Built from
amino acids
Contain
carbon, hydrogen, oxygen, and nitrogen (amino: contains nitrogen)
Amino Acids
n = 20
- essential, non-essential (your body can make them) , conditionally essential (usually your body can make it but if your food doesn’t supply the other things necessary to create them then your body will need them in your diet)
protein structure
Amino acids bind together to create chains
Dipeptide
2 amino acids bound together
Tripeptide
3 amino acids bound together
Structure =
Function (ex. hemoglobin
Protein Functions (8)
Protein needs increase significantly with…
acute illness
Fluid and Electrolyte Balance
Proteins cannot move freely across membranes
Cells cannot make water but they can make water water attracting proteins (oncotic pressure)
When protein leaks out fluid follows leading to excess fluid in interstitial spaces = edema
Acid-Base Balance
Changes in pH levels affect proteins negatively
Albumin gathers up extra hydrogen ions (acid) if excess OR provides hydrogen ions if there are too few = buffer
Energy and Glucose (remember: without energy, cells die)
Protein Function: Turnover
The continuous breakdown and synthesis of body proteins involving the recycling of amino acids
- the balance between protein synthesis and protein degradation
Protein Function: Nitrogen Balance
Protein Digestion & Absorption: Mouth and Salivary Glands
Chewing and crushing moisten protein-rich foods and mix them with saliva to be swallowed
Protein Digestion & Absorption: Stomach
Hydrochloric acid (HCl) uncoils protein strands and activates stomach enzymes:
Protein —> Pepsin, HCl —> smaller polypeptides
Protein Digestion & Absorption: Small Intestine and Pancreas
Pancreatic and small intestinal enzymes split polypeptides further:
Poly-peptides –> pancreatic and intestinal proteases –> tripeptides, dipeptides, amino acids
Then enzymes on the surface of the small intestinal cells hydrolyze these peptides and the cells absorb them
Peptides –> intestinal tripeptidases and dipeptidases –> Amino acids (absorbed)
How much is enough?
Can you have too much?
Risks of excessive protein intakes
Vegetarianism
Various Vegetarian dietary plans
Complementary Proteins
two or more protein foods whose amino acids from one provide the missing amino acids from the other
Protein Digestibility
measure of the amount of amino acids absorbed from a given protein intake