Proteins Flashcards
(35 cards)
What is protein composed of
- Carbon, Hydrogen and Nitrogen atoms arranged into amino acids linked in a chain
Amino acid definition
Building blocks of proteins, each contain an amino group an acid group, a hydrogen atom and a distinctive side group attached to a central carbon atom
What is a dipeptide
2 amino acids bonded together
How many essential amino acids are there
9
What are the 9 essential amino acids
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
What makes an amino acid essential
The body either cannot make at all or cannot make in sufficient quantity to meet its needs
Non-essential amino acids definition
The body can synthesise more than half of the amino acids for itself
Conditionally essential amino acids definition
Some non-essential amino acids can become essential under special circumstances
Examples of conditionally essential amino acids (4)
- Arginine
- Tyrosine
- Glutamine
- Glycine
Functions of protein (8)
- Structural and mechanical
- Transport
- Channels and pumps
- Acid base balance
- Fluid balance
- Antibodies
- Hormones
- Enzymes
Nitrogen balance
The difference between N intake and N losses (intake – losses)
Negative nitrogen balance
More nitrogen is lost than taken in:
- Injury
- Illness
- Starvation
- Inadequate protein intake
- Overtraining
Positive nitrogen balance
Intake exceeds output:
- Infants
- Pregnant women
- Those in recovery from illness, injury or starvation
- Athletes
Demination definition
Amino acids stripped of nitrogen
What does demination produce
Ammonia released into the bloodstream
Process of demination
The liver picks up the ammonia, converts it into urea which is transported in the blood then filtered out by the kidneys
How does the body use amino acids for energy
When glucose and fatty acids are in short supply, we can use protein for energy (Gluconeogenesis)
RNI for protein
- Percentages of daily intake
- RNI = 0.75g/kgBW
- Certain populations require more
What is the RNI of protein
0.75g/kgBW
Protein quality
Depends on the amino acids that are present, but also the digestibility of the food, and the needs of the individual
Protein digestion in the mouth
Proteins are crushed and moistened by saliva in the mouth
Protein digestion in the stomach
Hydrochloric acid denatures each proteins tangled structure so that digestive enzymes can access the peptide bonds
Protein digestion in the small intestine
When polypeptides enter the small intestine, pancreatic and intestinal proteases hydrolyse them further into short peptide chains, tripeptides, dipeptides and amino acids
Absorption of protein
The cells of the small intestine absorb amino acids and have peptidase enzymes on their surfaces that split most of the dipeptides and tripeptides into single amino acids
