Protein in Health and Disease Flashcards
How many amino acids emerged from biosynthetic pathways?
10
Explain protein turnover
It is the process by which cells produce proteins that are needed and dissemble proteins that are not used.
How many grams of protein a day and adult makes and degrades?
About 250 g
Essential amino acids must:
Be consumed in a diet
Non-essential amino acids may:
Be synthesised in the body.
Conditionally essential amino acids:
If diet provides inadequate amounts of precursors, can become essential
What amino acids are essential for children?
Arginine, histidine and cysteine
Complete protein:
Contains all essential aa
Incomplete protein:
Lacks at least one essential aa
List the non-essential amino acids
Alanine
Asparagine
Aspartate
Glutamate
Serine
List the conditionally essential amino acids
Arginine
Cysteine
Glutamine
Glycine
Proline
Tyrosine
List the essential amino acids
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
What is the recommended intake of protein for sedentary adults?
0.75g/kg/day
What are the key factors to assess dietary protein quality?
Digestibility and ability to provide the essential amino acids
Examples of a combination of foods for protein complementary
Milk and grains
Milk and legumes
Grains and legumes
What is Protein Efficiency Ratio (PER)?
Determines protein quality by measuring animal growth.
Computed value compared to a standard value of 2.5, the value corresponding to casein protein’s effect on growth.
Any value >2.5 indicates an excellent protein source.
PER = gain in body mass (g) protein intake (g)
Explain Biological Value to asses protein quality
Biological Value.
Measures the nitrogen retained in the human body from the test food, which is theoretically taken up by tissues and used. It cannot be measured directly. Measures the amount of excreted nitrogen from the test diet.
List 7 protein sources and their biological value
Eggs 100
Fish meal 92
Beef 78
Milk 78
Wheat 60
Corn 54
Wheat Gluten 40
Explain Protein Digestibility Corrected Amino Acid Score (PDCAAS)
Adopted by WHO 1989. A measure of a protein’s digestibility and its ability to provide adequate levels of essential amino acids for human needs. The test protein is compared to a standard amino acid profile. Scores from 0-1, with a score of 1.0 indicating maximum amino acid digestibility.
Based on the essential requirements of a pre-school-age child.
Explain the different scores of DIAAS
> 100 = Excellent quality
75-99 = Good quality
<74 = Poor quality
Facts about High Fibre
High fibre may help reduce serum cholesterol and prevent heart disease. It also aids digestion and prevents disorders of the GI tract. Fibre interferes with the absorption of bile in the intestines, so it is excreted instead - therefore, the liver has to make more bile salts and requires LDL cholesterol, so it is removed from the blood to make more bile salts.
Nutritional advantages of protein foods of animals over those of vegetable origin
Vitamin B12, Iron and Retinol
Protein requirements in infancy and childhood
0-6m = 2g/kg/day
6m-7y = 1.6g/kg/day
7-14y= 1g/kg/day
>14y = 0.75g/kg/day
Estimated loss of lean body mass between 35 - 70 years
20-25%
Ideal protein requirements for the elderly
1.0 to 1.3 g/kg/day dietary protein combined with twice-weekly progressive resistance exercise
Which amino acid appears to play an important role in the prevention of sarcopenia?
Leucine
Which patients need higher protein intake?
burn patients; their protein oxidation rates are 50% higher
1.5 to 2.0 g/kg
Which diet results in less proteolysis and more improvement in lean body mass?
High carbohydrate, high protein, low-fat diet
Recommendation for red meat intake
no more than 70g/day
How does meat increase cancer risk?
Haem forms N-nitroso compounds in the gut, damaging the gut lining.
Processed meat contains chemicals that generate N-nitroso compounds, e.g. nitrite preserves. Celery juice/salt is high in nitrates.
Cooking meat at high temp creates chemicals in meat that can increase cancer risk.
Eating red meat causes 13% of bowel cancer and 1.5% of UK cancers.
Explain how excess protein may affect kidney function
Increased protein increases urinary nitrogen.
It may increase the glomerular filtration rate (GFR), which is the rate at which plasma is filtered from capillaries into Bowman’s capsule. High GFR may increase pressure in kidneys - structural damage
Statements about conditionally essential amino acids
They may be essential in some populations and non-essential in other populations.
Whether or not amino acid is considered conditionally essential can depend on the life stage.
