Protein and Amino acid Flashcards
protein accounts for how much of our total body mass?
15-16%
structural proteins:
keratin in skin and hair
protein enzymes:
glycolysis, citric acid cycle
transport proteins:
glucose transporter, GLUT4, lipoprotein
protective proteins:
antibodies
Functional proteins:
actin and myosin in muscles
signalling proteins:
hormones, insulin and glucagon
what are all proteins composed of?
individual amino acids building blocks
Amino acids are nitrogen containing compounds. T or F
T
The 4th group is unique for each amino acid, why?
has implications for protein structure and function
how many amino acids are commonly found in proteins?
20
how are amino acids connected?
connected enzymatically through a peptide bond
how are proteins created through DNA?
DNA is converted to RNA, read by a ribosome that connects amino acids together to form the protein
what can happen to the protein if there is a change in the sequence of DNA?
dramatic changes on the proteins function
ex. altered polypeptide shape in red blood cells causes sicle cell disease
what three ways are proteins broken down?
- Mechanical (chewing)
- Chemically (HCL in the stomach)
- Enzymatically (stomach and pancreatic enzymes)
what are single amino acids and small peptides absorbed by?
mucosal cells of the small intestine
once the amino acids and peptides are absorbed by the mucosal cells, what happens next?
peptides are broken down further and amino acids are transported to the liver
how does the body recognize allergies?
Dietary proteins may be absorbed without being completely digested
The immune system may recognize these dietary proteins as a foreign antigen and mount an immune response
what are the 3 steps in the body for an allergic reaction?
- First time, immune system is stimulated (sensitization)
- recognition as a foreign substance
- An immune response is mounted and an allergic reaction occurs
what is the avg half life of a protein
~ 7 hours
essential amino acids:
histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine
non essential amino acids:
arginine, cysteine (cystine), glutamine, glycine, proline, tyrosine, alanine, asparagine, aspartic acid (aspartate), serine
can proteins be broken down for energy?
yes
can protein be stored for later?
yes
what are the steps to storing protein?
- first step is removing the nitrogen group (deamination)
- afterwards, the amino acid can enter the metabolic cycles to produce energy OR for storage as acetyl-CoA
the liver processes amino acids, the nitrogen group is removed which creates what?
ammonia which is toxic
what is ammonia combined with?
carbon dioxide
what does carbon dioxide and ammonia generate?
urea
how is urea excreted?
travels to the kidney and is excreted in the urine
what is Phenylketonuria (PKU)?
Genetic disease where the gene for PAH is mutated and produces a non functional enzyme
what is one of the common mutations for classic PKU?
a change from G to A at in the mRNA for the PAH gene
what protein does Phenylketonuria (PKU)
produce?
truncated protein which has lost of 99% of its activity
how can PKU be managed?
limiting the dietary intake of phenylalanine
how can brain damage be prevented with PKU?
must be detected early
are infants screened for PKU?
yes, at birth
why must aspartame be avoided for people with PKU?
artificial sweetener that is made from aspartate and phenylalanine
what are the most common sources of animal proteins in Canada ?
Meat, fish, eggs and dairy products
High intake of animal protein is associated with what?
high incidences of cardiovascular mortality
what are plant sources of protein?
legumes, vegetables and grains
- usually less expensive
what food is a good source of both protein and fiber while containing less saturated fat?
beans
High intake of plant protein is associated with?
decreased incidences of cardiovascular mortality
what are complete protein sources?
Animal proteins, they contain all the amino acids
what are incomplete protein sources? And why are they incomplete?
Plant proteins (apart from soy protein), still contain all the amino acids, but they may not be in the same proportions as human proteins
what are complementing protein sources?
plants containing complementary amino acids to provide all essential amino acids
how is protein quality assessed?
using a calculation called the DIAAS- Digestible Indispensable Amino Acid Score
what does the DIAAS- Digestible Indispensable Amino Acid Score assess in protein?
accounts for the amino acids composition of a food but also the amount of amino acids that are absorbed
what food group tends to have a higher score on the DIAAS?
meat
the recommendation dietary allowance (RDA) for protein is based on what?
based on weight and growth needs
when are protein and amino acid supplements worth it?
If dietary intake is deficient in protein
when are protein and amino acid supplements not worth it?
If protein is being consumed in the diet
Protein & Amino Acid Supplements will not help with immunity or muscle growth unless:
dietary intake was insufficient
when are plant based milk a good alternative for adults?
those who may be lactose an tolerant
should plant based milk be used as a replacement for human milk or infant formula?
NO
what is Kwashiorkor
severe protein malnutrition and bilateral extremity swelling
how does edema occur with Kwashiorkor?
without adequate protein, oncotic pull decreases and fluid remains in the tissues (edema)
