Proteins Flashcards
Protein Structure
Primary
Secondary
Tertiary
Quaternary
Proteins
Comprised of amino acids (AA)
Amino group contains nitrogen
Side chain determines properties
Amino Acids (AA)
Dispensable and indispensable amino acids.
-humans can synthesize 11
-9 others are indispensable amino acids.
How are proteins made?
Proteins are created through gene expression.
AA are linked together during translation to form proteins.
Our physiologic needs impact gene expression.
-down-regulation of one thing that is not needed
-up-regulation of other things that are more important
Up-Regulation (Physiological Adaptation)
Muscle hypertrophy, bone growth, increased capillary density, increase HDL production, increased muscle LPLase, and increased myoglobin.
Down-Regulation (Physiological Adaptation)
Sarcopenia (age-related muscle atrophy), insulin receptors (type II diabetes), testosterone and steroids, and inactivity/unloading.
Supplying AAs for Proteins
Complete proteins have all 9 indispensable AAs.
Incomplete proteins do not have all 9 indispensable AAs.
Protein synthesis can be slowed if indispensable AAs are not available (rare for North America).
Quality of Proteins
Amount of amino acids
-complete protein has all 9 indispensable AAs
-incomplete protein deficient in one or more indispensable AA
Digestibility
-protein digestibility corrected amino acids score (PDCAAS)
PDCAAS
Required for food labeling.
Based on AA requirement of 2-5 year olds.
Compares AA composition of food compared to what out bodies required.
Represents the most limiting indispensable AA.
-AA in the smallest/lowest supply for a food
-about 90% animal/soy proteins
-about 70-80% legumes
-60-90% for veggies and grains
Determined by fecal measure.
Like GI, PDCAAS changes based on food preparations and combinations.
Digestibility Indispensable Amino Acids (DIAAs)
The new kid on the block.
Focused on the digestibility of indispensable AAs.
Measured in the ileum, not the feces.
Created for food labels.
Starting to switch over from PDCAAS
PDCAAS vs DIAAs
PDCAAs
-fecal digestibility
-crude protein digestibility
-1 reference = children 2-5 years
DIAAs
-illeal digestibility
-individual AA digestibility
-3 references = birth to 6 months, 6 months to 3 yrs, older than 3 yrs
Neither account for special populations for pregnant and lactating, elderly, and malnourished populations
The bottom line with protein…
Protein quality (ie. amount and digestibility) applies when protein is in short supply.
Not a problem for some populations like North America.
Whey Protein
Complete protein from dairy.
Source of BCAAs.
Complementary Proteins
Mutual supplementation involves combining incomplete protein sources to make a complete protein.
One study found this could be done just by eating.
-don’t have to find complimentary combination if you eat enough calories in a day of whole foods
Protein Digestion
Mouth = proteins crushed, moistened
Stomach = HCl denatures proteins, pepsin cleaves into polypeptides
Pancreas = proteases create olgio-, tri-, dipeptides, and amino acids.
Microvilli = peptidases create AAs
-cells below microvilli turnover every three days = means if you are low on protein, body can use these cells as proteins known as labile protein reserve
AA/Peptide Absorption
AAs and peptides (di- and tri-) are absorbed.
AAs can compete for absorption sites.
60% of AAs absorbed as peptides.
Peptides are broken into AAs in enterocyte.
AA Absorption
Many AA are sodium dependent
-sodium concentration being lower in cell allows sodium and AA to move into cell, then must pump sodium back to maintain lower concentration in cell
Peptide Absorption
Di- and tripeptides are co-transported with hydrogen.
-hydrogen concentration lower in cell allows peptide to move across into the cell, then hydrogen pumped back out of cell while sodium moves into cell, then sodium must go back out of the cell by allowing potassium into the cell
AA Transport
Through hepatic portal system to liver
AA in the Liver
Adjusts the rate of AA metabolism according to the needs of the body
AA Reserves
Circulating amino acid pool = blood and lymph
Labile protein reserve = liver and visceral tissue
This means that lacking protein consumption one day won’t negatively affect the average person
AA Fate
Synthesis of new protein.
Direct oxidation as fuel/energy.
Conversion to glucose (gluconeogenesis).
Fluid/electrolyte balance.
Acid-base balance.
Protein Intakes for Adults
Most adults = 0.8 g/kg
Entomophagy
Means the eating of insects
Vegetarianism
Lower intake of fat, cholesterol, and total energy (don’t consume as much food because have greater volume).
Increased fibre and plant sterol consumption.
Increased phytochemical and antioxidant consumption.
Health Benefits of Vegetarianism
Lower blood pressure.
Reduce risk of heart disease.
Reduce risk of some types of cancer.
Fewer digestive problems.
Why does vegetarianism reduce digestive problems?
Due to gut bacteria being supported by fibre in vegetables.
-buffer gets bigger between microvilli and contents in the small intestine which keeps the microvilli strong (stops leaky gut syndrome which damages the walls of the small intestine due to lack of fibre)
Why vegetarianism?
Health benefits, ecological reasons, religious reasons, ethical reasons, and concerns over food safety
Challenges of Vegetarianism
Vegetarian diets can be low in vitamin B12, vitamin D, riboflavin, iron, calcium, zinc
Freegans
Eat discarded food by understanding the best before dates and when food is actually bad.
Considerations for a Vegetarian Diet
Vegetarians must plan a balanced and adequate diet, and includes complementary proteins or use soy products as a complete protein source.
Vegetarians can use a vegetarian food guide pyramid to design their diet.
