Photosynthesis and Cellular Respiration

1. Photosynthesis and Cellular Respiration

2. Objectives Section 1 • I can explain in detail the flow of energy through living systems • I can compare the chemical processes of autotrophs and heterotrophs • I can describe the role of ATP in metabolism • I can describe how energy is released by ATP.

3. Metabolism Metabolism: all of the chemical reactions that take place within an organism • Metabolic pathways alter molecules in a series of steps. • Enzymes selectively accelerate each step. • enzymes are regulated to maintain a balance of supply and demand.

4. Catabolic reactions give off energy by breaking down complicated molecules to simpler compounds. • Anabolic reactions useenergy to build complicated molecules from simpler compounds. • The energy released by catabolic pathways is used to drive anabolic pathways.

6. Autotrophs vs Heterotrophs • Autotrophs make their own food through anabolic reactions • Many autotrophs carry out photosynthesis • Heterotrophs can not make their own food • Heterotrophs must eat other organisms to obtain energy from food through catabolic reactions • Heterotrophs utilize cellular respiration

7. ATP • ATP powers cellular work • A cell does three main kinds of work: • Mechanical work, beating of cilia, contraction of muscle cells, and movement of chromosomes • Transport work, pumping substances across membranes against the direction of spontaneous movement • Chemical work, driving endergonic reactions such as the synthesis of polymers from monomers

8. ATP (adenosine triphosphate) is a type of nucleotide consisting of the nitrogenous base adenine, the sugar ribose, and a chain of three phosphate groups.

9. The bonds between phosphate groups can be broken by hydrolysis.

10. So what? • Energy is stored in these bonds. • So? • The breaking of the chemical bond releases the energy ATP + H2O→ ADP + P + ENERGY

11. Cellular Respiration • The process by which mitochondria break down glucose to make ATP • In order for our bodies to use the energy, the food must be broken down into a usable form • What is the usable form of energy? • What type of process breaks down molecules?

12. Objectives Section 3 (yes, we skipped to section 3, for now) • I can summarize how glucose is broken down in glycolysis. • I can describe how ATP is made in cellular respiration. • I can identify the role of fermentation in cellular respiration. • I can evaluate the importance of oxygen in aerobic respiration.

13. Overall Reaction C6H12O6 + 6O2→ 6CO2 + 6H2O + 38 ATP • Overall this is a three stage process • Glycolysis: • Occurs in the cytoplasm • Glucose is broken down • Krebs Cycle • Breaks down pyruvate into CO2 • Occurs in mitochondrial matrix • Electron Transport Chain • ATP is synthesized

14. Glycolysis • Glyco = glucose Lysis = break down • Occurs in the cytoplasm • This stage occurs in BOTH aerobic and anaerobic respiration • Glucose breaks down into 2 pyruvate (2 ATP are also made) • Glucose is a 6-carbon sugar • Pyruvate is a 3-carbon molecule (there are two of them) • See diagram on simple explanation handout

15. Reactants 1 glucose Enzymes are needed 2 ATP are needed to start Products 2 Pyruvates (go to next step) 4 ATP (2 are gained) 2 NADH (go to ETC) Glycolysis Reactants and Products

16. Intermediate step • Pyruvate is converted to acetyl CoA • Occurs in the cytoplasm • See diagram on simple explanation handout

17. Intermediate step Reactants and products Reactants • 2 pyruvate (from glycolysis) Products • 2 Acetyl CoA (go to next step) • 2 CO2 (given off as waste) • 2 NADH (go to ETC)

18. Krebs Cycle (Citric Acid Cycle) • Occurs in the matrix of mitochondria • A series of reactions occur (this is not just one step) • Main purpose is to generate electrons for use in ETC • 2 ATP is given off • See diagram on simple explanation handout

19. Krebs Cycle Reactants and Products Reactants • 2 Acetyl CoA Products • 2 ATP • 6 NADH (go to ETC) • 2 FADH2 (go to ETC) • 4 CO2 (given off as waste)

20. Electron Transport Chain • Occurs in inner membrane of mitochondria • Series (chain) of coupled redox reactions (electrons are transported through the chain) • Electrons carried to this step by NADH and FADH2 (produced in previous steps) • Oxygen is used in this step • Water is given off

21. Electron Transport Chain Reactants and Products Reactants • 10 NADH • 2 FADH2 • Oxygen Products • 34 ATP • H2O

22. Where do we get 38 ATP? • 2 ATP made in glycolysis • 2 ATP made in Krebs Cycle • 34 ATP made in ETC • 1 NADH = 3 ATP • 10 X 3 = 30 • 1 FADH2 = 2 ATP • 2 X 2 = 4

23. Anaerobic Respiration (Fermentation) • Glycolysis • Yields 2 pyruvate and 2 ATP • With no oxygen present, cellular respiration does not occur • ONLY 2 ATP ARE PRODUCED (compare to aerobic respiration)

24. Two Types of Fermentation Alcoholic Fermentation • Pyruvate converted to ethyl alcohol and CO2 • Carried out by yeast and some bacteria • Used in producing alcohol (both consumable and for ethanol), and for baking Lactic Acid Fermentation • Pyruvate converted to lactic acid • Carried out by muscles when working hard (muscles need ATP but can’t get O2 ) • Causes muscle soreness and cramps

25. Photosynthesis • Carried out by most (not all) autotrophs • 6CO2 + 6H2O + light energy→ C6H12O6 + 6O2 • Basically this reaction is the OPPOSITE of cellular respiration • See simple explanation handout and text

26. Steps of Photosynthesis • Light reaction (depends on light) • Traps sunlight • Produces electrons and ATP required to power the dark reaction • Oxygen given off here • Dark reaction, aka Calvin Cycle (does not directly depend on light) • Uses ATP and electrons from light reaction and CO2 to make glucose See diagram on simple explanation handout