Effects of Starvation

Question 1

after 7-10 days without food, what 3 things start to happen to the body

Answer 1

1. decreased metabolic rate:
2. conservation of protein
3. increased fatty acid oxidation

Question 2

what are 2 examples of decreased metabolic rate when you go >7-10 days without food?

Answer 2

• decreased activity
• body temperature

Question 3

how much does muscle protein breakdown decrease after >7-10days of starvation?

Answer 3

• decrease in muscle protein breakdown from 75g to 20g per day

Question 4

how much glucose does the brain use in the fed state vs greater/after than 3 weeks of fast and what does this decrease?

Answer 4

fed state: 75%, which is completely oxidised

> 3 weeks of fast: replaces 50% of the glucose with ketones,

this decreases complete oxidation and recycles glucose via gluconeogenesis

Question 5

in starvation > 7-10 days, hwo do blood cells/renal medulla absorb glucose?

Answer 5

via anaerobic glycolysis to pyruvate and lactate

Question 6

at >7-10 days starvation, what 4 things will happen to the liver

Answer 6

• loss of mass
• decreased protein synthesis
• peri-ortal fat accumulation (fatty liver)
• hepatic insufficiency/hepatic failure

Question 7

at >7-10 days starvation, what 3 things will happen to skeletal muscle?

Answer 7

• skeletal muscle will be catabolized for gluconeogenesis, leading to decreased mass
• skeletal muscle will use ketones rather than glucose, leading to slower contractions
• skeletal muscle will have dimished function, such as decreased respiratory function in intercostal muscles, so it would be harder to breathe.

Question 8

what largely determines muscle size?

Answer 8

proteins

Question 9

what 4 things can cause decreasing protein concentration?

Answer 9

• reduction in protein synthesis alone
• increase in protein breakdown alone
• reduction in protein synthesis AND increase in protein breakdown
• Increase in protein synthesis and even higher increase in protein breakdown

Question 10

what does the effect of fasting and re-feeding depend on?

Answer 10

depneds on length of fasting period and amount of energy available from other sources (apidose tissue, glycogen)

Question 11

how much of body weight can humans lose before it is detrimental?

Answer 11

50%

Question 12

why do subjects that are most obese survive the longest in starvation?

Answer 12

because they have the largest fat reserves

Question 13

what 5 things can cause skeletal muscle atrophy and give at least 2 examples each of when they occur?

Answer 13

• immobilisation (space flight, regular immobilisation [i.e injury], physical inactivity)
• disease-related atrophy (cancer, HIV, rheumatoid arthritis, renal failure, burns, sepsis)
• Drug-related (glucocorticoids)
• Inadequate nutritional intake or digestion (starvation, protein malnutrition, impaired digestion
• Ageing

Question 14

what is the 3 step process for the degradation of a muscle sarcomere?

Answer 14

1. Calpains disassemble the sarcomere at the Z-line by digesting Z-line proteins such as nebulin and fodrin, breaking the sarcomere up into smaller pieces
2. proteins from the sarcomere like myosin and actin are ubiquitnated in an ATP-dependent reaction involving ubiquitin ligases (E1-E3)
3. myosin, actin and other proteins are then digested by the 26S proteasome, which can not digest connected proteins

Question 16

outline where cathepsins and proteases are located what what they do

Answer 16

cathepsins:
- located in organelles called lysosomes
- degrade proteins in sarcomere

proteases:
- these proteases come from mast cells (immune cells)
- they contribute to skeletal muscle breakdown