Photosynthesis

Energy for Life

• What are autotrophs?

• Why are they important?

Energy for Life

• AUTOTROPHS are organisms that can make their own food.–Also called

PRODUCERS.–Ex. PLANTS,

ALGAE

Energy for Life• HETEROTROPHS are organisms that

depend on other organisms for food.

– Also called CONSUMERS.

– Ex. ANIMALS,BACTERIA

Energy for Life

• TWO biological processes are needed to create usable energy for organisms.

• Photosynthesis – the process that converts sunlight into sugar. (autotrophs only)

• Respiration – process that releases energy in sugar into usable energy for cells. (autotrophs and heterotrophs)

ATP

Adenine(nitrogen base)

Ribose(sugar)

3 Phosphate groups

• Adenosine triphosphate (ATP) – energy storage molecule.

ATP

• ATP is the universal currency for energy • ATP stores energy in the BONDS

BETWEEN THE PHOSPHATE GROUPS. • When a BOND IS BROKEN energy is

released.+ phosphate energy+ATP

(tri)ADP

(di)

Structure of a Chloroplast• A chloroplast is the structure in a plant cell where

photosynthesis occurs.Internal Structure:• Thylakoid membrane – internal membrane, look

like stacks of pancakes.• Lumen – space inside thylakoid membrane.• Grana – stacks of thylakoids.• Stroma – protein solution that thylakoids are

embedded in.

Structure of a Chloroplast

Pigments• Pigments are light absorbing molecules.• Each pigment absorbs and reflects different

wavelengths of light. (we see the reflected color)

Pigments

• CHLOROPHYLL is the primary pigment in photosynthesis. – Gives plants their GREEN color.

• CAROTENOIDS are accessory pigments that absorb light that chlorophyll cannot. – They are YELLOW, ORANGE, AND BROWN.

Checkpoint

• Why do leaves turn yellow, orange and brown in the fall?

• Production of chlorophyll is slowed down in the fall due to lower temperatures and less sunlight!

Pigments

Photosynthesis

6 CO2 + 6 H2O + sunlight C6H12O6 + 6O2

Photosynthesis song :)

Sunlight

Carbon Dioxide

Water

Glucose

Oxygen

Important Scientists

Involved in discovering processes of Photosynthesis

Van Helmont

• Measured plant mass and soil mass before and after 5 years of growth

• Most of gain in mass came from water

Priestly

• Candle with a jar over it would die out. Why?– Required oxygen

• Sprig of mint plus candle caused candle to last longer. Why?– Plant produced

oxygen

Ingenhousz

• Plant produced oxygen only in the presence of light

Photosynthesis

• There are two stages to photosynthesis, the light-dependent reactions and light-independent (dark) reactions.

Light-dependent Reactions• Occur in the THYLAKOID MEMBRANES.

1. Light is absorbed by chlorophyll in Photosystem II and electrons are excited.

– Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called a photosystem (a.k.a, light system)

2. The excited electrons move through a series of reactions – the electron transport chain.

Light-dependent Reactions

Light-dependent Reactions3. The light energy splits water molecules

into H and O2

4. The O2 is released into the atmosphere and the H bonds to a carrier molecule (NADPH) to be carried to the Dark Reactions.

5. Splitting the water also creates ATP.

Light Reactions

O2

LightReactions

NADPHATP

NADPHATP

Sunlight, water, and CO2

Chloroplast

Light- dependentReactions

Chloroplast

NADPH

ATP

The end products of the light reactions are NADPH, ATP, and O2

Light-independent Reactions

• Don’t Require LIGHT• Also called the DARK

REACTIONS OR THE CALVIN CYCLE.

• Occur in the STROMA

Melvin Calvin

Light-independent Reactions

1. Carbon dioxide enters the plant and attaches to a sugar molecule.

• This is called carbon fixation2. Carbon Dioxide, NADPH, and ATP

combine with enzymes to make glucose (C6H12O6) and more CO2.

3. NADPH becomes NADP+ and ATP becomes ADP +P

What happens in the Calvin Cycle?

Dark Reactions

Chloroplast

Light, water, and CO2

O2Glucose

CO2

Light- independent

Reactions

NADPHATP

ADP + PNADP+Chloroplast Carbon Fixation

Light- dependentReactions

Factors Affecting Photosynthesis

• Light Intensity – the more light the faster the rate of photosynthesis.

• CO2 Concentration – the more CO2, the faster the rate of photosynthesis.

• Temperature – rate of photosynthesis slows down at extremes of hot or cold.

Photosynthesis video