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LECTURE 10

LECTURE 10. Digestive System, Enzymes, Nutrition and Metabolism. TODAY’S MENU. Digestive System and Enzymes (pg 257-260) Nutrition and Metabolism (pg 265-271) Lab: . ENERGY AND ENZYMES. Energy is the capacity to do work. There are two types of energy: Potential (rest) and Kinetic (Motion)

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LECTURE 10

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  1. LECTURE 10 Digestive System, Enzymes, Nutrition and Metabolism

  2. TODAY’S MENU • Digestive System and Enzymes (pg 257-260) • Nutrition and Metabolism (pg 265-271) • Lab:

  3. ENERGY AND ENZYMES • Energy is the capacity to do work. • There are two types of energy: Potential (rest) and Kinetic (Motion) • Living things use the energy of sunlight to create stable conditions characteristic of life. • In living things chemical reactions are responsible for converting energy from one set of chemical substances (reactants) to another (products). • Chemical reactions are either exergonic (exothermic) or endergonic (endothermic)

  4. Exergonic reaction energy released reactants products • Exergonic Reactions Release Energy

  5. Endergonic reaction energy used products reactants • Endergonic Reactions Require an Input of Energy

  6. Burning glucose energy released 6 O O glucose oxygen O 6 O C O 6 H H carbon dioxide water

  7. Burning glucose (sugar): an exergonic reaction Photosynthesis: an endergonic reaction high high activation energy needed to ignite glucose glucose activation energy from light captured by photosynthesis glucose + O2 energy content of molecules energy content of molecules net energy captured by synthesizing glucose energy released by burning glucose CO2 + H2O CO2 + H2O low low progress of reaction progress of reaction Energy relations in exergonic and endergonic reactions

  8. How Is Cellular Energy Carried Between Coupled Reactions & Cells Control Their Metabolic Reactions? • ATP Is the Principal Energy Carrier in Cells • Cells Regulate the Amount and the Activity of Their Enzymes • At Body Temperatures, Spontaneous Reactions Proceed Too Slowly to Sustain Life • Catalysts Reduce Activation Energy • Catalysts lower activation energy, increasing the rate of reactions

  9. ATP synthesis: Energy is stored in ATP energy A P P P ATP A P P P phosphate ADP

  10. ATP breakdown: Energy of ATP is released energy A P P P A P P P ATP ADP phosphate

  11. + + Exergonic reaction: 100 units energy released ATP ADP P Endergonic reaction: 20 units energy + contracted muslce relaxed muscle Coupled reaction: + + + + 80 units energy released as heat ADP P ATP relaxed muscle contracted muslce Coupled Reactions Link Exergonic and Endergonic Reactions

  12. high activation energy without catalyst activation energy with catalyst energy content of molecules reactants products low progress of reaction

  13. ENZYMES • Enzymes Are Biological Catalysts that speeds up the rate of a reaction without themselves being used up or permanently altered • The Structure of Enzymes Allows Them to Catalyze Specific Reactions • Cells Regulate the Amount and the Activity of Their Enzymes

  14. substrates active site of enzyme enzyme The cycle of enzyme–substrate interactions 1) Substrate enter active site in a specific orientation 3) Substrates, bonded together, leave enzyme; enzyme ready for new set of substrates 2) Substrates and active site change shape, promoting reaction between substrates

  15. How Do Cells Control Their Metabolic Reactions? • Cells Regulate the Amount and the Activity of Their Enzymes • The Activity of Enzymes Is Influenced by Their Environment

  16. CH3 CH3 CH2 H C OH A B C D CH3 H C enzyme 1 enzyme 2 enzyme 3 enzyme 4 enzyme 5 H C NH3 H C NH3 COOH COOH Feedback inhibition: Isoleucine inhibits enzyme 1 isoleucine (end-product amino acid) threonine (substrate amino acid) Enzyme regulation by feedback inhibition

  17. Enzyme structure substrate active site enzyme allosteric regulatory site Allosteric inhibition allosteric regulator molecule Competitive inhibition Enzyme regulation by allosteric regulation and competitive inhibition

  18. ENZYMES PROPERTIES AND INHIBITION • They are proteins • They are denatured by heat (optimum temperature for most is 37oC) • pH affects the enzyme (optimum ph is around neutral (6-8). Exception pepsin • Inhibition: Feed back, Allosteric and Competitive inhibition • E.g Competitive inhibition: ethanol and methanol. Later causes blindness. Enzyme is alcohol dehydrogenase.

  19. DIGESTION • Digestion is the process by which food is physically grounded and broken down chemically, before they are absorbed into the body. • All digestive systems achieve this by the following tasks • 1. Ingestion • 2. Mechanical breakdown • 3. Chemical breakdown • 4. Absorption • 5. Elimination

  20. Different Digestive Systems • Within single cell (e.g Sponges) • Digestion in a Tube Allows Animals to Feed More Frequently • Digestive Specializations • Special Adaptations Allow Ruminants to Digest Cellulose • Intestinal Length Is Correlated with Diet • Teeth Evolved to Accommodate Different Diets • Birds Have Gizzards for Grinding Food

  21. esophagus anus omasum reticulum large intestine The ruminant digestive system

  22. (a) Omnivore (b) Carnivore (c) Herbivore (human) (cow) (lion) canine molars molars incisors premolar premolars molars incisors canine premolars canine incisors Teeth evolved to suit different diets

  23. Bird digestive adaptations rectum esophagus liver anus

  24. THE HUMAN DIGESTIVE SYSTEM • Adapted for processing a wide variety of different foods in our omnivorous diet. • The human digestive tract is divided into • 1. Primary digestive organs: mouth, esophagus, stomach, small intestine, large intestine (colon) and anus • 2. Accessory digestive organs: pancreas, liver, gall bladder and appendix

  25. salivary glands muscle layers The human digestive tract pharynx pyloric sphincter epiglottis folds duodenum esophagus liver stomach pancreas gallbladder transverse colon (large intestine) ascending colon (large intestine) descending colon (large intestine) small intestine rectum (behind bladder and pubic bone)

  26. How Do Humans Digest Food? • The Mechanical and Chemical Breakdown of Food Begins in the Mouth

  27. (a) Before swallowing roof of mouth food pharynx tongue epiglottis esophagus larynx (b) During swallowing epiglottis (folds over larynx) food (enters esophagus) larynx (moves up)

  28. How Do Humans Digest Food? • The Esophagus Conducts Food to the Stomach • Most Digestion Occurs in the Small Intestine • The Liver and Gallbladder Provide Bile, Important in Fat Breakdown • The Pancreas Supplies Several Digestive Secretions to the Small Intestine • The Digestive Process Is Completed by Cells of the Intestinal Wall • Most Absorption Occurs in the Small Intestine

  29. (a) Small intestine (c) Villus (d) Cells of villi (b) Fold of intestinal lining lacteal microvilli villi capillaries arteriole intestinal gland lymph vessel fold of intestinal lining venule The small intestine

  30. How Do Humans Digest Food? • Water Is Absorbed and Feces Are Formed in the Large Intestine • The Anus is for excretion of waste • Appendix: lymphoid tissue makes minor contribution to the body’s defense system • Digestion Is Controlled by the Nervous System and Hormones

  31. food stimulates gastrin secretion increased acidity inhibits stimulates acid secretion

  32. NUTRITION AND METABOLISM • Cells Continuously Expend Energy, Which Is Derived from Nutrients and Measured in Calories • Metabolism is the sum total of all the chemical reactions needed to sustain an organism’s life. • Energy to sustain all life comes from sunlight.

  33. Major Categories of Nutrients • Lipids Include Fats, Phospholipids, and Cholesterol • Animals Store Energy as Fat • Carbohydrates, Including Sugars and Starches, Are a Source of Quick Energy • Proteins, Composed of Amino Acids, Perform a Wide Range of Functions Within the Body • Minerals Are Elements Required by the Body • Vitamins Are Required in Small Amounts and Play Many Roles in Metabolism

  34. The Food Pyramid

  35. Rickets kwashiorkor Pellagra Symptoms of protein and vitamin deficiency

  36. Dietary Guidelines • Aim for fitness: • Aim for a healthy weight. • Be physically active each day. • Build a healthy base: • Let the Pyramid guide your food choices. • Choose a variety of grains daily, especially whole grains. • Choose a variety of fruits and vegetables daily.

  37. Dietary Guidelines • Keep food safe to eat. • Choose sensibly: • Choose a diet that is low in saturated fat and cholesterol and moderate in total fat. • Choose beverages and foods to moderate your intake of sugars. • Choose and prepare foods with less salt. • If you drink alcoholic beverages, do so in moderation.

  38. LAB • Assignment 2 & 3 combined • Assignment 5. • Assignment 2 & 3 is for the lab summary.

  39. ATP Catalyst Enzymes Division of the digestive tract Functions of different sections of the digestive tract Metabolism (definition) Major Nutrient categories KEY WORDS

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