Carbohydrate Metabolism

Which of the following are produced as a net result of glycolysis?

NADH and ATP

The most important monosaccharide for energy production is

glucose

glycogenesis

the conversion of glucose into glycogen

When a person is deprived of food, in which order does the body use the following sources to produce glucose?

1.conversion of glycogen to glucose 2.protein breakdown to amino acids used for gluconeogenesis 3.catabolism of lipids

The overall yield of ATP molecules from the complete catabolism of one molecule of glucose in humans and other mammals is ________.

32

Insulin increases the rate at which

A) glucose is converted to glycogen. B) glucose is converted to fat. C) glucose enters the cell. D) glucose is converted from glycogen. E) More than one response is correct. Answer: E

A high energy phosphate molecule involved in gluconeogenesis is ________.

GTP

Classify each pathway of carbohydrate metabolism as anabolic or catabolic. Justify your choice in each case.

Glycolysis is catabolic, because a large molecule is broken into smaller ones, with a net production of high-energy molecules. Gluconeogenesis is anabolic because it is a synthesis reaction. It consumes energy as ATP and GTP. Glycogenolysis is catabolic because it involves breaking larger molecules into smaller ones. Glycogenesis is anabolic because it consumes energy in the form of UTP in order to build a larger molecule from smaller ones.

Which of the following is not used as an energy source in metabolism?

UTC

When energy is needed and adequate oxygen is available, pyruvate is converted to

acetyl-SCoA

Which chemical is produced from pyruvate when it is metabolized in muscle cells under aerobic conditions?

acetyl-SCoA

The action of yeast on pyruvate is a process referred to as

alcoholic fermentation.

The enzyme that catalyzes cleavage of fructose 1,6-bisphosphate to dihydroxyacetone phosphate and D-glyceraldehyde-3-phosphate is ________.

aldolase

Steps 1-5 of glycolysis are referred to as the "energy investment" portion of the process because these steps

consume ATP instead of producing it.

Entry of monosaccharides other than glucose into the glycolysis pathway initially involves

conversion into phosphates.

Glycolysis occurs mainly in the

cytosol of all cells.

If a glucose tolerance test shows an abnormally high level of glucose in the blood after several hours, the person is possibly

diabetic.

All of the following statements concerning digestion are correct except

digestion begins in the stomach and is completed in the large intestine.

The first step of glycolysis involves ________ to form ________.

esterification; glucose-6-phosphate

Which chemical is produced from pyruvate when it is metabolized by yeast cells?

ethanol

Which of the following carbohydrates can also be used as fuel in glycolysis?

galactose, fructose, and mannose

The process of making glucose from noncarbohydrates is known as

gluconeogenesis.

Which conversion is accomplished during glycolysis?

glucose to pyruvate

Glycogenolysis does not occur in muscle tissue because it lacks which of the following enzymes?

glucose-6-phosphatase

The chemical resulting from steps 3-5 of glycolysis which is oxidized in step 6 is

glyceraldehyde 3-phosphate

Glycogenolysis can be correctly represented by which of the following pathways?

glycogen → glucose

Which pathway converts glucose to its storage form in animals?

glycogenesis

Which pathway produces glucose from its storage form in animals?

glycogenolysis

All of the following are reactions in the oxidation of glucose which produce energy except

glycogenolysis.

In an individual who is starving or fasting, the body meets its need for glucose first by the process of ________, and then by the process of ________.

glycogenolysis; gluconeogenesis

The pathway followed by glucose when energy is needed is

glycolysis.

A lack of insulin causes ________, a state in which the concentration of blood sugar is ________ than normal.

hyperglycemia; higher

When blood sugar levels are lower than normal, this condition is called

hypoglycemia

Overproduction of insulin causes ________, a state in which the concentration of blood sugar is ________ than normal.

hypoglycemia; lower

The diseases identified as diabetes are primarily associated with a malfunction of the hormone

insulin.

Hormones which regulate glucose metabolism are ________, ________, and ________.

insulin; glucagon; epinephrine

Conversion of dihydroxyacetone phosphate to D-glyceraldehyde 3-phosphate is a(an) ________.

isomerization

The conversion of glucose 6-phosphate to fructose 6-phosphate in the second step of glycolysis is a(an) ________ reaction.

isomerization

During gluconeogenesis pyruvate is formed from glycerol, certain amino acids and _________.

lactate

The pain and cramps that occur during physical exhaustion are associated with the formation of excess

lactate

Which chemical is produced from pyruvate when it is metabolized in muscle cells under anaerobic conditions?

lactate

Gluconeogenesis occurs mainly in the

liver

The major products of carbohydrate digestion are

monosaccharides

Glycogen is most commonly found in ________ cells and ________ cells.

muscle; liver

In the first step of glycolysis, the conversion of glucose to glucose 6-phosphate is known as

phosphorylation

The major function of the pentose phosphate pathway when energy for anabolic reactions is a priority is

producing NADPH.

The major function of the pentose phosphate pathway when nucleic acid synthesis is a priority is

producing ribose.

The most important goal of glucose metabolism is

production of ATP as an energy source for all cells.

All of the chemicals below are associated with the pentose phosphate pathway except

pyruvate

Which of the following is not a product of digestion?

pyruvate

The products of glycolysis important in metabolism are

pyruvate, ATP, and NADH.

Pyruvate is converted to lactate under anaerobic conditions because ________.

reduction of pyruvate provides NAD+ which is needed for glycolysis

The target molecule(s) for α-amylase is (are)

starch and glycogen.

When ATP is produced by direct transfer of a phosphate group instead of from reactions coupled to electron transport, the process is referred to as ________ phosphorylation.

substrate-level

pentose phosphate pathway

the conversion of glucose into carbohydrate molecules containing phosphate groups and five carbon atoms

glycolysis

the conversion of glucose into pyruvate

glycogenolysis

the conversion of glycogen into glucose

When a cell's need for NADPH or ribose-6-phosphate exceeds its need for ATP, glucose-6-phosphate is metabolized by

the pentose phosphate pathway.

gluconeogenesis

the production of glucose from noncarbohydrate sources

All of the following statements concerning digestion are correct except....

the same enzymes are used in the digestion of carbohydrates, lipids, and proteins.