QOD - _______ is a membrane

system found within the

chloroplast, that are a flat,

disc shaped structure.

QOD - _______ is a membrane

system found within the

chloroplast, that are a flat,

disc shaped structure.

PhotosynthesisPhotosynthesis

Chapter 9 Section 2 Chapter 9 Section 2

THE SUN: MAIN SOURCE OF ENERGY FOR LIFE ON

EARTH

Harvesting Light Energy

• Chloroplasts – organelle responsible for converting light energy into chemical energy (glucose)

Stru

ctur

e of

Chlo

ropl

ast

Parts:1. Outer membrane - permeable

2. Inner membrane – selectively

permeable3. Stroma – small area inside the

inner membrane4. Thylakoid – flat, discs that contain

pigments

5. Granum – Stack of thylakoids

6. Thylakoid membrane – structure

that is folded to create thylakoids

7. Pigments – substance the absorbs

the light energy and begins the

process of photosynthesis

Pigments

– Chlorophyll – reflects green and yellow (absorbs blues and reds) • Chlorophyll a –• Chlorophyll b –

– Carotenoids – reflect oranges, yellows and reds (absorbs blue and green)• Xanthrophyll – yellow• Carotene - orange

Why are plants green?

Reflected

light

Transmitted light

?

• When fall arrives, the leaves on trees turn red/orange/yellow, why is this? Which pigments are visible?

Now where

• Energy from the sun is absorbed by the pigments and then transferred to electrons at the reaction center.– Electrons becoming “excited”

• Gains energy and move to a higher energy level

Excitedstate

e

Heat

Light

Photon

Light(fluorescence)

Chlorophyllmolecule

Groundstate

2

(a) Absorption of a energy - sunlight

Excitation of chlorophyll in a chloroplast

e

Photosynthesis

• Consists of two phases– Light dependent phase (light is

required) – converts solar energy into chemical energy

– Light Independent (Calvin Cycle) (does not required light to occur) converts carbon dioxide and water to glucose

Light Dependent Phase

• 2 parts – First part creates ATP – Second part created NADPH (electron

carrying molecule)

Play

QOD – The sun’s energy is transferred to _______________ in the

reaction centers.

QOD – The sun’s energy is transferred to _______________ in the

reaction centers.

• Light Dependent Phase

– Occurs in the thylakoid membrane

Making ATP

Pigment

H2O ½ O2 + H2

2e-

2e-

Electron Transport Chain

ATP

Light

Indep

enden

t

Cycle

(Calv

in C

ycle)

To Part 2 making NADPH

ATP Synthase

H+

H+

Hydrolysis

• Breaking down of water into hydrogen and oxygen

Pigment

2 e-

2e-

NADP+

NADPH

e

2e-

+

Light Independent Cycle(Calvin Cycle)

Electron Transport Chain

Making NADPH

H+

H+

From Part I

From Part I

NADPH

• High energy electron carrying that takes that energy to the Light Independent cycle to make glucose

Making Sugar• The high energy carrying

molecules, ATP and NADPH combine with the carbon from carbon dioxide to make Glucose.

• Light Independent Cycle (Calvin Cycle) – occurs in stroma

Play

RuBP (5 carbon)

CO2

2 Pgal (3 carbon)

Rubisco – enzyme that attaches the carbon

6 carbon structure created is not stable and immediately breaks down into 2, 3 carbon structures

2, 3 carbon Goes through a series of step to be modified – uses ATP and NADPH

2 ATP

2 ADP

2 NADPH

2 NADP+

PGAL goes through a series of reaction to become a 5 carbon structure

1 Pgal drops down ever three rotations. This will later become glucose after six rotations

ATP

ADP

Step 1: Carbon Fixation

Step

2: T

rans

ferrin

g En

ergy

Step 3: Making Sugar

RuBP (5 carbon)

Step 4: Recycling

Calvin Cycle

ATP & NADPH enter from the light dependent cycle.

Cycle starts over

• Light Independent (Calvin Cycle)

– Occurs in the stroma of the chloroplast

• The Calvin cycle makes sugar from carbon dioxide– ATP generated by the light

reactions provides the energy for sugar synthesis

– The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose

LightChloroplast

Lightreactions

Calvincycle

NADP

ADP+ P

• The light reactions convert solar energy to chemical energy– Produce ATP &

NADPH

AN OVERVIEW OF PHOTOSYNTHESIS

Factors

• There are 3 environmental factors that affect photosynthesis– Levels of carbon dioxide– Temperature– Light intensity

• Questions?

• QUIZ WEDNESDAY!!!!!!!!