Proteins Flashcards
Protein make up how much body mass (%)
13 – 15% of body mass
What are five Functions of Proteins?
Make-up of Structures:
e.g. collagen, keratin in nails and hair.
Transport of substances across cell membranes
Hormones to allow chemical signals. Contraction using muscle fibres. Enzymes: catalyse cellular reactions
What’s the difference between Essential & Non-essential Amino Acids?
Essential
Cannot be synthesised in the body and they must be provided in the diet to maintain balance.
Non-essential amino acids
Can be synthesised in the body from metabolic intermediates by means of transamination as long as there is adequate nutrition.
How many amino acids are there?
20 in total
9 Essential
11 Non-Essential
At whole body level approximately what is protein turnover?
300g per day
Protein turnover rate in tissues
• Muscle % per day?
• Liver % per day?
- Muscle 1.15% per day
* Liver 12.1% per day
Protein Requirements
Intake approximately 1.4-2g per kg of body weight
How much protein post exercise is necessary
> 20 g high-quality protein post exercise is unnecessary
Protein Quality
The biological value (BV) of a protein food is determined by its content of EAAs.
biological value is the proportion of absorbed protein retained in the body.
What does DIASS stand for?
Digestible Indispensable Amino Acid Score
How many EAA exist in human body and how do you get them?
9 and Food.
Where does translation take place?
In the cytosol (ribosomes)
What does transfer RNA do?
AAs to ribosomes
What are the two groups proteins are composed into?
An amino group and a carboxyl group
Nitrogen Balance
• Nitrogen balance exists when nitrogen intake (protein) equals nitrogen excretion
NB=Nt -Nu -Nf -Ns =0
- Nt = total nitrogen intake from food
- Nu = nitrogen in urine
- Nf = nitrogen in faeces
- Ns = nitrogen in sweat
Metabolic pathways for amino acids
https://www.youtube.com/watch?v=l0V-Xmps1mE
What happens during the process of transamination?
Transfer of one amino group from one molecule to another
What does gluconeogenesis mean?
Formation of glucose from non-carbohydrate sources
Ammonia is toxic and can be excreted after it has been converted to?
Urea
The Urea Cycle
Disposes of excess nitrogen
AAs from protein breakdown form ammonia during the process of deamination.
This is toxic therefore excess nitrogen is excreted as urea in urine.
Approximately 60-90% of nitrogen in urine is in the form of urea.
Urea containing Nitrogen is excreted in urine at a rate of approximately 25-30g per day whilst the rate is higher in individuals with high protein intake.
Protein catabolism contributes (%)
Contributes only 2-5% of the body’s energy requirement or approximately 3-6% during prolonged exercise.
The glucose-alanine cycle
https://www.youtube.com/watch?v=V9CSKTFyaYw
What four steps make up Amino acid metabolism
- Protein synthesis
- Converted to other glucose and AAs (transamination)
- Lipids formation
- Glycogen formation
