Nutrition 2360 Nutr 2360
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This 9 page Class Notes was uploaded by KiaraMValentino on Thursday February 25, 2016. The Class Notes belongs to Nutr 2360 at Texas State University taught by Hannah Thornton in Spring 2016. Since its upload, it has received 30 views. For similar materials see Basic Nutrition in Nutrition and Food Sciences at Texas State University.
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Date Created: 02/25/16
Protein- Exam Two Structure of proteins Contains- hydrogen, carbon, oxygen, NITROGEN. Basic Unit- Amino Acids Amino Acids- building blocks for protein synthesis. Amino Acids Are supplied by protein containing foods and cell synthesis. Composed of: Nitrogen group (amino) Acid group (carboxyl) Hydrogen Side Chain (R) Makes it Unique. Non-essential amino acids- CAN be produced by the body. “dispensable.” Essential amino acids- CANNOT be produced by the body. Must be consumed in diet. “indispensable.” Conditionally essential amino acids - Essential during infancy, disease or trauma. These are amino acids that you cannot get enough of. Essential amino acids- histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine. These have a LONG preserved life. Non essential amino acids- alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine. Conditionally essential amino acids Phenylketonuria (PKU)- a genetic disorder where the body lacks the enzyme phenylalanine hydroxylase to convert to tyrosine. So, can’t produce tyrosine which becomes an essential amino acid. People with this disorder has to eat PARTICULAR pr otein in their diet. Complete Vs. Incomplete Complete proteins- All essential amino acids are present in very ADEQUATE amounts. Source: animal proteins (not gelatin) Incomplete proteins- INADEQUATE amounts of 1 or more essential amino acids. Source: plant proteins and gelatin Complementary proteins- Combines incomplete proteins to deliver ALL the essential amino acids. Example: legumes and grains (beans and rice) This is how vegetarians survive. Complementary proteins 1. Food- Legumes (peanuts, dry beans) a. Primary amino acid- methionine and tryptophan i. Creates a complete protein by being combined with- GRAINS, NUTS or SEEDS. 1. Complementary food proteins combinations- i. Hummus and pita bread ii. Bean Burrito 2. Food- Nuts and Seeds (cashews, walnuts, al monds, sunflower.) a. Primary amino acid- lysine i. Creates a complete protein by being combined with- LEGUMES. 1. Complementary food proteins- i. Vegetarian chili with kidney beans and cashews. 3. Food- Grains (wheat, rice, oats, corn) a. Primary amino acid- lysine i. Creates a complete protein by being combined with- LEGUMES 1. Complementary food proteins- i. Red beans and rice ii. Lentil soup and cornbread. Vegetarian diet TYPES: Vegan- NO animal products at all Lacto vegetarians- milk is OK, NO meat or eggs. Lacto ovo vegetarians- Milk and eggs OK, NO meat. CONCERNS: Nutrients- B12, calcium, iron, zinc, vitamin D, High Quality protein, riboflavin, omega 3 Fatty Acids. Focuses special concern on infants and children. PROS: Lower risk of- CVD, obesity, HTN (high blood pressure), cancer. Higher consumption of- fiber, potassium, magnesium, folate, antioxidants. Lower consumption of-cholesterol, saturated fat. CONS: Requires preparation and planning. Sources of protein Dietary protein In north America- 70% supplied by ANIMAL products. Worldwide- 35% of protein from animals. 65% from plants. Body proteins there is NO “storage form” of protein in the body. They are broken down and used to meet the needs of your body. Amino Acid Pool in cells Has protein turnover- constant breakdown, rebuilding, and repair of body and cellular proteins. It allows cells to respond to environmental changes. Cellular amino acid pool Input into amino acid pool- Breakdown of cellular proteins (tissue) Dietary protein Output of amino acid pool- Synthesis of cellular proteins Synthesis of non protein N- containing compounds Energy production Glucose production. Synthesis of AMINO ACIDS Transamination- the TRANSFER of an amino group. Forms non essential amino acids. From an existing amino acid to a carbon skeleton. Breakdown of AMINO ACIDS Deamination- the process of removing and excreting an amino group. An amino acid loses an amino group, the amino group then travels to the LIVER, it is the incorporated into the urea and excreted and the carbon Skeleton is used for energy. Protein synthesis Amino acids are linked together by: PEPTIDE BONDS and CONDENSATION REACTIONS. Dipeptides- 2 linked amino acids Polypeptides- MANY linked amino acids GENES: Proteins are synthesized in cells based on their DNA template. Synthesis of protein determined through gene expression. Gene- short segment of DNA providing the instructions for protein. DNA to RNA to Protein (transcription) (translation) DNA coded instructions determine the SHAPE and FUNCTION of proteins. Transcription- DNA becomes accessible to enzymes. Genetic code is TRANSCRIBED(copied) and mRNA (messenger RNA) is synthesized. mRNA then travels out of the nucleus. Translation- mRNA sequence is read by the ribosomes in the cytosol. Genetic code is TRANSLATED (nucleic acid to amino acid) Pairing specific amino acids with specific mRNA sequences. Amino acids and then joined by peptide bond s. Protein organization Primary structure- Simple polypeptide chain. Order of amino acids determines the 3D shape. Secondary structure- bonding between nearby amino acids form (H-H.) Tertiary structure- S-S bonds. Forms 3D shape. Shape=function. Quaternary structure- Subunits linked together. Genetic mutations Can occur because of… Changes in DNA sequence Change in Amino Acid sequence Change in protein shape and or function Denaturation Denaturation- is the process of altering a proteins 3D structure. It can occur with… Acid, alkaline, heat, enzymes and agitation. It can occur IN… Cooking, stomach and small intestine. Protein Digestion and absorption Digestion sequence Stomach- protein is partially digested by pepsin and hydrochloric acid. Pancreas- further protein digestion by enzymes are released by pancreas into the small intestine. Small intestine- place of final digestion of protein to amino acids. Liver- amino acids are absorbed into the portal vein and transported to liver and from there entered into the bloodstream. Large intestine- little dietary protein is present in feces. Absorption In small intestine- intact proteins that are NOT usually absorbed. In enterocytes- peptides are broken down to amino acids. Transport- amino acids are released into bloodstream and are sent to the liver via circulation. Protein Functions -Produces vital body structures (actin, myosin, collagen.) -Provides energy (4kcal/g) -Contributes to acid base balance (acts as a buffer) -Forms hormones, enzymes and neurotransmitters. (insulin, amylase, serotonin) - contributes to immune function (antibodies) - transport nutrients (albumin and hemoglobin) - form glucose (gluconeogenesis) - maintain fluid balance (prevent edema) protein digestion and absorption cooking denatures proteins. Example: meat becomes soft and falls apart Stomach Furthers the denaturation Small intestine Pancreatic proteases Proteins are NOT suppose to pass the membrane. Protein NEEDS AMDR- 10-35% kcal ADULT RDA- 0.8 g/kg Recovery States- 0.8-2 g/kg Athletes- 0.8-1.7 g/kg Calculating protein needs: Example: 175lb man with a healthy body weight and standard activity. -convert weight in pounds to KG by dividing 2.2 kg -multiply weight in KG by 0.8 g/kg -63.6 g/kg of protein needed per day. Protein for energy 4 kcal/g not a preferred energy source rarely>10% of total energy during prolonged exercise Muscle glycogen declines Amino Acid oxidation (breakdown) increases Especially BCAA Amino acids and energy production Glycogenic amino acids Converted to pyruvate Can enter gluconeogenesis or TCA cycle All amino acids are glycogenic EXCEPT leucine and lysine Ketogenic Amino acids Converted to Acetyl-CoA or other TCA cycle intermediates Can enter TCA cycle 7 amino acids are ketogenic (leucine and lysine only ketogenic) Amino Acid catabolism produces Converted to urea (in liver) Urea excreted in urine (via kidneys) Nitrogen Balance Positive (input>output) Input: Building tissues High dietary intake Output: Urinary nitrogen excretion Negative (input<output) Input: low dietary intake Output: tissue breakdown urinary nitrogen excretion Protein Status Aiming for NITROGEN EQUILIBRIUM Can support POSITIVE NITROGEN BALANCE in anabolic building situations. Ex: growth, pregnancy, weight training Prevents- Fevers, burns, infections, cancer, prolonged bed rest, inadequate energy intake to meet needs. Increase protein intake to prevent catabolism (breakdown) Protein energy malnutrition (PEM) PEM- long term protein and calorie deficiencies Loss of fat and muscle, decreases immunity. Types- Kwashiorkor: pure protein deficiency Characteristics: Edema, mild to moderate weight lose, maintenance of some muscle and subcutaneous fat, growth impairment 60-80% of normal weight for age, rapid onset, fatty liver. Marasmus: overall energy deficiency Characteristics: severe weight loss, wasting of musc le and body fat, severe growth impairment less than 60% of normal weight, develops gradually. High Protein Diet High Protein Burden on the kidneys and liver (sick people) Increased calcium excretion in urine Increased fluid excretion in urine Plant foods Animal foods Increased risk for heart disease Increased Red meat intake linked to colon cancer Recommendation IOM- Max 2 x RDA for protein (1.6 g/kg) BUT, in certain catabolic states, can provide more
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