ENERGY IN FOOD Enzymes and P H Digestive System 1

 Organisms must obtain energy to carry out life processes  Amount of energy in food is measured in Calories  Food also contains raw materials (nutrients) used to build/repair body tissues 2

 Nutrients supplied by food: 1. Water 2. Carbohydrates 3. Lipids 4. Proteins 5. Vitamins 6. Minerals 3

 Breaks up food – physically & chemically  Stores food for a short time  Absorbs digested nutrients and passes them into circulatory system  Stores & eliminates undigested materials from body 4

 Types of digestion: 1. Mechanical – physical breakdown of food by non-chemical means 2. Chemical – the use of enzymes & other chemicals to break down food 5

 Consumers must be able to break down food into molecules that can be absorbed & used by cells  In many multicellular organisms, this is accomplished by a digestive system 6

 Enzyme – specialized proteins that act as biological catalysts  Catalyst – substance that speeds up chemical reactions & remains unchanged by the reaction  All the activities of living things are controlled by chemical reactions  Without enzymes, these reactions would not happen and the organism would die 7

 Activation energy – amount of energy needed to get a chemical reaction started  Chemical reaction – the breaking down and/or forming of new compounds 8

 Are: a 3-dimentional protein  Have: a specific area that attaches to the chemical compound undergoing a change (active site)  Fit: like a puzzle piece to one type of compound (substrate) 9

 Need: specific pH range  Require: constant body temperature to work correctly 10

 When the enzyme bids with its specific substrate, changes occur in the enzyme at the active site  This change is called induced fit and it enhances the ability of the enzyme to break down the substrate 11

 Denature – a change in the shape of an enzyme; caused by change in pH or fever  If the enzyme is missing or denatured, the reaction cannot happen  Example: lactose intolerance 12

 Competitive: Chemicals that resemble the enzyme’s normal substrate Compete with substrate  Allosteric Chemicals that bond to a another part of the enzyme Changes shape of active site 13 Inhibitors – keep something from working correctly

Pathway of the Digestion 14

 Digestion begins in the mouth with: 1. Mechanical – teeth and tongue chop/mix food 2. Chemical – salivary glands add enzyme amylase to break down starches into simple sugars 15

 Food moves into pharynx at back of throat; opening for 2 tubes that lead to 2 systems 1. Esophagus – digestive 2. Trachea – respiratory  Epiglottis – flap of tissue that covers opening not being used 16

 Peristalsis – one way movement of materials through digestive system; controlled by smooth muscle contraction  Food moves down esophagus into stomach: 1. Has a pH of 2 (hydrochloric acid) 2. Secretes enzyme pepsin (acts on proteins) 3. Mechanical & physical digestion 17

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AAfter ~2 hours, food leaves stomach and enters small intestine: 1. 7 m long – 2.5 cm diameter 2. Multiple enzymes secreted to break down lipids and nucleic acids 3. Other enzymes used to complete break down of carbs and proteins 4. Most absorption of nutrients occurs 19

 Anatomy inside of small intestine: Villi – fingerlike projections that absorb nutrients from small intestine 20

 Accessory organs of small intestine: 1. Pancreas – secretes enzymes that work on carbs, protein and lipids; helps regulate blood sugar; also secretes sodium bicarbonate that neutralizes stomach acid 2. Liver – produces bile to dissolve fats 3. Gall bladder – stores bile 21

 Accessory organs of digestive system: 22

 After 4-6 hours what is left of your food enters large intestine: 1. ~1.5 m long – 6 cm diameter 2. 3 sections – cecum, colon & rectum 3. Absorbs water and salts 4. Colonies of E.coli break down rest of undigested material and produce Vitamin K (needed for blood clotting) 5. Solid waste is stored in rectum & excreted though anus 23

 Anatomy of large intestine: 24