Chapter 6

Metabolic pathways can be linear, _____, ________

1. Branched 2. cyclical

The electron transport chain is a cluster of membrane-embedded electron carriers that accept electrons from the coenzymes

1. Nadh 2. Fadh

Enzymes are biological ______ that are typically

1. catalysts 2. proteins

Until the optimal temperature is reached, raising the temperature has what effect on the speed of enzymatic reactions?

1. it increases their rate

The enzymes of the tricarboxylic acid cycle are found in the matrix in eukaryotes and in the in prokaryotes.

1. mitochondrial or mitochondrion 2. cytoplasm or cytosol

Enzymes function as biological catalysts, accelerating the conversion of one substance, the _________ , into another, the __________

1. substrate 2. product

The main energy currency of cells is the molecule called

ATP

onsider the three key central metabolic pathways (glycolysis, pentose phosphate pathway, and the TCA cycle). What three beneficial products of these pathways?

ATP precursor metabolites reducing power

The primary pathway used by many organisms to convert glucose to pyruvate is

glycolysis

In terms of their metabolism, prokaryotes are _______ with respect to compounds they use for energy and _______ in their biosynthetic processes.

highly diverse; remarkably similar

An atom that has a lower affinity (attraction) for electrons than another is described as ____ than the other

less electronegative

the electron transport chain consists of large protein-complexes embedded in a membrane. These pass electrons from one to the next, while simultaneously pumping

protons

Proton motive force is

the form of energy that results from the electrochemical gradient established by the electron transport chain

Metabolism is best defined as

the sum total of all chemical reactions in a cell

Certain intermediates of catabolic pathways, called precursor metabolites, are important because

they serve as carbon skeletons from which subunits of macromolecules can be made

Examples of electron carriers are proteins that contain heme, a molecule that holds an iron in its center. These are called

cytochromes

Proteins that function as biological catalysts are called

enzyme

All of the following accurately describe enzymes EXCEPT

enzymes provide energy to help reactions proceed more rapidly

Use the following four words to correctly complete the sentence: endergonic, exergonic, anabolism, catabolism. "Cells constantly produce ATP during reactions of and then use it to power reactions of

exergonic- catabolism- endergonic- anabolism

The reactions that capture radiant energy and convert it into chemical energy in the form of ATP are called the

light dependent

The series of sequential chemical reactions in a cell that converts a starting compound to an end product is called a _______ pathway

metabolic

The sum total of all chemical reactions in a cell is called

metabolism

The TCA cycle completes the ______ of glucose.

oxidation

The central metabolic pathway that generates reducing power in the form of NADPH is the

pentose phosphate pathway

In addition to yielding energy, catabolic pathways generate carbon intermediates that can be used in anabolic pathways for the biosynthesis of macromolecules. These carbon skeletons are called

precursor metabolites

Consider the three key central metabolic pathways (glycolysis, pentose phosphate pathway, and the TCA cycle). What three beneficial products of these pathways?

precursor metabolites ATP reducing power

The form of energy that results from the electrochemical gradient established by the electron transport chain is the

proton motive force

Proteins are composed of various combinations of usually how many different amino acids?

20

If the theoretical maximum ATP yield in prokaryotes from oxidative phosphorylation is 34 ATP for a single glucose molecule, what is the total ATP gain when substrate-level phosphorylation is included?

38 atp

With respect to their synthesis, how are amino acids typically grouped?

By structurally related families that share common biosynthesis pathways

Cells can quickly alter the activity of certain key enzymes, using other molecules that bind reversibly and distort them. This control of enzymes is called

allosteric regulation

Nucleotide subunits of DNA and RNA are composed of three units: a 5-carbon sugar, a phosphate group, and a nucleobase. They are initially synthesized

as ribonucleotides that can be converted to deoxyribonucleotides by replacing the 2' hydroxyl group with a hydrogen atom

In order to form lipids, how are fatty acids and glycerol synthesized?

Fatty acid chains are assembled from 2-carbon acetyl groups from the transition step; the precursor to glycerol comes from glycolysis.

Purines and pyrimidines are synthesized

in distinctly different manners

Atoms that are more electronegative than others _

have a higher affinity for electrons

Which of the following correctly describe cytochromes found in an electron transport chain?

Several different cytochromes exist. Cytochromes are proteins that contain heme, a molecule that holds an iron atom in its center.

In prokaryotes, the electron transport chain is located in the fBlank 1Blank 1 f , Incorrect Unavailable membrane, whereas in eukaryotic cells it is in the gBlank 2Blank 2 g , Incorrect Unavailable membrane of mitochondria.

1. cytoplasmic, plasma, or cell 2. internal

Consider how cells obtain energy to make ATP. The chemical that serves as the electron donor is the source, and the one that ultimately accepts those electrons is the electron acceptor.

1. energy 2. terminal

Lipid synthesis generally requires the components and acids.

1. glycerol 2. fatty

In oxidation-reduction reactions, or redox reactions, the substance that loses electrons is , and the substance that gains those electrons is

1. oxidized 2. reduced

Which of the following combinations of molecules is produced during the light-dependent reactions of photosynthesis and used in the light-independent reactions?

NADPH and ATP

Some enzymes act with the assistance of a non-protein component. This component is called a ; if that component is an organic molecule it can be called a

1. cofactor 2. coenzyme

All of the following are essential for an electron transport chain to function EXCEPT

Atp

Although the actual procedure is much more involved, the basic metabolism of wine-making involves inoculating grape juice with a special strain of the yeast Saccharomyces cerevisiae. S. cerevisiae will preferentially perform aerobic respiration on sugars in the juice but can also ferment those sugars to yield CO2 and alcohol, an important component of wine. Assume you inoculate a completely full container of juice and then close the lid. What will the yeast do?

They will grow aerobically, consume the O2 dissolved in the juice, and then switch to fermenting sugars to yield alcohol.

Identify each of the following by the most precise descriptive term as either a cofactor or coenzyme: magnesium:

1. cofactor 2. coenzyme 3. cofactor

What are the two main forms of energy?

1. Kinetic 2. Potential

Energy is the ability to do work and can exist as _______ energy (stored energy) and _____ energy (energy of motion)

1. Potential 2. Kinetic

Which of the following are reasons an organism might use fermentation?

A suitable inorganic terminal electron acceptor is not available. They lack an electron transport chain.

Oxidative phosphorylation, the mechanism by which cellular respiration uses the NADH and FADH2 generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP, involves what two steps?

ATP synthase uses the energy of the proton motive force to drive the synthesis of ATP. The electron transport chain generates a proton motive force.

When a cell processes glucose or other organic molecules through its central metabolic pathways, it does so to generate what three critical things?

ATP, reducing power, precursor metabolites

In respiring bacteria, how does ATP synthase generate ATP?

It uses the energy released from allowing protons to flow back into the cell to add a phosphate group to ADP.

Consider the following linear metabolic pathway of a bacterial cell: Starting compound → Intermediate-a → Intermediate-b → End Product. The first two reactions are catalyzed by enzymes A and B, respectively. If a mutant cell arose that was unable to produce enzyme B, what would be the impact on the other components of the pathway?

The cell could still produce intermediate-a but would be unable to produce intermediate-b or the end product.

What is the active site of an enzyme?

The critical site to which a substrate binds by weak forces.

Which of the following is an example of activation energy?

The energy of a small flame used to light the natural gas of a Bunsen burner.

In order for cells to obtain energy, they remove electrons from an energy source and ultimately donate them to the terminal electron acceptor. What does this tell us about the electron affinity of the energy source and the terminal electron acceptor?

The energy source has a lower affinity for electrons, and the terminal electron acceptor has a higher affinity for electrons.

Consider the figure showing the relationship between catabolism and anabolism. Which side shows catabolism, and which side shows anabolism?

The left side shows catabolism, and the right side shows anabolism.

In photosynthesis, what do the light reactions, or light-dependent reactions, accomplish?

They capture radiant energy and convert it to chemical energy in the form of ATP.

The light-independent reactions of photosynthesis occur _______ the light-dependent reactions, and function to _______.

after; synthesize organic compounds from CO2

True or false: With respect to the location of the electron transport chain, the inner membrane of mitochondria is analogous to the cytoplasmic membrane of bacterial cells.

True

For each six-carbon molecule of glucose that enters glycolysis, how many molecules of pyruvate are made, and how many carbon atoms does each pyruvate have?

Two molecules of pyruvate, each with three carbon atoms.

the ____ energy is the energy it takes to start a reaction

activation

The critical site of an enzyme to which a substrate binds by weak forces is called the

active site

Although the pentose phosphate pathway is used by cells to break down glucose, it is particularly important because of its contribution to

biosynthesis

Considering the general equation that describes photosynthesis, the rate of the process would be most influenced by the availability of _______ in the atmosphere.

c02

The energy released by ______ is captured by cells to make ATP; this ATP can then be used for biosynthesis, or

catabolism; anabolism

Glucose catabolism encompasses two key processes: (1) oxidizing glucose molecules to generate ATP, reducing power, and precursor metabolites; and (2) transferring the electrons carried by NADH and FADH2 to the terminal electron acceptor. The second process, transfer of electrons, is accomplished as part of which of the following?

cellular respiration fermentation

Consider the effect of temperature on enzyme activity. If the temperature is too high, proteins will _______ and no longer function.

denature

In oxidative phosphorylation, quinones, cytochromes, and flavoproteins are all

electron carriers

In addition to four protein complexes, the mitochondrial electron transport chain has two freely-moving ______, ubiquinone and cytochrome c, that serve to ______.

electron carriers; shuttle electrons between the complexes

The electron transport chain of mitochondria has ______ different protein complexes.

four

In the case of plants, algae, and cyanobacteria, the two major products of photosynthesis are

glucose and oxygen

As part of cellular respiration, a membrane-bound enzyme called ATP___ uses energy from a proton-motive force to add a phosphate group to ADP.

synthase

Which of the following are true statements about what happens to glucose inside a cell?

Glucose can be used in catabolism to yield energy, or the precursor metabolites generated from its breakdown can be used in anabolism. Some glucose might be oxidized to CO2, generating the maximum amount of ATP. Some glucose might enter glycolysis, only to be siphoned off as a precursor metabolite for biosynthesis.

The mechanism by which cellular respiration uses reducing power generated in glycolysis, the transition step, and the TCA cycle to synthesize ATP is

oxidative phosphorylation

Cells use ATP as the ready and immediate donor of free energy. ATP stands for

Adenosine Triphosphate

What happens to an organism if it lacks one or more enzymes in a given biosynthetic pathway?

It must have the end product provided from an external source.

Cells can quickly alter the activity of certain key enzymes, using other molecules that bind reversibly and distort them. This control of enzymes is called ___ regulation.

allosteric