Photosynthesis (Light Dependent and Calvin Cycle)

8/3/2019 Photosynthesis (Light Dependent and Calvin Cycle)

1/48

PhotosynthesisBountiful Blessings of Light and Nature


2/48

Photosynthesis

is a chemical process thatconverts carbon dioxide into organiccompounds, especially sugars, using the

energy from sunlight and water.


3/48

Where it all Happen

Photosynthesis takes place in the leaves ofthe plant.


4/48

External Structure of a Leaf


5/48

External Structure

Leaf: chlorophyll containing outgrowth of astem or branch; the site of photosynthesis.

Blade (lamina): main part of the leaf.

Vein: line dividing, but not completely, theleaf into sections.

Midrib: line dividing the leaf in two.


6/48

External Structure

Leafstalk (petiole): part of the leaf that isattached to the stem.

Stem: part of the plant that carries theleaves.

Sheath: part of the leaf that attaches thepetiole to the stem.

Stipules: small appendage at the base ofthe petiole.


7/48

Types of Leaves


8/48

Types of Leaves


9/48

Leaf Arrangement


10/48

Internal Structure of

a Leaf


11/48

The location and structure of chloroplastsoverview

LEAF CROSS SECTION MESOPHYLL CELLLEAF

Chloroplast

Mesophyll

CHLOROPLAST Intermembrane space

Outer

membrane

Innermembrane

Thylakoid

compartmentThylakoidStroma

Granum

StromaGrana


12/48

Internal Structure of a Leaf


13/48

Material Flow through the Internal Structure


14/48

Photosynthesis in

the Leaf


15/48

The location and structure of chloroplastsoverview

LEAF CROSS SECTIONMESOPHYLL CELL

LEAF

Chloroplast

Mesophyll

CHLOROPLAST Intermembrane space

Outer

membrane

Innermembrane

ThylakoidcompartmentThylakoid

Stroma

Granum

StromaGrana


16/48

Inside the Chloroplast (An Overview)


17/48

17

Chloroplast

Organelle where photosynthesistakesplace.

GranumThylakoid

Stroma

Outer Membrane

Inner Membrane

Thylakoid stacks are connected together


18/48

A Thylakoid Disc


19/48

A Thylakoid Disc


20/48

A Thylakoid Disc


21/48

A Thylakoid Disc


22/48

A Thylakoid Disc


23/48

A Thylakoid Disc


24/48

A Thylakoid Disc


25/48

A Thylakoid Disc


26/48

Light Dependent Reaction

Light R ti


27/48

NADP

2H+

ADP

ATP

PSII

PSI

XY

Light Reaction

NADPH2

Solar energy

H2O O2

Solarenergy is converted to chemical energy ia ATP &NADPH2.T hey are used in the Dark reaction

a

ADP

Light Reaction


28/48

2H+

ADP

ATP

PSII

PSI

X Y

Light Reaction

NADPH2

H2O

O2

PHOTOLYSIS of WATER

Exitedelectrons

arereleased

fromP

SII

Picked up by low enrgy electron accepter

SoloarEnerg

yisabsorbedbyPS

II

2H+O2

ADP

LIGHT REACTION Picked up by a low energy


29/48

NADP

2H+

ADP

ATP

PSII

PSI

X Y

LIGHT REACTION

NADPH2

H2O

O2

PHOTOLYSIS of WATER

ExitedelectronsarereleasedfromP

SII

picked up by a low

energy electronaccepter

Picked up by a low energyelectron accepter

Solarenerg

yisabsorbedby

PSII

O2

1

2

3

4

5

5

6

8

7

99

10

11

12


30/48

30

Light Reaction (Electron Flow)

Occurs in the Thylakoidmembranes

During the light reaction, thereare two possible routes forelectron flow:

A.Cyclic Electron FlowB.Noncyclic Electron Flow


31/48

31

Cyclic Electron Flow

Occurs in the thylakoid membrane. Uses Photosystem I only

P700 reaction center- chlorophyll a

Uses Electron Transport Chain(ETC)

Generates ATP only

ADP + ATPP


32/48

32

Noncyclic Electron Flow

Occurs in the thylakoid membrane Uses Photosystem II andPhotosystem I

P680 reaction center (PSII) -chlorophyll a P700 reaction center (PS I) -

chlorophyll a Uses Electron Transport Chain(ETC)

Generates O2, ATP and NADPH


33/48

33

Noncyclic Electron Flow

ADP + ATP NADP+ + H NADPH Oxygen comes from the splittingof H2O, not CO2

H2O 1/2 O2 + 2H+

P


34/48

34

Chemiosmosis

Powers ATP synthesis Takes place across the thylakoidmembrane

Uses ETC and ATP synthase(enzyme)

H+ move down their concentrationgradient through channels of ATPsynthase forming ATP from ADP


35/48

35

ChemiosmosisH+ H+

ATP Synthase

H+ H+ H+ H+

H+ H+ high H+

concentration

H+ADP + P ATP

PS II PS IE

TC

low H+concentration

H+Thylakoid

Space

Thylakoid

SUN (Proton Pumping)


36/48

36

Calvin Cycle

Carbon Fixation (light independentreaction) C3 plants (80% of plants on

earth) Occurs in the stroma Uses ATP and NADPH from lightreaction as energy

Uses CO2 To produce glucose: it takes 6turns and uses 18 ATP and 12

NADPH.


37/48



38/48



39/48



40/48



41/48



42/48


43/48


Ph t r spir ti n


44/48

44

Photorespiration

Occurs on hot, dry, bright days Stomates close

Fixation of O2 instead of CO2

Produces 2-C molecules instead of3-C sugar molecules

Produces no sugar molecules or noATP


45/48

45

Photorespiration

Because of photorespiration, plantshave special adaptations to limitthe effect of photorespiration:

1. C4 plants

2. CAM plants

C Plants


46/48

46

C4 Plants Hot, moist

environments 15% of plants(grasses, corn,sugarcane)

Photosynthesisoccurs in 2 places

Light reaction -

mesophyll cells Calvin cycle - bundlesheath cells

CAM Pl


47/48

47

CAM Plants

Hot, dry environments 5% of plants (cactus and iceplants)

Stomates closed during day Stomates open during the night Light reaction - occurs during

the day Calvin Cycle - occurs when CO2 ispresent


48/48

Cam plants close

their stomata inthe hottest part

of the day toconserve water

Photosynthesis (Light Dependent and Calvin Cycle)

Documents