Deck 3: Carbohydrates

Question 1

What is the nutritional significance of stereoisomers?

A) Some isomers cannot cyclize.
B) Certain metabolic enzymes require a particular structure.
C) Certain isomers cannot polarize light.
D) Some isomers have no anomeric carbon.

Answer 1

B

Question 2

Name the model that depicts cyclized monosaccharides as lying in a horizontal plane with the hydroxyl groups pointing down or up from the plane.

A) Haworth
B) Fischer projection
C) cyclized Fischer projection
D) stereoisomer

Answer 2

A

Question 3

Which hormonal changes occur in response to a fall in blood glucose concentration?

A) increased insulin, decreased glucagon
B) decreased insulin, increased glucagon
C) decreased insulin, decreased glucocorticoids
D) increased insulin, increased glucagon

Answer 3

B

Question 4

What is the key enzyme in digestion of polysaccharides?

A) starch amylopectin
B) β-amylase
C) α-dextranase
D) α-amylase

Question 5

The majority of energy in the typical American diet comes from:

A) fat.
B) protein.
C) carbohydrate.
D) vitamins.

Question 6

Choose the best description of the main method of glucose absorption.

A) passive diffusion down a concentration gradient
B) active transport with fructose
C) facilitated transport
D) active transport with sodium

Question 7

When compounds with 1 or more chiral carbon atoms and the same formula are arranged as mirror images they are said to be _____.

A) symmetrical
B) enantiomers
C) rotated
D) linear

Question 8

What is a likely reason that large quantities of fructose may cause gut discomfort?

A) Diffusion of fructose only occurs from low to high concentrations.
B) Facilitated diffusion is slower than active transport.
C) Active transport is saturable.
D) Pinocytosis reverses fructose and releases it to the gut.

Question 9

Which of the following homopolysaccharides made of glucose contributes the most energy to the ordinary diet?

A) amylose
B) amylopectin
C) glycogen
D) cellulose

Question 10

Sucrose digestion is initiated in the _____.

A) pylorus
B) fundus
C) duodenum
D) mouth

Question 11

The disaccharidases are synthesized by the _____.

A) pancreas
B) liver
C) enterocyte
D) chief cell

Question 12

A ketopentose is a carbohydrate containing

A) 5 carbons and a ketone group.
B) 6 carbons and an aldehyde group.
C) 3 carbons and an aldehyde group.
D) 7 carbons and a ketone group.

Question 13

Which of the following is the predominant monosaccharide produced by the digestion of all dietary carbohydrates?

A) ribose
B) fructose
C) galactose
D) glucose

Question 14

The glucose transporter that is sensitive to insulin is

A) GLUT1.
B) GLUT2.
C) GLUT4.
D) SGLT1.

Question 15

What is the most common digestible homopolysaccharide existing as both amylose and amylopectin?

A) glycogen
B) cellulose
C) hemicellulose
D) starch

Question 16

The enzyme needed to hydrolyze the α (1,6) bond of amylopectin is _____, which is secreted from the _____.

A) amylase, enterocyte
B) sucrase, pancreas
C) lactase, enterocyte
D) isomaltase, enterocyte

Question 17

What are the major dietary energy sources that are composed of two simple sugars?

A) disaccharides
B) polysaccharides
C) monosaccharides
D) trioses

Question 18

Which of the following carbon bonds is digested by α-amylase?

A) α (1-4)
B) α (1-6)
C) β (1-4)
D) β (1-6)

Question 19

In what form do carbohydrates enter the bloodstream?

A) starch
B) disaccharides
C) monosaccharides
D) ketoses

Question 20

A homopolysaccharide that is important in human diets is _____ and the end product formed from the complete digestion of this homopolysaccharide is _____.

A) cellulose; glucose
B) lactose; galactose
C) glycogen; glucose
D) starch; glucose

Question 21

During the end reaction of the electron transport chain, molecular oxygen becomes _____.

A) oxidized to carbon dioxide
B) reduced to water
C) NADH + H⁺
D) FADH₂

Question 22

Insulin is an anabolic hormone. Which process does insulin stimulate?

A) lipolysis
B) gluconeogenesis
C) glycogenesis
D) ketogenesis

Question 23

Electron flow through Complexes I, III, and IV is accompanied by the translocation of protons

A) from the matrix into the intermembrane space.
B) from the iron-sulfur centers into the cytosol.
C) from cytochrome c to cytochrome c1.
D) from cytochrome b to the iron-sulfur center.

Question 24

In what part of the cell does glycolysis occur?

A) mitochondrion
B) cytosol
C) nucleus
D) endoplasmic reticulum

Question 25

In what organelle are the enzymes that catalyze the citric acid cycle located?

A) cytoplasmic matrix
B) endoplasmic reticulum
C) mitochondrion
D) lysosome

Question 26

103 35. When oxygen is present in a tissue, less glucose is metabolized to pyruvate. Why?

A) Less lactate can accumulate in the presence of oxygen.
B) ATP accumulates and inhibits phosphofructokinase.
C) Metabolism slows in the presence of oxygen.
D) More glucose is converted to glycogen.

Question 27

The major end products of cellular oxidation of carbohydrate include:

A) carbon, nitrogen, and hydrogen.
B) water, carbon dioxide, and energy.
C) glucose and amino acids.
D) dietary fiber and ammonia.

Question 28

In the _____ galactose is eventually converted to _____.

A) hepatocyte, glucose
B) Kupffer cell, fructose
C) enterocyte, glucose
D) chylomicron, glucose

Question 29

Under anaerobic conditions within a cell, how many net ATPs are formed from one glucose molecule by substrate-level phosphorylation?

A) one
B) two
C) four
D) six

Question 30

In the complete oxidation of 1 mol of glucose, how many ATPs are formed?

A) 4-6
B) 8-12
C) 18-24
D) 32-38

Question 31

Due to a lack of the enzyme glucose-6-phosphatase, which tissue capable of glycogenesis cannot contribute to blood glucose levels between meals?

A) liver
B) muscle
C) brain
D) kidney

Question 32

Glycemic load considers the _____ in the food.

A) protein and carbohydrate content
B) fat and carbohydrate content
C) fat to carbohydrate ratio
D) quantity and quality of carbohydrate

Question 33

In which cellular site is most of the energy released when carbohydrates are oxidized to carbon dioxide and water?

A) cytoplast
B) reticuloendothelium
C) Golgi body
D) mitochondrion

Question 34

People with type 1 diabetes have

A) slow translocation of GLUT4 receptors from the Golgi body.
B) lack of mRNA synthesis for GLUT4 receptors in adipocytes or myocytes.
C) increased glycogenesis in myocytes after a meal.
D) below-normal glucokinase activity because of low insulin levels.

Question 35

Electrons carried by one mole NADH + H⁺ enter the electron transport chain at Complex I and generate _____ mole(s) ATP as they are sequentially oxidized.

A) 0.5
B) 1.5
C) 2.5
D) 3.5

Question 36

Two hormones that stimulate glycogenolysis in the muscle and liver, respectively, are _____.

A) cortisol and epinephrine
B) epinephrine and glucagon
C) insulin and epinephrine
D) glucagon and insulin

Question 37

Glycolysis is a process involving:

A) synthesis of fatty acids.
B) reactions that convert glucose to glycogen.
C) reactions that convert glucose to pyruvate.
D) reactions that convert glycogen to protein.

Question 38

Alcohol in beverages is degraded mainly in the liver cytosol with the production of one NADH for each ethanol molecule. Predict what effect consumption of alcohol would have on the activity of the liver malate-aspartate shuttle.

A) no change
B) increased
C) decreased
D) reversed

Question 39

The formation of ATP by compounds with a more negative phosphate group transfer potential than -7,300 cal is called _____.

A) transfer phosphorylation
B) oxidative phosphorylation
C) coupled reactions
D) substrate-level phosphorylation

Question 40

The enzyme ATP synthase is believed to catalyze the formation of ATP, as described by the _____ theory.

A) leakage
B) hydrogen pump
C) protein channel
D) chemiosmotic

Question 41

Which tissue has the least activity of the pentose phosphate pathway?

A) liver
B) adrenal cortex
C) mammary gland
D) skeletal muscle

Question 42

When fructose-sweetened beverages are consumed in research studies, plasma triglycerides levels are:

A) always elevated.
B) sometimes elevated.
C) never elevated.
D) elevated only in women.

Question 43

Glucagon stimulates hepatic gluconeogenesis and suppresses glycolysis by reducing the concentration of _____, a positive modulator of phosphofructokinase.

A) fructose-2,6-bisphosphate
B) fructose-1,6-bisphosphate
C) glucose-6-phosphate
D) glucose-1-phosphate

Question 44

The purpose of the hexose monophosphate shunt is to produce

A) pentose phosphates and NADPH.
B) DNA and RNA.
C) fatty acids.
D) reducing substrates.

Question 45

Which statement is true?

A) The use of high-fructose corn syrup in U.S. products increased between 1970 and 1998, but has since leveled off.
B) Between 2000 and 2010, use of high-fructose corn syrup in the U.S. food supply was about twice the use of table sugars.
C) High-fructose corn syrup and corn syrup are two names for the same product.
D) All high-fructose corn syrup sold in the U.S. is made from corn.

Question 46

Muscle lactate is converted to glucose in the liver and returned to the muscle by means of the _____.

A) malate-aspartate shuttle
B) electron transport chain
C) Cori cycle
D) pentose phosphate pathway

Question 47

All of the following enzymes are negatively regulated (allosterically inhibited) by increasing levels of ATP EXCEPT _____.

A) phosphofructokinase
B) pyruvate dehydrogenase complex
C) hexokinase
D) citrate synthase

Question 48

All of the following are substrates for gluconeogenesis EXCEPT

A) fatty acids.
B) lactate.
C) glycerol.
D) glucogenic amino acids.

Question 49

Which tissue metabolizes fructose?

A) muscle
B) adipose tissue
C) liver
D) all of these

Question 50

If an individual with no blood sugar abnormalities when eating regularly presented with severe hypoglycemia after 30 hours of fasting, which enzyme would you suspect might be malfunctioning?

A) phosphofructokinase
B) pyruvate kinase
C) fructose-1,6-bisphosphatase
D) glucose-6-phosphatase

Question 51

Gluconeogenesis is essentially the reversal of which pathway?

A) glycogenesis
B) glycolysis
C) TCA cycle
D) lipogenesis

Question 52

The fructose : glucose ratio of high-fructose corn syrup is approximately _____.

A) 100:1
B) 80:20
C) 50:50
D) 25:75