Overview of Photosynthesis

Transcription

1 Photosynthesis

2 Overview of Photosynthesis

3 During photosynthesis, autotrophs/producers use the sun s energy to make carbohydrate molecules from water and carbon dioxide, releasing oxygen as a by-product

4 Equation: 6CO2 + 6H20 +light energy Reactants C6H12O6 + 6O2 products

5 6CO2 + 6H20 C6H12O6 + 6O2 This equation means: 6 molecules of carbon dioxide plus 6 molecules of water, with the help of light energy are converted into glucose and six molecules of oxygen.

6 Chloroplasts Photosynthesis occurs in the chloroplast of the plant cell

7 membrane

8 Inside the thylakoids is chlorophyll Chlorophyll is a green pigment Pigment: molecule that absorbs certain wavelengths of light and reflects others. The reflected wavelength is what determines what color you see. Chlorophyll absorbs violet, blue, and red and reflects green.

9 Photosynthesis occurs in two stages: Stage 1: Light dependant Reactions occurs in thylakoid membranes of the chloroplast

10 Picture Overview What are the two main parts of the chloroplast where the reactions occur? Stage 1: Thylakoid membranes 2: STROMA

11 Light dependent reaction SElaE

12 Solar energy boosts electrons to a higher energy level In the thylakoid membrane, photosystems contain: 1. A pigment complex that absorbs solar energy 2. An electron-acceptor molecule A pigment complex consists of antenna molecules and a reaction center. Antenna chlorophyll molecules absorb light and pass energy to the reaction center. In the reaction center, excited electrons are passed to electron acceptors. 6-12

13 Figure Solar energy boosts electrons to a higher energy level 6-13

14 Photosystems Two types of photosystems participate in the light reactions: Photosystem I (PS I) Reaction center in PS I absorbs light with a wavelength of 700 nm Photosystem II (PS II) Reaction center in PS II absorbs light with a wavelength of 680 nm 6-14

15 Chloroplasts use electrons energized by solar energy to generate ATP. First step-light/solar energy is converted into energy in chlorophyll a electrons (e-) (PSII) When the light hits the chlorphyll pigments it charges their electrons up. Charged/excited electrons leave the chlorophyll and go down an electron transport chain of pigments PS I- This is where the escaped electrons move to a different electron-acceptor molecule and NADP + NADPH

16 Restoring PSII When electrons leave the chlorophyll a in photosystem II, they need to be replaced by more! The photons that hit PSII also provide energy for photolysis-the splitting of water with light.

17 Light reaction: 6CO2 + 6H20 C6H12O6 + 6O2 Photolysis-Requires the reactants water and sunlight Every 2 Water molecules are broken down into 3 pieces by a special enzyme: 1) Four Hydrogen protons (H+) build up inside thylakoid compartment of chloroplast 2) Oxygen gas (O 2 ) is released from the plant chloroplast as a waste product 3)Four Excited Electrons (e-) go to the group of pigments called photosystem II to replace the electrons lost from the electron transport C

18 6-18

19 Animated summary of light reaction in thylakoid of grana 72/bio13.swf

20 *Remember thefour Hydrogen protons from water? (H+) build up inside thylakoid compartment of chloroplast. The proton pump is an indirect active transport used by chloroplasts to produce ATP. The enzyme pumps hydrogen protons through the thylakoid and out to the stroma. It gets its energy from the potential energy of the high concentration gradient of H+ protons inside thylakoid created by splitting the water. When hydrogen protons go from higher to lower concentration, ATP is produced.

21 Figure

22 The purpose of the light reaction: Energy from the light, electron transport chain and proton pump is used to make NADPH in addition to ATP. These energy molecules are needed in the next stage

23 Stage 2 of photosynthesis: Calvin Cycle AKA Light Independent- 6CO2 + 6H20 C6H12O6 + 6O2 Happens in the stroma of the chloroplast Requires the ATP and NADPH energy from the light dependant reactions as well as the gas reactant CO 2 6 CO 2 are required to build one carbohydrate, glucose (C6H12O6 ) THE PURPOSE OF THIS REACTION IS TO FIX CARBON FROM CO2 INTO GLUCOSE.

24

25

26 Stage 1: Light dependent reaction Chloroplast Light Granum/Thylakoid Chlorophyll and photosystems Water Stage 2: Light independent reaction: ATP and NADPH Oxygen Carbon Dioxide (CO2) Calvin/light independent cycle Glucose (C6H12O6

27

28 Photosynthesis Flow Map RAW Materials/Reactants Products Enters through the Photo-lysis of light dependent reaction: Made with Gas waste from the reaction & used in 1) 2) 3) Makes the energy molecules, here. Uses the energy molecules: This process is called: Occurs in the: Occurs in the: