Presentation is loading. Please wait.

Presentation is loading. Please wait.

Section Objectives Relate the structure of chloroplasts to the events in photosynthesis Describe light-dependent reactions. Explain the reactions and.

Similar presentations


Presentation on theme: "Section Objectives Relate the structure of chloroplasts to the events in photosynthesis Describe light-dependent reactions. Explain the reactions and."— Presentation transcript:

1

2 Section Objectives Relate the structure of chloroplasts to the events in photosynthesis Describe light-dependent reactions. Explain the reactions and products of the light- independent Calvin cycle. Ch. 8.2

3 Photosynthesis: Life from Light and Air

4 Trapping Energy from Sunlight The process that uses the sun’s energy to make simple sugars is called photosynthesis.

5 AN OVERVIEW OF PHOTOSYNTHESIS Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water PHOTOSYNTHESIS

6 Plants are energy producers Like animals, plants need energy to live – unlike animals, plants don’t need to eat food to make that energy Plants make both FOOD & ENERGY – animals are heterotrophs(consumers) – plants are autotrophs (producers)

7 How do plants make energy & food? Plants use the energy from the sun – to make ATP energy – to make sugars glucose, sucrose, cellulose, starch, & more sun ATP sugars

8 H2OH2O Building plants from sunlight & air Photosynthesis – 2 separate processes – ENERGY building reactions collect sun energy use it to make ATP – SUGAR building reactions take the ATP energy collect CO 2 from air & H 2 O from ground use all to build sugars ATP sun sugars + carbon dioxide CO 2 sugars C 6 H 12 O 6 CO 2 water H 2 O +

9 What do plants need to grow? The “factory” for trapping energy & making sugars – chloroplast Fuels – sunlight – carbon dioxide – water The Products - Oxygen & Glucose The Helpers – Enzymes H2OH2O sugars enzymes CO 2 sun O2

10 Bring In – light – CO 2 –H2O–H2O Let Out –O2–O2 Move Around – sugars So what does a plant need? 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ roots shoot leaves

11 H2OH2O Photosynthesis ENERGY building reactions SUGAR building reactions ATP ADP CO 2 sugar sun used immediately to synthesize sugars

12 Chloroplasts Chloroplasts in cell Leaf Leaves Chloroplast absorb sunlight & CO 2 make ENERGY & SUGAR Chloroplasts contain Chlorophyll CO 2 Chloroplast sun

13 Stomates & Guard Cells in the leaf Function of stomates – CO 2 in – O 2 out – H 2 O out gets to leaves for photosynthesis Function of guard cells – open & close stomates guard cell stomate

14 An overview of photosynthesis LIGHT REACTIONS (in grana CALVIN CYCLE (in stroma NADPH ATP NADP+ ADP +P O2 Sugar H2O CO2 O2 Light Chloroplast

15 Trapping Energy from Sunlight Photosynthesis happens in two phases. 1.The light-dependent reactions convert light energy into chemical energy. (ATP) 2. The molecules of ATP produced in the light-dependent reactions are then used to fuel the Calvin Cycle or light-independent reactions that produce simple sugars. The general equation for photosynthesis is written as 6CO 2 + 6H 2 O→C 6 H 12 O 6 + 6O 2

16 THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY Visible radiation drives the light reactions Certain wavelengths of visible light drive the light reactions of photosynthesis Visible light Wavelength (nm) Gamma rays X-rays UVInfrared Micro- waves Radio waves

17 pigments in the chloroplast To trap the energy in the sun’s light, the thylakoid membranes contain pigments, molecules that absorb specific wavelengths of sunlight. Wavelengths that are NOT absorbed are reflected (bounce off) or transmitted (pass through) So the material in which the pigment is found appears to be the color of the wavelengths that are NOT absorbed Photosynthetic pigments: can absorb light energy & make it available for conversion to chemical energy. Absorbed light Reflected light Light Chloroplast

18 pigments in the chloroplast Chlorophyll a: most common pigment in chloroplast (absorbs blue &red light and reflects green light thus giving the chloroplast a green color)(chloro = green phylla + leaf) Accessory pigments: additional pigments that absorb different wavelengths (carotene, chlorophyll b, & xanthophyll)

19

20 Light-Dependent Reactions absorption of light energy by chlorophyll As sunlight strikes the chlorophyll molecules in a photosystem of the thylakoid membrane, the energy in the light is transferred to electrons. These highly energized, or excited, electrons are passed from chlorophyll to an electron transport chain, a series of proteins embedded in the thylakoid membrane. At each step along the transport chain, the electrons lose energy.

21 Photolysis Energized electrons Energy from the energized electrons pump H + ions and change NAPD + to NADPH. The H + ions move from high to low and turn the ATP synthase and change ADP + P to ATP Oxygen by-product

22 Light-Dependent Reactions Chemiosmosis: This “lost” energy can be used to form ATP from ADP, or to pump hydrogen ions into the center of the thylakoid disc..

23 Light-Dependent Reactions The electrons are transferred to the stroma of the chloroplast. To do this, an electron carrier molecule called NADP is used. NADP can combine with two excited electrons and a hydrogen ion (H + ) to become NADPH. NADPH will play an important role in the light- independent reactions.

24 Restoring electrons To replace the lost electrons, molecules of water are split in the first photosystem. This reaction is called photolysis. The O 2 liberated by photosynthesis is made from the oxygen in water H 2 O     O 2 + 2e - Chlorophyll 2e - H2OH2O O 2 + 2H + 2

25 Restoring electrons The oxygen produced by photolysis is released into the air and supplies the oxygen we breathe. The electrons are returned to chlorophyll. The hydrogen ions are pumped into the thylakoid, where they accumulate in high concentration.

26 Light Dependent Reactions: Summary Absorptions of light energy by chlorophyll-takes place in thylakoid 1. Split water molecule (PHOTOLYSIS) Oxygen combines with other oxygen to produce O 2 which is given off as a by-product 2. Hydrogen produced by splitting of water is attached to hydrogen carrier NADP -> NADPH (energy in this molecule) 3. Then energy from “excited electrons”is used to take ADP + P ->ATP

27 Light Independent Reactions or The Calvin Cycle CO 2 put into organic molecules called Carbon fixation Does not require light but must have ATP and NADPH which are produced by light dependent reactions Called Calvin Cycle (Melvin Calvin won Nobel prize in chemistry) Takes place in stroma of chloroplast

28 Light Independent Reactions or The Calvin Cycle The Calvin cycle constructs G3P (a sugar) using – carbon from atmospheric CO 2 – electrons and H + from NADPH – energy from ATP Energy-rich sugar (G3P) is then converted into glucose CALVIN CYCLE INPUT OUTPUT:

29 Bring In – light – CO 2 –H2O–H2O Let Out –O2–O2 Move Around – sugars So what does a plant need? 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ roots shoot leaves

30 An overview of photosynthesis LIGHT REACTIONS (in grana CALVIN CYCLE (in stroma NADPH ATP NADP+ ADP +P Sugar H2O CO2 O2 Light Chloroplast

31 Factors Affecting Rate of Photosynthesis 1.Temperature: increases rate up to a certain point 2.Light Intensity: increases rate up to a certain point 3.CO2 level: Increases rate up to a certain point 4.Water: decrease water, decrease photosynthesis 5.Minerals; Ex. Magnesium, Nitrogen


Download ppt "Section Objectives Relate the structure of chloroplasts to the events in photosynthesis Describe light-dependent reactions. Explain the reactions and."

Similar presentations


Ads by Google