Lecture 15

Question 1

Describe the generation and function of ATP

Answer 1

Generated by the combustion of carbohydrates, fatty acids, and proteins; ATP energizes synthesis of cellular components, muscle contraction, active transport across membranes, glandular secretion, and nerve conduction

Question 2

Explain how phosphocreatine functions as an accessory storage depot for energy and as an “ATP buffer”

Answer 2

Has a high energy phosphate bond (13,000 cal); 3-8x more abundant than ATP; cannot participate directly in energy transfer, but can transfer energy interchangeably with ATP

Question 3

Differentiate between essential and nonessential AA

Answer 3

Essential = cannot be synthesized in the body or are not synthesized easily or in quantities

Nonessential = formation depends on alpha-keto acid precursors

Question 4

Describe a peptide linkage

Answer 4

Bond between the carbonyl carbon of one AA and the amine nitrogen of the other AA

Question 5

List/describe the steps in the formation of a peptide bond

Answer 5

1. AA + ATP -> AA-AMP + 2Pi
2. AA-AMP + tRNA -> AA-tRNA + AMP
3. Attachment of tRNA to mRNA via codon-anticodon pairing
4. Formation of peptide bond with second AA using peptidyl transferase + GTP

Question 6

Be able to diagram the ornithine (urea) cycle

Answer 6

Slide 14

Question 7

Differentiate which parts of the ornithine (urea) cycle occur in the mitochondria and which parts occur in the cytoplasm

Answer 7

Mitochondria:

1. Ammonia + CO2 -> carbamoyl phosphate
2. Carbamoyl phosphate + ornithine -> citrulline

Cytoplasm:

3. Citrulline + aspartate -> argininosuccinate
4. Argininosuccinate -> arginine + fumarate
5. Arginine -> urea + ornithine

Fumarate can enter TCA cycle

Question 8

Describe the formation of urea in the liver

Answer 8

Slide 14

Question 9

Describe the relationship between the rate of a chemical reaction and the concentrations of substrate and enzymes

Answer 9

When substrate concentration is high, reaction rate is determined almost entirely by the concentration of enzyme

When enzyme concentration is high, reaction rate becomes directly proportional to concentration of substrate and enzyme

Question 10

Give examples of reaction rates that are determined almost entirely by concentration of enzyme

Answer 10

Absorption of substances from intestinal tract and renal tubules when concentrations of the substrate are low compared to transport enzymes

Question 11

Define the rate-limiting step in a series of reactions

Answer 11

Step in the series of reactions that is the slowest

Question 12

What is the major rate-limiting factor in almost all energy metabolism in the body?

Answer 12

ADP is the major rate-limiting factor for almost all energy metabolism in the body

Question 13

Describe the relationship of heat to reaction rates and metabolism

Answer 13

35% of energy in foods becomes heat during ATP formation; more heat is produced in the transfer of energy from ATP to the functional system of cells; no more than 27% of energy from food is used by the functional systems; most of this 27% is finally converted to heat

Question 14

Describe the factors that influence metabolic rate

Answer 14

Arousal vs sleeping, skeletal muscle, age, thyroid activity, testosterone, growth hormone, fever, sleep, and malnutrition

Question 15

Define basal metabolic rate; explain how it is calculated; what is its relationship to age and gender?

Answer 15

BMR = metabolic rate when the body is at rest

Calculated by the rate of oxygen utilization

Higher in men than women and decreases with age