Flashcards in Nutrition Chapter 7 Deck (25):
What is the structure of an amino acid?
an amino group, an acid group, a hydrogen, a side chain (different for each amino acid)
What are the 9 essential amino acids?
histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
What is an essential amino acid?
amino acids that must be obtained from food because the body can't make them
What is transamination?
transfer of an amino group from 1 amino acid to a carbon skeleton to form a new amino acid
What is deamination?
cleaving off an amino group, amino group joins urea, carbon skeleton used for other things
How are protein synthesized?
amino acids are linked together through a peptide bond (condensation reaction)
amino group of one AA attaches to the acid group of another AA
How does protein synthesis happen?
occurs in the ribosomes
transcription - mRNA formed from DNA
translation - mRNA used to synthesis polypeptide chains
How are proteins organized?
primary, secondary, tertiary, quaternary structure
folding determines the overall shape and therefore function of the protein.
How is protein denatured?
exposure to acid, base, heat, enzymes (pepsin in the stomach)
What is BV?
biological value, measure of how efficiently the absorbed food protein in converted to tissue protein
nitrogen retained/nitrogen absorbed = bv
What is PER?
protein efficiency ration, measure of food protein quality
weight gain (g)/protein consumed = PER
What is CS?
mg of limiting AA per g of protein/mg of limiting AA per g protein of an "ideal" protein
What is PDCAAS?
protein digestibility corrected amino acid score
most widely used measure of quality
CS x digestibility
What is protein quality evaluation?
ability of a protein to support body growth and maintenance
only applies when amount consumed is less than or equal to the body's needs
What is the recommended intake of protein?
8-10% of kcal
enough to maintain nitrogen balance
replace what is lost
RDA for adults = .8g / kg body weight (56 g for men and 46 g for women - avg. weight)
What happens to excess protein?
it can't be stored as protein, carbon skeletons used for energy or stored as fat
How is protein digested in the stomach?
HCl denatures the protein, the enzyme pepsin uses hydrolysis reactions to start breaking the long polypeptide chains into shorter chains
What is pepsin?
pepsin is an enzyme that is stored as pepsinogen in the cells of the stomach, its release is controlled by the hormone gastrin
How is protein digested in the SI?
walls of the SI release the hormones secretin and CCK, this stimulates the pancreas to release proteases that digest the chains into individual AAs or short chains, peptidases break down short chains
How is protein absorbed?
active transport, travel to the liver via the portal vein where they join the amino acid pool
What are the functions of protein?
produce vital body structures
maintain fluid balance
contribute to immune function
synthesize hormones, enzymes and neurotransmitters
What is PEM?
protein energy malnutrition
usually occurs as marasmus or kwashiorkor
What is kwashiorkor?
acute development, usually when a new child is born and the older one no longer gets nursed or an underlying disease or infection
causes edema, fatty liver, growth impairment, moderate weight loss
What is marasmus?
develops slowly, severe deficiency of energy
causes severe weight loss, wasting and stunting