Photosynthesis and Respiration

Photosynthesis: Extremely important in relation to energy for life Energy comes from ‘food’ but it really all starts with energy from the Sun ‘Plants’ are autotrophs, other organisms (including humans) are heterotrophs

I’m talking about more than trees…

Photosynthesis creates stored energy in the form of sugars (ex: glucose, starch etc). Sunlight + CO2 + water  Sugar + oxygen

Examples of stored energy in chemical compounds: wax to be burned food to be digested ATP to be broken up Breaking bonds releases energy Two stages of photosynthesis: 1st: produces O2 and ATP 2nd: produces ADP and sugars

1. List six things that energy from ATP can be used to do. 2. Compare the energy-storing capacity of molecules of ATP to molecules of glucose. 3. What was the original thought-provoking question that ultimately led to the discovery of photosynthesis? 4. Describe the experiment and findings (conclusions) of: A) Jan von Helmont, B) Priestley, C) Ingenhousz 5. a) What substance allows plants to photosynthesize? b) In what organelle is this substance found? 6. Why are plants green in colour? 7. a) What is the name of the stage in photosynthesis that doesn’t require light? B) Why is it named this? 8. Name three factors that affect photosynthesis rates.

Stages/steps of Cellular Respiration: 1) Glycolysis: The lysis (‘breaking’) of glycogen (a bunch of glucose). 1 molecule glucose  2 molecules pyruvic acid. Occurs in cytoplasm. Then: 2) Kreb’s cycle: Pyruvic acid is broken up to release energy (ATP). CO2 is a by product and is released in your breath. Occurs in mitochondria. and then: 3) Electron transport chain: High energy electrons and hydrogen ions move across the membrane of the mitochondrion. In the process, they turn ADP into huge amounts of ATP.

Glycolysis  small amount of energy Other two stages  lots of energy If it all happened in one step, too much energy would be lost/wasted to heat Cells therefore do it slowly, in several steps, using small bits of energy to make ATP. Efficiency still only about 38%, the other 62% is released as heat.

What if there is no oxygen present? If glycolosis happens anaerobically, cellular respiration will not happen; it will lead to fermentation instead: A few examples: a) Alcoholic fermentation: Produces ethyl alcohol and CO2 gas (yeast to rise bread, make alcohol) b) Lactic acid fermentation: -Lactic acid accumulates in muscles when the body cannot supply enough oxygen (rapid exercise). -To produce cheese, yogurt etc. with the help of prokaryotes.

Types of cells that do it: Tying it all together: Photosynthesis: Cellular Respiration: Function: Location: Reactants: Products: Equation: Types of cells that do it:

Tying it all together: Function: Location: Reactants: Products: Photosynthesis: Cellular Respiration: Function: Energy storage Energy release Location: Chloroplasts Mitochondria Reactants: CO2 and H2O Glucose(C6H12O6) +O2 Products: Equation:  Glucose + O2 Glucose + O2  Organisms that do it: Plants, algae, bacteria (autotrophs only) All eukaryotes, some prokaryotes

Page 217: #’s 1-8 Page 237: #’s 1-4, and 7, 8, 10, 13 Review questions: Page 217: #’s 1-8 Page 237: #’s 1-4, and 7, 8, 10, 13

Page 217, questions 1-8: 1. b (plants) 2. b (ATP) 3. b (van Helmont) 4. d (water and carbon dioxide) 5. c (reflects green light) 6. a (sugars and oxygen) 7. d (chloroplast, plastid) 8. a (light absorption)

Page 237 answers: 1. c (ATP) 2. b (glycolosis) 3. b (cellular respiration) 4. c (all of the above) 7. c (mitochondrion) 8. b (convert ADP to ATP) 10. b (oxygen debt) 13. if oxygen, cellular respiration continues if no oxygen, fermentation continues