Protein

Question 1

How many essential amino acids are there?

Answer 1

9

Question 2

Functions of proteins

Answer 2

Cell growth and maintenance
Enzymes
Transporters
Antibodies
Energy

Question 3

Recommended intake as a percentage of total energy intake

Answer 3

15-25%

Question 4

RDI amount

Answer 4

Females 0.74g/kg

Males 0.85g/kg

Question 5

Digestibility of animal, plant and soy/legume protein

Answer 5

Animal- 90-99%
Plant 70-90%
Soy/legume 90%

Question 6

Explain nitrogen balance

Answer 6

Nitrogen is the element we get from protein. We are in nitrogen balance when intake equals expenditure.

Question 7

How much protein is lost daily

Answer 7

3g nitrogen lost in urine. If no intake obligatory loss leads to muscle wastage

Question 8

Storage of excess amino acids

Answer 8

Cannot be stored readily so are deaminated to give ammonia and a carbon skeleton

Question 9

Ammonia conversion

Answer 9

Ammonia is converted to urea, uric acid and creatinine in the liver and then excreted via the kidneys. Increased serum of these indicates renal pathology.

Question 10

Name and describe two protein energy deficiencies

Answer 10

Kwashiorkor- protein intake minimal but total calorie intake ok. Rapid onset and acute protein energy malnutrition. Oedema, fat liver, growth 60-80% age
Marasmus- frank starvation. Severe weight loss, no oedema, no fatty liver. Growth

Question 11

First three (pre duodenal) steps of protein digestion.

Answer 11

1. Chewing/crushing
2. Denaturing of proteins by Hcl
3. Pepsinogen (chief cells), converted to pepsin by HCl, breaks down proteins to polypeptides and some free aa.

Question 12

Duodenal steps of protein digestion

Answer 12

1. chemo and mechano nerve receptors detect the fatty acids and proteins and signal the pancreas to release endopeptidases that include proelastase, trypsinogen, chromotrypisinogen and carboxypeptidase A and B
2. The inactive trypsinogen is activated to trypsin by enteropeptidases. Trypsin the activates the other endopeptidases
3. the activated endopeptidases break the polypeptides into dipeptides and tripeptides
4. The di and tripeptides are broken down to aa by dipeptidases, tripeptidases and aminopeptidases released by enteroendocrine cells.

Question 13

How do the aa enter the bloodstream?

Answer 13

Facilitated diffusion

Question 14

Hormonal regulators:

Gastrin

Answer 14

Released by G cells in the pyloric antrum. Stimulates ECL cells to produce histamine which in turn stimulates parietal cells to make HCl

Question 15

Hormonal regulators: Cholecystokinins

Answer 15

Released by enteroendocrine I cells in the duodenum. Stimulate the release of bile and pancreatic enzymes

Question 16

Hormonal regulators: Secretin

Answer 16

Released by enteroendocrine S cells in the duodenum. Inhibits gastric acid production and stimulates HCO3- secretion.