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Nutrition Concepts !Class Notes : October 7, 2013 October 7, 2013 !Protein Synthesis DNA makes RNA makes protein !RNA is the copy of the code mRNA- messenger RNA (copy of DNA)!tRNA- transfer RNA(vehicles for amino acids that are used to make a protein)!Ribosome- protein making machine mRNA is the supervisor in the ribosome that tells to put in which order to make a protein • DNA makes RNA makes PROTEIN • Step 1: Transcription • DNA makes mRNA!• (mRNA attaches to a ribosome) • Step 2: Translation • mRNA specifies the sequence of the amino acids Protein Synthesis- Review • The code to make a protein is carried by a strand of mRNA. • The process by which mRNA is made from a DNA template is transcription. • A ribosome is a structure upon which amino acids are sequenced into proteins. • The process where the ordering, or sequencing of amino acids by the mRNA is called translation. Protein Expression (DNA makes RNA makes Protein) • Gene expression definitions* • Process by which a cell converts the genetic !code into RNA and protein • When a cell makes a protein under direction of a gene • Cells regulate gene expression based on: • Type of protein needed!• How much, how fast • Nutrigenomics: the foods we eat influence gene expression Date October 7, 2013 Class Nutrition Concepts Page OneRoles of Proteins structural materials, enzymes, hormones, regulators of fluid balance, etc. Proteins as Enzymes •Enzymes are: proteins that facilitate chemical reactions!• Catalysts, but are not changed in the process • Some:!Are catabolic enzymes – break down • i.e. lipase!Are anabolic enzymes – build up • i.e. building of bones !Transform – i.e. amino acids into glucose to energy during starvation (red blood cells and brains can only use glucose) Proteins as Hormones • Some hormones are proteins • Hormones are messengers • Released in response to changes/challenges • Transported in blood to target tissues!• Example: • Insulin is released from the PANCREAS in response to HIGH BLOOD SUGAR. The insulin sends the message to increase uptake of glucose from the blood to glycogen storage in the liver. • Glucagon is released from the PANCREAS in response to LOW BLOOD SUGAR. The glucagon sends the message to increase release of glucose to the blood from glycogen storage in the liver. Proteins as Regulators of Fluid Balance • Proteins help maintain fluid balance – the proper types and amounts of fluid in each compartment of the body • Normally proteins are found in cells, not in between (interstitial spaces) •Reasons proteins leak out: (ALL LOW PROTEIN)- after leak out, attract water 1. Excessive protein losses from inflammation or critical illness 2. inadequate protein synthesis (liver disease) 3. inadequate dietary intake of protein!- Proteins attracts water, so leaking of proteins into spaces between cells causes edema/swelling !!Page 2Proteins as buffers • Acid solution contains abundance of H, which have a positive charge • Proteins have a negative charge and attract or release H to maintain pH and prevent: • Denaturation of proteins in: • Acidosis - higher than normal acidity in blood and !body fluids • Alkalosis - higher-than-normal alkalinity (base) in the blood and body fluids !Proteins as antibodies • Proteins as antibodies defend the body against disease • Antibodies = army • large proteins of the blood and body fluids!that the immune system makes in response to attack by foreign invaders • Antibodies have specificity • Immunity – memory!!Roles of Proteins - Review • Proteins can act as hormones, which act as a messenger. • Body proteins attract water (causing edema/swelling) and hydrogen, thus acting as a buffer. This actions prevents acidosis and alkalosis, and the resulting denaturation of protein.!• Proteins can act as transporters, carrying proteins through the body or across cell membrane, in which case they act as pumps. An example of this is the transport of sodium and potassium to maintain the appropriate concentrations of these minerals inside and outside of the cell. • The body produces giant protein molecules, called antibodies to inactivate/fight against foreign invaders, or antigens.!!Review of Protein Metabolism • In each cell, proteins are continuously made & broken down -> • Protein Turnover - degradation and synthesis of protein Page 3• Releases amino acids (what that does/product of protein turnover) Preview of Protein Metabolism • Amino acid pool (very short term storage) !• Supply of amino acids from:! Broken down protein •Dietary protein!• Remains fairly constant (if not in diet, body can go to that pool) !• Used for:! Protein synthesis! Energy – nitrogen removed from amino acids, can make glucose from the amino acids and use for energy • Nitrogen balance (amino group and that nitrogen in all proteins) - for adults • The amount of nitrogen consumed as compared with the amount of !nitrogen excreted in a given period of time (times of growth) • Zero nitrogen balance or nitrogen equilibrium !• Nitrogen in = nitrogen out •Positive nitrogen balance !• Nitrogen intake > Nitrogen excretion (take in more nitrogen than excreting, using that nitrogen -body says I need more protein to exercise/in pregnancy) !• Examples: Infants, pregnant women, children, athletes, adolescents, someone recovering from protein deficiency •Negative nitrogen balance !• Nitrogen intake < Nitrogen excretion !• Examples: burn victims, stress, injuries !Proteins are used to make other compounds such as...!Neurotransmitters (epinephrine) !Melanin (brown pigment)!Thyroxin (helps balance our metabolic rate)!Niacin and Serotonin • Protein can be broken down for energy & glucose • No storage site for protein (we have to go to the muscle, lean body tissue) !• Carbohydrates – liver glycogen !• Fats – Triglycerides in adipose tissue • Starvation over time !• Body breaks down lean body tissue (muscle) and fat • Adequate intake of carbohydrates and fats is protein sparing. Page 4• Proteins (in excess) can be used to make fat (high protein diets can still contribute to weight gain by being turned into fat) • When energy and protein exceed needs and !carbohydrate intake is adequate • Can contribute to weight gain • Deaminating amino acids (can make the nonessential from the essential (?)) ! •


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UD NTDT 200 - Protein Synthesis

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