Photosynthesis: How Do Organisms Get Energy From the Sun? - PowerPoint PPT Presentation

About This Presentation
Title:

Photosynthesis: How Do Organisms Get Energy From the Sun?

Description:

Most chlorophyll molecules along with the carotenoids form an energy gathering system called an antenna complex. – PowerPoint PPT presentation

Number of Views:105
Avg rating:3.0/5.0
Slides: 47
Provided by: mgil3
Category:

less

Transcript and Presenter's Notes

Title: Photosynthesis: How Do Organisms Get Energy From the Sun?


1
Photosynthesis How Do Organisms Get Energy From
the Sun?
  • Chapter 7

2
Johann Baptista van Helmont
  • Christian, Chemist, Physician, Philosopher
  • Recognized gas as a form of matter
  • Aristotle claimed plants extract materials from
    the soil
  • Planted a 5 lb. willow tree in 200 lbs. of soil
  • Gave only water for 5 years
  • Tree weighed 169 lbs soil lost 2 oz.
  • But, he thought the weight came from the water.

3
  • Hydroponics
  • Microscopists discover stomata in plant leaves

4
(No Transcript)
5
(No Transcript)
6
(No Transcript)
7
Joseph Priestly
  • Put a candle in a bell jar ?
  • Candle goes out
  • Put a mouse in a bell jar ?
  • Mouse dies
  • Put a plant and a mouse in a bell jar ?
  • Mouse lives

8
Photosynthesis
  • 6 CO2 6 H2O ? C6H12O6 6 O2
  • C6H12O6 6 O2 ? 6 CO2 6 H2O
  • Cellular respiration
  • Plants, algae and many photosynthetic bacteria
    can harness the suns energy and turn it into
    sugar.
  • Autotrophs

9
  • What about proteins?
  • Proteins contain C,H,O, and N.
  • Nitrogen and other trace elements are taken in
    from the soil.
  • Fertilizer - 1055
  • Nitrogen Phosphorus Potassium

10
Do plants always breathe out oxygen?
  • When plants break down glucose for energy they do
    it in the same manner as other organisms, and
    then they give off CO2.
  • They cannot give off oxygen if there is no light.

11
  • Photosynthesis is a two step process
  • one set of reactions requires light
  • the second set of reactions does not light
    independent (dark) reactions
  • The light reactions are called photophosphorylatio
    n because they use light to add a phosphate group
    to ADP to make ATP.

12
Light
  • Its a particle
  • discrete units photons
  • travels in a straight line
  • No, its a wave
  • wavelength can we see it?
  • What color is it?

13
ROY G BIV
14
(No Transcript)
15
Why do plants appear green?
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
  • Pigments have electrons that can be more easily
    excited.
  • Chlorophylls alpha and beta absorb most of the
    photons in plants.
  • Carotenoids yellow and orange pigments that
    transfer energy to chlorophyll
  • Phycobilins red and blue pigments in red algae
    and cyanobacteria

20
(No Transcript)
21
  • Very few chlorophyll molecules actually
    photosynthesize.
  • Most chlorophyll molecules along with the
    carotenoids form an energy gathering system
    called an antenna complex.
  • Energy is transferred to a photochemical reaction
    center.

22
(No Transcript)
23
So, in a nutshell
  1. Chlorophyll and carotenoids absorb light.
  2. The energy is transferred to the reaction center.
  3. The energy splits oxygen from water and forms
    chemical bonds.

24
  • Plants have two distinct sets of reactions
  • Photosystem I
  • Photosystem II
  • Photosystem I absorbs light of 700nm best
  • (P700)
  • Photosystem II absorbs light of 680 nm (also
    into the blue and violet range)
  • (P680)

25
What does this have to do with me?
  • Plants grown indoors need a range of light colors
    to grow well.
  • Fluorescent bulbs have very little 700 nm light.
  • Incandescent bulbs have very little 680 nm light.
  • Use both for maximum growth.

26
  • The action takes place across the thylakoid
    membrane.
  • Chlorophyll is found in the thylakoid membrane in
    association with proteins.

27
(No Transcript)
28
  • When P700 absorbs light, electrons are excited,
    move to outer orbitals, and P700 becomes a good
    electron donor.
  • When it gives up its electron, it becomes
    oxidized.
  • The electron can then travel one of two paths
  • Cyclic photophosphorylation electron is given
    to an electron transport chain, ATP is formed and
    the electron is given back to P700

29
(No Transcript)
30
  • Noncyclic Photophosphorylation electron is
    transferred to NADP ? NADPH.
  • This provides the reducing power for the
    formation of glucose.
  • But now P700 is left oxidized. Where do we get
    the electrons to reduce it again?
  • From Photosystem II !

31
(No Transcript)
32
  • Photosystem II uses P680
  • The electrons from P 680 go into their own
    electron transport chain where ATP is produced by
    noncyclic photophosphorylation. The final
    electron acceptor is P700.
  • But now P680 is oxidized. Where can it get
    electrons?

33
  • It gets them by splitting water and releasing
    oxygen.
  • Water H, electrons and O2
  • Until cyanobacteria figured out how to do this,
    there was very little oxygen in the Earths
    atmosphere.

34
(No Transcript)
35
(No Transcript)
36
(No Transcript)
37
  • Now we have ATP and NADPH formed ?
  • The light-independent reactions which make
    glucose.
  • Glucose is a more stable energy storage molecule
    than ATP.
  • In the stroma, the Calvin cycle takes the
    hydrogens from water, the carbon and oxygen from
    carbon dioxide and makes glucose.

38
Calvin Cycle
  • Capturing carbon
  • CO2 ribulose biphosphate ? 6 carbon compound ?
    2 3-carbon molecules
  • This is catalyzed by an enzyme called ribulose
    biphosphate carboxylase or Rubisco
  • This is a very slow reaction, so plants produce a
    lot of it.
  • It is probably the most abundant protein on the
    planet!!

39
  • 2. Making sugar
  • The end product of the Calvin Cycle is a three
    carbon compound called glyceraldehyde phosphate.
  • Some enters the cytosol of the cell, where it
    can be turned into glucose, fats or amino acids.
  • 3. Regenerating ribulose biphosphate
  • Some remains in the Calvin cycle and is used to
    make more ribulose biphosphate.

40
(No Transcript)
41
  • It takes 18 molecules of ATP and 12 molecules of
    NADPH to make one molecule of glucose.

42
(No Transcript)
43
What factors affect photosynthesis?
  • Wavelength of light
  • Intensity of the light
  • Length of the day
  • Length of the growing season
  • Pollution
  • Other taller vegetation
  • Availability of carbon dioxide and water

44
Balance between CO2 and H2O
  • If the stomata are open all the time, the plant
    could dehydrate.
  • If the stomata are closed all the time, CO2 cant
    get in and O2 cant leave.
  • Hot, dry conditions ? photorespiration, wastes
    about half of carbohydrate produced.

45
  • Some plants make a 4 carbon molecule instead of
    the 3 carbon phosphoglycerate.
  • This is oxaloacetic acid ? 3-carbon molecule ?
    glucose production and CO2 which goes back to the
    Calvin Cycle.
  • These plants are called C4 plants.
  • Corn and sugar cane survive well in hot, dry
    climates.
  • The other plants are called C3 plants.

46
Desert plants
  • Cacti use a modified C4 pathway callled
    crassulacean acid metabolism or CAM. These plants
    open the stomata only at night and store CO2 in
    a four carbon molecule for use the next day.
  • Requires a lot of energy, so growth rates are
    very slow.
Write a Comment
User Comments (0)
About PowerShow.com