Lecture 6 Flashcards
functions of proteins
- all biological enzymes are made of protein
- makes hormones (like insulin and glucagon
- actin and myosin
- collagen
- all antibodies
- carriers of fatty acids, oxygen, iron, vit A, copper
- in blood
- energy source when carbs are limited
What are the 9 essential amino acids
- leucine
- isoleucine
- valine
- tryptophan
- threonine
- histidine
- methionine
- lysine
- phenylalanine
Rationale for glutamine supplements
- appears to be conditionally essential when the body is exposed to metabolic stress or trauma
- muscle glutamine concentrations associated with rates of MPS in animal models
- prolonged exercise and periods of heavy training are associated with a decrease in the plasma glutamine concentration
- using the idea that
Goal for glutamine supplements
to replenish stores in order to increase muscle mass accretion and enhance immune function after intense and repetitive resistance exercise
What happens in the stomach to proteins?
- HCl from cells in the stomach unfolds proteins
- pepsinogen becomes pepsin with the help of HCl
- pepsin digests protein into large peptide fragments
What happens in the small intestine to proteins
- CCK triggers the pancreas to secrete digestive enzymes once digestion products leave the stomach
- digestive enzymes are activated and continue to break down peptides into di/tri and free a.a’s which are taken up by intestinal cells
Whey
- rapidly digested and results in quick rise in plasma AA’s
- stimulates protein synthesis to a greater extent than casein
Casein
- forms a curd and takes longer to empty from the stomach
- casein reduces muscle protein breakdown better than whey protein
Soy protein
- digested faster than whole milk protein which contains whey and casein
- overall more like a fast protein but slower than whey
What is protein turnover
- constant flux between making new muscle and breaking down muscle protein
- goal is for increasing muscle size is for muscle protein synthesis
What are the 3 branched chain amino acids
- leucine
- isoleucine
- valine
HMB
- derived from breakdown of leucine
- hypothesized to inhibit muscle protein breakdown and increase muscle synthesis especially with resistance training
- 3g/day may be effective and more benefits with creatine
- HMB may provide greater benefit to untrained people who start weight training compared with previously conditioned athletes
Complete protein
contains all essential AA’s in amounts that meet or exceed the amounts needed by humans
ex. animal proteins or soy protein
Incomplete protein
-too low in one or more of the essential AAs to support human growth and development
cannot serve as a sole source of protein in the diet
Fatigue
inability to maintain a desired level of intensity
Central Fatigue Hypothesis from Newsholme
- fatigue during endurance exercise is related to an over-abundance of serotonin in the brain
- serotonin causes drowsiness and fatigue
- serotonin is synthesized from 5-OH tryptamine which is derived from tryptophan
Central Fatigue Theory 1
- during exercise BCAA’s are taken up by muscle and oxidized for energy
- when muscle glycogen stores are depleted BCAA uptake is accelerated
- greater uptake of BCAA’s late in exercise leads to lower blood BCAA levels levels and an increased ratio of tryptophan/BCAA
- as a result tryptophan enters the brain in greater amounts and more serotonin produciton
Central Fatigue Theory II
- as exercise progresses more free fatty acids are liberated from triglyceride stores and blood level of FFA goes up
- FFA’s and tryptophan are both transported in the blood albumen
- as FFA levels goes up more tryptophan is displaced from binding sites to albumen and the “free” tryptophan concentration rises leaving even more tryptophan available to enter the brain
Central Fatigue Theory III
- increased tryptophan into brain=more serotonin=central fatigue=stop exercise
- used as a rationale for development and sale of BCAA supplements
- large doses of BCAA touted as a means to “bump” tryptophan off carriers decrease tryptophan and serotonin levels in the brain and prevent fatigue
RDA for protein
0.8g/kg/body weight/day
Protein recommendations for endurance athletes
1.2-1.4g/kg/day
Protein recommendations for strength athletes
1.2-1.7g/kg/day
Protein recommendations for vegetarian athletes
1.3-1.8g/kg/day
Downside to high protein diets
- increase urinary output due to high protein load may increase chances of dehydration
- diets high in protein may lack appropriate amounts of carbs, fibre and some vitamins and minerals (which could impair exercise performance)
- excessively fatty protein sources could increase risk of CVD
- protein rich diets are high in phosphorus which can be harmful to individuals with kidney disease
- may increase calcium loss in urine
