] this powerpoint presentation has been adapted from life 4e-lewis, gaffin, hoefnagels and parker....
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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
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 10.17
ATP Production: See page 108
Go to Light Reaction animationGo to Calvin Cycle animation
Overview of Photosynthesis
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
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 10.18
Overview of Photosynthesis
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
Calvin Cycle; see pg.111
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.
Calvin Cycle; see pg.111
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.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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