Exam 3 Flashcards
What is the basic structure of an amino acid?
What are the essential amino acids?
PVT TIM HALL
Phenylalanine
Tryptophan
Histidine
Valine
Isoleucine
(Arginine)
Threonine
Methionine
Leucine
Lysine
The other 11 are non-essential amino acids, what does that mean?
They can be synthesized by the body and we don’t have to provide it ourselves.
What is a complete protein?
Complete proteins contain all 9 essential amino acids in the required ratios.
What is an incomplete protein?
An incomplete protein is missing one or more essential amino acids.
Where do you find both complete and incomplete proteins in the diet?
Sources of complete proteins are from animal sources (meat, dairy, eggs).
Plant based proteins are typically incomplete proteins. Multiple sources of plant proteins should be combined to make a complete protein.
Protein recommendations for vegetarians and vegans
It’s recommended that they consume ~10% more protein than estimated requirements to ensure adequate essential amino acid intake and to account for the lower digestibility of plant proteins.
What are good protein sources for vegetarians and vegans?
- Black beans, chickpeas and other legumes
- Nuts and seeds
- Milk and dairy (for vegetarians)
- Quinoa
- Tempeh and Tofu
What is Nitrogen balance?
Nitrogen balance is a method to measure whole body protein balance.
Protein balance = synthesis – degradation
Nitrogen balance = nitrogen intake (protein) – nitrogen excretion (urea in urine)
What do the different protein balances mean?
When individuals are in protein balance (or nitrogen balance), there is no overall net gain or loss of protein.
Positive balance indicates protein accumulation, usually as a result of building muscle mass.
Negative balance indicates protein loss, which typically only occurs under sustained protein deficient diets and severe illness.
What is nitrogen balance during exercise like?
when beginning an exercise program, individuals will go into negative protein balance for the first 1-2 weeks. After this time period, nitrogen balance can be maintained without increasing protein intake.
Increases over the RDA will allow athletes to maintain positive nitrogen balance and build muscle mass.
Protein AMDR
The AMDR for protein is 10-35% of total caloric intake.
Protein RDA for sedentary adults
The RDA for protein for healthy, sedentary adults is 0.8 g/kg.
Protein recommendation for endurance athletes?
The recommendation for endurance athletes is 1.2-2.0 g/kg.
Protein recommendation for strength athletes?
The recommendation for strength athletes is 1.6-2.0 g/kg.
Do wesern diets supply enough protein?
Typically, western diets supply an abundance of high quality protein and deficiency is relatively uncommon. The general population has an intake substantially higher than the RDA.
Protein intake and aging
Aging adults also benefit from a higher protein intake than the RDA. High levels of protein stimulate muscle protein synthesis and help combat the muscle mass loss associated with aging.
Protein intake during weight loss correlation?
There is good evidence that a higher protein intake (on the order of a strength athlete’s recommendation) during weight loss will aid in retaining lean body mass.
How is protein digested? (Step by step)
Mechanical digestion begins in the mouth with chewing.
Chemical digestion begins in the stomach. HCl denatures proteins- breaking down the 3D structure. Pepsin breaks down proteins into smaller fragments (peptides).
In the small intestine, pancreatic enzymes called peptidases break down peptides to small strings of 1-3 amino acids.
Amino acids are absorbed into the intestinal cell and then the blood through transporters.
Amino acids are absorbed by cells and used for synthesizing new proteins, oxidation for energy or use in other metabolic intermediates. Some amino acids can be modified to form other (non-essential) amino acids when needed.
Amino acid transport into muscle cells is greatly enhanced by insulin.
What are some of the functions of protein other than maintaining and building muscle mass?
Enzymes used during chemical reactions
Component of the immune system
Involved in fluid, electrolyte, and acid/base balance
Many hormones are either proteins or transported through protein carriers
Provide structure (bones, teeth, etc.) and required for maintenance of tissues and organs.
Can be oxidized for energy
How are we able to measure protein metabolism?
This is done by infusing a known amount of amino acids with stable isotope tracers into the subject. The stable isotopes allow researchers to track protein synthesis, degradation, and oxidation.
Which amino acids can be used as stable isotope tracers? Why?
Only essential amino acids (EAA) can be used as stable isotope tracers because non-essential amino acids can be synthesized. This would result in an unknown portion of amino acids coming from the stable isotope and some coming from synthesis. By using only essential amino acids, the researcher knows the level of amino acid pools (only what was given to the subject).
Since branched chain amino acids are preferentially oxidized, the amino acid with the stable isotope tracer should be an essential amino acid and a branched chain amino acid.
What does the rate of appearance and disappearance correlate to?
In the blood, the rate of disappearance of the tracer indicates protein synthesis while the rate of appearance indicates degradation.
What aspect of protein metabolism can we measure through CO2 production?
Oxidation of proteins can also be measured through CO2 production.
Protein intake before exercise
The high CHO snack/meal consumed before exercise can contain some protein. However, there is no pre-exercise protein recommendations.
There is no good evidence of a change in muscle protein synthesis when protein is consumed prior to exercise.
There is no good evidence to support acute protein intake enhancing performance.
Protein intake during exercise?
It is not typically recommended to take protein during exercise.
One exception is during long (2 hours or more) intermittent resistant exercise, protein ingestion will facilitate muscle protein synthesis.
A second exception is for ultra-endurance events. Protein intake in this case may enhance recovery.
When is it most critical to consume protein? Why?
Post-Exercise. This is the most critical time for protein intake. Even if the athlete is not focusing on increasing muscle mass, post exercise protein intake is still important. A protein + CHO drink or meal is most effective for maximal glycogen replenishing and muscle protein synthesis (MPS)
How much protein should be consumed post-exercise and within what time frame?
Until recently, it has been recommended to consume 0.25-0.3g/kg of high quality protein within 2 hours of exercise to maximize MPS (for most people, this translates to 15-25 g). However, recent studies have shown that the effect of exercise on MPS lasts about 24 hours, so it is probably not necessary to eat within 2 hours of exercise.
What type of protein is recommended post-exercise?
High quality protein with high leucine levels is recommended. Leucine is important because it is a potent stimulator of MPS.
Quickly digesting protein is also ideal- whey protein digests quickly and drinks are better than solid food.
Chocolate milk is a good recovery drink because it is high in CHO, digests quickly, and has high leucine content.
Other protein powders/supplements meeting these requirements are also good recovery drinks, although they can quickly become very pricey.
When is muscle protein synthesis increased optimally?
MPS is increased optimally when 0.25-0.3 g/kg of high quality are consumed during frequent meals/snacks that total the RDA. This recommendation translates to 15-25 g per meal for most individuals.
What stimulates Muscle Protein Synthesis? (MPS)
muscle contraction, resistance exercise, insulin, testosterone, growth hormone, essential amino acids (especially leucine), and adequate caloric intake.
What stimulates muscle protein breakdown? (MBS)
intense or prolonged exercise, when beginning an exercise program (first 4-10 days), glucagon, cortisol, and inflammation factors.
Difference in MPS & MBS in sedentary vs active situation?
In a sedentary situation, the MPS roughly equals MPB.
Under resistance exercise conditions, MPS increases and there is net protein gain. MPS will remain elevated for 24 hours post exercise.
Arginine and citrulline as ergogenic aids
Claims to be a vasodilator and enhance blood flow to muscles. This is only effective in cardiac patients. Healthy individuals do not benefit from supplementation.
Arginine, lysine and ornithine as ergogenic aids
Claims to increase growth hormone and is not found to be effective.
Branched chain amino acids as ergogenic aids
Claims to spare glycogen and decrease muscle degradation, especially during endurance activities. There is some evidence of enhanced alertness and decreased perceived exertion during prolonged exercise. These data are very mixed and not yet conclusive. Branched chain amino acids are not necessary as long as the athlete has sufficient carbohydrate available.
Carnitine as an ergogenic aid
May be effective in increasing fat oxidation
β-alanine as an ergogenic aid
May enhance training capacity, specifically in short duration high intensity exercises. Increases intracellular acid-base buffering capacity
What are the risks associated with low protein intake?
individuals who restrict caloric intake are at risk of inadequate protein intake. Very low protein diets can result in muscle wasting and weakness.
What are the risks associated with high protein intake?
high protein intake is not generally harmful in healthy individuals. Protein eaten in excess of protein synthesis needs will be oxidized for energy.
What takes place during the oxidation of amino acids?
Amino acids are oxidized through a variety of pathways. Eventually, they will all be converted to acetyl CoA and enter the TCA cycle.
Branched chain amino acids are preferentially oxidized- meaning they are oxidized first for energy. Leucine, isoleucine and valine are the three branched chain amino acids.
Are there any specific recommendations for vitamins for athletes?
Highly active individuals may have higher vitamin needs, but there are currently no recommendations specific to athletes.
Most athletes are not deficient in vitamins because they have relatively high kcal intake.
Athletes who are restricting calories are at risk for low vitamin intake.
If an athlete is deficient in a vitamin, he/she will likely experience decreased performance. Resolving this deficiency will aid the athlete’s performance.
How is fluid distributed throughout the body?
Isotonic solution
The concentration of solutes is equal inside the cell (intracellular fluid) and outside the cell (extracellular fluid). Water moves equally in and out of the barrier (cell membrane). This is the normal situation inside our bodies.
Hypotonic solution
The concertation of solutes outside the cell is lower than the inside. The fluid outside the cell is hypotonic in reference to the fluid inside the cell. This makes water flow into the cell. This can happen in the blood by overhydrating during exercise
Hypertonic solution
The concentration of solutes outside the cell is higher than the inside. Water flows out of the cell. This can happen in the blood during severe dehydration
Mechanism of ADH
Due to heat and or exercise, excessive water is lost through sweat.
This water loss comes from the blood, creating a hypertonic solution (higher solute/electrolyte concentration) in the blood.
The hypothalamus detects this change in blood osmolality and releases ADH.
ADH travels to the kidney and stimulates increased water reabsorption.
Reabsorbed water from the kidney returns to the blood.
Blood osmolality returns to normal. Body water and blood volume are maintained.
