Ch. 6 Cellular Respiration

1. Ch. 6 Cellular Respiration 6.16 – 6.18

2. Cells use many kinds of organic molecules as fuel for cellular respiration • Where do we obtain most of our calories? • From fats, proteins, sucrose (di) and starch (poly) • How are three types of food molecules used in glycolysis? • Enzymes in our digestive tract hydrolyze starch (polysaccharide) to glucose, which is then broken down in glycolysis • Proteins can be used as fuel but first must be digested to their amino acid monomers • Fats can be used after the cell hydrolyzes them to glycerol & fatty acids. • How are carbohydrates stored? • Stored as a polysaccharide, such as glycogen, in our liver & muscle cells. • How is glycogen used between meals? • Glycogen is hydrolyzed to glucose to serve as fuel between meals.

3. What does the cell use amino acids for? • To make its own proteins, or convert excess amino acids to other organic compounds such as pyruvic acid, Acetyl CoA or as an organic acid in the Krebs.

4. Why do fats make an excellent source of fuel? • The many hydrogen atoms covalently bonded to carbon, that the cell can break for energy, and of course the many energy rich electrons. • Can fats be used in cellular respiration? • Yes, by being converted to intermediates.

5. What is the advantage for animals storing energy as fat? • Compact storage of fat. 1 gram of fat yields twice as much ATP as 1 gram of starch. • What does this tell us about the dieters difficulty to burn fat? • To get rid of fat, we need to expend the same large amount of energy stored in the fat in the first place.

6. Are all food molecules destined to become ATP? • No, the cell needs food’s raw material to make molecules for repair & growth. (Biosynthesis) • What two process are essential for biosynthesis? • Metabolism & cellular respiration

7. Where does the fuel for cellular respiration ultimately come from? • Photosynthesis • What ingredient does a plant need to make food by photosynthesis? • CO2 & H2O & energy from the sun!