Flashcards in Chapter Six - Protein Deck (51):
What is Protein? (3)
1. Component of every living cell
2. Made of amino acids
3. Every amino acid contains nitrogen (proteins are about 16% nitrogen by weight)
Calculation for protein intake
Nitrogen intake (g) X 6.25 = protein intake (g)
What is an amino group?
True or False: all amino acids have the same side chain.
False, the side chain is unique to each amino acid.
What is the side chain for glycine?
What is the side chain for methionine?
CH2 - CH2 - S - CH3
What is the side chain for phenylalanine?
CH2 - ring structure
What is PKU?
Phenylketonuria, people with this cannot normally metabolize phenylalanine and it accumulates in the body and results in damage to the CNS. Phenylalanine is found in aspartame and nutrasweet.
What does phenylalanine break down to in normal metabolism?
What does phenylalanine break down to in people with PKU?
What are the essential amino acids?
Methionine, phenylalanine, isoleucine, leucine, lysine, histidine, threonine, tryptophan, valine.
What reaction causes a peptide bond?
Dehydration reaction (takes water out).
What is the primary structure of a protein?
The linear sequence of amino acids.
What is the secondary structure of a protein?
Shapes within parts of the protein. (Helical, beta pleated sheet, linear)
What is the tertiary structure of a protein?
Final 3D structure of the protein, determined by the amino acid sequence of the protein.
What is critical to the function of a protein?
The protein's shape, altering the amino acid sequence can change the protein function dramatically.
How many amino acid chains are in insulin?
Two amino acid chains. There are only 3 amino acids that make the difference between the insulin of a pig, human, and cow.
What is denaturation?
Changing the shape of the protein by altering the bonds of the protein through heat or chemicals, making the protein change shape and loose its function.
What does a change in a single amino acid in the hemoglobin protein result in?
Sickle cell anemia.
What foods provide most of our protein?
Cereal products, dairy products, meats.
What proteins help regulate body processes?
Some hormones (e.g. insulin), enzymes (e.g. lipase, amylase, trypsin), neurotransmitters (e.g. serotonin).
What proteins help with growth and repair of tissues?
Muscle proteins (collagen, actin and myosin [muscle contraction and relaxation]).
What is normal turnover?
The breakdown and replacement of all body tissues/organs.
What proteins help with immune defence?
What proteins help with transportation?
Hemoglobin (oxygen), transferrin (blood transport protein for iron).
Where does most of protein digestion start?
The stomach, with hydrochloric acid denaturing proteins. Pepsin is an active enzyme that breaks apart proteins into peptide.
What pre-enzymes come from the pancreas?
Trypsinogen and chymotrypsinogen.
What active enzymes come from the small intestine?
Intestinal enterokinase, which activates trypsinogen.
What does Trypsin do?
Activates various intestinal pre-peptidases and chymotrypsinogen, and works together with chymotrypsin to cleave peptides into smaller peptides.
What pre-enzymes does the small intestine secrete?
Various intestinal pre-peptidases, activated into various peptidases.
What is the end result of the small intestine digestion?
The absorption of amino acids (mostly di- and tri-peptides) into the mucosa and then into the portal vein and onto the liver.
What do amino acids do in the liver?
Synthesis of amino acids into required body proteins (enzymes), immediately used for energy by the liver (if needed), or converted to glucose stores (glycogen) or fat stores in adipose tissue. The rest go to the bloodstream.
What is an amino acid pool?
Not the storage of amino acids, contains the amino acids from the liver and body tissue breakdown. This pool lasts for a few hours at most. The amino acids are used for the synthesis of body proteins that are required. Excess amino acids are broken down into free ammonia and the carbon-skeleton.
What is deanimation?
The breakdown of amino acids, separating the amino group (NH2) and turning it into ammonia and then urea (in the liver) which is taken to the kidneys for excretion.
What happens to the carbon skeleton?
1. Converted to glucose (gluconeogenesis) if there is not enough dietary carbohydrates.
2. Used as energy directly
3. Fat synthesis by the liver
What is protein quality determined by?
The digestibility of protein, the types of the amino acids in the protein, and the proportion of those amino acids.
What is a good quality protein?
It has to be completely digestible (animal proteins over plant proteins [except soybeans]). It has to contain all the essential amino acids in proportions similar to that required by the body.
What are complementary proteins?
Proteins that contain high levels of different essential amino acids, making sure people get the correct proportions of amino acids.
What is the PDCAAS?
Pro digestibility Corrected Amino Acid Score.
What is the calculation for the PDCAAS?
Amino acid score x protein digestibility.
What has the highest protein digestibility?
Isolated soy protein, casein, egg whites, beef [Most to least].
What amino acids are grains low in?
What amino acids are legumes low in?
Who needs a positive nitrogen balance?
Periods of growth (infants, children, teens), pregnancy, athletic training (if LBM is being added), or repairing (broken bones).
What is the AMDR of proteins?
10%-35% of kcal.
What is the RDA for proteins for adults?
What are the protein requirements for endurance athletes?
What are the protein requirements for power athletes?
What concerns are there with absorption and transport of amino acid supplements in the GI tract and brain?
Overpowering transporters, making a risk of amino acid imbalance.
Which are absorbed better: di-and-tri-peptides or individual amino acids?