Energy-

Where does it come from?

Cells use energy in chemical form

The major molecule used is ATP

ADP + P + Energy -> ATP

ATP -> ADP + P + Energy

(There are other energy carriers, but ATP is the most important one.)

Photosynthesis

I. Historical Background

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Jan van Helmont (1600's)

- Flemish physician

- grew small willow tree in a pot for 5 years adding only water

weighed plant after 5 years results= gained 75 kg. but no change in soil

he concluded that new plant matter came from the water

Joseph Priestley

- English chemist

-Experimented with plants and how they grow in air

"damaged " by a burning candle.

When candle was placed in a container no oxygen could enter so candle went out.

Plants can grow in area where candle was burned while animals cannot

First indication that plants interact with air.

- plants could restore air to support a flame or an animal

Antoine Lavoisier

Showed oxygen removed from air during burning

plants give off oxygen into the air

Jan Ingenhousz

plants give oxygen to air only in sunlight

Jean Seneber

Swiss clergyman

found that plants take in CO2 during growth in sunlight

scientists during 1800's found the basic requirements for plant growth

-CO2

-H2O

-light

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Photosynthesis

A. green plants capture energy of sun light transform it into chemical energy

B. when green plants carry out process

- use C02 and water to make glucose

- release oxygen

Autotrophs

- organisms capable making food from simple inorganic substances

- two major types of autotrophs:

phototrophs

- use light energy to drive reactions needed to make food

chemoautotrophs

-certain kinds of bacteria

- oxidize inorganic chemicals for energy to drive their food making reaction

(Heterotrophs

- organisms that can't make own food

- must depend on other plants and animals)

Light Energy

-sunlight form of energy known as radiation

radiation travels in waves

wavelength= distance between crest of one wave and the crest of the next wave

- sunlight mixture of all visible wavelengths

- if all wavelengths of light are reflected equally by an object, it appears white to human eye

- when rays of light passes through a prism the rays of different lengths are bent by different amounts light spreads out forming a spectrum

- colors appear in order of wavelength

-shortest=violet -> longest=red

- photon= particles of light- has fixed amount of energy

- shorter wavelength more energy per photons

-light striking matter=some photons absorbed

- in photosynthesis organisms, absorbed energy used to make chemical bond energy

-pigment=substance that absorbs light

- absorption spectrum=different color, or wavelength, of light absorbed by a particular pigment.

Photosynthetic Pigment

A. Chlorophylls

- most important and abundant photosynthetic pigments

-two types

-chlorophyll A

- primary photosynthetic pigment

- involved conversion of light energy to chemical energy

- chlorophyll B

- carotenes

- xanthophylls

- absorb light

- transfer energy to chlorophyll A

The chloroplasts

- chloroplasts

- photosynthesis occurs here

- organelles containing photosynthetic membranes

- thylakoids

photosynthetic membranes rearranged in form of flattened sac

- grana

-stacks of thylakoids

- stroma

regions between the grana

Light Reactions

A. begin when pigments in membranes of chloroplasts absorb light

B. chlorophyll molecules in membranes are packed into two light absorbing forms photosystems 1 and 2

- linked structurally and functionally

photosystem 2 absorbs light

electrons passed to ETC.

This chain uses energy of electrons passed to photosystem 1

when photosystem 1 absorbs light electrons in it are passed to NaDP+ to form NADPH.

photosystem 2 provides continuous supply of electrons for reactions,

when it absorbs light and loses electrons it replaces the lost ones by taking electrons from H20.

As a result O2's made. Both photosystems absorb light energy

one generates ATP the other NADPH.

These high energy products are used to power the remaining reactions of

photosynthesis-dark reactions.

Chemiosmosis-

ATP synthesized due to the concentration gradient of protons

ATP synthase-enzyme that acts to produce ATP

Dark Reactions

take place in stroma while light reactions in membranes

CO2, which diffuses to stroma from the external environment is used to form glucose.

Carbon fixation=

incorporation of CO2into organic

compound during photosynthesis.

Occurs through series of enzyme controlled reactions called the Calvin cycle.

Starting and ending product of Calvin cycle is a 5 carbon sugar- ribulosebisphosphate

RuBP

Begins when RuBP reacts with CO2phosphoglyceric acid (PGA) is the result. PGA is then converted into PGAL

ATP + NADPH provide energy

+ Hydrogen for reactions.

Most of PGAL used to make more RuBP so cycle can continue

for every 6 CO2's (in cycle) 12 PGAL formed.

10 of these used to form 6RuBP while 2 PGAL react to form 1 glucose.

Chemistry Of Photosynthesis

6C02 + 12H20 -> light -> C6H12O6 + 6O2 + 6H20

summary for conversion light -> chemical energy

light reaction

-series of reactions requiring light

Dark reactions

carbon fixation occurs

- light not required

C4 plants

In addition to the Calvin cycle some plants have another pathway that

improves efficiency of the Calvin cycle.

Some flowering plants use more then the Calvin cycle to fix CO2

In C4 plants CO2 is first fixed in some leaf cells into a four carbon

compound

This compound is transported to leaf cells where the Calvin cycle

operates

The C4 is broken down and releases the CO2.

The CO2 enters the Calvin cycle and produces glucose.

The extra photosynthetic pathway called the C4 pathway.

Photosynthetic and Chemosynthetic bacteria

- most familiar of this bacteria is the blue green bacteria

- this group is photosynthetic

- they carry out photosynthesis just like plants do

-Some carry out chemosynthesis a process in which carbon fixed by using the energy by inorganic substances.

Heterotrophic Plants

- Some plants have developed heterotrophic methods of nutrition. In

addition to or instead of photosynthesis

LAB Seeds and light

Problems:

Do plants need light to germinate?

Do plants need light to produce leaves?

Do plants need light to produce pigment in their leaves?

Procedure: AGIC

Data:

Start date 2/2/99

End date 2/9/99

Observations:

Conclusions:

LAB: Leaf chromotography

What pigment(s) give plants their color?

Is(Are) all the pigment(s) green?

Do all the pigments have the same properties?

Procedure: AGIC

Data:

Observations of filters

LAB: Microscope observations of leaves.

Problem: What visible adaptations do leaves have?

Procedure: AGIC

Data:

leaf drawings- prepared leaves

observations of stomata

LAB-Rates of photosynthesis

Problem/Procedure

As Given on Pages 124-125 (MB)

Data: as indicated in sections A & B on page 125

Report: Answer all questions on pages 124-125, especially A-10, B-16 and Analysis 1-5.

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