Chapter 9 Energy in a Cell

Section 9.1 The Need for Energy Explain why organisms need a supply of energy. Describe how energy is stored and released by ATP.

ATP: The Energy unit of the Cell CH2 H OH N C HC NH2 Adenine Ribose Phosphate groups - CH ATP (adenosine triphosphate,三磷酸腺苷）

Cell Energy use in Active Transport

Energy is released from ATP (-30.54 kJ/mol) When the terminal phosphate bond is broken

Section 9.2 Photosynthesis: Trapping the Sun’s Energy Relate the structure of chloroplasts to the events in photosynthesis. Describe light-dependent reactions. Explain the reactions and products of the lightindependent Calvin cycle.

Trapping Energy from Sunlight The process that uses the sun’s energy to make simple sugars is called photosynthesis(光合作用). (P 225) 6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2 O

Leaf cross section Vein Mesophyll Stomata CO2 O2

P 184

The Light-Dependent reactions （光反应） Reflected Chloroplast Absorbed light Granum Transmitted Pigments- light absorbing molecules Chlorophyll a (main pigment in photosystem 1) Chlorophyll b (main pigment in photosystem 2)

The Light-Dependent reactions Photolysis

3H+= 1 ATP Chemiosmosis: Movement of chemicals across a selectively- permeable membrane

H2O CO2 [CH2O] O2 (sugar) Light NADP  ADP + P CALVIN LIGHT REACTIONS CYCLE Chloroplast [CH2O] (sugar) NADPH NADP  ADP + P O2 ATP

The Light-Independent reactions

Final Numbers Use Produce Light-Dependent Reactions Sunlight NADPH H2O ATP O2 Use Produce Light-Independent Reactions (Calvin Cycle) NADPH RuBP ATP PGAL (Which form sugars) CO2 NADP+/ADP/Pi

P 242

Section9.3 Getting Energy to Make ATP Compare and contrast cellular respiration and fermentation. Explain how cells obtain energy from cellular respiration.

Cellular Respiration (p 231) The process by which mitochondria break down food molecules to produce ATP is called cellular respiration(细胞呼吸). C6H12O6 + 6O2 = 6CO2 + 6H2O + ATP

Oxidative phosphorylation: electron transport and chemiosmosis Cellular Respiration Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Oxidative Mitochondrion Cytosol Aerobic Reactions Anaerobic Reactions

Cellular Respiration Glycolysis (糖酵解) Total NADH 2 FADH2 ATP -2+4= 2 Glycolysis (糖酵解) in the cytoplasm，break down glucose, into two molecules of pyruvic acid a (3-C) is anaerobic—no oxygen is required. 2 ATP go in, 4 come out; Net Gain of 2 ATP Also produces 2 NADH

Cellular Respiration Total NADH 2+2= 4 FADH2 ATP 2 CO2

Krebs Cycle Total NADH 4+6= 10 FADH2 2 ATP 2+2= 4 CO2 2+4= 6

Electron Transport Chain Total NADH -10 FADH2 -2 ATP 4+34= 38 CO2 6 H2O （电子传递链） 2H+ = 1 ATP

Final Numbers…

Cellular Respiration

Fermentation (发酵) In the absence of oxygen，cells can still produce ATP through fermentation There are two major types of fermentation: lactic acid fermentation （乳酸发酵） and alcoholic fermentation（酒精发酵）.

Glucose CYTOSOL Pyruvate Ethanol or lactate No O2 present Fermentation O2 present Cellular respiration Ethanol or lactate Acetyl CoA MITOCHONDRION Citric acid cycle

Lactic Acid Fermentation Fermentation allows constant energy supply during exercise Lactic acid can not be changed back into pyruvic acid in the cells Liver has enzymes designed to convert lactic acid Lactic acid builds up too fast and changes the pH of muscle cells Change in pH slows performance and weakens the muscle cells

Alcohol Fermentation

P 235

Comparing Photosynthesis and Cellular Respiration

That’s all