How do we get the energy, building blocks, and important molecules out of our food?

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1 Why do we need to eat food? To get a source of energy To get building blocks (raw materials) for growth/repair/maintenance/ energy storage To get the homeostasis molecules needed to keep our body "machinery" working properly (like the oil in an engine) -- water, minerals (elements important to body), vitamins, electrolytes How do we get the energy, building blocks, and important molecules out of our food? Digestive system uses enzymes to break down food into molecules that are small enough for absorption into blood. The body then uses these smaller molecules several ways: 1. mitochondria "burn" them to release energy 2. body "machinery" uses them to maintain homeostasis -- to make reactions happen, to keep the blood and cells isotonic, to keep organs working, etc. 3. body connects them into new macromolecules necessary for growth/ repair/maintenance/energy storage

2 Synthesizing macromolecules requires energy. Examples of synthesis: o Proteins: amino acids strung together by ribosomes o Polysaccharides/complex carbs: glycogen made from stringing together monosaccharides, glycogen is stored in liver and muscles; in plants, carbs are stored as starch; cell walls made of cellulose (fiber) o Lipids: synthesized in smooth ER

3 Read p. 273 (1 st 2 paragraphs). Answer the following questions: 1. What is starch? 2. Where does starch come from? 3. What organisms can get energy from the starch? 4. How do organisms get energy out of the starch? 5. Why can t we absorb the starch we eat? 6. Read #3, p What is the function of the digestive system? Read What happens to the food you eat? (p ) and answer the following questions: 7. Explain 2 different ways we can become hungry. 8. How do we respond to hunger? (2 ways)

4 9. Chewing increases surface area and moistens food with saliva. 10. Proteins are broken down into amino acids. Carbohydrates are broken down into simple sugars. 11. Enzymes are proteins that speed up molecular reactions. 12. Substrates are the molecules enzymes work on. The substrates fit with the enzymes like a lock and key, so the enzymes are very specific. 13. Enzymes break down food in digestion. 15. Most of the absorption of nutrients takes place in the small intestine. 16. The liver stores excess nutrients from the blood and releases them when the levels get low.

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6 functions macromolecule/ sketch elements monomers/ sketch digestion location/ enqymes Fats/lipids store energy, building blocks for hormones & cell membranes Carbon, Hydrogen, a little Oxygen fatty acids lipase in small intestine carbohydrates fuel for body (source of energy) complex carbs/polysaccharides: starch (plant storage molecules), glycogen (in liver & muscles), cellulose (fiber -- plant cell walls) Carbon, Hydrogen, Oxygen simple sugars/ monosaccharides C H O amylase in small intestine and mouth proteins building, repairing & maintaining body tissues, enzymes Carbon, Hydrogen, Oxygen, Nitrogen amino acids pepsin in stomach, proteases in small intestine

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8 (homeostasis molecules include different vitamins (which give foods different colors, so dietitians advise us to "eat a rainbow"), water, electrolytes, antioxidants January 13, 2012

9 Macromolecules -- "take home" lessons from assembling paper proteins, lipids, and polysaccharides 1. building blocks are interchangeable, allowing body to build many different macromolecules from a small number of building blocks (only 20 different amino acids), can put blocks in different orders, repeat some, vary length of macromolecule, having a limited number of building blocks is very efficient, like reusing Lego blocks in many different sets 2. scissors represent enzymes which cut building blocks out of food; tape represents enzymes that put them together into macromolecules; just as taping them together requires effort, synthesizing macromolecules requires energy

10 Major elements in living things: C H O N P S (Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorous, Sulfur)

11 1. What are atoms? Almost unimaginably tiny building blocks of all matter, what everything is made of 2. What are chemical bonds? What connects atoms in molecules, holds them together in a predictable way (we can predict how the atoms will fit together) 3. Energy_ is stored in the the structure of a molecule s bonds_ and _atoms_. 4. What are molecules? Molecules result when 2 or more atoms are held together by chemical bonds 5. What determines the number of bonds that an atom can form? The number of valence electrons (electrons in outer shell) 6. How many bonds can carbon form? Four

12 7. What are exothermic reactions? Reactions that give off energy (as heat) when bonds are broken in the reactants and new bonds are formed in the products; the products store less energy than the reactants 8. What are endothermic reactions? Reactions that take in energy (as heat) when bonds are broken in the reactants and new bonds are formed in the products; the products store more energy than the reactants 9. What is the difference between an endothermic process and an endothermic reaction? Reactions involve breaking and reforming chemical bonds; but some processes that absorb heat DO NOT break and form chemical bonds; example: a change in state (like melting ice)

13 10. In humans, the thousands of different chemical reactions that constantly occur in our cells depend primarily on _chemical energy. Thanks to evolutionary adaptations, these reactions can take place in a _controlled manner. January 13, 2012

14 Read the bottom of p. 289, top of 290. Answer the following: 1. What determines the amount of energy in a substance? 2. Answer the questions with blue diamonds on p. 288.

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16 p lab on endo- and exothermic reactions January 13, 2012

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18 1st reaction -- energy comes 2nd reaction -- energy goes

19 Read Energy Is Converted and Conserved (p ) and answer the following questions: 1. Energy can be converted from one form_to_ another. 2. What is potential energy? stored energy -- boulder on top of a hill, roller coaster going up hill (inactive energy) 3. What is kinetic energy? active energy -- boulder falling, roller coaster going down hill (energy of movement) 4. What two things can happen when potential energy is converted into kinetic energy? may be captured and made useful or be wasted 5. Why do organisms convert energy from one form to another? Give an example. Their energy needs can vary, so organisms convert energy into the form that best matches their needs. If they don't need much energy because they are resting, they can store potential energy in large molecules (such as glycogen). If they need energy for motion, they can convert this stored energy into mechanical energy. 6. The stronger the chemical _bond, the _greater_ the energy required to _break_ it. 7. Define ionic bond and covalent bond and tell which is stronger. ionic bonds -- atoms become ions when lose or gain electrons, ions held together by attraction of ions' opposite charges covalent bonds -- held together through atoms' sharing of electrons; stronger bonds than ionic

20 8. What is the energy of activation and how is it useful to living things? "start-up" energy needed to set off a reaction (like a spark), useful that activation energy is fairly large for most reactions because it makes molecules in our body stable 9. What provided the activation energy for the grain explosion? spark Why doesn t the body use such a strategy? Adding heat would increase all the chemical reactions in the body, not just the specific ones the body needs to have happen at a specific time. This added heat would, for instance, increase the breakdown of the body's structure (such as muscles) and of its stored food energy. 10. What are enzymes? In what 2 ways do enzymes affect chemical reactions in the body? large protein molecules that help the right chemical reactions take place in cells at the right time; 1. reduce the amount of start-up energy required for a reaction 2. affect only specific reactions (not all the reactions in a cell) 11. How does the form (shape) of the enzyme make it able to affect reactions in these 2 ways? 1. hold substrates in just right orientations so that reactions are more likely to happen 2. only the specific molecules involved in the reaction will fit into the active sites 12. Enzymes are not changed in chemical reactions. 13. What is ATP? What is its function? How does the body get ATP? adenosine triphosphate functions as carrier of small amounts of energy needed for cell processes; can provide energy for all cell organelles; like an ATM, ATP can provide small amounts of money/energy in a form that is accepted everywhere body gets ATP from breaking down long-term storage molecules