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What Are Proteins?

What Are Proteins?

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What Are Proteins?

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  1. What Are Proteins? • Proteins: large, complex molecules found in cells of all living things • Dictated by genetic material (DNA) • Contain carbon, hydrogen, oxygen, nitrogen • Made from 20 different amino acids The Building Blocks of Proteins

  2. Amino Acids • Nine essential amino acids • Cannot be produced in sufficient quantities to meet physiological needs • Must be obtained from food • Nonessential amino acids • Can be synthesized in sufficient quantities

  3. Protein in the Diet • For protein synthesis, all essential amino acids must be available to the cell • Limitingamino acid • Essential amino acid that is missing or in the smallest supply • Slows down or halts protein synthesis • Inadequate energy consumption • Limits protein synthesis

  4. Protein in the Diet • Incomplete protein (low quality): insufficient essential amino acids • Does not support growth and health • Complete protein(high quality): sufficient amounts of all nine essential amino acids • Derived from animal and soy protein

  5. Protein in the Diet • Mutual supplementation: combine two or more incomplete protein sources to make a complete protein • Complementary proteins: two or more foods are combined to supply all nine essential amino acids for a complete protein

  6. Functions of Proteins • Cell growth, repair, maintenance • Enzymes and hormones • Fluid and electrolyte balance • Acid−base balance • Immune system • Energy source • Nutrient transport and storage

  7. Protein Adequacy • Nitrogen balance determines protein needs • Positive nitrogen balance • Negative nitrogen balance • In nitrogen balance Nitrogen Balance

  8. RDA for Protein • RDA = 0.8 g per kg body weight per day • Recommended percentage of energy is 10−35% of total energy intake • Protein needs are higher during growth and development (children, adolescents, and pregnant/lactating women)

  9. Too Much Protein Can Be Harmful • High cholesterol and heart disease • Animal-protein-rich diets are associated with high blood cholesterol levels (saturated fat) • Contribution to bone loss • High-protein diets increase calcium excretion and possibly lead to bone loss

  10. Too Much Protein Can Be Harmful • Kidney disease • High protein intakes are associated with an increased risk among susceptible individuals • People with diabetes have higher rates of kidney disease and may benefit from a lower-protein diet • Maximum of 2 g of protein per kilogram body weight each day is safe for healthy people Fat Synthesis from Excess Protein

  11. Protein Sources • Meats • Milk-based products • Soy products • Legumes • Whole grains • Nuts • Quorn

  12. Vegetarian Diets • Vegetarianism: restricting the diet to foods of plant origin • People chose vegetarianism for: • Health benefits • Ecological reasons • Religious reasons • Ethical reasons • Concerns over food safety

  13. Health Benefits of Vegetarianism • Lower fat and total energy intake • Lower blood pressure • Reduced risk of heart disease • Fewer digestive problems • Reduced risk of some cancers • Reduced risk of kidney disease, kidney stones, and gallstones

  14. Challenges of Vegetarian Diets • Can be low in some nutrients • Associated with disordered eating • Varied and adequate diet planning • Soy and complementary proteins • Vegetarian Food Guide Pyramid • Special attention to vitamins D, B12, and riboflavin (B2); minerals zinc and iron

  15. Protein-Energy Malnutrition • Protein-energy malnutrition: caused by inadequate protein and energy intake • Common forms: • Marasmus • Kwashiorkor

  16. Marasmus • Grossly inadequate energy and nutrient intake • Consequences of marasmus: • Wasting and weakening of muscles (heart) • Stunted brain development and learning • Depressed metabolism • Stunted physical growth • Deterioration of the intestinal lining (anemia) • Severely weakened immune system • Fluid and electrolyte imbalances

  17. Kwashiorkor • Disease resulting from low protein intake • Kwashiorkor symptoms include: • Some weight loss and muscle wasting • Retarded growth and development • Edema resulting in distention of the belly • Fatty degeneration of the liver • Loss of appetite, sadness, irritability, apathy • Skin problems and hair loss

  18. Genetic Disorders • Numerous disorders are caused by defective DNA • Genetic disorders include: • Phenylketonuria • Sickle cell anemia • Cystic fibrosis

  19. Hormones that are protein or have protein component

  20. Short polypeptides and small proteins • Hypothalamus • Pituitary gland • Parathyroid glad • Pancreas (discussed in relation to carbohydrates)

  21. Major Endocrine Organs: Pituitary (Hypophysis) • Pituitary gland – two-lobed organ that secretes nine major hormones • Neurohypophysis – posterior lobe (neural tissue) and the infundibulum • Receives, stores, and releases hormones from the hypothalamus • Adenohypophysis – anterior lobe, made up of glandular tissue • Synthesizes and secretes a number of hormones

  22. Pituitary-Hypothalamic Relationships: Posterior Lobe • Is a down growth of hypothalamic neural tissue • Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract) • Nuclei of the hypothalamus synthesize oxytocin and antidiuretic hormone (ADH) • These hormones are transported to the posterior pituitary • Stores antidiuretic hormone (ADH) and oxytocin • ADH and oxytocin are released in response to nerve impulses • Both use PIP-calcium second-messenger mechanism at their targets

  23. Neurohypophysis hormones Hormones that are produced in the hypothalamus and stored in the neurohypophysis

  24. Oxytocin • Stimulates uterine contractions during childbirth by mobilizing Ca2+ through a PIP2-Ca2+ second-messenger system • Also triggers milk ejection in women producing milk • Plays a role in sexual arousal and orgasm in males and females

  25. Antidiuretic Hormone (ADH) • Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood • What can cause changes in blood concentration? • Body fluids – water • Electrolytes – in the ECF – mainly sodium

  26. Water • Water • Essential for life • Amount needed varies with gender, age, body size, health status, physical activity level, environment • Sources of drinking water: carbonated, mineral, distilled, purified, tap, bottled ABC Video Bottled Water

  27. Body Fluids • Body fluid is the liquid portion of cells and tissues • Characterized by its ability to move freely and changeably, adapting to the shape of the container that holds it • About 50−70% of healthy adult body weight • Intra cellular fluid (ICF) and Intracellular fluid (ECF)

  28. Body Fluids • Fluid composition of tissue varies by: • Tissue type: lean tissues have higher fluid content than fat tissues • Gender: males have more lean tissue and therefore more body fluid than females • Age: decrease in body water results partly from loss of lean tissue as people age

  29. Sodium functions • Major positively charged electrolyte in the extracellular fluid • Blood pressure and acid−base balance • Nerve impulse transmission • Muscle contraction and relaxation • Assists in glucose absorption from the small intestine

  30. Sodium intake • AI: 1,500 mg, most recommend < 2,300 mg/day • Processed foods are high in sodium • High blood pressure more common from high-sodium diets • Excessive intake may increase urinary calcium excretion in some people, which in turn may increase the risk for bone loss

  31. Too much sodium • What if you consume too much sodium? • Hypernatremia is an abnormally high blood sodium concentration • Patients with congestive heart failure or kidney disease cannot effectively excrete sodium • Causes high blood volume, edema (swelling), and high blood pressure

  32. Not enough Sodium • What if you don’t consume enough sodium? • Hyponatremia is an abnormally low blood sodium level • From prolonged sweating, vomiting, diarrhea • Symptoms: headaches, dizziness, fatigue, nausea, vomiting, and muscle cramps • If untreated: seizures, coma, and death

  33. Functions of Electrolytes • Electrolytes help regulate fluid balance • Cell membranes are permeable to water, but not freely permeable to electrolytes • Water moves by osmosis to areas where the concentration of solute is high (low water concentration) • This action provides a means to control movement of water into and out of the cells

  34. Water and fluid balance • What happens if we drink too much water? • Becoming overhydrated is rare • Dilution of blood sodium concentration • What happens if we don’t drink enough water? • Dehydration • Leading cause of death around the world Water Balance

  35. Fluid Balance • Thirst mechanism (hypothalamus) prompts us to drink when it is stimulated by • Increased concentration of salt and other dissolved substances in the blood • A reduction in blood volume and blood pressure, such as during profuse sweating, vomiting, diarrhea, or low fluid intake • Dry mouth and throat from reduced saliva • ADH signals the kidneys to retain water

  36. Fluid Balance – gain fluids • Body gains fluids • Water enters the body through beverages • Some foods have very high water content • Water from metabolic reactions contributes 10−14% of daily water need

  37. Fluid Balance – fluid loss • Sensible water loss • Kidneys excrete water as urine • Sweat during exercise or in hot environment • Insensible water loss • Skin (not sweating) or lungs during exhalation • Significant loss • Illness, injury, exercise, high altitude, pregnancy, breastfeeding, diuretics

  38. Antidiuretic Hormone (ADH) – works when body lacks water or high in sodium • If solute concentration is high • Osmoreceptors depolarize and transmit impulses to hypothalamic neurons • ADH is synthesized and released, inhibiting urine formation • We will talk about this hormone in details with the urinary system

  39. The anterior lobe • Is an out pocketing of the oral mucosa from epithelial tissue • There is no direct neural contact with the hypothalamus • Hormone production is regulated by the hypothalamus • Regulatory factors from the hypothalamus arrive directly to the adenohypophysis through the hypophyseal portal system

  40. Hypophyseal portal system • Portal system - a system of blood vessels that begins and ends in capillaries. The blood, after passing through one capillary bed, is passing through a second capillary network. • All blood entering the portal system will reach the target cells before returning to the general circulation

  41. Pituitary-Hypothalamic Relationships: anterior Lobe • The hypophyseal portal system, consisting of: • The primary capillary plexus in the infundibulum • The hypophyseal portal veins • The secondary capillary plexus

  42. Activity of the Adenohypophysis is regulated by the hypothalamus • The hypothalamus sends a chemical stimulus to the anterior pituitary • Releasing hormones stimulate the synthesis and release of hormones • Inhibiting hormones shut off the synthesis and release of hormones • The hormones of the anterior pituitary (7) are called tropic/trophic hormones because they “turn on” other glands or organs

  43. Anterior Pituitary Hormones • All are proteins • TSH, ACTH, FSH, and LH are all tropic hormones (regulate the secretory action of other endocrine glands)

  44. Tropic Hormones of Hypothalamus and Anterior Pituitary

  45. Anterior pituitary hormones

  46. Anterior pituitary hormones

  47. Anterior pituitary hormones

  48. Normal Growth in Humans • Growth is a continuous process that varies in rate, and depends on four factors • Growth hormone and several other hormones (for example – hormones that control calcium and glucose) • An adequate diet • Absence of chronic stress • Genetic potential for growth