stomate

transpirationgas exchange

PHOTOSYNTHESIS!!

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Photosynthesis Overview

Energy for all life on Earth ultimately comes from photosynthesis.

6CO2 + 12H2O C6H12O6 + 6H2O + 6O2

Photosynthesis is carried out by:Cyanobacteria,Some protists,+ Land plants

• Chloroplasts– double membrane– stroma

• fluid-filled interior– thylakoid sacs– grana stacks

• Thylakoid membrane contains– chlorophyll molecules– electron transport chain– ATP synthase

• H+ gradient built up within thylakoid sac

H+ H+

H+H+

H+H+

H+ H+H+H+

H+

outer membrane inner membrane

thylakoidgranum

stroma

thylakoid

chloroplast

ATP

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Pigments

Pigments: molecules that absorb visible light

Each pigment has a characteristic absorption spectrum, the range it is capable of absorbing.

--chlorophyll a – primary pigment--chlorophyll b – secondary pigment-- carotenoids – accessory pigments

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Why are plants green??

Two stages of photosynthesis:

1. Light-dependent reactions• Requires light as a source of energy

Step 1: chlorophyll uses energy from sun to split water molecules

Step 2: water molecules split into H & OStep 3: O2 released to atmosphereStep 4: chlorophyll stores some light energy in ATP

Photo

phosphoryl

ation A process

Adding aphospate group

Using light

Light Reactions

O2

H2O

Energy BuildingReactions

ATP

produces ATP produces NADPH releases O2 as a

waste product

sunlight

H2O ATP O2lightenergy ++ + NADPH

NADPH

Thylakoid Structure

Non-cyclic

2. Light-Independent reactions (Calvin Cycle)• Part of photosynthesis that doesn’t require

light

Step 1: hydrogen which split from H2O combines with CO2 using energy stored in ATP

Step 2: this combination forms glucose (C6H12O6)Step 3: water is formed (byproduct)

Making Sugar

The energy captured in the Lt-Dep is now used to fix CO2 and make sugar.

Calvin Cycle

sugars

CO2

SugarBuildingReactions

ADP

builds sugars uses ATP &

NADPH recycles ADP &

NADP back to make more

ATP & NADPHATP

NADPH

NADP

CO2 C6H12O6 ++ + NADPATP + NADPH ADP

Putting it all togetherCO2 H2O C6H12O6 O2

lightenergy + ++

SugarBuildingReactions

Energy BuildingReactions

Plants make both:energy

ATP & NADPH sugars

sunlight

O2

H2O

sugars

CO2

ADP

ATP

NADPH

NADP

*respiration occurs in plant cells also, when they need to release the energy stored in glucose

H2O

Energy cycle

Photosynthesis

Cellular Respiration

sun

glucose O2CO2

plants

animals, plants

ATPThe Great Circleof Life,Mufasa!

CO2 H2O C6H12O6 O2lightenergy + ++

even thoughthis equationis a bit of a lie…it makes a better story

CO2 H2OC6H12O6 O2ATPenergy+ ++

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