Chapter 10 Practice

In order for the cell to be able to input energy into necessary endergonic reactions, energy-generating processes such as photosynthesis, fermentation, and respiration are used to produce ___

ATP

The energy made available during cell respiration and fermentation is used to make _________blank, which is then available to provide energy for cellular work.

ATP

Which of the following is/are true about enzymes?

All of the above choices are correct (Enzymes are catalysts that speed up reactions.; Enzymes are highly specific for the substrates they react with and catalyze only one or a limited set of possible reactions with those substrates.; Enzymes are proteins that can be denatured by changes in pH or temperature.)

Consider a biochemical pathway that branches to form two different products. If the end product of one of the branches is present in a large amount, at what point would the pathway be regulated to ensure adequate production of the end product of the alternative pathway while slowing or stopping production of the product already present in excess?

At the point where the two pathways branch

In the electron transport chain, why do electrons flow in one direction from NADH to O2 rather than the reverse direction, or randomly?

Electrons flow from NADH to O2 because NADH has the most negative reduction potential and O2 the most positive with electron carriers in between, each becoming more positive to direct the electron flow.

The most commonly used practical form of energy used in cells is adenosine diphosphate. (T/F)

False

When the end product of a pathway inhibits catalysis of the first step of that pathway, this phenomenon is called _______

Feedback inhibition

Which strategy can be used for regulation of metabolism?

Feedback inhibition Allosteric regulation Regulation of enzyme synthesis Covalent Modification of enzymes

What nucleoside triphosphate, other than ATP, provides some of the energy for protein synthesis?

GTP

How does the binding of a regulatory molecule to the allosteric site affect the activity of an enzyme? (Check all that apply.)

It may change the affinity of the enzyme for its substrate. It may change the maximum velocity of the enzyme. It may decrease the activity of the enzyme. It may increase the activity of the enzyme. It may change the shape of the enzyme.

Which of the following is used as an electron carrier by living organisms?

NAD+ NADP+ Ubiquinone

The energy required to bring the substrates of a reaction together in the correct way to reach the transition state is called _______

activation energy

The substrate of an enzyme binds at the ________

active site

Which of the following are components of the ATP molecule? (Check all that apply.)

adenine ribose three phosphates

Enzyme activity can be controlled by ________

allosteric regulation, covalent modification and feedback (end product) inhibition

________blank reactions build new organic molecules from smaller inorganic and organic compounds.

anabolic

Cells carry out three major types of work; which of the following involves the synthesis of macromolecules as well as the breakdown of substances for their energy?

chemical work

A nonprotein component of an enzyme that is loosely attached to the protein component is referred to as a(n) ______

coenzyme

A molecule that binds noncovalently to an enzyme at the active site and thereby prevents a substrate from binding and reacting is a(n) __________ inhibitor.

competitive

Enzymes function as catalysts by ________

concentrating the substrates and correctly orienting them at the active site

Enzymes catalyze a reaction by

decreasing the activation energy of the reaction

Disruption of an enzyme's structure with loss of activity caused by extremes of pH, temperature, or other factors is called _____

denaturation

A chemical reaction that requires an input of energy in order to proceed is __________.

endergonic

Cells must efficiently transfer energy from their energy-trapping systems to the systems actually carrying out work and also use various metabolic processes to replace the energy used in doing work. This is called the

energy cycle

The most specific term usually used to describe a substance in a biological system that increases the rate of a reaction without being permanently changed by the reaction is a(n) ______

enzyme

Enzymes decrease the overall free energy change in a chemical reaction. (T/F)

false

When the amount of enzyme present is held constant, the rate of a reaction will continue to increase as long as the substrate concentration increases. (T/F)

false

A bacterial biosynthetic pathway synthesizes an amino acid in a series of steps, each catalyzed by a different enzyme. The bacteria is transferred to fresh media where the amino acid is present in abundance. The amino acid binds to a regulatory site on the first enzyme in the pathway, effectively shutting down the entire process. This is an example of __________

feedback inhibition

A complete enzyme that consists of a protein component and a nonprotein component is called a(n) _______

holoenzyme

The binding of a positive allosteric regulator molecule will ______

increase the ability of the substrate to bind to the catalytic site

In metabolic channeling, the regulation of metabolic pathways is controlled by the __________ of metabolites and enzymes involved in the pathway.

location

Cells carry out three major types of work. Which of the following involves energy for cell motility and the movement of structures within cells?

mechanical work

_______blank is the total of all chemical reactions occurring in the cell.

metabolism

Where is the electron transport chain located in bacterial cells?

plasma membrane

Feedback inhibition, covalent modification, and allosteric regulation are all examples of ________

posttranslational regulation

The nonprotein component of an enzyme that is firmly attached to the protein is called a(n) _______

prosthetic group

The standard reduction potential of a redox reaction is a measure of the tendency of the __________ to __________ electrons.

reductant; gain

In allosteric regulation, effector molecules usually bind ____

reversibly and noncovalently

RNA molecules that have catalytic activity are known as _______

ribozymes

The reacting molecules in an enzyme-catalyzed reaction are called ________

substrates

Metabolic channeling involves the localization of __________ in different parts of a cell in order to influence the activity of metabolic pathways.

substrates and enzymes

in a branched pathway with many end products, an abundance of one of the end products will usually inhibit _______

the first committed step in the branch of the pathway leading to the production of that particular product

Enzymes are usually named based on _______

the substrates they act on and the type of reaction they catalyze

A complex formed during a reaction that resembles both the substrate and the product is called the _________blank state complex.

transition

Cells carry out three major types of work; which of the following involves nutrient uptake and waste elimination?

transport work

Covalent modification of enzymes most commonly uses phosphoryl, methyl, and adenyl groups. (T/F)

true

Each enzyme normally has specific pH and temperature optima at which they function best. (T/F)

true

Isoenzymes are different enzymes that catalyze the same reaction but can be regulated independently of one another. (T/F)

true

Some endergonic reactions can be made to proceed forward if they are coupled to hydrolysis of one or more of the phosphates of ATP. (T/F)

true

The equilibrium constant for a redox reaction is called the standard reduction potential. (t/f)

true