BI 218 CH 13 (RocketMix HW)

Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ needed for glycolysis?

Fermentation

How many oxidation reactions occur during the citric acid cycle?

Four: one for each dehydrogenase that participates in the cycle

Which of these glycolytic reactions is catalyzed by a kinase?

Fructose 6-phosphate → fructose 1,6-bisphosphate

During the citric acid cycle, the acetyl group in acetyl CoA is:

oxidized to produce CO2.

What is the fate of pyruvate in the cell?

(A) It can be converted to acetyl CoA. (B) It can be converted to alanine. (C) It can be converted to glucose. (D) It can be converted to lactate. (E) All of the above (Correct!)

Intermediates formed in glycolysis and the citric acid cycle are used by the cell to synthesize:

A) amino acids. (B) lipids. (C) nucleotides. (D) All of the above (CORRECT)

When fatty acids are oxidized to acetyl CoA, each cycle of the reaction removes how many carbon atoms from the fatty acid molecule?

2

From one glucose molecule, how much net energy (in the form of ATP and NADH) is produced during glycolysis?

2 ATP, 2 NADH

How much ATP must be invested during the first part of glycolysis for each molecule of glucose broken down?

2 Molecules

The complete oxidation of glucose to H2O and CO2 produces about how many molecules of ATP per molecule of glucose?

30

How many steps in glycolysis involve the action of a kinase?

4

Which is NOT required for the citric acid cycle to take place?

ATP

Most of the energy released by oxidizing glucose is saved in the high-energy bonds of:

ATP and other activated carriers.

Which two-carbon molecule enters the citric acid cycle?

Acetyl CoA

Which of the following describes a breakdown process in which enzymes degrade complex molecules into simpler ones?

Catabolism

In plants, fats and starch are stored in which part of the cell?

Chloroplast

The citric acid cycle converts the carbon atoms in acetyl CoA to which of the following?

CO2

In plant cells, the citric acid cycle takes place in the chloroplast.

False

Metabolism can be tightly regulated because the substrates involved in metabolic reactions are each recognized by only a single, unique enzyme.

False

The oxygen consumed during the oxidation of glucose in animal cells is returned to the atmosphere as CO2.

False

When ATP and fuel molecules such as fatty acids are abundant, the enzymes involved in glycolysis operate in the reverse direction, using pyruvate to produce glucose.

False

After a normal overnight fast, most of the acetyl CoA entering the citric acid cycle is derived from what type of molecule?

Fatty Acids

When ATP is abundant, which is likely to occur?

Gluconeogenesis and glycogen synthesis

When food is plentiful, animals can store glucose as:

Glycogen

For many anaerobic microorganisms, which metabolic pathway is the principle source of ATP?

Glycolysis

In the electron-transport chain, the oxygen atoms in O2 become part of which of the following molecules?

H2O molecules

Which reaction releases the most energy?

Hydrolysis of 1,3-bisphosphoglycerate to 3-phosphoglycerate

Experiments performed by Hans Krebs in the 1930s revealed that the set of reactions that oxidize food molecules and produce CO2 occurs in a cycle. In one experiment, Krebs exposed pigeon muscles to malonate, a compound that inhibits succinate dehydrogenase—the enzyme that converts succinate to fumarate, indicated in red in the linear representation of the reactions of the citric acid cycle (see figure). Which of the following observations, made in malonate-treated muscle, led Krebs to believe that this set of reactions is cyclical?

If oxaloacetate were added, succinate would accumulate.

The chemistry of many metabolic reactions was deciphered using molecules labeled with radioactive isotopes. If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after one turn of the cycle?

In oxaloacetate

If acetyl CoA labeled with radioactive 14C in both carbon positions were fed into the citric acid cycle, where would the radioactivity be after two turns of the cycle?

In oxaloacetate and in CO2

What type of enzyme catalyzes the rearrangement of chemical bonds within a single molecule?

Isomerase

In humans and other mammals, gluconeogenesis is most likely to occur in which type of cells?

Liver Cells

What type of enzyme catalyzes the shifting of a chemical group from one position in a molecule to another?

Mutase

Although the citric acid cycle itself does not use O2, it requires a functioning electron-transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle?

NAD+

In eukaryotic cells, what is the final electron acceptor in the electron-transport chain?

O2

Which of the following is NOT required for glycolysis to occur?

O2

In cells that cannot carry out fermentation, which products derived from glycolysis would accumulate under anaerobic conditions?

Pyruvate and NADH

When nutrients are plentiful, plants can store glucose as:

Starch

In the citric acid cycle, diagrammed here, CO2 is released in which steps? https://s3.amazonaws.com/RM_Images/20160117001236452_raw.jpg

Steps 3 and 4

Which of the following is true?

Sugars and fats are both converted to acetyl CoA in the mitochondria.Correct!

Which of the following locations is NOT used for the digestion of polymeric food molecules into monomeric subunits?

The cell cytosol

Which of the following generates the largest amount of ATP?

The electron-transport chain

What does it mean for a bond to be "high energy," such as the bonds between phosphate groups in ATP?

The hydrolysis of the bond is energetically favorable.

Where does the oxidative (oxygen-dependent) stage of the breakdown of food molecules occur in a eukaryotic cell?

The mitochondrion

In the absence of oxygen, in cells that cannot carry out fermentation, glycolysis would halt at which step?

The oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate

What does the term gluconeogenesis refer to?

The synthesis of glucose from small organic molecules such as pyruvate

For each molecule of acetyl CoA that enters the citric acid cycle, what activated carriers are produced?

Three NADH, one FADH2, one GTP

Both plants and animals store fats in the form of triacylglycerol.

True

Glycolysis can continue in the absence of oxygen, but only in cells that can carry out fermentation.

True

The oxygen atoms required for the citric acid cycle to produce CO2 ultimately derive from:

Water

In the first step of the citric acid cycle:

a two-carbon molecule is combined with a four-carbon molecule to form citrate

In step 6 of glycolysis, glyceraldehyde 3-phosphate, which has one phosphate group, is converted into 1,3-bisphosphoglycerate, which has two. The extra phosphate group comes from:

inorganic phosphate.

Useful energy is obtained by cells when sugars derived from food are broken down by:

glycolysis, the citric acid cycle, and oxidative phosphorylation

The enzyme glycogen phosphorylase, which breaks down glycogen, is:

inhibited by glucose 6-phosphate and by ATP.

The end products of glycolysis are:

pyruvate, ATP, and NADH.

The synthesis of ATP in glycolysis occurs by:

substrate-level phosphorylation.

The NADH generated during glycolysis feeds its high-energy electrons to:

the electron-transport chain.

The phosphorylation of glucose in step 1 of glycolysis:

traps the sugar inside the cell.