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Chapter 8: Photosynthesis

Freshman Biology

Esther Lin

on 1 November 2014

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Transcript of Chapter 8: Photosynthesis

CH 8 Essential Questions
8.1 - How do organisms store energy?

8.2 - What cellular structures and molecules are involved in photosynthesis?

8.3 - How do photosynthetic organisms convert the sun's energy to chemical energy?
Energy - the ability to do work
The most important molecule cells use to obtain and release energy is
ATP (Adenosine Triphosphate)
ATP can release and store energy by breaking or forming bonds between phosphate

When there are only
2 phosphate groups
attached, the molecule is called . ADP (adenosine diphosphate)
Why do cells need energy?
Many biological processes require energy
such as:
- Active transport
- Movement
- Synthesis of proteins
- Growth
- Digestion
ATP = Cellular energy currency
Organisms that make their own food
ex. plants
Organisms that consume other organisms for food
ex. animals/humans
Think about it...
Is the energy plants get from the sun the same energy we get from eating plants? ?
Can you trace the energy from hamburgers back to the primary producer?
The process that uses light to produce food molecules
Photosynthetic organisms capture energy from the sun with light-absorbing pigments called
Chlorophyll absorbs light in the blue-violet and red regions of the visible spectrum, but not in the green region, as shown in the graph.

Leaves reflect green light, which is why plants look green!
When temperature decrease, chlorophyll molecules
breakdown, causing the red/orange pigments
to be seen
- Where photosynthesis takes place
- Contain photosynthetic membranes called thylakoids which look like stacks of pancakes
(fluid portion)
Energy Collection
Light is a form of Energy!
-When light energy is absorbed by chloroplasts, it is transformed into high-energy electrons, which power photosynthesis.
Energy Collection
(fluid portion)
(photosynthetic membranes)
These are cells from a plant leaf.
What are the
green circles
inside the cells?

- uses light energy to convert water and carbon dioxide (CO2) into energy rich sugars and Oxygen (O2)
6 CO + 6 H O C H O + 6 O
2 2 6 12 6 2
Carbon Dioxide + Water Sugars + Oxygen
Plants use sugars created in photosynthesis to produce complex carbohydrates such as starches
Energy from these starches can be used to synthesize lipids and proteins
- This part of the reaction uses energy from the sun to produce ATP and NADPH
- takes place within the thylakoid membranes
(waste product)
(source of electrons)
(absorbed from atmosphere)
- ATP and NADPH molecules are used to produce high energy sugars from CO2
- Takes place in the Stroma
This water plant was put in a test tube, placed by the window and observed after 30 minutes.

Do you see any signs of photosynthesis?
Would these observations change if the plant was exposed to less light?
Photosystem II
Photosystem I
- Light is absorbed by the pigments, creating High-Energy electrons which then enter the Electron Transport Chain to produce ATP
- Low-energy electrons are re-energized with light and continue to another Electron Transport Chain
-As electrons move down the chain, they are pumped from the stroma to the thylakoid, creating a gradient
-This causes ADP and NADP+ into ATP and NADPH (ENERGY!)
Summary of Light-Dependent Reactions
Use the figure on page 237 of your text to draw out the Light-Dependent Reactions and write a flow chart describing the steps in this process
Light-Dependent Reactions
Light-Independent Reactions
- Use sunlight to make Energy
- Uses energy (from light-dependent reactions) to make High-Energy Sugars
CO2 enters the cell and with the help of energy (ATP & NADPH), the cell builds carbohydrates (sugars)
Calvin Cycle
The sugars and other compounds produced allow the plant to grow!
When other organisms eat plants, they use the energy stored in these compounds
In small groups, make a flow chart of the entire process of photosynthesis and be prepared to share with the class
What are the reactants and products of photosynthesis?
What do you think would happen if there was a shortage of one of the reactants?
Electron Transport chain
(Inside the chloroplast)
Full transcript