophylls a and b.

A nonpolypeptide compound that binds to the apoenzyme and serves as a cofactor is called

coenzyme.

Consider the following two chemical equations: A. glucose + fructose → sucrose + H2O, ΔG = +27 kJ/mole (or +6.5 kcal/mole) B. glucose + fructose + ATP → sucrose + ADP + Pi, ΔG = −5 kJ/mole (or −1.2 kcal/mole) The overall free energy change in the chemical equations (A) and (B) above is accomplished by

combining an endergonic and an exergonic reaction.

Amino acids are metabolized by reactions in which the amino group (2NH2) is first removed, this is known as ________.

deamination

According to the second law of thermodynamics, the amount of usable energy available to do work in the universe ____ over time.

decreases

How many carbon fixation reactions make up the Calvin cycle?

13

The electron transport chain forms a concentration gradient for H+, which diffuses through ATP synthase complexes, producing ____.

ATP

Which is the energy source that drives the Calvin cycle?

ATP and NADPH

What happens in the second phase of the Calvin cycle?

ATP and NADPH are used to convert the PGA molecules to glyceraldehyde-3-phosphate.

In a reaction in which the rate of the reverse reaction is equal to the rate of the forward reaction, a state of ____ is attained.

dynamic equilibrium

Total bond energy is essentially equivalent to the total potential energy of the system, a quantity known as ____________.

enthalpy

Every type of chemical bond contains a certain amount of energy. The total bond energy, which is essentially equivalent to the total potential energy of the system, is a quantity known as

enthalpy.

The reaction ATP + H2O → ADP + Pi is classified as an

exergonic reaction

How does anaerobic respiration differ from aerobic respiration?

Anaerobic respiration utilizes NO3− as the terminal electron acceptor.

Which of the following statement is correct in the context of this equation H = G + TS?

As entropy increases, the amount of free energy decreases.

An organism can exchange matter and energy with its surroundings. Thus, any change in an organism's energy content must be balanced by a corresponding change in the energy content of the surroundings. As such, an organism is referred to as a(n)

open system

Capacity to do work as a result of position or state is known as _______.

potential energy

In C3 plants, the ____ are typically closed at night and open during the daytime to allow for gas exchange.

stomata

The maintenance of a high ATP to ADP ratio within cells ensures that

the hydrolysis of ATP to ADP will be strongly exergonic.

Most vitamins are coenzymes.

true

Photorespiration is a wasteful process that could be largely avoided if rubisco would bind only CO2.

true

The reactions of the citric acid cycle take place in the matrix of the mitochondrion.

true

Glycolysis yields a net energy profit of ____ ATP molecules per molecule of glucose.

two

In order for a cell to maintain a high degree of order, it must constantly

use energy

What is the ultimate source of energy for almost all living organisms?

The sun

Chlorophyll and accessory photosynthetic pigments are associated with which part of the chloroplast?

Thylakoid membranes

What is the role of the oxygen molecules required for aerobic respiration?

To accept the low energy electrons at the end of the electron transport chain

What is the function of coenzyme Q?

To transfer electrons

Which of the following statements is contrary to the second law of thermodynamics?

Total entropy in the universe is decreasing with time.

How many electrons are needed to reduce one molecule of NADP+ to NADPH?

Two

Which of the following is an exploited product of lactate fermentation?

Yogurt

The graph in the accompanying figure represents the

absorption spectra for chlorophylls a and b.

If yeasts are grown under anaerobic conditions, pyruvate is converted first to ____ and then to ____.

acetaldehyde; ethyl alcohol

During the first phase of glycolysis, two ____ reactions take place to transfer a phosphate group from ATP to the sugar because glucose is relatively stable and not easily broken down.

phosphorylation

Land plants, algae, and certain prokaryotes are known as _______.

photoautotrophs

The energy of a(n) ____ is inversely proportional to its wavelength.

photon

By definition, substances that absorb visible light are called

pigments

The energy released during the chain of electron transport molecules is used to create a(n) ____ gradient across the inner mitochondrial membrane for chemiosmosis.

proton

A glucose molecule that is metabolized via aerobic respiration has been completely broken down and released as CO2 by the end of

the citric acid cycle.

What does the oxidative decarboxylation of two pyruvates yield?

2 acetyl CoA + 2 CO2 + 2 NADH

A. glucose + fructose → sucrose + H2O, ΔG = +27 kJ/mole (or +6.5 kcal/mole) B. glucose + fructose + ATP → sucrose + ADP + Pi, ΔG = −5 kJ/mole (or −1.2 kcal/mole) What is the overall ΔG?

22 kJ/mole

Where is NADPH formed in the accompanying diagram? You Answered

3

Using the labels in the accompanying figure, where are chloroplasts found in the greatest density?

3 and 4

The complete aerobic metabolism of one molecule of glucose yields a maximum of how many ATPs?

36 to 38

Carbon is fixed in which part of the accompanying diagram?

4

What is needed in the following reaction: ____ + Pi + energy → ADP.

AMP

In glycolysis, glucose receives two phosphate groups from ____, thus forming fructose-1,6-bisphosphate.

ATP

In the electron transport chain, exergonic redox processes drive the endergonic reaction in which

ATP is produced by phosphorylation of ADP.

How are chlorophyll molecules attached to thylakoid membranes?

By a long hydrocarbon side chain

Which reaction is the aerobic respiration of glucose?

C6H12O6 + 6 O2 + 6 H2O → 6 CO2 + 12 H2O + energy

What is the first step in the Calvin cycle?

CO2 attaches to RuBP.

What are the reactants of the Calvin cycle?

CO2, ATP, and NADPH

Peter Mitchell demonstrated ATP production by aerobic bacteria to prove what process?

Chemiosmosis

Which of these absorbs light primarily in the blue and red regions of the visible spectrum and is the main pigment of photosynthesis?

Chlorophyll

Which is a product from the first reaction of the citric acid cycle?

Citrate

What is the series of reactions in which the acetyl portion of acetyl CoA is degraded to CO2 and ATP is synthesized?

Citric acid cycle

Cyclic electron transport is different from noncyclic electron transport in that cyclic electron transport produces NADPH.

False

FAD becomes oxidized when it accepts hydrogen atoms and their electrons.

False

For each glucose molecule that begins cellular respiration, the citric acid cycle must turn once.

False

If yeast cells are incubated under anaerobic conditions, the pyruvate they produce is converted to lactate.

False

In competitive inhibition, the inhibitor binds to the enzyme at the allosteric site.

False

In liver cells, each pair NADH produced via glycolysis results in two ATP molecules in the electron transport chain.

False

In noncompetitive inhibition, the inhibitor binds to the active site of the enzyme.

False

In photosynthesis, the oxygen atoms released as O2 comes from CO2.

False

Most plants are known as photoheterotrophs.

False

Surrounding the grana is the thylakoid lumen.

False

The cell maintains a ratio of ATP to ADP that is at the equilibrium point.

False

The conversion of polysaccharides to monosaccharides is an example of an anabolic reaction.

False

In glycolysis, a phosphorylated sugar (fructose-1,6-bisphosphate) is split, forming two molecules of

G3P

Ribulose phosphate is synthesized from which molecule?

G3P

Which type of electromagnetic waves has the shortest wavelength?

Gamma waves

What is the primary function of the leaf structure labeled as 5 in the accompanying figure?

Gas exchange

Select the phosphorylation reaction.

Glucose + ATP → glucose-P + ADP

Which of the following molecules can be used as a substrate for cellular respiration?

Glucose, lipids, proteins, and fatty acids

Which of the following is a series of reactions in which glucose is degraded to pyruvate and electrons are transferred to carriers?

Glycolysis

A group of thylakoid discs make up what part of the chloroplast?

Granum

What color does chlorophyll reflect?

Green

What are the reactants of the light-dependent reactions of photosynthesis?

H2O, ADP, and NADP+

In C4 plants, reactions that fix CO2 into four-carbon compounds occur in what type of cells?

Mesophyll cells

Which chemical process occurs in which a substance loses electrons?

Oxidation

What is it called when ATP synthesis is coupled to the redox reactions in the electron transport chain?

Oxidative phosphorylation

Which of the following statements about lactic acid fermentation is FALSE?

Oxygen is the final electron acceptor of this pathway.

_____________ is a protein-digesting enzyme in the very acidic stomach juice.

Pepsin

What is the reaction in which a phosphate group is transferred from ATP to the sugar?

Phosphorylation

The synthesis of ATP during photosynthesis or respiration is the result of what process?

Phosphorylation of ADP

Match the stage of cellular respiration to its description. -Protons diffuse through the ATP synthase complex. -The first process that occurs in the mitochondrion. -GDP is phosphorylated. -NADH is oxidized. -Pyruvate is an end product. -Oxaloacetate reacts with an acetyl group. -Fructose-1,6-bisphosphate is split into two sugars. -FAD is converted to FADH2. -Oxygen is the final electron acceptor. -Glucose is phosphorylated.

-Electron transport and chemiosmosis -Formation of acetyl CoA -Citric acid cycle -Electron transport and chemiosmosis -Glycolysis -Citric acid cycle -Glycolysis -Citric acid cycle -Electron transport and chemiosmosis -Glycolysis

Match the component of the Calvin cycle with its description. -Two of these molecules leave the Calvin cycle and react, forming glucose or fructose. - Catalyzes the "fixation" of carbon dioxide -Functions as a CO2-acceptor molecule -Phosphorylates PGA

-G3P -Rubisco -RuBP -ATP

Enzyme names are usually derived from the name of its substrate followed by which suffix?

-ase

During photosynthesis, ____ is reduced and ____ is oxidized.

CO2; H2O

Which of the following are accessory photosynthetic pigments that expand the spectrum of light to provide energy for photosynthesis?

Carotenoids and chlorophyll b

Which refers to an organic, non-polypeptide compound that binds to the apoenzyme and serves as a cofactor?

Coenzyme

How do competitive inhibitors hinder biochemical reactions?

Competitive inhibitors reduce the concentration of substrate.

In eukaryotes, where does glycolysis occur?

Cytosol

What is the reaction in which part of a carboxyl group (—COOH) is removed from the substrate as a molecule of CO2?

Decarboxylation

What is the reaction in which two hydrogen atoms are removed from the substrate and transferred to NAD+ or FAD?

Dehydrogenation

In which of the following aerobic respiration stages does a chain of several electrons transport molecules and release energy to form a proton gradient?

Electron transport and chemiosmosis

During chemiosmosis, what must be transferred from NADH and FADH2 to electron acceptor molecules?

Electrons

Why type of energy is represented by a positive change in G?

Endergonic

During aerobic respiration, what molecule is degraded to form acetyl coenzyme A?

Pyruvate

According to the graph in the accompanying figure, chlorophyll absorbs light most strongly in what region of the electromagnetic spectrum?

Red and blue wavelengths

In which part of the chloroplast do the carbon fixation reactions take place?

Stroma

What is the fluid-filled sac within the inner membrane of a chloroplast called?

Stroma

What is it called when a phosphate group is transferred to ADP from a phosphorylated intermediate?

Substrate-level phosphorylation

Which of the following steps in the citric acid cycle directly produces a molecule of ATP (or GTP)?

Succinyl CoA → succinate

What is the chemical reaction illustrated in the figure?

The energy investment phase of glycolysis

Which best describes the energy of activation?

The energy required to break existing bonds

Which of the following statements about the electron transport chain is true?

The proton gradient established during electron transport is a form of potential energy.

What would happen if you were to increase the temperature in an enzyme-catalyzed reaction?

The rate of reaction will increase and then decrease rapidly.