Photosynthesis Chapter 8

Energy & Life

Energy The ability to do work. Can be stored in chemical bonds. Cells need energy to do things like active transport, dividing, moving, and producing and storing proteins. http://www.youtube.com/watch?v=qyb UFnY7Y8w

Autotrophs vs. Heterotrophs Organisms that make their own food. AKA: producers Ex: plants Organisms that obtain energy from the food that they eat. AKA: consumers or decomposers Ex: sheep, wolves, mushrooms

ATP (adenosine triphosphate) The main energy storage compound for living things. ATP is NOT good to store lots of energy for a long time (glucose is used then). Has three phosphate groups.

ADP (adenosine diphosphate) Same as ATP, but with only two phosphate groups. When a cell has extra energy, it stores it by adding a phosphate group to ADP, making ATP. To release the energy, the bond is broken, converting ATP back to ADP. Video Clip: ATP, The Energy Currency

Photosynthesis: An Overview

Light & Pigment White light is actually a mixture of different wavelengths of light. Pigments: light absorbing molecules that gather the sun’s energy. The plant’s principle pigment is chlorophyll. Energy absorbed by chlorophyll is transferred directly to electrons in the chlorophyll molecule. These high energy electrons make photosynthesis work.

So why are leaves green? Look at the wavelengths of light that chlorophyll absorbs & uses in photosynthesis The colors that are left are reflected back and that is what you see.

Electron Carriers NADP+: can accept 2 high-energy electrons by bonding with an H+; an “uncharged” energy carrier Similar to ADP NADPH: the “charged” version Similar to ATP

6H2O + 6CO2 ----------> C6H12O6+ 6O2 Photosynthesis: An Overview ● The process that captures light energy and uses it to make carbohydrates (glucose). sunlight 6H2O + 6CO2 ----------> C6H12O6+ 6O2 Water: Comes in through the roots Carbon Dioxide: Comes in from the air Glucose: Stored as chemical energy Oxygen: leaves back to the air

Where does it take Place? In the chloroplasts.

Photosynthesis 2 Parts: Light dependent reactions Light independent reactions (AKA dark reactions or the Calvin Cycle)

The Process of Photosynthesis

Light Dependent Reactions Where? The granum 1.) chlorophyll absorbs light 2.) H2O is split; O2 is released 3.) ATP & energy carriers (NADPH) are formed & take the energy (stored in their bonds) to the light independent reaction

Light Independent Reactions/ The Calvin Cycle Where? The stroma 1.) ATP & NADPH are broken down (ADP & NADP+) are recycled back to the light dependent reaction 2.) the energy released is used to convert CO2 to C6H12O6

Factors Affecting Photosynthesis Temperature Best between 0 & 35˚C Light intensity A higher intensity increases the rate of photosynthesis until a maximum rate is reached. Water A shortage can stop photosynthesis. Video Clip: Photosynthesis http://www.youtube.com/watch?v=LgYPeeABoUs

Cellular Respiration & Fermentation Chapter 9

Cellular Respiration: An Overview

calorie The amount of energy needed to raise 1g of H2O 1○ C. When burned, 1g of glucose releases 3811 calories of heat energy. Food labels show Calories (= 1000 calories).

Two more Electron Carriers NAD+ & FAD: “uncharged” energy carriers Similar to ADP NADH & FADH2: the “charged” versions Similar to ATP

C6H12O6 + 6O2 ----------> 6H2O + 6CO2 Cellular Respiration Releases energy (ATP) by breaking down food in the presence of oxygen. C6H12O6 + 6O2 ----------> 6H2O + 6CO2 Oxygen: taken in from the air Water: released as waste Carbon Dioxide: released into the air Glucose: Plants- have it stored from photosynthesis; Animals- get it from food

The Process of Cellular Respiration

Cellular Respiration Three parts: Glycolysis Kreb’s cycle Electron Transport Chain

Glycolysis Where? The cytoplasm 1.) C6H12O6 is split to form 2 pyruvic acids (2C3H6O3) 2.) the energy is captured in ATP & energy carriers (NADH)

Kreb’s Cycle Where? The mitochondria 1.) 2 pyruvic acids (2C3H6O3) are broken down into CO2 2.) the energy is captured in ATP & energy carriers (NADH& FADH2)

Electron Transport Chain Where? The mitochondria 1.) Energy carriers (NADH & FADH2) are broken apart; the energy released is used to make ATP 2.) O2 bonds with leftover H+ to make H2O Video Clip: Glycolysis & Cellular Respiration

Fermentation

Aerobic vs. Anaerobic When O2 is present & all of cellular respiration occurs, 36 ATPs are made from 1 C6H12O6. Aerobic: reactions that require oxygen (the Kreb’s cycle & electron transport chain) When there is no O2, only glycolysis occurs & 2 ATPs are made from 1 C6H12O6. Anaerobic: reactions that do not need oxygen (glycolysis)

Glycolysis Advantage: ATP can be made without oxygen Disadvantage: the cell will run out of NAD+ & glycolysis will stop So… Fermentation occurs!

Fermentation Allows glycolysis to continue by converting NADH into NAD+ Anaerobic Two types: Alcoholic fermentation Pyruvic acid + NADH -> alcohol + CO2 + NAD+ Lactic Acid fermentation Pyruvic acid + NADH -> lactic acid + NAD+