protein Flashcards
protein digestion in the mouth
protein are crushed and moistened
protein digestion in the stomach
hydrolysis of protein by hydrochorlic acid denaturation
- pepsin initiates protein digestion by cleaving proteins into small polypeptides and amino acid
protein digestion in the SM
pancreatic and intestinal protease hydrolyze theses further into short chains, dipeptides, and AAs
- peptidase further breaks any chains into individual AA
protein absorption
specific carriers transports amino acids into cells
- once inside cells, AA can be used for energy or to synthesize compounds
- If AA are not used by the cells, they are transported to the liver
protein metabolism
-Proteins are continually being made and
broken down: turnover
-Breakdown releases AAs, forming an AA
pool
-These AAs can be used to make body
proteins or other N containing
compounds, or the C backbone can be
used for energy (gluconeogenesis)
-Turnover and nitrogen balance go hand in
hand, usually synthesis balances with
degradation, and intake from food
balances with N excretion in urine, feces, sweat
protein breakdown
-protein in your body is always breaking down and being recycled into new proteins
-the body does not store protein as it does with fat and glucose/glycogen
-AA in the pool are used, turned over stored and excreted rather fast
dietary protein intake
AMDR= 10-35%
2-3 serving
1/4 plate
RDA is 0.8/kg athletes needs 1-2g/kg
intake recommendation
-Choose lean meats and poultry and
prepare with little to no added sodium or
saturated fat
-Choose beans, peas, lentils, tofu, nuts and
seeds more often
-Choose unsweetened lower fat dairy
products
-Choose unsweetened fortified low sodium
soy beverages
*careful when judging protein intake as a
percentage of energy intake, consider the
number of grams and compare it with RDA
who needs more protein
-Pregnant women
-Training athletes - leucine!!
-Growing kids
-Sick or trauma patients
-Wound healing
-Low calorie diets (15% more)
-Vegetarians (10% more)
conditionally essential
Sometimes a non-essential AA becomes
essential under special circumstances
If the diet fails to supply enough or if the
body cannot make the conversion for some
reason (genetic condition, disease), then that
AA becomes conditionally essential
Phenylalanine -> tyrosine cannot happen
with PKU, so tyrosine becomes conditionally
essential
limiting amino acid
-The body can make all non-essential amino
acids given nitrogen and fragments from
carbohydrates and energy
-There are 9 amino acids that the body
cannot make either at all or in sufficient
quantities
-These must be supplied by the diet
denaturation
- secondary and tertiary structures get destroyed but primary structure is retained
-chemical action, heat, or agitation= renders the molecule nonfunctional
-cooking eggs and meats, digestion
(despite the change in structure, all AA are still present = nutritionally beneficial
Protein
Synthesis
The sequence of AA determines the shape
which supports a certain protein function
if you mix up the order of adding ingredients
or in copying the recipe, the product will not
turn out
Quaternary
Two or more tertiary polypeptides
mixed together
Tertiary
Coiled chain now all tangled up, more twists and folds resulting
from attractions or repulsions between AAs and surrounding fluids
Hydrophilic side ends up on the outer surface, and hydrophobic
groups tuck themselves inside
primary
Amino acid chain; AA put together in chain with
peptide bonds
Secondary
Amino acid chain is now coiled
Determined by weak electrical attractions within the chain
These folds and twists gives proteins strength and rigidity
Acid Base Balance
Blood likes to be at a certain pH
Proteins have a negative charge on their surface
So they attract H+ ions to decrease acidity = acting as
buffers
They release the H+ to blood if alkaline
Extremes: acidosis or alkalosis denatures protein
rendering it nonfunctional…. ex. hemoglobin cannot
carry O2
Proteins are specific
If a foreign protein enters the body it is attacked
The body learns how to make antibodies (made of protein) to
attack specific protein invaders… allergies
Essential Amino Acids
We have 20 AA, 9 of which are essential
These 20 AA in various combinations make all body proteins
Conditional or Dispensable
The body can make these amino acids out of other amino acids
Conditional means that a certain amino acid depends on another
essential for it to be made
protein function
Source of glucose = energy
Transport: lipoproteins transport across cell
membranes
Energy: 4kcal/g; goal is to not use it for energy
due to all other functions
muscle contraction
Functions: Regulatory
Hormones: chemical messengers Enzymes: facilitating chemical reactions
Acid base balance Tissue & body fluid balance - proteins attract
water
Immunological: antibody synthesis
Functions:
Structure
Repair
Growth
Tissue health & maintenance
Development
muscles, blood, organs, skin, hair, nails, bones
