Starter

1. Starter • Describe the structure and main function of the following organelles: • Nucleus • Flagella • Contractile Vacuole

2. Starter • Nucleus, a spherical structure surrounded by a porous membrane that contains genetic information for the control of the functioning of the cell. • Flagella, made up of fibers that contract making the flagellum move from side to side and important in the movement of the cell.

3. Starter • Contractile vacuole, is a membrane bound organelle found in aquatic protiststhat pumps water from within the cell to the outside to maintain osmotic equilibrium(water balances within the cell). 2 / 3 correct for Achieved

4. Starter • Describe where most of the chloroplasts would be found inside this cell and explain why they are found there. • Cells like Euglena are rarely visible, unless you use a microscope. Explain why single cells like this never grow larger.

5. Starter • Description of where most chloroplast are found in this cell, eg. near the outer edge of the cell. Explanation why most chloroplasts are found in this position, eg. light intensity is highest here for efficient photosynthesis.

6. Starter • Description of why single cells never grow larger, eg the surface area to volume ratio decreases so that they cannot absorb materials efficiently. Explanation of why single cells never grow larger, eg so that the cell must divide to increase the surface area to volume ratio again so that it will function more efficiently. This keeps the cell size small.

7. Respiration

8. Respiration • Respiration involves the breakdown of glucose to produce water, carbon dioxide and energy. C6H12O6 + 6O2enzymes 6H2O + 6CO2 + Energy • The majority of respiration occurs in the mitochondria.

9. Respiration • The energy is stored as chemical energy in molecules of adenosine triphosphate (ATP). • The ATP is formed when a molecule of adenosine diphosphate (ADP) and a phosphate group combine. + → Adenosine P P P Adenosine P P P

10. Respiration • Energy is released when ATP is broken down into ADP. Energy Adenosine P P P

11. Respiration ATP Energy released from breakdown of ATP Energy from breakdown of glucose ADP + P

12. Respiration • Respiration occurs in four stages: • Glycolysis • Transition Reactions • Krebs Cycle • Electron Transport Chain

13. 1. Glycolysis • Glycolysis is the sequence of reactions, occurring in the cytoplasm, that converts glucose (C6) into pyruvate (C3) and a small amount of ATP. Glucose Pyruvate ATP C6H12O6→ 2CH3COCOOH + 2ATP

14. 1. Glycolysis • If conditions inside the cell are anaerobic then pyruvate remains in the cytoplasm to be broken down. • In animals the pyruvate forms lactic acid (causes muscle cramps). • In plants pyruvate forms ethanol and CO2 (fermentation).

15. 1. Glycolysis • Two NAD+ molecules (coenzymes) collect hydrogen and become NADH. • They carry this hydrogen to the mitochondria and then pass it to the electron transport chain. • Coenzyme – organic, non-protein molecules that carry chemical groups between enzymes.

16. 1. Glycolysis C6 Glucose 2 ADP NAD+ Numerous chemical reactions 2 ATP 2 x Pyruvate NADH C3

17. 1. Glycolysis • Some organisms (e.g. anaerobic bacteria) use glycolysis as their only energy source. • A much greater amount of ATP is produced if the pyruvate is then broken down inside the mitochondria.

18. 2. Transition Reactions • The pyruvate enters the mitochondria where it is broken down into acetyl (C2), CO2 and Hydrogen. • Coenzyme A (CoA) binds to the acetyl group (COCH3) and is changed to acetyl coenzyme A (Acetyl CoA).

19. NADH CO2 C3 2 x Pyruvate Acetyl CoA C2 CoA Acetyl Group enters Krebs Cycle

20. 2. Transition Reactions • This is an important link where the acetyl group is carried to the matrix of the mitochondria. • Other food molecules (fats and proteins) can enter the respiration process, as they can be broken down to acetyl groups. • The CoA does not enter the mitochondria and returns to pick up another acetyl group.

21. 3. Krebs Cycle • Takes place in the inner matrix of the mitochondria. • During the process carbon dioxide is released as a waste product and a small amount of ATP is synthesized. • Many NAD+’s get filled with hydrogen (NADH) and are carried to the electron transport chain.

22. Krebs Cycle ATP ADP NAD+ NADH C6 CO2 C2 Acetyl Group C5 C4 ADP ATP CO2 NAD+ NADH

23. 4. Electron Transport Chain • The electron transport chain (respiratory chain) is located in the cristae of the mitochondria. • On the membranes are many cytochromes, which pass the hydrogen down the chain. • The oxidation and reduction actions release enough energy to charge about 3 ATP per Hydrogen bouncing down the chain.

24. 4. Electron Transport Chain • At the end of the process the low-energy hydrogen reacts with the oxygen breathed in and forms water. O2 + 4H+ + 4e-→ 2H2O • If no oxygen is available respiration stops at glycolysis.

25. Mitochondria Crista ATP 2H + ½ O → H2O Cytochromes

26. Summary

27. CO2 2 ATP Glycolysis CoA Krebs Cycle Acetyl CoA CO2 NAD+ NADH NADH NAD+ Electron Transport Chain 2 ATP 34 ATP 2H + ½ O2→ H2O

28. Factors Affecting Respiration • Rate of Respiration refers to the speed at which glucose is broken down to produce energy. • This can be affected by: • Amount of oxygen present. • Amount of glucose/fat present. • The energy demand. • Temperature.

29. Homework • Complete Biozone Pg. 297 – 298