PHOTOSYNTHESIS - PowerPoint PPT Presentation

1 / 64
About This Presentation
Title:

PHOTOSYNTHESIS

Description:

PHOTOSYNTHESIS 6.1 * * * * The Process of Photosynthesis does NOT Happen all at Once; it occurs in THREE STAGES: NADP+ is organic compound that accepts electrons ... – PowerPoint PPT presentation

Number of Views:293
Avg rating:3.0/5.0
Slides: 65
Provided by: randolph79
Category:

less

Transcript and Presenter's Notes

Title: PHOTOSYNTHESIS


1
PHOTOSYNTHESIS
  • 6.1

2
  • The main form of energy from the sun is in the
    form of electromagnetic radiation
  • Visible radiation (white light) used for
    photosynthesis
  • Remember ROY G. BIV?

3
The electromagnetic spectrum
4
  • A Red Object absorbs the blue and green
    wavelengths and reflects the red wavelengths

5
  • Why are plants green?

6
  • pigment a compound that absorbs light
  • different pigments absorb different wavelengths
    of white light.
  • chlorophyll is a pigment that absorbs red blue
    light (photons) so green is reflected or
    transmitted.
  • Chlorophyll is located in the thylakoid membranes
  • So, Plants are green because the green wavelength
    is reflected, not absorbed.

7
2 types of chlorophyll
  • Chlorophyll a involved in light reactions
  • Chlorophyll b assists in capturing light energy
    accessory pigment
  • Carotenoids accessory pigments captures more
    light energy
  • Red, orange yellow

8
The electromagnetic wavelengths and the
wavelengths that are absorbed by the chlorophyll
9
  • During the fall, what causes the leaves to change
    colors?

10
Fall Colors
  • In addition to the chlorophyll pigments, there
    are other pigments present
  • During the fall, the green chlorophyll pigments
    are greatly reduced revealing the other pigments
  • Carotenoids are pigments that are either red,
    orange, or yellow

11
(No Transcript)
12
Photosynthesis is -
  • conversion of light energy into chemical energy
    that is stored in organic compounds
    (carbohydrates gt glucose)
  • Used by autotrophs such as
  • Plants
  • Algae
  • Some bacteria (prokaryotes)

13
(No Transcript)
14
  • glucose - energy-rich chemical produced through
    photosynthesis
  • C6H12O6
  • Biochemical pathway series of reactions where
    the product of one reaction is consumed in the
    next
  • E.g. photosynthesis product is glucose which is
    used in cellular respiration to make ATP

(carbohydrate)
15
Remember Redox Reactionreduction/oxidation
  • The transfer of one or more electrons from one
    reactant to another
  • Two types
  • 1. Oxidation is the loss of e-
  • 2. Reduction is the gain of e-

16
Oxidation Reaction
  • The loss of electrons from a substance or the
    gain of oxygen.

Carbon dioxide
Oxygen
Water
17
Reduction Reaction
  • The gain of electrons to a substance or the loss
    of oxygen.

18
Photosynthesis equation
  • Light energy
  • 6CO2 6H2O C6H12O6 6O2
  • Chlorophyll
  • Reactants Carbon dioxide and water
  • Products glucose and oxygen which is a
    byproduct

19
  • Where does photosynthesis take place?

20
Plants
  • Mainly occurs in the leaves
  • a. stoma - pores
  • b. mesophyll cells

21
Mesophyll Cell of Leaf

Photosynthesis occurs in these cells!
22
Stomata (stoma)
  • Pores in a plants cuticle through which water
    vapor and gases (CO2 O2) are exchanged between
    the plant and the atmosphere.

Stoma
Found on the underside of leaves
23
Chloroplast
  • Organelle where photosynthesis takes place.

Thylakoid stacks are connected together
24
Parts
  • chloroplasts dbl membrane organelle that
    absorbs light energy
  • Thylakoids flattened sacs contain pigment -
    chlorophyll
  • Grana (pl granum) layered thylakoids (like
    pancakes)
  • Stroma solution around thylakoids
  • Stomata pore on underside of leaf where O2 is
    released and CO2 enters
  • Stroma chloroplast

cytosol cytoplasm
25
Thylakoid

Grana make up the inner membrane
26
  • What do cells use for energy?

27
Energy for Life on Earth
  • Sunlight is the ULTIMATE energy for all life on
    Earth
  • Plants store energy in the chemical bonds of
    sugars
  • Chemical energy is released as ATP during
    cellular respiration

28
Structure of ATP
  • ATP stands for adenosine triphosphate
  • It is composed of the nitrogen base ADENINE, the
    pentose (5C) sugar RIBOSE, and three PHOSPHATE
    groups
  • The LAST phosphate group is bonded with a HIGH
    ENERGY chemical bond
  • This bond can be BROKEN to release ENERGY for
    CELLS to use

29
Removing a Phosphate from ATP
  • Breaking the LAST PHOSPHATE bond from ATP, will
    ---
  • Release ENERGY for cells to use
  • Form ADP (adenosine diphosphate)
  • Produce a FREE PHOSPHATE GROUP

30
High Energy Phosphate Bond
31
FREE PHOSPHATE can be re-attached to ADP
reforming ATP Process called Phosphorylation
32
Phosphorylation
33
Photosynthesis
SUN
  • 1. Light Reaction -
  • Produces energy from solar power (photons) in
    the form of ATP and NADPH.
  • 2. Calvin Cycle
  • Also called Carbon Fixation or Carbon Cycle,
    Uses energy (ATP and NADPH) from light reaction
    to make sugar (glucose).

34
  • 3 stages of photosynthesis-

35
Stages
  • STAGE 1 - LIGHT REACTIONS - energy from sun is
    used to split water into H an O2
  •  STAGE 2 energy is converted to chemical energy
    stored in ATP NADPH in stroma
  • STAGE 3 - CALVIN CYCLE where carbon is fixed into
    glucose

36
Light Reaction (Electron Flow)
  • Occurs in the Thylakoid membranes
  • 2 possible routes for electron flow
  • Use Photosystem I and Electron Transport Chain
    (ETC) and generate ATP only
  • OR use Photosystem II and Photosystem I with ETC
    and generate O2, ATP and NADPH

37
(No Transcript)
38
Photosynthesis animation
  • http//www.mhhe.com/biosci/genbio/biolink/j_explor
    ations/ch09expl.htm

39
ELECTRON TRANSPORT - LIGHT REACTIONS in 5 steps
40
Photosystem I and II
  • Step 1 light excites e- in photosystem II
  • Step 2 e- move to primary e- acceptor Step 3
    e- move along electron transport chain (etc)
  • Step 4 light excites e- in photosystem I
  • Step 5 e- move along 2nd (etc)
  • End NADP combine H to make NADPH

41
Light reaction animation
  • http//www.science.smith.edu/departments/Biology/B
    io231/ltrxn.html

42
Electron transport chain song
  • Play the "Come On Down (The Electron Transport
    Chain)" song performed by Sam Reid. 

43
Photolysis photo-chemical splitting of water
(restoring photosystem II)
44
Chemiosmosis synthesis of ATP
  • Powers ATP synthesis
  • Takes place across the thylakoid membrane
  • Uses ETC and ATP synthase
  • H move down their concentration gradient forming
    ATP from ADP
  • Concentration of protons is greater in thylakoid
    than stroma

45
(No Transcript)
46
Chemiosmosis
47
The Calvin Cycle
  • 6.2

48
Calvin Cycle -
  • Biochemical pathway in photosynthesis that
    produces organic compounds using ATP NADPH
  • Carbon fixation carbon atoms from CO2 are
    bonded or fixed into carbohydrates
  • occurs in stroma

49
(No Transcript)
50
Calvin Cycle
  • Carbon Fixation
  • C3 plants (80 of plants on earth)
  • Occurs in the stroma
  • Uses ATP and NADPH from light reaction as energy
  • Uses CO2
  • To produce glucose it takes 6 turns and uses 18
    ATP and 12 NADPH.

51
Chloroplast
52
Calvin Cycle (C3 fixation)
53
Calvin Cycle
  • Remember C3 Calvin Cycle

54
Step 1 -
  • CO2 diffuses fr cytosol combines with RuBP
    which splits into pair of PGA

55
Step 2 -
  • PGA gets phosphate gr fr ATP gets proton fr NADPH
    to become PGAL
  • Reaction produces ADP, NADP phosphate to be
    used again

56
Step 3 -
  • PGAL converts back to RuBP
  • Allows Calvin cycle to continue

57
Alternates
  • C3 plants use Calvin cycle exclusively
  • Form 3-carbon compounds
  • C4 pathway evolved in hot, dry climate
  • Form 4-carbon compounds
  • Partially close stomata
  • E.g. Corn, sugar cane, crabgrass
  • CAM open stomata at night, close in day
  • Grow slow, lose less water
  • E.g. cactus, pineapple

58
C4 Plants
  • Hot, moist environments
  • 15 of plants (grasses, corn, sugarcane)
  • Photosynthesis occurs in 2 places
  • Light reaction - mesophyll cells
  • Calvin cycle - bundle sheath cells

59
C4 Plants
60
CAM Plants
  • Hot, dry environments
  • 5 of plants (cactus and ice plants)
  • Stomates closed during day
  • Stomates open during the night
  • Light reaction - occurs during the day
  • Calvin Cycle - occurs when CO2 is present

61
CAM Plants
62
Rate of photosynthesis is effected by - light
intensity, CO2 or temperature
  • High intensity or high CO2 high rate
  • Growth graph levels off (plateau)
  • High temp initial high rate but peaks
  • Rate drops when stomata closes

63
Recap
  • Photosynthesis converts light energy into
    chemical energy thru series of biochemical
    pathways
  • Electrons excite in photosystem II move along
    ETC to photosystem I
  • electrons are replaced when water is split
  • oxygen is byproduct
  • ATP synthesized across thylakoid
  • Calvin cycle carbon is fixed sugar produced
  • 3 turns produce PGAL (PGAL keeps cycle going
  • Other pathways C3, C4, CAM

64
References
  • www.biologyjunction.com
Write a Comment
User Comments (0)
About PowerShow.com