DO NOW:

Answer the following question:

A plant was planted six months ago that weighed 12 oz (including the soil) in the window. Now the plant and soil weigh 22 oz!!! How is this possible? (No soil was added, and wet soil does not account for the answer).

Plants and Light

How do plants get their energy?

Photosynthesis!!! which means?

Using light to make energy.

Photo= light Synthesis= to make

2 Types of organisms…

Autotrophs make their own food

Heterotrophs must obtain food from environment (eat)

What are plants?

Autotrophs!!!

2 Types of Autotrophs…

1)Photoautotrophs-

2)Chemoautotrophs-

organisms that use light to make food

organisms that use chemicals to make food.

plants

bacteria

Photosynthesis in brief…

Plants are autotrophs, relying on photosynthesis to make food (glucose).

What’s required for photosynthesis?Light, CO2, and water…

…sugar and oxygen are given off

Light Energy!!!

Light is a form of radiation, which travels in what are called waves…

Let’s see some examples…

wavelength

Smaller wavelength, but greater frequency…

So…

Sunlight is a mixture of all visible wavelengths…what color is it?

White!!!

White light can be broken down into different colors using a prism, which diffracts the light to form a spectrum.

Spectrum?

A spectrum is simply a distribution of light, arranged in order according to its energy…

Good Ole Roy!!!

How can you remember the colors?

Listed backwards, they spell:

ROY G. BIV

Why are they arranged this way?

It’s due to wavelength…

380 430 500 560 600 750

Why do we see colors?

When we see color, it is due to reflected light.

This dot, absorbs all light, but that in the red end of the spectrum.

Umm Hmm…

Substances that absorb light are called pigments.

Umm, what doesn’t absorb light?

Anything that’s white!!!

Photosynthetic Pigments

By far, the most important pigment in plants, is chlorophyll.

All plants have 2 types of chlorophyll:

chlorophyll a and

chlorophyll bgreen

Other Pigments

Besides chlorophyll, plants have other pigments:

carotene (orange) and

xanthophyll (yellow)

Pigments continued…

Why don’t we see the other pigments?

They’re masked by chlorophyll, which is present in great quantities.

Why are the other pigments there?

They absorb light at different wavelengths than chlorophyll.

Light

ReflectedLight

Chloroplast

Absorbedlight

Granum

Transmittedlight

Figure 10.7

Photosynthesis again…

Where does photosynthesis occur?

Plants!!!

More specifically?

Chloroplasts!!!

Anatomy of a Chloroplast:

Chloroplasts contain flattened sacs of photosynthetic membranes called thylakoids.

A bunch of thylakoids make up grana.

The fluid surrounding the grana is called stroma.

Why are chloroplasts necessary?

Chlorophyll is contained within the grana…

Chlorophyll can absorb energy without stroma present, but it immediately gives off the energy as heat or light.

Necessity of chloroplasts continued.

For chlorophyll to produce food for the plant, all of the enzymes contained within the stroma are necessary.

thylakoid

grana

stroma

Photosynthesis

Overall reaction

6CO2 + 12H2OLight C6H12O6 + 6O2 + 6H2O

Takes place over many steps…

Photosynthesis Dissected:

Divided into 2 types of reactions:

1)Light-dependent reactions

2)Light-independent reactions

Light-dependent reactions

Requires light

Take place in the grana of chloroplast

Store energy in high energy molecules – ATP– NADPH

Light Dependent Reactions

Chlorophyll a and b absorb blue-violet and red-orange light from sun and excite electronsTransfer excited electrons to NADP (carrier) and convert ADP to ATPSome electrons split water called photolysis

Oxygen is released

photosystem II

photosystem I

H2O 2H+ + ½ O2

2e-

2e-

ADPATP 2e-

NADP+ + H+ + 2e- NADPH

Excitedstate

Ene

rgy

of e

lect

ion Heat

Photon(fluorescence)

Chlorophyllmolecule

GroundstatePhoton

e–

Figure 10.11 A

MillmakesATP

ATP

e–

e–e–

e–

e–

Pho

ton

Photosystem II Photosystem I

e–

e–

NADPH

Pho

ton

Figure 10.14 

Light-independent Reactions

Energy from the light dependent reactions is used to power the light-independent reactions.

Do not necessarily occur in the dark, but they don’t require light.

Light-independent continued…

Occur in the stroma of the chloroplast

Series of enzyme controlled steps to convert CO2 and H into glucose.

The reaction:

CO2 goes through a process known as carbon fixation.

CO2 reacts with a 5 carbon sugar called ribulose bisphosphate (RuBP), and then enters the Calvin Cycle

Light Independent Reactions

H from NAPH2 from light reactions

Carbon dioxide from environmentRequire products from light reactions so stop shortly after light reactions endWater is also a by-product

Light reactions:• Are carried out by molecules in the thylakoid membranes• Convert light energy to the chemical energy of ATP and NADPH• Split H2O and release O2 to the atmosphere

Calvin cycle reactions:• Take place in the stroma• Use ATP and NADPH to convert CO2 to the sugar G3P• Return ADP, inorganic phosphate, and NADP+ to the light reactions

O2

CO2H2O

Light

Light reaction Calvin cycle

NADP+

ADP

ATP

NADPH

+ P 1

RuBP 3-Phosphoglycerate

Amino acidsFatty acids

Starch(storage)

Sucrose (export)

G3P

Photosystem IIElectron transport chain

Photosystem I

Chloroplast

Figure 10.21

Factors influencing photosynthesis:

There are 3 main factors influencing the rate:

1)Light intensity

2)Temperature

3)Water and mineral availability

4)Carbon dioxide level

Photosynthesis vs Cellular Respiration

In brief, they are exact opposites: photosynthesis stores energy in glucose, respiration releases energy.

Photosynthesis vs Cellular Respiration

Photosynthesis:

6CO2 + 12H2OLight

C6H12O6 + 6O2 + 6H2O

Photosynthesis vs Cellular Respiration

Photosynthesis:

6CO2 + 12H2OLight

C6H12O6 + 6O2 + 6H2O

Respiration:

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

Vein

Leaf cross section

Figure 10.3

Mesophyll

CO2 O2Stomata