Chapter 8Chapter 8

PhotosynthesisPhotosynthesis

PhotosynthesisPhotosynthesis PhotosynthesisPhotosynthesis – The process that plants use to – The process that plants use to

convert energy from the sun.convert energy from the sun. The process by which plants and some other The process by which plants and some other

organisms convert light energy to useable chemical organisms convert light energy to useable chemical energy.energy.

The Student of the Day will be able to answer this question.The Student of the Day will be able to answer this question.

What element is Organic Chem. centered around?What element is Organic Chem. centered around? What is a molecule made of 6 Carbons? What is a molecule made of 6 Carbons? A plant makes sugar molecules which store energy A plant makes sugar molecules which store energy

and allow the plant to grow and reproduce.and allow the plant to grow and reproduce.

How does a plant get energy?How does a plant get energy?

Plants need supplies in order to make Plants need supplies in order to make sugar.sugar.

Where do you think the Carbon comes Where do you think the Carbon comes from?from?

Where do you think the Hydrogen comes Where do you think the Hydrogen comes from?from?

A plant will take in three things in order to A plant will take in three things in order to make a sugar molecule; Carbon Dioxide, make a sugar molecule; Carbon Dioxide, Water and Sunlight.Water and Sunlight.

What else does a plant make?What else does a plant make?

Along with the 1 sugar molecule that a plant will make during Along with the 1 sugar molecule that a plant will make during photosynthesis a plant makes Oxygen molecules as a waste photosynthesis a plant makes Oxygen molecules as a waste product.product.

What does a plant do with the Oxygen molecules that it makes?What does a plant do with the Oxygen molecules that it makes?

COCO22 + + HH22OO + + sunlightsunlight C C66HH1212OO66 + + OO22 + +

Think about it!Think about it!

• How many Carbons are in the sugar How many Carbons are in the sugar molecule? Hydrogen? Oxygen?molecule? Hydrogen? Oxygen?

• How many Carbons are in the reactant? How many Carbons are in the reactant? Hydrogen? Oxygen?Hydrogen? Oxygen?

• This molecular equation is not balanced.This molecular equation is not balanced.• 66COCO22 + 6 + 6HH22OO + + sunlightsunlight C C66HH1212OO66 + 6 + 6OO22

• The equation now has the same number of The equation now has the same number of atoms in the product as it does in the atoms in the product as it does in the reactant.reactant.

COCO22 + + HH22OO + + sunlightsunlight C C66HH1212OO66 + + OO22

Where does this process take place?Where does this process take place?

What are the leaves of a plant made of?What are the leaves of a plant made of? The organelle inside a plant cell where The organelle inside a plant cell where

photosynthesis takes place is the photosynthesis takes place is the chloroplast.chloroplast.

Inside a chloroplast are tiny discs that look Inside a chloroplast are tiny discs that look like a stack of nickels called thylakoids.like a stack of nickels called thylakoids.

Inside the thylakoid are pigments.Inside the thylakoid are pigments. The pigment inside the thylakoid will absorb The pigment inside the thylakoid will absorb

light from the sun. light from the sun.

ChloroplastChloroplast

Visible Light SpectrumVisible Light Spectrum

The sun produces The sun produces many different sized many different sized waves. A small waves. A small percentage of these percentage of these waves we can see or waves we can see or hear. The rest of the hear. The rest of the waves our brains waves our brains cannot comprehend.cannot comprehend.

More about light wavesMore about light waves Certain light waves that come down from Certain light waves that come down from

the sun are absorbed while others are the sun are absorbed while others are reflected.reflected.

For example your shirt is absorbing and/or For example your shirt is absorbing and/or reflecting all types of color.reflecting all types of color.

If you are wearing a white shirt, it is If you are wearing a white shirt, it is reflecting all of the colors back to your eye.reflecting all of the colors back to your eye.

Those that are wearing black shirt are Those that are wearing black shirt are absorbing all of the waves of color.absorbing all of the waves of color.

Story time: Very Stupid criminal!Story time: Very Stupid criminal!

PigmentsPigments There are four types of pigment in the thylakoid There are four types of pigment in the thylakoid

that we will learn about.that we will learn about.1. 1. Chlorophyll AChlorophyll A – absorbs all – absorbs allspectrums of light except for green andspectrums of light except for green and

bluesblues2. 2. Chlorophyll BChlorophyll B - absorbs all - absorbs allspectrums of light except for yellows,spectrums of light except for yellows,

greens and some blues.greens and some blues.3. 3. CarotenoidsCarotenoids - absorbs all - absorbs all

spectrums of light except for reds,spectrums of light except for reds, orangesorangesand yellows.and yellows.

4. 4. XanthophyllXanthophyll - absorbs all - absorbs allspectrums of light except for yellow.spectrums of light except for yellow.

Absorption Spectra of photosynthesis Absorption Spectra of photosynthesis pigments.pigments.

Sample Paper Sample Paper ChromatographyChromatography

Stages of PhotosynthesisStages of Photosynthesis There are three important stages of photosynthesis.There are three important stages of photosynthesis.

Light Dependant Reaction – Light Dependant Reaction – needs light in order to needs light in order to function.function.

There are two steps in the Light Dependant Rxn.There are two steps in the Light Dependant Rxn.- Light Absorption - Light Absorption - Electron Transport - Electron Transport

Light Independent – Light Independent – Does not mean that it has to be Does not mean that it has to be dark to work. It can work both at night & at daytime.dark to work. It can work both at night & at daytime.

- Calvin Cycle- Calvin Cycle

3 Stages of 3 Stages of PhotosynthesisPhotosynthesis

Stage 1: Light Stage 1: Light AbsorptionAbsorption Step 1: Step 1: Light hits the thylakoid in the plant Light hits the thylakoid in the plant

cell and the pigment absorbs the energy.cell and the pigment absorbs the energy. Step 2:Step 2: When the light hits the thylakoid it When the light hits the thylakoid it

excites an electron in the pigment. The e- excites an electron in the pigment. The e- jumps to a higher energy level and moves jumps to a higher energy level and moves to a molecule near the thylakoid.to a molecule near the thylakoid.

Step 3:Step 3: An enzyme takes water into the An enzyme takes water into the cell and breaks it into 2 Hcell and breaks it into 2 H atoms and an O atoms and an O atom. The H atoms are stripped of their atom. The H atoms are stripped of their electron which replace the electron that has electron which replace the electron that has just been bumped up. What do you think just been bumped up. What do you think happens to the Oxygen?happens to the Oxygen?

Here’s how light absorption works.Here’s how light absorption works.

Stage 2: Electron Stage 2: Electron TransportTransport Electron Transport ChainElectron Transport Chain – Series of molecules – Series of molecules through which excited e-s are passed along the through which excited e-s are passed along the thylakoid membrane.thylakoid membrane.

Step 1 – The excited e-s is passed through a Step 1 – The excited e-s is passed through a series of molecules.series of molecules.

Step 2 – The energy lost by the electron causes Step 2 – The energy lost by the electron causes more Hydrogen to move into the thylakoid. more Hydrogen to move into the thylakoid. Where do the Hydrogen come from? This Where do the Hydrogen come from? This causes a concentration gradient.causes a concentration gradient.

If you need to move against a concentration If you need to move against a concentration gradient what do you need?gradient what do you need?

Stage 2: Electron Transport Cont.Stage 2: Electron Transport Cont.

One pump places a phosphate onto ADP One pump places a phosphate onto ADP making ATP.making ATP.

Another pump takes the leftover Hydrogen Another pump takes the leftover Hydrogen and puts it onto a molecule called NADP and puts it onto a molecule called NADP which turns it into NADPH.which turns it into NADPH.

NADPH is an e- carrier that provides the high NADPH is an e- carrier that provides the high energy electron needed to make Carbon-energy electron needed to make Carbon-Hydrogen bonds in the next Stage (The Hydrogen bonds in the next Stage (The Calvin Cycle.Calvin Cycle.

Light Independent Light Independent ReactionReaction So far we have talked about water and light So far we have talked about water and light

energy. What part of photosynthesis haven’t energy. What part of photosynthesis haven’t we talked about?we talked about?

Carbon Dioxide FixationCarbon Dioxide Fixation – The transfer of – The transfer of COCO22 to organic compounds. The process of to organic compounds. The process of

making Cmaking C66HH1212OO66..

The most common Carbon Dioxide Fixation The most common Carbon Dioxide Fixation reaction that occurs in photosynthesis is the reaction that occurs in photosynthesis is the Calvin CycleCalvin Cycle..

Calvin CycleCalvin Cycle

1.1. 3 3 CO CO22 molecules are added to molecules are added to 33 5-Carbon 5-Carbon

compounds.compounds.

2. The 2. The 33 6-Carbon compounds split into 6-Carbon compounds split into 66 3- 3-Cabon compounds.Cabon compounds.

Calvin Cycle ContinuedCalvin Cycle Continued A phosphate from ATP & an e- from NADPH A phosphate from ATP & an e- from NADPH

turn the 3 Carbon Compounds into 3 Carbon turn the 3 Carbon Compounds into 3 Carbon sugars.sugars.

3.3. One 3 Carbon sugar is used to make One 3 Carbon sugar is used to make carbohydrates for energy storage.carbohydrates for energy storage.

4.4. The other The other 5 5 3-Carbon sugars turn into 3-Carbon sugars turn into 3 3 5-5-Carbon compounds used to continue the Carbon compounds used to continue the cycle.cycle.

Factors that would affect photosynthesis: Factors that would affect photosynthesis: Light, CO2 and temp. (enzyme activity)Light, CO2 and temp. (enzyme activity)