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:Adenosine Triphosphate

• energy-carrying molecule

• Used for short term storage & releasing of energy

Adenine

Ribose

3 Phosphate Groups

high energy bonds

ADP and ATP are constantly being recycled by the living cell

Use energy to ADD phosphate group

Break bond to LOSEphosphate group to release energy

IN

OUT

NADP+ and NADPH are similar with adding a Hydrogen

ATP

ADP is like a partially-charged battery, while ATP is said to be fully-charged.

ADP ATP

Energy

EnergyAdenosine triphosphate (ATP)

Partiallychargedbattery

Fullychargedbattery

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

Absorption of Light byChlorophyll a and Chlorophyll b

Section 8-2

Figure 8-5 Chlorophyll Light AbsorptionPigments = molecules that reflect/absorb light

Chlorophyll in chloroplasts photo-sensitive

membrane captures solar energy

Xanthophylls

Carotenoids

Chloroplasts

In a plant

Micrograph of a chloroplast

Chloroplasts Structure

Light Energy

Chloroplast

CO2 + H2O Sugars + O2

Section 8-2

Photosynthesis: Reactants and ProductsPhotosynthesis time for a SCIENCE video

Photosynthesis

PART 1. Light-Dependent Reactions In the thylakoid Chlorophyll absorbs sun’s energy Energy transferred to electrons

Like “Hot potatoes”

H20 SPLIT & O2 is by products

Charge up & Carry Energy NADP+ NADPH ADP ATP

Think of these like an oven mitt to carry “hot potatoes”

PhotosynthesisPart 2. Light-Independent = Calvin Cycle (sunlight not directly needed) In the stroma CO2 comes in and NADPH and ATP convert it

to glucose (C6H12O6)

The Photosynthesis Equation

light

6CO2 + 6H2O C6H12O6 + 6O2 Carbon Water Glucose OxygenDioxide (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 CO2 apart, then reassemble the carbons into glucose.

Called carbon fixation: taking carbon from an inorganic molecule (atmospheric CO2) and making an organic molecule out of it (glucose)

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