protein digestion 1 WF

Question 1

nitrogen balance key points?

Answer 1

body protein continually turned over
broken down into amino acids to be used for:
-reconversion to body protein
-synthesise other compounds
-energy production (particularly in starvation) to glucose, ketone bodies

Question 2

recommended daily protein intake per kg body weight in different age groups?

Answer 2

highest in babies, slowly decreases as age increases - plateaus in adulthood

Question 3

what can cause increase in daily protein intake?

Answer 3

nursing (as a mother)
athletes

Question 4

nutritional value of protein - how is this measured?

Answer 4

measured in net protein utilization (NPU)
a measure of the ability of a protein to sustain growth

fractional incorporation of the amino acids into body protein

weight of amino acids incorporated into protein divided by weight of amino acids supplied in the diet

Question 5

what protein sources have the highest NPU values?

Answer 5

human milk (95%)
hens egg (87%)
cows milk (81%)
veg sources have lower NPU values

Question 6

essential and non-essential amino acids?

Answer 6

essential - cannot be synthesized in the body
non-essential - can be synthesized from other amino acids in the diet

Question 7

essential amino acids?

Answer 7

isoleucine
leucine
lysine
methionine
phenylalanine
threonine
tryptophan
valine

Question 8

metabolic classification of aminoacids

Answer 8

glucogenic, ketogenic, or both
essential and non essential

Question 9

essential amino acid content of vegetables? what does this mean for vegetarians/vegans?

Answer 9

varies in different veg, so if veggie/vegan make sure you vary your veg intake.

Question 10

what is Kwashiorkor? symptoms

Answer 10

protein malnutrition but adequate energy intake

swollen belly due to large liver
oedema due to albumin deficiency
muscle wasting
diarrhoea

Question 11

what is Marasmus?

Answer 11

body weight less than 60% of expected value
inadequate intake of protein and anergy (calorie intake?)

Question 12

positive nitrogen balance?

Answer 12

growth, pregnancy
excretion less than intake due to more protein synthesis than degradation

Question 13

negative nitrogen balance - protein deprivation?

Answer 13

insufficient dietary protein
protein breakdown and excretion continues

Question 14

negative protein balance - essential amino acid deficiency?

Answer 14

protein synthesis won’t proceed as it should
breakdown exceeds synthesis

Question 15

negative nitrogen balance - trauma, disease?

Answer 15

hormonal changes mean protein is broken down faster than it is synthesised

Question 16

half-lives of proteins?

Answer 16

insulin ~mins
intestinal proteins 1-2 days
albumin 20 days
haemoglobin 120 days
collagen months

Question 17

degradation of extracellular proteins?

Answer 17

protein ready for degradation, binds to receptor and taken up by endocytosis into endosome.
fuse with lysosomes (degradative enzymes eg caspases, low pH).
degrade captured protein, amino acids liberated into the cell. membrane returns to the surface with the receptors.

Question 18

degradation of intracellular proteins?

Answer 18

small protein called ubiquitin attaches to target protein, acts as label for degradation
degradation carried out by proteasome. ubiquitin spared and reused.

Question 19

STOP