Exercise and Starvation B&B

Question 1

what is the use of creatine kinase in muscles?

Answer 1

creatine is converted to phosphocreatine in muscles via creatinine kinase —> this can serve as a phosphate donor to convert ADP to ATP

source of quick ATP during exercise, since the TCA cycle is slow

Question 2

creatine vs creatinine

Answer 2

creatine is converted to phosphocreatine via creatinine kinase in muscles, as a source of phosphate for ADP—>ATP conversion

in plasma, creatine spontaneously converts to creatinine, which is excreted by kidneys - proportional to muscle mass

Question 3

the activity of which enzymes does calcium enhance during exercise in the following pathways?
a. glycogen breakdown
b. TCA cycle

Answer 3

a. glycogen breakdown - glycogen phosphokinase A (phosphorylates glycogen phosphorylase)

b. TCA cycle - isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase

Question 4

describe the effects of glucagon and epinephrine on fatty acid metabolism

Answer 4

inhibit acetyl CoA carboxylase, which converts acetyl CoA to malonyl CoA (ABC enzyme, requires biotin)

this causes levels of malonyl CoA to fall, which is an inhibitor of beta oxidation (inhibits carnitine palmoitoyl transferase 1) —> therefore beta oxidation is disinhibited

Question 5

what is the dominant source of glucose between meals?

Answer 5

glycogen breakdown

(gluconeogensis becomes more contributory once glycogen stores run out, ~24hours)

Question 6

how does the alanine cycle produce glucose?

Answer 6

in muscle, NH4+ is combined with glutamate to make alanine, which travels to liver

in liver, alanine combines with alpha-KG to make glutamate (+ NH4+) and pyruvate

pyruvate is used to make glucose via gluconeogenesis, which goes back to muscle

Question 7

how does the Cori cycle contribute to gluconeogenesis?

Answer 7

in muscle, pyruvate (from glycolysis) is converted to lactate, which travels to liver

in liver, lactate is converted back to pyruvate, which is converted to glucose via gluconeogenesis

glucose travels back to muscle

Question 8

describe how glycerol contributes to gluconeogensis

Answer 8

glycerol (from fatty acid breakdown) is converted to glycerol-3-phosphate via glycerol kinase

this is then converted to dihydroxyacetone phosphate, which is a gluconeogenesis intermediate

Question 9

what kind of fatty acids can be used to produce glucose via gluconeogenesis? describe how

Answer 9

odd chain FA broken down to 3C propionyl-CoA, which can be converted to succinyl CoA (TCA cycle) via propionyl-CoA carboxylase (ABC enzyme, requires biotin)

[even chain FA are completely consumed via beta oxidation]

Question 10

how does Kwashiorkor present?

Answer 10

form of malnutrition due to inadequate protein intake

hypoalbuminemia —> edema, swollen legs and abdomen

Question 11

how does Marasmus present?

Answer 11

form of malnutrition due to inadequate energy intake (insufficient total calories)

—> muscle and fat wasting

Question 12

in which clinical scenario does hypoketotic hypoglycemia occur?

Answer 12

occurs with mitochondrial disorders

loss of beta oxidation = loss of ketones

loss of gluconeogensis (cannot convert pyruvate to oxaloacetate)

Question 13

after glycogen stores are depleted (~24h), the liver produces glucose via gluconeogenesis from ___, ____, and _____

Answer 13

amino acids, glycerol, lactate

Question 14

how do amino acids become substrates for gluconeogenesis?

Answer 14

1. in muscle, alanine transferase transfers amino groups of amino acids to pyruvate to form alanine
2. alanine travels to liver and is broken down again to pyruvate
3. pyruvate is converted to glucose via gluconeogenesis

Question 15

what type of adipose tissue is associated with an increased risk for cardiovascular disease and diabetes? (more than the other type)

Answer 15

visceral adipose and “apple shape” body - linked to insulin resistance and CV disease

[subcutaneous adipose and “pear shape” body are not as associated]