Pathways related to cellular respiration

1. Pathways related to cellular respiration Section 2.3 Pg. 117

2. Outline • CATABOLISM • protein • lipids • ANAEROBIC PATHWAYS • ethanol fermentation • lactate fermentation • EXERCISE PHYSIOLOGY • VO2 max

3. CATABOLISM • Nutrients are catabolised to obtain substrates for cellular respiration • We need energy!!!

4. Carbohydrates • First choice for catabolism • Polysaccharides will be broken down into simple sugars glycolysis, etc.

6. PROTEIN • Can be broken down and converted to compounds required for cellular respiration • Proteins are composed of mainly C, H, and O, but they all have Nitrogen in them as well

7. Proteins are catabolised to amino acids by hydrolysis • The AA’s are first deaminated – their amino groups are removed • Ammonia, NH3, is excreted as waste • Only the carbon skeleton of the AA remains

8. The carbon skeleton can be converted to either:

9. End result: free energy of the AA is transferred to ATP

11. Lipid catabolism Triglycerides  glycerol + fatty acids

12. Glycerol: • Either converted to glucose (gluconeogenesis) • Or converted to DHAP (3-C intermediate in glycolysis)

13. Fatty acids: • Transported to mitochondrial matrix • A series of steps adds a co-A to the fatty acid • Molecules undergo ß-oxidation - the cleavage of a 2-carbon acetyl group from the end • Acetyl group is converted to acetyl co-A  enters Krebs

14. The process of ß-oxidation yields: 1 NADH and 1 FADH2 for every cleavage 1 ATP is required for each cleavage reaction Example: Lauric acid – 12-carbon fatty acid 5 cleavage reactions produce 6 acetyl co-A molecules + 5 NADH + 5 FADH2

15. Taking into account the additional NADH and FADH2 produced in the Krebs cycle, as well as the ATP..  Fat metabolism yields more energy than carbohydrate metabolism

16. ANAEROBIC PATHWAYS • When oxygen is not available: • O2 can’t accept electrons from the ETC • NADH can’t be oxidized to re-form NAD+ • Glycolysis is inhibited

17. Alternative pathways allow glycolysis to continue.

18. Fermentation involves transferring the hydrogens to other molecules, instead of to the ETC Types: • Ethanol fermentation • Lactic acid (lactate) fermentation

19. Ethanol fermentation

20. NADH passes its electrons to acetaldehyde. • The product is ethanol. • Ethanol and CO2 are released as waste. Uses? • Breadmaking • Beer and winemaking

21. LACTIC ACID FERMENTATION During strenuous exercise, muscle cells consume oxygen too quickly. Lactic acid fermentation begins.

22. LACTIC ACID FERMENTATION

23. NADH transfers its hydrogens to pyruvate in the cytoplasm • Lactate is produced.

24. Lactate is acidic. Accumulation in muscle tissue causes stiffness, soreness, and fatigue. Later on... • Lactate gets transported to the liver, and is oxidized back to pyruvate Krebs

25. EXERCISE PHYSIOLOGY • Studies the body’s physiological responses to exercise. Aerobic fitness • A measure of the ability of the circulatory system to supply oxygen to the body’s cells. • An indicator of overall physical fitness.

26. Maximum oxygen consumption (VO2max) • The max. volume of O2that the body’s cells consume during maximal physical exertion • Expressed in mL/kg/min • Higher VO2 max values indicate higher aerobic fitness.

27. Trends: • Average for a North American is 35 mL/kg/min • Generally higher for males • Generally decreases with age

28. HOMEWORK Pg. 124 #1-11