Protein

isoleucine, leucine, methionine, phenylalanine, tryptophan, valine, threonine, lysine, histidine

• deficiency of essential amino acids or some other metabolic problems and diseases can turn a nonessential amino acid into an essential one

primary structure of a protein: linear chain of amino acids

2-dimension conformation: helical information, through H-bonds

tertiary structure: folding of the secondary structures as well as bonds and covalent linkages between amino acids

• each has a common structure: central carbon linked to an amino group, to a carboxylic acid group, to hydrogen and to an R group

fish, meat, dairy, nuts, beans (legumes)

0,8 g/ kg of body weight

• during periods of body growth: 1.5 g/ kg of body weight for a 6-month infant

AMDR: 10-35%

measure of the extent to which the dietary protein meets the body’s needs, and can be obtained and used by the body

• to meed body needs the product must contain all the essential amino acids in the necessarx wuantities

• to avoid deficiency of essential amino acids

• two or more foods together meet the body’s needs for essential amino acids

• e.g.: rice (low in lysine but rich in methionine and cysteine) + peas (rich in lysine but low in methionine and cysteine)

• or: rice + black beans

• oats + black beans

• oats with peas

1. stomach acid: catalyzed by pepsin enzyme breaks down dietary protein

2. pancreatic enzymes (proteases, peptidases) secreted into the small intestine, breakdown polypeptides and oligopeptide into smaller pieces

3. on surface of the cells lining the small intestine other peptidases continue the digestion process: breaking down oligopeptide into dipeptides and tripeptides into amino acids

4. enterocytes internalize single amino acids, dipeptides and tripeptides => further breakdown

5. dietary amino acids are secreted into bloodstream and available to cells through the body for protein synthesis

6. Amino acids are going to amino acid pools of cells, and can be used by the cells for building body proteins

7. or: they can be used for energy (gluconeogenesis)

• protein structure is important for its function!

• enzymatic and hormonal activities

• strucutre

• growth

• maintenance of the body

• immune activities

• blood clotting

• acid base

• fluid balance in the body

• muscle contraction and body movement

• transport of nutrients such as vitamins, mienrals, lipids in the bloodstream

• Source of energy for cells

mutation is an abnormal base in the DNA Sequence => transcription and translation of the wrong DNA sequence leads to mutant or abnormal protein which may not fold properly and may not have normal function

1. excessive calcium loss from the body

2. potential stress on the kidneys, especially for long term diabetics and in cases where people take protein and or amino acids supplements (as opposed to obtaining all protein from foods)

3. over long term: increased risk of some cardiovascular or other chronic diseases if the high protein intake involves high meat animal product consumption

1. increase bone loss and loss of muscle

2. in developing countries: severe protein-energy malnutrition

   1. kwashiorkor: severe protein deficiency coupled with a mild energy deficiency: there is some fat storage in the body from carbs + fats

   2. marasmus: severe deficiency of energy and protein; body is emaciated and fat stores depleted

   Both! impair body growth in children and increase risk of infections and of a range of other health problems

3. Phenylketonuria (PKU): genetic mutations. result in the loss of function of an enzyme (phenylalanine hydroxylase) that normally catalyzes the conversion of phenylalanine to tyrosine)

   1. tyrosine becomes an essential amino acid

   2. abnormal enzyme structures: cant efficiently catalyze the conversion of phenylalanine to tyrosine => phenylalanine and toxic metabolites build up in the body

   3. if a child with it don’t get a phenylalanine-reduced diet: damage of brain and intellectual disability and epileptic seizures

• genetic mutations that result in an abnormal hemoglobin protein

• mutant hemoglobin doesn’t adopt a normal protein structure => abnormal shape

• health problems: lysis or breakage of red blood cells, obstruction of blood vessels by the sickle-shaped red blood cells

• severe protein-energy malnutrition in developing countries

• severe protein deficiency coupled with a mild energy deficiency, because there is some fat storage left from fats and carbohydrates

• increases risk of infections and other health problems

• impair body growth

-severe protein-energy malnutrition in developing countries

• severe protein and severe energy deficiency

• impair body growth in children and increase risk of infections and other health problems

• genetic mutation

• result in loss of enzyme function of phenylalanine hydroxylase

  • normally catalyzes conversion of phenylalanine to tyrosine

• because of the loss of function => tyrosine becomes an essential amino acid

• Abnormal enzyme structures: can’t efficiently catalyze the conversion of phenylalanine to tyrosine

  • phenylalanine and toxic metabolites build up in the body

• if children with phenylketonuria don’t get a phenylalanine-reduced diet, they evolve damage their brain and intellectual disabilities and epileptic seizures

1. partial protein digestion due to stomach acid and pepsin enzyme

2. pancreatic peptidases and proteases secreted into the small intestine break down the polypeptides and oligopeptides

3. cell peptidases in small intestine (enterocyte cell surface) continue the breakdown to amino acids

4. enterocytes take the amino acids and small peptides and internalize them

5. amino acids are transported throughout the body via the bloodstream

• Digestible indispensable Amino Acid Score (DIAAS)

• Protein digestibility-corrected amino acid score (PDCAAS)

• both for ranking protein quality!