Photosynthesis: An Overview
Chapter 8

ATP
Energy Storage

How do heterotrophic organisms get energy?


Consume “food.”
Macromolecules that provide energy:



Lipids
Proteins
Carbohydrates
How do they use energy?

ATP:
Adenine
3 Phosphate Groups
Ribose high energy bonds
• energy-carrying molecule
• Used for short term storage & releasing of energy

IN
Use energy to ADD phosphate group
Break bond to LOSE phosphate group to release energy
OUT
ADP and ATP are constantly being recycled by the living cell

ADP ATP
Partially charged battery
Energy
Energy
Adenosine triphosphate (ATP)
Fully charged battery
ATP
ADP is like a partially -charged battery, while ATP is said to be fully -charged.
NADP+ and NADPH are similar with adding a Hydrogen

Why do cells need energy?
•
•
•

To carry out active transport
Such as ion pumps
To move organelles within the cell
•
To synthesize (make) proteins & sugars for life functions
ONE sugar molecule stores x90 more energy than ATP

Photosynthesis
Gathering Light Energy from the Sun

PSN uses Visible Light from the SUN
•
Travels in wavelengths
•
Distance between crests determines color & energy
•
Color seen is reflected, all others are absorbed

Chlorophyll
Absorption of Light by
Chlorophyll a and Chlorophyll b

 in chloroplasts photo-sensitive membrane captures solar energy
Carotenoids
Xanthophylls

Chloroplasts
In a plant
Micrograph of a chloroplast

Chloroplasts Structure

Photosynthesis time for a SCIENCE video
Section 8-2
Photosynthesis: Reactants and Products
Light Energy
CO
2
+ H
2
O
Chloroplast
Sugars + O
2

Photosynthesis
PART 1. Light-Dependent Reactions

In the thylakoid


Chlorophyll absorbs sun’s energy

Energy transferred to electrons
Like “Hot potatoes”
 H
2
0 SPLIT & O
2 is by products



Charge up & Carry Energy
NADP+  NADPH
ADP  ATP
 Think of these like an oven mitt to carry “hot potatoes”

Photosynthesis
Part 2. Light-Independent = Calvin Cycle

(sunlight not directly needed)


In the stroma
CO
2
(C comes in and NADPH and ATP convert it to glucose
6
H
12
O
6
)

The Photosynthesis Equation light
6CO
2
+ 6H
2
Carbon Water
O C
6
H
12
O
6
+ 6O
2
Glucose Oxygen
Dioxide (Sugar)

8.3 The Reactions of Photosynthesis

Light-dependent Reactions




Photosystem: light capturing unit containing chlorophyll
Electron transport system: electron carrier molecules that shuttle electrons, energy released to make ATP
Electrons in chlorophyll must be replaced by electrons from water so that cycle may continue; oxygen is liberated from the light reactions
Light reactions make ATP and NADPH used to fuel the reactions of the Calvin cycle (light independent reactions)

Light Independent Reaction /Calvin Cycle


ATP and NADPH from light reactions used to break CO
2 apart, then reassemble the carbons into glucose.
Called carbon fixation: taking carbon from an inorganic molecule (atmospheric CO
2 molecule out of it (glucose)
) and making an organic

In your comp book:

Label the parts of a chloroplast on diagram provided p. 231

Organize information:
Light-dependent reactions
Light-independent reactions
Definition
Where take place
Reactants
Products