] This powerpoint presentation has been adapted from Life 4e-Lewis, Gaffin, Hoefnagels and Parker....

This powerpoint presentation has been adapted from Life 4e-Lewis, Gaffin, Hoefnagels and Parker. Publishers-McGraw-Hill 1998 and Principles of Anatomy and Physiology,Tortora and Grabowski.Publishers- John Wiley & sons, Inc. 2000

photoautotroph

AUTOTROPHYObtaining energy from a

non-living world

chemoautotroph

PhotoautotrophsConvert CO2 and H2O to sugars

utilizing light E (blue and red)Examples: plants, algae, some

bacteria Chemoautotrophs

Some convert CO2 and H2S to sugars utilizing chemicals(energy) such as H2S.

Examples: some bacteria (hydrothermal vents)

Two types of Autotrophs

Autotrophy is the energy basis for all life on this planet.Directly keeps the autotroph alive (can make its own sugar)

Indirectly keeps all of the heterotrophs alive(get eaten!)

Autotrophy produces glucoseGlucose will be used for:

Cellular respirationModified with minerals/other molecules to become:

Nucleotides, amino acids, lipids, other carbohydrates

Energy FlowEnergy flows in one direction through an

ecosystem.

Route of energy flow is determined by an ecosystem’s trophic structure.

photo- or chemoautotrophs

animals that eat producers (primary consumers)

animals that eat herbivores(Secondary consumers)

animals that eat carnivores(tertiary consumers)

Food web - several species function at more than one trophic level.

I strongly suggest you view and use what is appropriate from the

following link:http://photoscience.la.asu.edu/photosyn/education/learn.html

PHOTOSYNTHESIS 6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O Several consequences to this

evolutionary advance/mutation.Oxygen gas (O2 ) slowly built up in

atmosphere- Aerobic respiration now a possibility

UVOzone forms (3 O2 2 O3)

Life can now leave the safety of the water and

colonize land

Light (see page 103)Visible light makes up only a small portion

of the electromagnetic spectrum.

Characteristics of Visible Light:

is a spectrum of colors/wavelengths ranging from violet to red

consists of packets of energy called photons

photons travel in waves, having a measurable wavelength () measured in nanometers (nm)10-9

A photon’s energy is inversely related to its wavelength ()......the shorter the ()..., the greater

the energy it possesses.Which of the following photons

possess the greatest amount of energy?

Green photons = 530nm

Red photons = 660nm

Blue photons = 450nm

What happens to light when it strikes an object?

reflected (bounces off)

Only absorbed wavelengths of light function in photosynthesis.

transmitted (passes through)

absorbed

Photosynthetic PigmentsMolecules that capture photon energy by absorbing certain wavelengths of light.

Primary pigmentsChlorophylls a & b - bluish green pigments found in plants, green algae & some bacteria.

See page 105

Chlorophyll a is the dominant pigment in plant photosynthesis.

Accessory PigmentsCarotenoids - orange, yellow pigments found in plants, algae, bacteria.

Anthocyanins - reds and purples

Each pigment absorbs a particular range of wavelengths.

See page 105

Leaf- See page 728Chloroplasts- See page 104

Sites of photosynthesis in plants & algae.Concentrated in the palisade mesophyll cells of most plants.

Chloroplast structure: See page 104

Stroma - gelatinous matrix; contains ribosomes, DNA & various enzymes.

Thylakoid - flattened membranous sac; embedded with photosynthetic pigments.

Chloroplast

Photosynthesis.CO2 from atmosphere, H2O from soil

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

Requires correct enzymes and pigments plus sunlight (red and blue,) ATP, NADPH to convert the reactants into the products

Stomata/Stoma - pores extending through the leaf epidermisStomata regulate gas (CO2,O2 and H2O) exchange with the environment.

Usually based on their different concentration gradients, CO2 will diffuse into the leaf; H2O and O2 will diffuse out of the leaf.

Photosynthesis occurs in two biochemical pathways:

Light reactions - harvest photon energy to synthesize ATP & NADPH. Splits H20

Calvin cycle reactions - use ATP and NADPH from light reactions to reduce (add hydrogen/electrons) to CO2 forming carbohydrates.

Overview of Photosynthesis

Light Reactionsrequire lightoccur in thylakoids of

chloroplasts involve photosystems II & I (light

harvesting systems).Photosystems

contain antenna complex that captures photon energy & passes it to a reaction center.

Light Reactions of Photosynthesis

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 10.13

Light Reactions

1. Light drives both photosystems (PS).

2. Water splits, O2 formed & electron to PS II

3. excited electron enters ETC. ATP is made, similar to respiration.

4. electron replaces the one lost in PS I.

5. electron from PS I enters ETC.

6. This ETC produces NADPH


Fig. 10.17

ATP Production: See page 108

Go to Light Reaction animationGo to Calvin Cycle animation

Carbon Reactions(Calvin cycle; C3 cycle) occurs in stroma of chloroplasts

requires ATP & NADPH (from light reactions), and CO2 from atmosphere.

Produces- H2O and 2 PGALs (glucose)

Calvin Cycle; see pg.111


Fig. 10.18

Calvin Cycle Steps CO2 combines with the 5-carbon sugar RuBP This reaction is catalyzed by the enzyme

RUBISCO The resulting unstable 6-carbon compound

breaks down into 2 molecules of 3-carbon PGA The PGA molecules get energy from ATP and

a H from NADPH to form PGAL. The PGAL gets rearranged and another ATP

is used to recycle into RuBP.

It takes 3 “turns” of the cycle to release one PGAL.

It takes 2 PGALs to make a glucose. So… it takes 6 turns of the cycle to make

a glucose. Each turn of the cycle is started by the

entrance of one CO2. So look back at the overall equation. It

takes 6CO2 to make one C6H12O6.

Calvin Cycle

Plants that use only the Calvin cycle to fix carbon are called C3 plants.

Ex. cereals, peanuts, tobacco, spinach, sugar beets, soybeans, most trees & lawn grasses.

Photorespiration: See page 118Process that counters

photosynthesis.Occurs when stomata close under

hot, dry conditions:O2 levels in plant leaf increaseCO2 levels in plant leaf decrease

Under these conditions, rubisco attaches to O2 (rather than to CO2).Thus,less PGAL is produced (up to

50%).

Photorespiration and Special Adaptations

No known function of photorespiration

Photosynthesis has produced all atmospheric O2. So when photosynthesis and Rubisco are thought to have evolved there was little to no O2 therefore photorespiration was not a problem.

C3 because first stable molecule is a 3 Carbon sugar

C4 and CAM Photosynthesis: See pages 119-120Adaptations that allow certain

plants to conserve water and reduce photorespiration when exposed to higher temperatures.

C4 PhotosynthesisC4 plants reduce photorespiration

by physically separating the light reactions and Calvin cycle.

Leaf anatomy of a

C4 plant vs. C3

plant

C4 Photosynthesis: Light reactions

occur in chloroplasts of mesophyll cells.

Calvin cycle occurs in chloroplasts of bundle sheath cells.

CAM PhotosynthesisCAM plants reduce photorespiration by

acquiring CO2 at night. Therefore don’t have to open stomata and dehydrate during hot days. Night:

mesophyll cells fix CO2 as malic acid

malic acid is stored in vacuoles.

Day: malic acid releases

CO2 which enters Calvin cycle.

Malic acid


Fig. 10.19

Rate of photosynthesisRate= activity per unit of timeLight intensity,water conc., temperature, conc. of oxygen and carbon dioxideAll affect the rate of photosynthesis

Light- see page 115increasing light= increasing rate of photosynthesis until light saturation point, then declines.Why?

CO2-

increasing CO2 similar curve except no decline (reaches saturation)

See page 116 Temperature

As temperature increases so does rate of photosynthesis, then it declines to zero.

Why?

See page 116 Limiting factors Light, temperature etc. all

interact with each other.Factors in shortest supply have

the greatest effect on the rate of photosynthesis. These are called limiting factors..

Sugar made in the chloroplasts supplies the entire plant with chemical energy and carbon skeletons to synthesize all the major organic molecules of cells.About 50% of the organic material

is consumed as fuel for cellular respiration in plant mitochondria.

Carbohydrate in the form of the disaccharide sucrose travels via the veins to nonphotosynthetic cells.

There, it provides fuel for respiration and the raw materials for anabolic pathways including synthesis of proteins and lipids and building the extracellular polysaccharide cellulose.


] This powerpoint presentation has been adapted from Life 4e-Lewis, Gaffin, Hoefnagels and Parker....

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