Chapter 8 - Photosynthesis. 8.1 Energy and Life

Transcription

1 Chapter 8 - Photosynthesis 8.1 Energy and Life

2 All activities performed by a cell require energy (the ability to do work) Cells must obtain and use energy

3 ATP Most energy in a cell is stored and released by adenosine triphosphate (ATP) Structure Adenine molecule, ribose (sugar) molecule, and three phosphate groups

4 Energy is stored and released from the phosphate group bonds ATP does not store energy when it is in the form of ADP (only 2 phosphates) ATP stores energy when it has all three phosphates. It s like a fully charged battery.

5 Energy is stored when a phosphate group is added to adenosine diphosphate (ADP) ADP + p + energy ATP Energy is released when a phosphate group is removed ATP ADP + p + energy Energy can be continuously added and released this way

6 Used to power many functions in cell Active transport Movement (muscle cells) Chemical reactions

7 ATP does not store energy for long periods of time Molecules such as sugar (glucose) are produced to store energy Stored energy is used to produce ATP when needed

8 How organisms obtain energy Heterotrophs organisms that obtain food by eating other organisms (animals, fungi) Autotrophs organisms that can make their own food (plants, algae) Photosynthesis sunlight energy is used to produce glucose (sugar) Energy in sunlight is converted into chemical energy Chemosynthesis inorganic chemicals are used to produce food

9 Chapter 8 - Photosynthesis 8.2 Photosynthesis: An Overview

10 Light and pigments Different colors of sunlight (energy) travel at specific wavelengths of light

11 Pigments molecules that absorb specific colors of light Chlorophyll absorbs all light except green, which is reflected (so, plants appear green) Carotenoids (Carotene) - an accessory pigment in plants that absorbs all light except for red, orange, or yellow (usually seen in Autumn leaves)

12 The Chloroplast Structure Grana - Stacks of membrane sacks (singular = Granum) Thylakoid the membrane sacks of grana Chlorophyll is located on membrane of thylakoid, where light absorption occurs Stroma Internal space surrounding grana

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15 Structure of the chloroplast

16 Functions of photosynthetic structures

17 Chapter 8 - Photosynthesis 8.3 Photosynthesis

18 The Process 2 Steps: 1. Light-dependent reactions uses sunlight to produce two energy carriers: NADPH and ATP 2. Light-independent reactions uses carbon dioxide (CO 2 ) to produce glucose, using energy from NADPH and ATP (from step 1)

19 1. Light-dependent Reactions Requires sunlight to work Occurs on the membrane of the thylakoid in the chloroplast Clusters of chlorophyll, called photosystems, absorb sunlight and excite electrons Electrons were provided when H 2 O was broken down to form O 2, which is then released as a waste

20 Electrons are passed along a chain of molecules Energy from this is used to produce 2 molecules: NADPH is made from NADP+ ATP is made from ADP

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22 2. Light-independent reactions Occurs in the stroma (open space) of the chloroplast Does not require sunlight

23 Also called the Calvin Cycle Continuous chain of chemical reactions in which energy is used to convert CO 2 into glucose CO 2 enters cycle and is combined with a 5-carbon sugar Molecules are then rearranged using energy from the NADPH and ATP made during the light-dependent reactions By the end of the cycle, some carbon molecules are used to make glucose, while the rest continue the Calvin cycle

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25 Overall Reaction: (you must know this equation!) (sunlight) 6 CO H 2 O ----> C 6 H 12 O O 2

26 Light-Dependent Reactions:

27 8.3 Worksheet Light-Dependent Reactions Summary Photosystem II Electron Transport Chain PSII absorbs light, which increases electron energy. Electrons are passed to the Electron Transport Chain. Water is broken down to replace the lost electrons. H + and O 2 Energy from electrons is used by proteins in ETC to pump H + ions from the stroma into the thylakoid space. Electrons are passed to PSI. Photosystem I Energy in electrons declined, so light is absorbed again to reenergize electrons. Electrons are passed down another ETC, where NADP + picks up the electrons and H + ions to become NADPH. Hydrogen Ion Movement and ATP Formation H + ions were building up in thylakoid space. Concentration (charge gradient) causes H + ions to diffuse out of thylakoid through ATP synthase, which generates production of ATP.

28 How does ATP synthase produce ATP? H + ions pass though the enzyme, causing ATP synthase to rotate. This produces the energy needed to bind ADP to a phosphate group, to produce ATP. When sunlight excites electrons in chlorophyll, how do the electrons change? The electrons take on a great deal of energy, which causes them to move to a higher energy level. What does the Calvin cycle use to produce sugars? They use CO 2 and energy from ATP and NADPH from the light-dependent reactions to make sugar.

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