copyright pearson prentice hall. 8-1 energy and life

Copyright Pearson Prentice Hall

Chapter 8Photosynthesis


8-1 Energy and Life


• Energy – the ability to do work

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


Chemical energy and ATP

• Adenosine Triphosphate

• ATP

• Energy storing molecules

• Made up of…

• 1 adenine

• 1 ribose

• 3 phosphates


Adenine

Ribose 3 Phosphates


• 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


Using Biochemical Energy

• Cells use energy to….

• Maintain homeostasis

• Maintain body warmth

• Move cells

• Transmit nerve impulses


8-2 Photosynthesis: An Overview


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


• 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


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 relighted and would remain lighted for a while

• The plant produced the substance required for burning


The Photosynthesis Equation

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

•The equation for photosynthesis is:

6CO2 + 6H2O C6H12O6 + 6O2

carbon dioxide + water glucose + oxygen

Light

Light


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


8-3 The Reactions of Photosynthesis


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


Granum

Thylakoid Stroma


• Photosynthesis occurs in 2 Phases

1. Light Dependent Reaction

2. Light Independent Reaction


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


• ADP → ATP

• H2O → 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)


Light

Dependent

Reaction

O2

ATP

NADPH

H2O


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 CO2 is added to the cycle each time, it takes a total of 6 rounds of the cycle to form 1 glucose


• 6CO2 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 (C6H12O6)

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

Light

Dependent

Reaction

O2

ADP

NADP

Light

Independent

Reaction

C6H12O6

6CO2

ATP

NADPH

H2O

RuBP12 PGA

12 PGAL

2 PGAL

10 PGAL

copyright pearson prentice hall. 8-1 energy and life

Documents

suns energy

energy of sunlight

treein photosynthesis

steady supply of energy

basic energy source

green slide

life slide

overview slide