Outcome: Explain the process of

photosynthesis.

Warm-up:

1. Compare the two types of cells. Give examples for each.

2. Using double bubble map, differentiate plants and animal

cells.

3. What organelles is needed for photosynthesis to take place?

Carbon Cycle

The Carbon Cycle

3

Carbon is the primary element of living things.

Plants fix carbon when they use sunlight and CO2 to make

sugars.

Animals eat the sugars in the plants, some animals eat the

animals that eat the plants

Animals use O2 and the sugars to exhale CO2

Overview: The Process That Feeds the Biosphere

Photosynthesis

Is the process that converts solar energy into chemical energy

Photosynthesis

Complete the photosynthesis gizmo

Plants and other autotrophs

Are the producers of the biosphere

Autotrophs

7

• Organisms that can make their own food.

– Photoautotrophs: Use sun energy to make organic compounds (glucose) from light.

– Chemoautotrophs: Use chemical energy to makes organic compounds from chemical energy contained in inorganic substances

Plants are photoautotrophs

They use the energy of sunlight to make organic molecules from water

and carbon dioxide

Figure 10.1

Photosynthesis

Occurs in plants, algae, certain other protists, and some prokaryotes

These organisms use light energy to drive the synthesis of organic molecules from carbon dioxide and (in most cases) water. They feed not only themselves, but the entire living world. (a) On land, plants are the predominant producers of food. In aquatic environments, photosynthetic organisms include (b) multicellular algae, such as this kelp; (c) some unicellular protists, such as Euglena; (d) the prokaryotes called cyanobacteria; and (e) other photosynthetic prokaryotes, such as these purple sulfur bacteria, which produce sulfur (spherical globules) (c, d, e: LMs).

(a) Plants

(b) Multicellular algae

(c) Unicellular protist 10 m

40 m (d) Cyanobacteria

1.5 m (e) Pruple sulfur bacteria

Figure 10.2

Transfer and Use of Matter and Energy

Photosynthesis

EQUATION

REACTANTS

What happens to the products?

Products

How do autotrophs make their own

food?

12

Photoautotrophs

Most autotrophs use

sunlight to make their own

food.

Chemoautotrophs

Some have found another

way, using chemical energy

(stored in bonds) to make

food.

Photosynthesis

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Takes place in the chloroplasts of plant cells.

Pigment molecules (chlorophyll) absorb energy from the sun,

and use that energy to power photosynthesis.

How do plants use sunlight to make

food?

Pigments present in the cell absorb light (energy)

Plants have many pigments to help absorb the light energy.

Notice that they do not absorb light at these colors – this is why plants are green;

they reflect back green light. In the fall, the green pigments die off, leaving only the

carotenoids behind (which reflect back orange and red light)

Where does photosynthesis occur?

Chloroplasts

Chloroplasts

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What types of organisms use

photosynthesis?

Autotrophs

Chloroplasts: The Sites of Photosynthesis in

Plants

The leaves of plants

Are the major sites of photosynthesis

Vein

Leaf cross section

Figure 10.3

Mesophyll

CO2 O2 Stomata

Chloroplasts

Are the organelles in which photosynthesis occurs

Contain thylakoids and grana

Chloroplast

Mesophyll

5 µm

Outer membrane

Intermembrane space

Inner membrane

Thylakoid space

Thylakoid Granum Stroma

1 µm

The Two Stages of Photosynthesis: A

Preview

Photosynthesis consists of two processes

The light reactions

The Calvin cycle

What is ATP?

ATP: Basic energy source of all cells

Adenosine ribose 3 phosphates

What is ADP? ADP: Uncharged ATP; contains SOME energy, but less than ATP.

Like a rechargeable battery.

Store Energy: in chemical bond by adding a phosphate

Release Energy: from chemical bond by breaking off a phosphate

How do you recharge ADP?

23

ATP is not good for storing large amounts of energy over

long periods of time, thus it is more efficient to only keep a

small amount on hand in the cell.

Cells regenerate ATP from ADP and phosphate ions using the

energy stored in food (sugars)

Light Reactions

Energy from the sun is used to make ATP from ADP by

splitting water (creates O2 and H+). This molecule is easily

broken down to release energy.

Energy is stored in the phosphate bonds.

Looks like a nucleotide, but with extra phosphate groups

Photosynthesis Light Dependent Reactions

Light

O2

H2O ATP

NADPH

Organic

Compounds

(sugars)

CO2

Calvin

Cycle

Light Independent Reactions

ADP

NADP

Light Dependent Reactions 1. Electrons in chlorophyll are energized by light.

2. Electrons travel along a protein chain; energy used to make ATP and NADPH.

2H+ + 2NADP + 4e- 2NADPH

ADP + P ATP

3. Water is “spilt” by an enzyme, supplies materials for step 2, O2 given off as by-product.

2H2O 4H+ +O2 + 4e-

Light dependent reaction

The light reactions

Occur in the grana

Split water, release oxygen, produce ATP, and form NADPH

The light reactions convert solar energy to the chemical energy of ATP

and NADPH

Light Independent Reactions

1. ATP & NADPH (energy rich, but unstable) enter the Calvin

cycle, along with CO2.

2. Energy of ATP & NADPH powers enzymes, converting CO2 into

stable, high energy sugars.

3. ATP & NADPH are used up; become ADP & NADP, which are

reenergized during the light reactions.

Dark Reactions

ATP produced during the Light Reactions is used in the Dark

Reactions to “fix” carbon into sugar.

CO2 acts as the carbon source, ATP is broken down into

ADP.

The Calvin cycle

Occurs in the stroma

Forms sugar from carbon dioxide, using ATP for energy and NADPH

for reducing power

An overview of photosynthesis

H2O CO2

Light

LIGHT REACTIONS CALVIN CYCLE

Chloroplast

[CH2O] (sugar)

NADPH

NADP

ADP

+ P

O2 Figure 10.5

ATP

How do Plants do It?

The entire process of photosynthesis process of making

sugars from CO2 and sunlight is aided by enzymes.

These enzymes are the most important enzymes on the

planet – they make life possible.

Factors that Affect Photosynthesis

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Light – rate of photosynthesis increases until all the pigments

are being used.

CO2 – the Calvin cycle only takes in so much CO2 at once.

Once all the enzymes are occupied, the reaction is going

maximum speed.

Temperature – unfavorable temperatures may inactivate

certain enzymes.

Photosynthesis Summary