Protein

Question 1

Functions

Answer 1

Carry and store materials
Provide strength
Some require minerals for activation

Can be denatured by heat or pH

Building materials for growth and maintenance- matrix of collagen is filled with minerals to provide strength to bones and teeth. Replaces tissues including skin etc. 
Enzymes 
Hormones 
Regulators of fluid balance- plasma protein attracts water, maintain the volume of body fluids to prevent oeadema, maintain the composition of body fluids 
Acid base regulators 
Transporters 
Antibodies
Source of energy

Question 2

Digestion and absorption of protein

Answer 2

Stomach acid (HCl) and enzymes facilitate the digestion of protein. It is first denatured, then broken down to polypeptides(by the enzyme pepsin).
The smaller intestine continues to break down protein down, protease hydrolysed proteins into short peptide chains called olgiopeptides, which contain four to nine amino acids. Peptidases split proteins into amino acids.
Protein absorbed:
- used by intestinal cells for energy or synthesis of necessary compounds.
- transported to the liver
- taking enzyme supplements or consuming predigesting proteins is unnecessary.

Send to the liver and undergoes anabolism (protein and AA synthesis) or catabolism, where nitrogen is a byproduct and released in urea, and the remainder is stores as glucose, fatty acids or ketones.

Question 3

Anabolism of protein

Answer 3

If all AA available then complete protein synthesis.

If not all aa present, release of incomplete polypeptide chains, degradation and no protein formed.

Question 4

Nutrients and gene expression

Answer 4

Cells regulate gene expression to make the type of protein needed for that cells.
Epigenetics refers to a nutrients ability to activate or silence genes without interfering with the genetic sequence.

Question 5

Protein metabolism

Answer 5

Protein turnover is the continual making and breaking down of protein. Amino acid pool is the supply of amino acids that are available.

Amino acids from food- exogenous
Amino acids from within body- endogenous

Zero nitrogen balance is nitrogen equilibrium, when input = output
Positive means nitrogen consumed more than excreted
Neg is more nitrogen excreted

There is no readily available storage form of protein, tissue is broken down for energy if needed.

Deamination AA- nitrogen containing a groups are removed, ammonia is released into bloodstream, ammonia is converted into urea by the liver, kidneys filter urea out of the blood. Excess protein is deamination and converted into fat, nitrogen excreted.

Question 6

Protein in foods

Answer 6

Protein quality- digestibility depends on proteins food source, good source include animal proteins, plant proteins and soy and legumes.
Cells must dismantle to produce essential amino acids if they are not provided in the diet.
Limiting amino acids are those essential amino acids that are supplied in less than the amount needed to support protein synthesis.

Complementary proteins- combining plant foods that together contain all the essential amino acids

Question 7

Classifying dietary proteins

Answer 7

High quality- complete AA profile and 90-99% digestibility (animal food sources)

Low quality protein- incomplete AA profile and 70-90% digestibility (plant food sources)

Measurement:
Biological value
-% nitrogen retained by the body
- >70% high BV
Net protein utilisation (NPU)
- Amt of protein actually available to the body, considers digestibility
Protein digestibility corrected amino acid score is a measure of protein quality, compares amino acid composition of a protein to human AA requirements, adjusts for digestibility

Question 8

RI of protein

Answer 8

Protein energy malnutrition (PEM)
Classifying PEM
- chronic PEM and acute PEM
- maramus- severe deprivation of food over time, chronic starvation, common in poverty stricken regions
- kwashiorkor- sudden food deprivation with oedema abdomen, protein deficiency
- infections- lack of antibodies, fever, fluid imbalance, anemia

Question 9

Health effects of high protein diets

Answer 9

Cancer
Osteoporosis
Weight control
Kidney disease

Question 10

RDI for protein

Answer 10

0.75g/kg for women
0.84g/kg for men
25% protein as energy is UL

Question 11

Amino acids

Answer 11

Building blocks of protein.
20 common with 9 essential.
Non-essential also called dispensable amino acids, ones which the body can create.

Essential also called indispensable, must be supplied by the foods people consume.

Linked by peptide bonds in condensation reactions.