Ch. 6 Cellular RespirationCh. 6 Cellular Respiration

6.16 – 6.186.16 – 6.18

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.

• 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.

• 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.

• 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.

• 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

• 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!