Biochem: Carbohydrates

Question 1

_________ are absorbed by enterocytes in the small intestine.

Answer 1

Monosaccharides

Question 2

What are the three major disaccharides and what are their components?

Answer 2

MLS

Maltose = glucose + glucose
Lactose = glucose + galactose
Sucrose = glucose + fructose

Question 3

T/F: Glycosaminogylcans (GAGs) are repeating disaccharides.

Answer 3

True

High viscosity and low compressibility

Question 4

T/F: GAGs are negatively charged and attract water.

Answer 4

True

Question 5

What is the most abundant GAG?

Answer 5

Chondroitin sulfate

Question 6

What are the only two GAGs that do not end in “sulfate”?

Answer 6

Heparin and hyaluronic acid

Question 7

Why do PGs attract water?

Answer 7

Large number of alcohol groups

Question 8

The central protein in a PG contains which two amino acids?

Answer 8

Serine and threonine

Question 9

Cariogenic bacteria synthesize _______ and ________ from their metabolism of dietary _________.

Answer 9

glucans (dextrans); fructans (levans); sucrose

Question 10

Strep Mutans contains which enzyme that hydrolyzes sucrose to form dextrans (glucans)?

Answer 10

glucosyl transferase

Question 11

T/F: Glycogen is stored in the liver.

Answer 11

True

Question 12

What is the major buffer found in saliva?

Answer 12

Bicarbonate

Question 13

What is the major antibody found in saliva?

Answer 13

IgA

Question 14

Which gland produces the majority of the saliva?

Answer 14

Submandibular

Question 15

During glycolysis glucose gets converted to __________.

Answer 15

pyruvate

Question 16

When oxygen is present, pyruvate will be converted to _________. Without oxygen, pyruvate will be converted to ________.

Answer 16

Acetyl-CoA (Kreb’s Cycle); Lactic acid

Question 17

What three major coenzymes make up the pyruvate dehydrogenase complex?

Answer 17

1. Coenzyme A
2. NAD
3. Thiamine

Question 18

What is the function of the pyruvate dehydrogenase complex?

Answer 18

To get pyruvate into the mitochondria

Question 19

What is the first step of the citric acid cycle?

Answer 19

Citrate synthase converts Acetyl-CoA, Oxaloacetate, and water into citrate

Question 20

What happens to convert pyruvate to Acetyl-CoA?

Answer 20

Oxidation by pyruvate dehydrogenase

Glycolysis -> Kreb’s Cycle

Question 21

What happens to convert pyruvate to lactic acid?

Answer 21

Reduction by lactate dehydrogenase

Anaerobic

Question 22

What happens to convert pyruvate to oxaloacetate?

Answer 22

Carboxylation by pyruvate carboxylase

Gluconeogenesis and replenish TCA cycle

Question 23

What happens to convert pyruvate to alanine?

Answer 23

Transamination by alanine aminotransferase

Amino acid synthesis

Question 24

If Acetyl-CoA is not acted on by citrate synthase, what are the other possible routes?

Answer 24

Acetyl-CoA is either converted to Malonyl-CoA or HMG-CoA

Question 25

What enzyme converts Acetyl-CoA to Malonyl-CoA?

Answer 25

Acetyl-CoA carboxylase Occurs in cytosol in liver; rate limiting step in fatty acid synthesis

Question 26

What are the two routes for HMG-CoA?

Answer 26

1. Cholesterol synthesis via HMG-CoA reductase | 2. Ketone body synthesis via HMG-CoA lyase

Question 27

What are the three major components of gluconeogenesis?

Answer 27

LAG Lactate, amino acids, glycerol

Question 28

What is the net yield of ATP through glycolysis (cytosol)?

Answer 28

uses two, makes four Net = +2

Question 29

What is the net yield of ATP in the TCA cycle (mitochondrial matrix)?

Answer 29

Net = +2

Question 30

What is the net yield of ATP in the ETC (inner mitochondrial membrane)?

Answer 30

+34

Question 31

What enzyme allows glucose to be brought from the blood into tissue?

Answer 31

Hexokinase/glucokinase uses an ATP to convert glucose (blood) to glucose-6-phosphate (tissues)

Question 32

What is the purpose of the pentose phosphate shunt?

Answer 32

Produce ribose (DNA synthesis) and NADPH (fatty acid and steroid synthesis)

Question 33

Which part of the nervous system would stimulate glucagon release?

Answer 33

Sympathetics Would result in gluconeogenesis to put glucose into the blood stream

Question 34

Which part of the nervous system would stimulate insulin release?

Answer 34

Parasympathetic

Question 35

T/F: Acetyl-CoA is used in gluconeogenesis to make new glucose.

Answer 35

False LAG Lactate, amino acids, glycerol

Question 36

T/F: Insulin will stimulate glycogenolysis.

Answer 36

False Insulin -> glycogenesis (store glucose) Glucagon -> glycogenolysis (lyse glycogen to release glucose)

Question 37

What is the goal of the cori cycle?

Answer 37

Lactate from muscles is brought to liver to convert to glucose

Question 38

T/F: Glycogen phosphorylase converts glycogen to glucose-1-phosphate.

Answer 38

True Stimulated by glucagon, epinephrine

Question 39

Describe how glucose is converted into glycogen?

Answer 39

glucose -> glucose-6-phosphate -> glucose-1-phosphate -> UDP-glucose Glycogen synthase attaches UDP-glucose to the nonreducing end of glycogen

Question 40

T/F: Ketone bodies can be a source of energy for the brain when in fasting.

Answer 40

True