photosynthesis lecture ppt

7/28/2019 Photosynthesis LECTURE PPT

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LECTURE ONPHOTOSYNTHESIS


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By the end of this lecture you will be able to:

1. Understand that ENERGY can be transformed from one form to another.2. Know that energy exist in two forms; free energy - available for doing work

or as heat - a form unavailable for doing work.

3. Appreciate that the Sun provides most of the energy needed for life onEarth.

4. Explain why photosynthesis is so important to energy and material flow forlife on earth.

5. Know why plants tend to be green in appearance.

LEARNING OBJECTIVES

. quate t e organe e o p otosynt es s n eu aryotes w t t e c orop ast.7. Describe the organization of the chloroplast.8. Understand that photosynthesis is a two fold process composed of the

light-dependent reactions (i.e., light reactions) and the lightindependent reactions (i.e. Calvin Cycle or Dark Reactions).

9. Tell where the light reactions and the CO2 fixation reactions occur in the

chloroplast.10. Define chlorophylls giving their basic composition and structure.11. Draw the absorption spectrum of chlorophyll and compare it to the action

spectrum of photosynthesis.12. Define the Reaction Centers and Antennae and describe how it operates.13. Describe cyclic photophosphorylation of photosynthesis.

14. Describe noncyclic photophosphorylation of photosynthesis.


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Energy can be transformed fromone form to another

FREE ENERGY

(available for work)vs.

HEATnot available for work


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THE SUN: MAIN SOURCE OFENERGY FOR LIFE ON EARTH


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Almost all plants are photosynthetic autotrophs, asare some bacteria and protists

Autotrophs generate their own organic matter through

photosynthesis Sunlight energy is transformed to energy stored in the

form of chemical bonds

THE BASICS OF PHOTOSYNTHESIS

(a) Mosses, ferns, andflowering plants

(b) Kelp

(c) Euglena (d) Cyanobacteria


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Light Energy Harvested by Plants &Other Photosynthetic Autotrophs

6 CO2 + 6 H2O + light energy C6H12O6 + 6O2


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Food Chain


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THE FOOD WEB


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WHWHY ARY ARE PE PLANLANTS GTS GREREEN?EN?

It's not that easy bein' greenHaving to spend each day the color of the leavesWhen I think it could be nicer being red or yellow or goldOr something much more colorful like that

Kermit the Frog


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Electromagnetic Spectrum andVisible Light

Gammarays X-rays UV

Infrared &Microwaves Radio waves

Visible light

Wavelength (nm)


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Different wavelengths of visible light are seen by

the human eye as different colors.

WHYWHY AREARE PLAPLANTSNTS GREGREEN?EN?

Gamma

raysX-rays UV Infrared

Micro-

waves

Radio

waves

Visible light

Wavelength (nm)


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The feathers of male cardinals

are loaded with carotenoidpigments. These pigmentsabsorb some wavelengths of

light and reflect others.

Sunlight minus absorbedSunlight minus absorbedwavelengths or colorswavelengths or colorsequals the apparent colorequals the apparent colorof an object.of an object.


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Why are plants green?

Transmitted light


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WHYWHY AREARE PLAPLANTSNTS GREGREEN?EN?

Plant Cells

have GreenChloroplasts

The thylakoidmembrane of thechloroplast is

impregnated withphotosyntheticpigments (i.e.,chlorophylls,carotenoids).


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Chloroplastsabsorb lightenergy and Light

Reflectedlight

THE COLOR OF LIGHT SEEN IS THE

COLOR NOT ABSORBED

convert it tochemical energy

Absorbedlight

Transmittedlight

Chloroplast


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Photosynthesis is the process by which

autotrophic organisms use light energy tomake sugar and oxygen gas from carbon

AN OVERVIEW OF PHOTOSYNTHESIS

Carbondioxide

Water Glucose Oxygengas

PHOTOSYNTHESIS


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Th lvin l m k

Light

Chloroplast

LightCalvinc cle

NADP++++

ADP+ P

The light reactionsconvert solarenergy to chemical

energy Produce ATP & NADPH

AN OVERVIEW OF PHOTOSYNTHESIS

sugar from carbondioxide ATP generated by the light

reactions provides the energyfor sugar synthesis

The NADPH produced by thelight reactions provides theelectrons for the reduction of

carbon dioxide to glucose

reactions


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Chloroplasts: Sites of Photosynthesis Photosynthesis

Occurs in chloroplasts, organelles in certainplants

All green plant parts have chloroplasts and carry

out p otosynt es s The leaves have the most chloroplasts

The green color comes from chlorophyll in thechloroplasts

The pigments absorb light energy


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In most plants, photosynthesis occursprimarily in the leaves, in the chloroplasts

A chloroplast contains:

stroma, a fluid

Photosynthesis occurs in chloroplasts

grana, stacks of thylakoids The thylakoids contain chlorophyll

Chlorophyll is the green pigment that captures

light for photosynthesis


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The location and structure of chloroplasts

LEAF CROSS SECTION MESOPHYLL CELL

LEAF

Chloroplast

Mesophyll

CHLOROPLAST Intermembrane space

Outermembrane

Innermembrane

Thylakoid

compartmentThylakoidStroma

Granum

StromaGrana


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Chloroplasts contain several pigments

Chloroplast Pigments

Chlorophyll a Chlorophyll b

Carotenoids

Figure 7.7


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Chlorophyll a & b Chl a has a methylgroup

Chl b has a carbonylgroup

orp yr n r ngdelocalized e-

Phytol tail


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Different pigments absorb light

differently


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Excitedstate

e

Heat

Light

2

Excitation of chlorophyll

in a chloroplast

Loss of energy due to heatcauses the photons of light to be

less energetic.Less energy translates into

longer wavelength.

Energy = (Plancks constant) x

(velocity of light)/(wavelength oflight)

Transition toward the red end of

the visible spectrum.

e

Photon

Light

(fluorescence)

Chlorophyllmolecule

Groundstate

(a) Absorption of a photon

(b) fluorescence of isolated chlorophyll in solution


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Primaryelectron acceptor

Molecular Game of Hot Potato

Photon

Reactioncenter

PHOTOSYSTEM

Pigmentmolecules

of antenna


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Cyclic Photophosphorylation Process for ATP generation associated with

some Photosynthetic Bacteria

Reaction Center => 700 nm


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Two types of

photosystemscooperate in the

Water-splittingphotosystem

NADPH-producingphotosystem

ATPmill


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Noncyclic Photophosphorylation Photosystem II regains electrons by splitting

water, leaving O2 gas as a by-product

Photons

PHOTOSYSTEM I

PHOTOSYSTEM II

Energy forsynthesis of

by chemiosmosis


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The O2 liberated by photosynthesis is made

from the oxygen in water (H+

and e-

)

Plants produce OPlants produce O22

gas by splitting Hgas by splitting H22OO


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Primaryelectronacceptor

Energyto make


Light

NADP++++

2

3

How the Light Reactions Generate ATP and NADPH

2 H++++ + 1/2

Water-splittingphotosystem

Reaction-center

chlorophyll

Light


NADPH-producingphotosystem1


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Two connected photosystems collectphotons of light and transfer the energy to

In the light reactions, electron transportIn the light reactions, electron transportchains generate ATP, NADPH, & Ochains generate ATP, NADPH, & O22

The excited electrons are passed from theprimary electron acceptor to electron

transport chains Their energy ends up in ATP and NADPH


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The electron transport chains are arranged

with the photosystems in the thylakoidmembranes and pump H+ through that

Chemiosmosis powers ATP

synthesis in the light reactions

The flow of H+ back through the membrane isharnessed by ATP synthase to make ATP

In the stroma, the H+ ions combine with NADP+

to form NADPH


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The production of ATP by chemiosmosis in

photosynthesis

Thylakoidcompartment(high H+) Light Light

Thylakoid

membrane

Stroma(low H+)

Antennamolecules

ELECTRON TRANSPORTCHAIN

PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE


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A Photosynthesis Road Map

Chloroplast

Light

Stack ofthylakoids ADP

+ P

NADP++++

Stroma

reactions cycle

Sugar used for

Cellular respiration

Cellulose

Starch

Other organic compounds


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Review: Photosynthesis uses lightenergy to make food molecules

Light

Chloroplast A summary of

the chemical

Photosystem IIElectrontransport

chainsPhotosystem I

CALVINCYCLE Stroma

LIGHT REACTIONS CALVIN CYCLE

Cellularrespiration

Cellulose

Starch

Otherorganiccompounds

photosynthesis


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It's not thatIt's not that

easy bein'easy bein'

is essential foris essential for

life on earth!life on earth!

photosynthesis lecture ppt

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