Lecture 4 - Proteins Flashcards
What is EAR?
estimated average requirment - where the intake at which the risk of inadequacy is 50 %
What is RDA?
Recommended dietary allowance - intake at which the risk of inadequacy is 2-3%
What is AI?
Adequate intake - does not bear a predictable relation to the EAR and RDA. Based on the estimate of nutrient intake in healthy people.
What is UL?
Tolerable upper level intake - intake above the UL, higher risk of adverse effects.
What is the goal of having protein in the diet?
To replace the amino acids that are degraded in the body.
Unlike fats and CHO, there is a …… for protein in the diet
requirement
Functions of glycine?
- ) aminolaevulinic acid, a key intermediate in heme synthesis is made from glycine and succinyl CoA
- ) Required for detoxification reactions in the liver
- ) Principal inhibitory transmitter in the brain stem and spinal cord
- ) Occurs at every 3rd AA residue in collagen (the most abundant protein in the body)
Function of tryptophan?
Precursor of the NT serotonin
Function of Histidine?
decarboxylated to histamine which is used in an immune response or the physiological function of teh gut.
Function of arginine?
precursor of NO and creatine
Function of lysine ?
lysine residue interacts with glutamine when factor x111a converts low tensile fibrin polymer into a high tensile strength clot.
Functions of glutamine?
- ) substrate for protein synthesis
- ) contols acid base balance
- ) Substrate for hepatic ureagenesis
- ) Substrate for hepatic gluconeogenesis
- ) Fuel for intestinal enterocytes
- ) Ammonia scavenger
- ) Substrate for citrulline and arginine synthesis
- ) Nitrogen donor
- )Nitrogen transport
- ) Stimulates glycogen syntheses
- ) Arginine NO metabolism
What are the determinants of the nutritional quality of protein?
- ) content of indispensable AAs
2. ) extent to which the indispensable AAs are available to host metabolism
What are the classes of protein?
1st class - animal proteins
2nd class - plant proteins
How do we measure the quality of proteins?
PDCAAS - based on the profile of AAs and digestibility of the protein.
PDCAAS of different foods (Egg, milk, beef/chicken/fish, gelatin, soybean, kidney beans, whole wheat bread)?
Egg - 1
Milk - 1
Beef/fish/poultry - 0.82-0.92
gelatin - 0.08 - totally deficient in tryptophan and deficient in isoleucine, threonine
soybean - 1
kidney beans - 0.68 - deficient in methionine but rich in lysine
whole weat bread - 0.40 - deficient in lysine but rich in methionine
What if nitrogen intake is more than excretion or the oppsoite?
more than excretion - tissue gorwth and total body protein increases
less than excretion - total body protein decreases
how much protein lost in fracture of femur, muscle wound, 35 % burns, gastrectomy, typhoid fever?
fracture of femur - 900 g muscle wound - 1350-1900 g 35 % burns - 1400-1650 g gastrectomy - 645-850 g typhoid fever - 685 g
What are the body requirements for protein?
usually 0.8g per kg for adults and for athletes 1 g /kg
children - 2g per kg per day
whatis kwashiorkor?
Pure protein deficiency in children
what is maramus?
energy deficiency where there is a reduced number of T lymphocytes and so there are defects in the generation of phagocytic cells and production of immunoglobulins. Many die from secondary infectin rather than starvation.
Where does the most common protein energy malabsorption occur in the USA?
In hospitals after a response to infection, trauma or surgery. There is accelerated rate of lipolysis, proteolysis and gluconeogenesis. The net result is that there is low serum albumin or decreased cellular immunity.
What can increased protein intake result in?
increased protein breakdown products like urea. Since there is more urea it has to be eliminated by the kidneys. So high protein diets increase water loss and can cause problems if the kidneys cannot concentrate urine.
What is the problem with taking supplements of one kind of amino acid like arginine?
They all use the same transport systems so when one amino acid is taken up, another amino acid will have its absorption slowed down. This is a problem for people who use supplements like arginine. Where it shares the transport system with lysine and it upsets the AA balance in the body.
What can cause a protein allergy?
When a protein in the diet is absorbed without being fully digested.
What are the essential amino acids?
9 of them
- ) Histidine
- ) Esoleucine
- ) Leucine
- ) Lysine
- ) Methionine
- ) Phenylalanine
- ) Threonine
- ) Tryptophan
- ) Valine
In infants arginine is also essential
What are the essential precursors and for what essential amino acids?
Cysteine - methionine (precursor)
Tyrosine - phenylalanine (precursor)
What are the non essential amino acids?
Alanine
Aspartate
Glutamate
What are the semi-essential amino acids?
Arginine Asparagine Glutamine Glycine Proline Serine
Alaine comes from pyruvate
Aspartate from oxaloacetate
Glutamate from alpha-KG
