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Question 1

Amino Acid Metabolism

Answer 1

Single amino acids circulating in blood
Cellular Uptake
Used as precursors for N-containing compounds
Carbon used as sources of energy
Nitrogen must be removed in order to be excreted

Question 2

Cellular uptake of amino acids: Specific transporters

Answer 2

Differ in:
Specificity
Expression

Defects in:
Cystinuria
Hartnup Disease

Question 3

Glucogenic Degradation of Amino Acids

Answer 3

Carbons used to create glucose in the liver
- Produce intermediates of the TCA Cycle

All non-essential amino acids can be used to produce glucose

Question 4

Ketogenic Degradation of amino acids

Answer 4

Carbons used to create ketone bodies or their precursors
- Acetyl-CoA or acetoacetate
Lysine and leucine are strictly ketogenic

Question 5

amino acids that can be glucogenic or ketogenic

Answer 5

Tryptophan, isoleucine, threonine, phenylalanine and tyrosine

Question 6

Nitrogen Balance

Answer 6

When balanced, the amount of nitrogen incorporated into macromolecules each day exactly equals the amount excreted from the body.

Positive nitrogen balance occurs during growth
- Amount incorporated exceeds the amount excreted

Negative nitrogen balance occurs from malnutrition
- Amount excreted exceeds the amount incorporated

Question 7

Marasmus

Answer 7

Reduction in the total number of calories in an infant’s diet
child’s weight falls below 60% for normal sex, height and age
significant loss of body fat and muscle occurs due to catabolism of fats and protein, an adaptive strategy to use lipids and amino acids as energy sources.

Question 8

Kwashiorkor

Answer 8

A protein-energy malnutrition (PEM)
Protein deprivation with adequate caloric intake
normal or nearly normal body weight and height for age
Often, the child has been weaned too early and subsequently fed a low-protein, high-carbohydrate diet.

Question 9

Essential Amino Acids and Malnutrition

Answer 9

Insufficient essential amino acid intake results in decreased protein synthesis.

Hypoalbuminemia

• Albumin makes up 55-60% of the total serum protein.
• Albumin plays important roles in buffering and maintaining osmotic pressure.
• – Results in generalized edema and distended abdomen

Hypopigmentation

Question 10

essential amino acid for kids but not adults

Answer 10

arginine

Question 11

Synthesis of Amino Acids

Answer 11

Non-Essential Amino Acids:

9 synthesized from glucose alone
Tyrosine synthesized from phenylalanine
Cysteine acquires sulfur from methionine (essential)

Question 12

Review: Maintenance of Blood Glucose Levels

Answer 12

Maintained by liver

Glycogenolysis
During fasting
Mostly depleted after more than 12 hours

Gluconeogenesis
During starvation
Increases as glycogen reserves decrease
Only source after 24 hours of fasting

Question 13

Glycogen

Answer 13

Mainly in liver and skeletal muscle
a-1,4-glycosidic bonds
-Make up glycosyl units

a-1,6- glycosidic bonds
- Initiate branching

Glycogen Formation Process

• Glucose is phosphorylated to G-6-P
• Formation of UDP-Glucose
• Glycogen synthase
• – Transfers glucose units from UDP-G to the end of glycogen chains
• Branching enzyme
• – Moves units to form a branch

Question 14

Glycogenolysis

Answer 14

Glycogen phophorylase
- Removes glucose units one at a time from ends forming G-1-P

Debranching enzyme
- Removes a-1,6 linked glucose residues as G-1-P

Phosphoglucomutase
- Creates G6P from G1P

Glucose-6-phosphatase

• Only in liver
• Converts to glucose to enter bloodstream