Lecture 15

Question 1

How is ATP generated?

Answer 1

By the combustion of carbohydrates, fatty acids, and proteins

Question 2

What does ATP energize?

Answer 2

Synthesis of cellular components, muscle contraction, active transport across membranes, glandular secretion, nerve conduction

Question 3

What does phosphocreatine function as?

Answer 3

Accessory storage depot for energy and as an ATP buffer

Question 4

Explain how phosphocreatine functions as an accessory storage depot for energy as an ATP buffer.

Answer 4

Has high energy phosphate bond, is 208x more abundant than ATP, cannot participate directly in energy transfer, can transfer energy interchangeably with ATP

Question 5

What is the difference between essential and nonessential amino acids?

Answer 5

Essential amino acids cannot be synthesized in the body or are not synthesized easily or in quantities (must get from consumption)
Nonessential (can be made by body) formation depends on alpha-keto acid precursors

Question 6

Describe a peptide linkage.

Answer 6

Among the most important intracellular processes that require energy; Covalent chemical bond linking consecutive amino acids together (C1 to N2)

Question 7

Describe the pathway for the synthesis of alanine from pyruvic acid.

Answer 7

Glutamine + pyruvic acid → (transaminase) → alpha-ketoglutamic acid + alanine

Question 8

What is transamination?

Answer 8

Chemical reaction that transfers an amino group to a ketoacid to form new amino acids, promoted by several enzymes

Question 9

List the steps in the formation of a peptide bond.

Answer 9

Amino acid + ATP → amino acid-AMP + 2Pi
Amino acid-AMP + tRNA → amino acid-tRNA + AMP
Attachment of tRNA to mRNA via codon anticodon pairing
Formation of peptide bond with second amino acid using peptidyl transferase + GTP

Question 10

T or F: Since 4 high-energy phosphate bonds are needed to form one peptide linkage, each peptide bond stores 1/4 of the energy in calories.

Answer 10

False. 4 high-energy phosphate bonds are needed to form one peptide linkage, but each peptide bond only stores 500-5000 cal.

Question 11

List out the ornithine cycle, and differentiate which parts of the cycle occur in the mitochondria and which parts occur in the cytoplasm.

Answer 11

Mitochondria:
Ammonia + CO2 → carbamoyl phosphate
Carbamoyl phosphate + ornithine → citrulline

Cytoplasm:
Citrulline + aspartate → argininosuccinate
Argininosuccinate → arginine + fumarate
Arginine → urea + ornithine

Question 12

At the end of the ornithine cycle, where can fumarate then enter?

Answer 12

CAC

Question 13

What happens to excess amino acids in body fluids?

Answer 13

Degraded and used for energy

Question 14

What is the first step of deamination?

Answer 14

Generally involved transamination

Question 15

What is one of the end products of the first step of deamination?

Answer 15

Ammonia

Question 16

What combines to form urea?

Answer 16

2 molecules of ammonia + 1 molecule of CO2

Question 17

Where is urea formed?

Answer 17

Liver

Question 18

T or F: The urea cycle is the ornithine cycle.

Answer 18

True.

Question 19

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

Answer 19

Rate of overall chemical reaction is determined by the concentration of the enzyme and the concentration of the substrate

Question 20

When substrate concentration is high, what determines reaction rate?

Answer 20

Enzyme concentration

Question 21

What is reaction rate determined by when enzyme concentration is high?

Answer 21

Reaction rate becomes directly proportional to concentration of substrate and enzyme

Question 22

Define the rate-limiting step in a series of reactions.

Answer 22

Overall rate of a series of chemical reactions is determined by the rate of the reaction of the slowest step in the series

Question 23

T or F: Most chemical reactions in the body occur in series.

Answer 23

True.

Question 24

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

Answer 24

ADP

Question 25

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

Answer 25

Cellular concentrations of ADP are low, chemical reactions that depend on ADP as one of the substrates is very slow, ATP is converted to ADP during cellular activity so ADP concentration increases during cellular activity, increased concentration of ADP increases reaction rates

Question 26

What are examples of ADP substrate dependence?

Answer 26

All oxidative metabolic pathways, other pathways for the release of energy

Question 27

Describe the relationship of heat to reaction rates and metabolism.

Answer 27

About 35% of energy in foods becomes heat during ATP formation, more heat is produced in transfer of energy from ATP to functional systems of cells, no more than 27% of energy from food is used by functional systems (most of 27% is finally converted to heat)

Question 28

Describe the factors that influence metabolic rate.

Answer 28

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

Question 29

Which is one of the best known stimuli for increasing the rate of thyroid stimulating hormone?

Answer 29

Cold

Question 30

Define basal metabolic rate.

Answer 30

Rate of energy expenditure per unit time by endothermic animals at rest

Question 31

Explain how BMR is calculated.

Answer 31

Whole-body metabolic rate can be calculated from rate of oxygen utilization Metabolize 1 L of oxygen with glucose = 5.01 cal, fat = 4.7 cal, protein = 4.6 cal Energy liberated per L of oxygen with average diet averages about 4.825 cal = energy equivalent of oxygen

Question 32

What is the difference between glycogenolysis and gluconeogenesis.

Answer 32

``` Glycogenolysis = breakdown of glycogen (n) to glucose 1-P and glycogen (n-1) Gluconeogenesis = synthesis of glucose from molecules that are not carbohydrates ```

Question 33

How many calories does the average 70 kg man laying in bed all day use?

Answer 33

1650 cal/day

Question 34

How much more energy does walking upstairs require versus sleeping in bed all day?

Answer 34

17x more

Question 35

What does BMR normally average?

Answer 35

65-70 cal/hour

Question 36

Describe the relationship between thyroxine and BMR.

Answer 36

Thyroxine increases the rate of chemical reactions in cell and increases MR; Maximal secretion may increase MR 50-100% above normal, loss of thyroid secretion decreases MR to 40-60% of normal

Question 37

Describe the relationship between testosterone and BMR.

Answer 37

Can increase MR 10-15%; Mainly related to anabolic effect of increase in skeletal muscle mass

Question 38

Describe the relationship between malnutrition and BMR.

Answer 38

Malnutrition results in reduced food substances in the cells, resulting in marked reduction in MR; Process may accompany final stage of many diseases

Question 39

Describe the relationship between age and BMR.

Answer 39

BMR decreases with age. Much of the decline in BMR with increasing age is probably related to loss of muscle mass and replacement with adipose tissue with a lower rate of metabolism.