Chemical Energy, ATP, &
Photosynthesis
Chapter 4
Sections 4.1, 4.2, and 4.3

4.1 How do living things get
ATP?
 ATP is the energy carrier in living things – it is usable energy for the cell (chemical potential
energy).
 ATP stands for Adenosine triphosphate.
 Living things get ATP from breaking down
carbon based molecules. (carbohydrates & lipids)
Starch molecule
Glucose molecule

This is how it works phosphate removed

Let’s see how it works
 https://www.youtube.com/watch?v=SCOPNyXy_ aU

4.2 & 4.3 Photosynthesis
 The process of photosynthesis captures energy from sunlight and converts it into sugar (glucose - CPE).
 This process happens in organisms called autotrophs or producers. (Need to make their own food)
 This process takes place in and organelle called the chloroplast.
 The chloroplast has a green pigment in it called chlorophyll that is responsible for capturing the light energy.

2
3. 6H
2
O
Let’s label the inside of a chloroplast
1.
4. thylakoid
Contains: chlorophyll chloroplast
5. 6O
2
6. Energy carrying molecules are being transferred to light independent reactions
7. 6CO
2 from the atmosphere
stroma (fluid outside the thylakoids) 1 six-carbon sugar
8. Light independent reaction
9 C
6
H
12
O
6
(glucose)

So how does photosynthesis work?
The first stage of photosynthesis is called the Light
Dependent Stage.
Purpose: To capture and transfer energy.
 First, light is captured by the chlorophyll in the
thylakoid.
 Thylakoids: membrane enclosed compartments; membrane contains chlorophyll & other lightabsorbing molecules.
 Grana: stacks of thylakoids

The Light Dependent Stage
 Second, the energy is transferred along the thylakoid membrane and water is broken down.
Oxygen molecules get released at this point.
 Third, energy is then transferred to ATP to be used for the second stage of photosynthesis.

So how does photosynthesis work?
The second stage of photosynthesis is called the Light
Independent Stage/ Calvin Cycle/ Dark Cycle.
 This process takes place in the stroma.
 Stroma: The fluid outside of the thylakoids.
 First, carbon dioxide is added from the atmosphere to help in the chemical reactions.
 Second, a molecule of a simple sugar (glucose) is formed. This molecule stores some of the energy captured from the sun.

The chemical formula for photosynthesis
 6CO
2
+ 6H
2
O + light C
Carbon dioxide plus water plus light yields
6
H
12
O
6
+ 6O
2
Glucose and oxygen
(reactants)
(products )

What kind of energy transformation takes place in photosynthesis?
 Radiant (light)  Chemical (with a loss of heat of course!)

 http://www.youtube.com/watch?v=eo5XndJaz-Y

Chemosynthesis
 Some organisms still make their own food, but they
do not use light - they use chemicals.
 Chemosynthesis is the process of using chemical energy to make carbon based molecules.
 This is because they are found in areas (ex: deep in the ocean) that never receive light.