Part 1: PhotosynthesisPart 1: PhotosynthesisSection 4.2 & 4.3Section 4.2 & 4.3

Important molecules in cellular energy:

• CO2 = carbon dioxide gas

• H2O = water

• C6H12O6 = glucose (sugar)

• O2 = oxygen gas

Important molecules in cellular energy:• ATP = chemical

energy

• NADPH = energy molecule that receives and gives away e- (electrons) to drive chemical reactions

ATP gets recycled AdenosineTriphosphate

Gains a P to make energy

Loses a P to use energy

ATP

ADP

ADP = AdenosineDIphosphate – It’s ATP that is missing 1 P!

NADPH gets recycled, too Nicotinamide Adenine Dinucleotide Phosphate(+ Hydrogen)

It cycles from NADPH to NADP+ back to NADPH, etc.

It carries electrons (held by H) and gives them away during the second stage of photosynthesis – the Calvin Cycle.

NADPH

NADP+

Photosynthesis:Photosynthesis: the process for the process for the conversion of light energy into the conversion of light energy into chemical energy (ATP) stored in chemical energy (ATP) stored in organic compounds (glucose)organic compounds (glucose)

Photosynthesis EquationPhotosynthesis Equation

Carbondioxide

Water Glucose Oxygengas

PHOTOSYNTHESIS

Photosynthesis happens in 2 Photosynthesis happens in 2 parts:parts:

Step 1:Step 1: Light DependentLight Dependent- light is - light is absorbed to make energy for light absorbed to make energy for light independent.independent.

• Happens in the Happens in the thylakoid membranethylakoid membrane of a of a chloroplastchloroplast

Step 2:Step 2: Light Independent (Calvin Light Independent (Calvin Cycle)Cycle)– uses energy from the light – uses energy from the light reactions to make sugar.reactions to make sugar.

• Happens in the Happens in the stromastroma of a chloroplast of a chloroplast

Sketch this chloroplast!Sketch this chloroplast!

ChloroplastsChloroplasts

Overview of Overview of PhotosynthesisPhotosynthesis

LightChloroplast

LIGHTREACTIONS

(in grana)

CALVINCYCLE

(in stroma)

Electrons

H2O

O2

CO2

NADP+

ADP + P

Sugar

ATP

NADPH

Light Reactions – Detailed steps:1) Light is absorbed by chlorophyll

2) H2O molecules are split to provide e- and H+ that will enter an electron transport chain to produce:

ATP NADPH

3) Oxygen from the splitting of H2O is released as waste

Will be used in the Calvin Cycle

2 H2 H22O O e- + 4 H e- + 4 H++ + O + O22

Time for video clips!• http://youtu.be/sQK3Yr4Sc_k

(2:42)

Check for Understanding

1. What happens to the oxygen created during the light reactions of photosynthesis?

a. It is used in the next step of photosynthesis

b. It is discarded as a waste product

c. It is used to make water

d. It becomes a part of glucose

Check for Understanding

2. What is the general purpose of the light reactions of photosynthesis?

a. To make oxygen

b. To convert chemical energy into light energy

c. To convert light energy into chemical energy

d. To make glucose.

The Calvin CycleThe Calvin Cycle

The Calvin CycleThe Calvin Cycle(sometimes called (sometimes called ““the Dark Reactionsthe Dark Reactions””))

Calvin CycleCalvin Cycle: Creates glucose using : Creates glucose using ATP and NADPH from the light ATP and NADPH from the light reactions as well as COreactions as well as CO22 from the air from the air Happens in the Happens in the liquid stroma liquid stroma of a of a

chloroplastchloroplast

Carbon FixationCarbon Fixation: the incorporation : the incorporation (adding) of CO(adding) of CO22 into organic into organic

compounds compounds Happens in Calvin CycleHappens in Calvin Cycle

Plant Food The plant stores the excess sugar as starch in the roots, seeds, and fruit of the plant.

Check for Understanding

2. What is the general purpose of the light independent reactions (Calvin cycle) of photosynthesis?

a. To make oxygen

b. To convert chemical energy into light energy

c. To convert light energy into chemical energy

d. To make glucose.

H2O

Energy overviewEnergy overview

Photosynthesis

Cellular Respiration

sun

glucose O2CO2

plants

animals, plants

ATPThe Great Circleof Life,Mufasa!