13.1 Ecologists Study Relationships

13.1 Ecologists Study Relationships

PHOTOSYNTHESIS

4.2 Overview of Photosynthesis

KEY CONCEPTPhotosynthesis is a series of chemical reactions that transform light energy into chemical energy stored in food.

4.2 Overview of Photosynthesis

Chemical Equation of Photosynthesis

6CO2 + 6H2O C6H12O6 + 6O2

Carbon dioxide + Water Glucose + Oxygen

REACTANTS PRODUCTS

Carbon dioxide Glucose (sugar)

Water Oxygen

Sunlight Energy

Sunlight Energy

4.2 Overview of Photosynthesis

• CO2 enters leaves through guard cell/stomata by diffusion

4.2 Overview of Photosynthesis

• H2O enters roots through osmosis.

4.2 Overview of Photosynthesis

• In plants, Photosynthesis occurs in chloroplasts

4.2 Overview of Photosynthesis

Structure of the Chloroplast Organelle

Thylakoids- coin shaped compartments

surrounded by a membrane filled

with chlorophyll

Grana –

Stacks of thylakoids

Chlorophyll – green colored molecule

in thylakoid membrane

Stroma –

Fluid filled space between grana

chloroplast

stroma

grana (thylakoids)

4.2 Overview of Photosynthesis

. Chloroplast vs. Chlorophyllchloroplast

leaf cell

leaf

• Chloroplasts organelles contain the green pigmented molecule chlorophyll

•Chloroplast = Organelle•Chlorophyll= Molecule

4.2 Overview of Photosynthesis

2 Stages of Photosynthesis Reactions

1. Light Dependent Reactions

*Require light energy

2.Light Independent Reactions

*Do NOT require light energy

4.2 Overview of Photosynthesis

Light-Dependent Reactions .

*Light energy and Water are needed

*Occur in the chloroplast thylakoid membrane

*Produces high energy molecules that will transfer their energy to the Light Independent Rxns.

*Waste byproduct is Oxygen

4.2 Overview of Photosynthesis

Stage 1: LIGHT DEPENDENT REACTIONS

4.2 Overview of Photosynthesis

Steps of the Light Dependent Reactions

1. Light energy “excites” electrons in a chlorophyll molecule.

2. The “excited”, high energy electrons are passed from one protein molecule to another along the electron transport chain in the thylakoid membrane and are used to make 2 energy carrier molecules

3. Enzymes split the water molecule: H2O 2H+ + 2e- + O-

* The 2e- replace the electrons the chlorophyll molecule lost

* Oxygen gas is released

4.2 Overview of Photosynthesis

• Light-Independent Reactions (Calvin Cycle)

• Do NOT require light energy – can happen in the dark• Source of Energy: the energy carrier molecules made in

the light rxns • Occurs in the stroma fluid • CO2 needed. • Glucose molecules made

4.2 Overview of Photosynthesis

Steps of the Light Independent Reactions (Calvin Cycle)

1. CO2 molecules diffuse across the stroma.2. CO2 is rearranged using H+ from the breakdown of water and Energy from energy carrying molecules made in the light dependent reactions to make glucose. Carbon gets ”fixed” into Carbohydrates, Lipids, Proteins

4.2 Overview of Photosynthesis

Big Picture of Energy Transformation in Photosynthesis

• Light Dependent Reactions – • Capture and Transform Light Energy into chemical energy

temporarily stored in energy carrier molecules.

• Light Independent Reactions – • Transform E from the energy carrier molecules made in

Light Dependent reactions to stored chemical energy in glucose

4.2 Overview of Photosynthesis

The Big Picture

• Write the chemical equation for Photosynthesis using logic or memory – No Notes Allowed!!

4.2 Overview of Photosynthesis

The Big Picture

Write the chemical equation for Photosynthesis using logic

or memory – No Notes Allowed!!

6CO2 + 6H2O C6H12O6 + 6O2

4.2 Overview of Photosynthesis

Sample Exam Question

• Using a microscope, a student observes a small, green organelle in a plant cell.

• What is the name of this organelle?

• Which energy transformation occurs first within the organelle?

A. ATP to light

B. Light to Chemical

C. Heat to Electrical

D. Chemical to Chemical

4.2 Overview of Photosynthesis

Sample Exam Question

• Using a microscope, a student observes a small, green organelle in a plant cell.

• What is the name of this organelle? Chloroplast

• Which energy transformation occurs first within the organelle?

A. ATP to light

B. Light to Chemical

C. Heat to Electrical

D. Chemical to Chemical

4.2 Overview of Photosynthesis

• Photosynthesis is series of chemical reactions that involve the transformation of energy from one form to another. The many reactions of photosynthesis are grouped into two set of reactions. Name each reaction set. Explain the energy transformation that occurs in each.

4.2 Overview of Photosynthesis

• Photosynthesis is series of chemical reactions that involve the transformation of energy from one form to another. The many reactions of photosynthesis are grouped into two set of reactions. Name each reaction set. Explain the energy transformation that occurs in each.

• Light Dependent Rxns

Light Energy .> Chemical E stored in energy carrying molecules

• Light Dependent Rxns

Chemical E in energy carriers > Chemical E stored in glucose

4.2 Overview of Photosynthesis

• Overall Energy Transformation in Photosynthesis

• Light Energy > Chemical Energy stored in Glucose

4.2 Overview of Photosynthesis

Sample Exam Question

• Photosynthesis and cellular respiration are two major processes in which carbon atoms are cycled through the bodies of living things.

4.2 Overview of Photosynthesis

• The equation for the overall process is:

6CO2 + 6H2O C6H12O6 + 6O2

C6H12O6

granum (stack of thylakoids)

thylakoid

sunlight

1 six-carbon sugar

6H2O

6CO2

6O2

chloroplastchloroplast1

2

43

energy

stroma (fluid outside the thylakoids)

4.2 Overview of Photosynthesis

Water is absorbed by osmosis through the roots