Mastering Biology: An Intro to Metabolism

As ATP begins to build up in a cell, metabolism slows down. How does this happen?

ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function. (ATP acts as an inhibitor, not an activator.)(Excess ATP acts as an allosteric inhibitor. It deactivates enzymes by reversibly changing their shape.)

Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?

ATP can be regenerated by the addition of a phosphate group to ADP.

Which of the following correctly states the relationship between anabolic and catabolic pathways?

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Which of the following statements correctly describes cofactors and coenzymes?

Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.

How does ATP drive mechanical work inside a cell?

By binding to motor proteins

How does ATP drive transport work inside a cell?

By phosphorylating a transport protein

How does ATP drive transport work inside a cell?

By phosphorylating a transport protein (Mechanical work is driven by ATP binding to motor proteins.)(Chemical work is driven by ATP providing free energy to facilitate the formation of polymers from monomers.)(ATP adds a phosphate to a transport protein for this kind of work. A phosphate is not removed from the protein.)

Which of the following is a polymer?

Cellulose, a plant cell wall component

Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?

Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site.

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture

DNA

Which of the following states the relevance of the first law of thermodynamics to biology?

Energy can be freely transformed among different forms as long as the total energy is conserved.

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?

Energy input into the organism must be occurring to drive the decrease in entropy.

Which of the following statements about enzymes is true?

Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.

The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which of the following statements accurately defines energy coupling?

Exergonic reactions drive endergonic reactions.

Which of the following reactions would be endergonic?

Glucose + fructose → sucrose

In general, the hydrolysis of ATP drives cellular work by

In general, the hydrolysis of ATP drives cellular work by

The sex hormones estrogen, progesterone, and testosterone belong to which class of molecules?

Lipids

Which of the following is true regarding metabolic pathways?

Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.

Generally, animals cannot digest (hydrolyze) the glycosidic linkages between the glucose molecules in cellulose. How then do cows get enough nutrients from eating grass?

Microorganisms in their digestive tracts hydrolyze the cellulose to individual glucose units.

What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components?

Positive

Which of these statements about enzyme inhibitors is true?

The action of inhibitors may be reversible or irreversible.

Which of the following statements about the active site of an enzyme is correct?

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

Which of the following statements is correct regarding ATP?

The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.

At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What statement best explains the difference in how pH affects the function of this enzyme?

The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.

What best characterizes the role of ATP in cellular metabolism?

The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

The peptide bond is __________.

a covalent bond joining amino acids together to form a polypeptide

he components of nucleic acids are __________.

a nitrogenous base, a pentose sugar, and a phosphate

Sickle-cell anemia is a disease that is caused by __________ in the __________ of the protein.

a single amino acid change; primary structure

Nitrogenous bases are classified as either purines or pyrimidines. Examples of purines are __________.

adenine and guanine

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of

allosteric regulation

Protein molecules are polymers (chains) of __________.

amino acid molecules

Sugars have a(n) __________ group that interacts with a _________ group that forms ring structures when the dry molecule is placed in water.

carbonyl (-C=O); hydroxyl (-OH)

Which type of protein shields a newly forming protein from cytoplasmic influences while it is folding into its functional form?

chaperonins

At a conference, the speaker's grand finale was sautéing mealworms (insect larvae) in butter and serving them to the audience. They were crunchy (like popcorn hulls) because their exoskeletons contain the polysaccharide __________.

chitlin

The molecule with four fused rings that is found in animal membranes and is the precursor of vertebrate sex hormones is __________.

cholesterol

When comparing saturated and naturally occurring unsaturated fats, the unsaturated fats have __________ and are __________ at room temperature.

cis double bonds; liquids

In living organisms, DNA exists as a __________ with the strand(s) __________.

double helix; running antiparallel

ATP adds a phosphate to a transport protein for this kind of work. A phosphate is not removed from the protein.

feedback inhibition

A polysaccharide that is used for storing energy in human muscle and liver cells is

glycogen

The subunits (monomers) in cellulose are linked together by

glycosidic linkages

Enzyme activity is affected by pH because

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

The proper three-dimensional shape and folding of a protein is assisted by _________.

molecules called chaperonins

The tertiary structure of a protein includes all of the following interactions except _________ bonds.

peptide

The lipids that form the main structural component of cell membranes are __________.

phospholipids

The sequence of amino acids in a protein is called the __________ structure of the protein.

primary

An exergonic (spontaneous) reaction is a chemical reaction that

releases energy when proceeding in the forward direction

One characteristic shared by sucrose, lactose, and maltose is that __________.

they are all disaccharides

In a dehydration synthesis reaction, __________ is always formed as a by-product of the reaction.

water

__________ is always involved in hydrolysis reactions.

water