Proteins and Amino Acids 02 24 2014 What do proteins do Build new tissue Functional unit a few to thousands amino acids o Enzymes o Hormones o Antibodies Physiology metabolism o Fluid and electrolyte balance o Acid base balance o Energy o Transportation o Blood clotting How much protein do we need The dietary Reference Intakes recommendation for protein intake depends on size and stage of growth DRI recommended intake is 8 grams per kilogram of body weight Minimum is 10 percent of total calories Athletes may need slightly more 1 0 gram per kg Classification of Amino Acids Essential AA s o Phenylaline valine tryptophan threonine isoleucine methionine histidine leucine lysine Other AA s o Alanine arginine aspagarnine aspartic acid cysteine glutamic acid glutamine glycine proline serine tyrosine selenocysteine Protein Structure The amine group links with the acidic end of the next amino acid AA with electrically charged side chains are attracted to H2O AA with neutral side chains are repelled by water seek each other Consequently proteins have very convoluted shapes Peptide Bonds chains Hemoglobin Valine Leucine Tyrosine are single amino acids with different side They can bond to form a strand of amino acids part of a protein Quaternary A heme structure holds the iron Protein Denaturation Protein structure and function are disrupted by a variety of things o Heat acid alcohol base salts Amino Acid Metabolism Carried to the liver o Used by the liver or released into the blood to be taken up by other cells Cells can then use the amino acids to o Make their proteins for their own use o Make proteins that are released into the lymph or blood for other uses When necessary body cells can use amino acids for energy Protein deficiencies Marasmus chronic inadequate food intake o Inadequate energy vitamin mineral and protein intake o Person is shriveled and lean all over Kwashiorkor o Swollen belly and skin rash are present o Severe acute malnutrition Too little protein to support body functions Malnutrition in the United States PEM is not unknown in the US where millions live on the edge of hunger Protein Quality o Inner cities US indian reservations rural areas some elderly people hungry and homeless children people suffering from anorexia nervosa people with AIDs or cancer If a diet does not contain the essential amino acids in adequate quantities protein synthesis in the body can be slowed A food that contains all nine essential amino acids is called a complete protein Most plant foods do not contain all 9 essential amino acids o Legumes are the exception notably soybeans This may have implications for vegetarians Complimentary Proteins Two or more proteins whose amino acid assortments complement each other in such a way that the essential amino acids missing from one are supplied by the other Protein Quality adequate Probably not an issue in countries where overall dietary intake is o If it is an issue its only for vegans More of an issue in countries where dietary sources of protein are limited Benefits of Vegetarian Diet chronic diseases Strong evidence links vegetarian diets with reduced incidences of o Some benefits include Less obesity Defense against certain cancers Less heart disease Less high blood pressure May help prevent diabetes osteoporosis diverticular disease gallstones and rheumatoid arthritis Are vegetarian diets healthier Some of these effects may arise more from what vegetarians include in the diet abundant fruit legumes veggies and whole grains than from what they emit A balanced adequate diet in which lean meats and seafood eggs and milk play a part in addition to fruits vegetables and whole grains can be very healthy Both meat eaters and lacto ovo vegetarians can rely on their diets during critical times of life A vegan diet can pose challenges o Meat provides abundant iron znc and vitamin b needed by everyone but in particular by pregnant women children and Both vegetarian and meat containing diets if not properly balanced adolescents can lack nutrients Poorly planned meat eater s diets may lack vitamin A vitamin C foliate and fiber among others Poorly planned vegetarian diets typically lack iron zinc calcium omega 3 fatty acids vitamin D and vitamin B Are vegetarian diets more environmentally friendly Meat industry responsible for more greenhouse gas emissions than the transportation industry Raising livestock also leads to land and water degradation due to overgrazing waste products in the environment Growing corn for feed contributes to monoculture less land to grow fruits vegetables environment expensive Meat raised locally and or organically will have lower impact on the Cows fed grass have lower impact on the environment and the nutritional content of the meat is more favorable for humans What about fruits and veggies grown far away and transported Is this better than meat raised locally Protein excess Diets high in protein rich foods o Often associated with obesity and its many accompanying o Animal protein sources in particular can be high in saturated A known contributor to atherosclerosis and heart The effect of animal protein itself on heart health is health risks fat disease uncertain Substituting plant protein for animal protein improves indicators of heart disease risk Animals fed experimentally high protein diets often develop enlarged kidneys or livers In humans a high protein diet worsens existing kidney problems and may accelerate a decline in only mildly impaired kidneys o One of the most effective treatments for people with established kidney problems is to reduce protein intakes to slow the progression of their disease o Peotein of high biological value Protein excess Protein intake and calcium o Evidence is mixed about whether high intakes of protein from animal sources especially when accompanied by very low calcium and low fruit and vegetable intakes can accelerate adult bone loss o No doubt exists that feeding purified protein to human subjects causes calcium to be spilled from the urine o Diets high in protein particularly animal protein correlate with a higher incidence of hip fractures in some populations However the reverse may be true in malnourished elderly individuals in whom protein deficiency and hip fracture often occur together Restoring dietary protein and giving certain calcium and vitamin D supplements can improve bone status High protein diets Forces body to use proteins for energy Tissue proteins and dietary proteins Limit
View Full Document
Unlocking...