Photosynthesis

1
Photosynthesis

• All organisms use energy to carry out the
  functions of life.

2
Agenda

• What are the reactants and products of
  photosynthesis?
• What are the colors of the visible light
  spectrum?
• In what cellular organelle does photosynthesis
  take place?
• Why is photosynthesis important?
• How is the process of photosynthesis in C4, C3,
  and CAM plants different?

• Go over Vocabulary Definitions
• Photosynthesis Web Activity
• Notes Photosynthesis-light pigments
• Worksheet Absorption of Chlorophyll

3
Importance of Photosynthesis

• Transforms sunlight energy into chemical energy
  stored in molecules (bonds)
• Bond energy within triose phosphate formed in
  photosynthesis is transferred between organisms
  within the food pyramid (more energy at bottom
  than top)
• Triose phosphate (glyceraldehyde 3-phosphate) is
  converted to carbohydrates, lipids, amino acids
• Photosynthesis releases oxygen to atmosphere

4
Reactants
Biochemical Reaction
Products

• Triose phosphate (Glucose)
• Oxygen

• Sunlight
• Water
• Carbon dioxide

H2O CO2 light energy ? (C6H12O6) O2
5
Capturing the Light

• Light dependent reactions take place in
  chloroplast
• found in mesophyll
• of leaf.
• Grana within
• thylakoid membrane
• Stroma-solution
• Surrounding grana

6
Light and Pigments

• Sun light appears white, but it is actually
  composed of a variety of colors called the
  Visible Spectrum.
• Light can be reflected, absorbed or transmitted
  by an object.
• Pigment absorb light, therefore the light
  reflected or transmitted no longer appears white

7

Peaks indicate Light absorbed
Trough where light is reflected
8

• The color you see is what is reflected.
• Ex. Chlorophyll (a,b) absorbs blue and red light,
  but reflects green light

9
Review
What are the reactants and products of
photosynthesis? What are the colors of the
visible light spectrum? In what cellular
organelle does photosynthesis take place? Why is
photosynthesis important?

• Complete the Absorption of Chlorophyll Worksheet

10
Agenda
How does the structure of a chloroplast lead to
light absorption? What are the variety of
pigments found in the thylakoid of a chloroplast?

• Review Light Absorption
• Review Vocabulary
• Notes Structure of Leaf pigment
• Complete Pigments Light Absorption PSSA
  Worksheet

11
Structure of Leaf

• Leaves are a plant's main photosynthetic organs.
• Gases and water vapor come in and out of a
  leaf through its stoma.

12

• Epidermis
• Outer layer which produces a waxy waterproof
  coating.
• undersurface produces guard cells, which swell
  and shrink to close and open the pores (stomata)
  which control the loss of water vapor
  (transpiration) and the entry of carbon dioxide.
• Mesophyll
• contain the photosynthetic cells of the leaf.
• long columnar cells nearer the surface (palisade
  parenchyma)
• looser irregular cells beneath (the spongy
  mesophyll parenchyma).

13
Log onto

• http//www.phschool.com/science/biology_place/bioc
  oach/photosynth/intro.html

• Select
• 4 Structure of a Leaf
• 6 Chloroplast Structure

14
Chloroplast Pigments

• Within the thylakoid are a variety of pigments.
• Chlorophyll a- yellow/green
• Chlorophyll b- blue/green
• Carotenoids - orange
• Each pigment absorbs a different wavelength of
  light.

15
(No Transcript)
16

• Chlorophyll a is directly involved in the light
  reactions of photosynthesis
• Chlorophyll b and carotenoids are considered to
  be accessory pigments, assisting Chlorophyll a in
  capturing light energy.

17
Review
How does the structure of a chloroplast lead to
light absorption? What are the variety of
pigments found in the thylakoid of a chloroplast?

• Complete Pigments Light Absorption PSSA
  Worksheet

18
Agenda
What occurs during photolysis? How does the
structure of a photosystem lead to it
function? What is the main purpose of the light
dependent phase of photosynthesis?

• Vocabulary Quiz
• Notes Photolysis light Reaction
• Complete Section 6-1 Review Worksheet
  Photosynthesis PSSA Worksheet

19
Photolysis

• Splitting of water molecules
• Oxygen is released through stomata
• H picked up by NADP and pumped through thylakoid
  to stroma for Calvin cycle
• Carbon Dioxide is absorbed through stomata and
  used in the Calvin cycle

20
Light Dependent Phase-thylakoid

• Groups of chlorophyll and carotenoid pigment
  molecules are found in the thylakoid membrane
• Photosystem I
• Photosystem II
• Accessory pigment molecules in both photosystems
  absorb light energy causing electrons to become
  excited.
• Energy is passed within the photosystem through
  pigment molecules to chlorophyll a

21
(No Transcript)
22
Electron Transport Chain

• Aided by enzymes, therefore affected by
  temperature
• Excited electrons leave chlorophyll a molecules
  to a primary electron acceptor in the stroma of
  the chloroplast
• Electron acceptor donates electrons to a series
  of molecules located in the thylakoid
• allowing protons(H) to move into the thylakoid

23
Electron Transport Chain cont.

• Photosystem I electrons are replaced by electrons
  from Photosystem II
• Photosystem II gets the electrons from splitting
  water, for every 2 water split, 4 electrons are
  available
• If this did not happen, photosynthesis would stop

24
(No Transcript)
25
Chemiosmosis/ATP Synthase

• Relies on a concentration gradient of protons
  across the thylakoid membrane.
• Protons are pushed through ATP Synthase in the
  thylaloid membrane
• Adds a phosphate group to ADP making ATP

26
(No Transcript)
27
Review
What occurs during photolysis? How does the
structure of a photosystem lead to it
function? What is the main purpose of the light
dependent phase of photosynthesis?

• Complete Section 6-1 Review Worksheet
• Complete Photosynthesis Light Absorption PSSA
  Worksheet

28
Agenda
What is the main purpose of the light independent
phase of photosynthesis? How is the process of
photosynthesis in C4, C3, and CAM plants
different?

• Review
• Lab Plant Stoma
• Notes Light Independent Phase Alternative
  Pathways
• Complete Biochemistry of Photosynthesis PSSA
  Worksheet

29
Light Independent Phase

• Also called the Calvin Cycle
• Produces organic compounds, using the energy
  stored in ATP and NADPH in the light reactions
  and carbon dioxide
• Steps
• CO2 diffuses into stroma combining with an enzyme
  (RuBP), the molecule is split and becomes 3-PGA
• Each PGA is converted to another
  molecule(3-phosphate) in a 2 part step
• One receives a P from ATP, and the other receives
  a Proton (H) from NADPH
• One G3P leaves to make carbohydrates
• One is converted back to RuBP to be used again

30
(No Transcript)
31
Summary
32
Carried out by Plants

• C3 plants.
• because the CO2 is first incorporated into a
  3-carbon compound.
• Stomata are open during the day.
• Photosynthesis takes place throughout the leaf.
• Most plants are C3.
• C4 plants.
• because the CO2 is first incorporated into a
  4-carbon compound.
• Stomata are partially open during hottest part of
  the day.
• into the plant very quickly, and then it
  "delivers" the CO2 directly to RUBISCO for
  photosynthesis.
• Photosynthesis takes place in inner cells
• Ex. Corn, Sugar Cane, Crab grass
• CAM plants. CAM stands for Crassulacean Acid
  Metabolism
• because the CO2 is stored in the form of an acid
  before use in photosynthesis.
• Stomata open at night (when evaporation rates are
  usually lower) and are usually closed during the
  day. CAM plants include many succulents such as
  cactus, agaves, bromeliads and also some orchids

33
Review

• What is the main purpose of the calvin cycle of
  photosynthesis?

• Complete Biochemistry of Photosynthesis PSSA
  Worksheet