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8-1 Energy and Life

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• Energy – the ability to do work

• Organisms and their cells need a steady supply of energy in order to function

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Chemical energy and ATP

• Adenosine Triphosphate

• ATP

• Energy storing molecules

• Made up of…

• 1 adenine

• 1 ribose

• 3 phosphates

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Adenine

Ribose

3 Phosphates

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• Adenosine Diphosphate

• ADP

• Cells store energy by bonding a third phosphate group to ADP to make ATP

• Made up of…

• 1 adenine

• 1 ribose

• 2 phosphates

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Using Biochemical Energy

• Cells use energy to….

• Maintain homeostasis

• Maintain body warmth

• Move cells

• Transmit nerve impulses

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8-2 Photosynthesis: An

Overview

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Van Helmont’s Experiment

• In the 1600s, Jan van Helmont wanted to find out if plants grew by taking material out of the soil

• He determined the mass of a pot of dry soil and a small seedling

• Planted the seedling in the pot, and watered it regularly.

• After 5 years the seedling was a small tree and had gained 75kg, but the soil’s mass was almost unchanged

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• Van Helmont concluded that the gain in mass came from water because water was the only thing he had added

• Although van Helmont did not realize it, carbon dioxide in the air made a major contribution to the mass of his tree

• In photosynthesis, the carbon in carbon dioxide is used to make glucose

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Priestley Experiment – 100 Years Later…

• He took a candle, placed a glass jar over it and watched as the flame gradually died

• He reasoned that the flame needed something in the air to keep burning

• He placed a sprig of mint into the jar for a few days

• He found that the candle could be relit and would remain lit for a while

• The plant produced the substance required for burning

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The Photosynthesis Equation

•Photosynthesis – plants trap the sun’s energy and make glucose

•The equation for photosynthesis is:

6CO

2

+ 6H

2

Light

O C

6

H

12

O

6

+ 6O

2

Light carbon dioxide + water glucose + oxygen

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Light and Pigments

• How do plants capture the energy of sunlight?

• Pigments – light absorbing molecules in plants

• Two main types of chlorophyll

Chlorophyll a

Chlorophyll b

• Chlorophyll does not absorb green light waves

• Green light is reflected by leaves which is why plants look green

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8-3 The Reactions of

Photosynthesis

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Inside a Chloroplast

• In plants, photosynthesis takes place inside chloroplasts

• Parts of a chloroplast

• Thylakoid – disk-like membranes that contain chlorophyll

• Grana – a stack of thylakoids

• Stroma – liquid surrounding the thylakoids

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Granum

Thylakoid Stroma

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• Photosynthesis occurs in 2 Phases

1. Light Dependent Reaction

2. Light Independent Reaction

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Light Dependent Reaction

• First phase of photosynthesis

• Takes place in thylakoid

• Sunlight strikes chlorophyll molecules in the thylakoid

• Energy in the light is transferred to electrons

• Highly energized electrons pass from chlorophyll to electron transport chain

• Electron Transport Chain – a series of proteins embedded in the thylakoid membrane

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• ADP → ATP

• H

2

O → H + H + O

• Oxygen leaves the plant and goes out into the atmosphere

• Hydrogen combines with NADP

• NADP → NADPH

• NADPH – an electron carrier (carries energy)

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H

2

O

Light

Dependent

Reaction

ATP

NADPH

O

2

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Light Independent Reactions

• Second phase of photosynthesis

• Does not require light

• Occurs in the stroma

• Also called the Calvin Cycle

• Each glucose molecule made contains 6 carbon atoms

• Only one molecule of CO

2 is added to the cycle each time, it takes a total of 6 rounds of the cycle to form 1 glucose

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• 6CO

2 combines with RUBP and makes 12 PGA

• 12 PGA combines with ATP and NADPH and makes 12 PGAL

• 2 PGAL are used to make 1 glucose (C

6

H

12

O

6

)

• 10 PGAL are used to make more RUBP to keep the reaction going

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H

2

O

6CO

2

Light

Dependent

Reaction

ADP

NADP

ATP

NADPH

Light

Independent

Reaction

O

2

C

6

H

12

O

6