Chapter 8 Photosynthesis

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Chapter 8 Photosynthesis
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8-1 Energy and Life
8-1 Energy and Life
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Autotrophs
8-1 Energy and Life

• Make their own food

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Heterotrophs
8-1 Energy and Life

• Cannot make their own food

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Chemical Energy and ATP
8-1 Energy and Life

• The principal chemical compounds that cells use
  to store and release energy is called ATP
  adenosine triphosphate

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Storing Energy
8-1 Energy and Life

• ATP stores energy in the third phosphate
• ATP is like a fully charged battery

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Releasing Energy
8-1 Energy and Life
Q How is the energy in ATP released?

• A Break bond between the second and 3rd
  phosphates

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ADP
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8-1 Energy and Life
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Using Biomechanical Energy
8-1 Energy and Life

• Active Transport
• Movement of organelles through cell
• Sythesis of proteins and nucleic acids
• Produce light
• Blink of firefly caused by an enzyme powered by
  ATP

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ATP Availability
8-1 Energy and Life

• Most cells only have enough ATP for a few seconds
  of activity
• Why?
• Not good at storing energy over the long term
• Glucose stores 90X the chemical energy of ATP
• Cells generate ATP from ADP as needed by using
  the energy in foods like glucose

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8-2 Photosynthesisan Overview
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During Photosynthesis
8-2 Photosynthesis an Overview

• Organisms (plants?) absorb light energy from the
  sun and store it in organic compounds.
• Energy is crucial to all life, without it work
  could not be done.

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8-2 Photosynthesis an Overview
AN OVERVIEW OF PHOTOSYNTHESIS
Photosynthesis is the process by which
autotrophic organisms use light energy to make
sugar and oxygen gas from carbon dioxide and
water
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8-2 Photosynthesis an Overview
An example of basic photosynthesis
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The Photosynthesis Equation
8-2 Photosynthesis an Overview
light
CO2

H2O

C6H12O6
O2
(Carbon Dioxide)
(Water)
(Sun)
(Glucose)
(Oxygen)
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Because light is a form of energy
8-2 Photosynthesis an Overview

• Anything that absorbs light also absorbs the
  energy from that light
• When chlorophyll absorbs light, much of the
  energy is transferred to electrons in the
  chlorophyll molecule, raising the energy level of
  these electrons
• These high-energy electrons make photosynthesis
  work

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Photosynthesis
8-2 Photosynthesis an Overview
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Chloroplasts
8-2 Photosynthesis an Overview

• The site of Light Dependent Reactions
• These organelles are surrounded by a double
  membrane and contain an inner membrane separate
  into disk like sacs called thylakoids
• Thylakoid are arranged into granum, or neat
  stacks
• Each thylakoid contains the green pigment
  chlorophyll
• The light absorbing pigments are organized into
  photosystems, which transfer energy during the
  light reactions

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8-2 Photosynthesis an Overview
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Pigments in chloroplasts
8-2 Photosynthesis an Overview

• Chloroplasts absorb all other color pigments,
  leaving green to be reflected resulting in a
  plants color.
• Chlorophyll a and b are
• two are the 2 most
• common types of chlorophyll
• Chlorophyll b absorbs colors or
• light energy NOT absorbed by
• chlorophyll a

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8-2 Photosynthesis an Overview
Absorption of Light by Chlorophyll a and
Chlorophyll b
Absorption of Light by Chlorophyll a and
Chlorophyll b
Chlorophyll b
Chlorophyll a
V
B
G
Y
O
R
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8-3 The Reactions of Photosynthesis
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8-3 Reactions of Photosynthesis
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Thylakoids
8-3 Reactions of Photosynthesis

• Sac-like photosynthetic membranes arranged in
  stacks

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Grana
8-3 Reactions of Photosynthesis

• Stacks of thylakoids

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Stroma
8-3 Reactions of Photosynthesis

• The region outside the thylakoid

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Scientists describe the reactions of
photosynthesis in two parts
8-3 Reactions of Photosynthesis

1. Light dependent reactions (in the thylakoid
   membranes)
2. Light independent reactions (takes place in
   stroma)

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8-3 Reactions of Photosynthesis
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Photosynthesis Consists of 2 Stages
8-3 Reactions of Photosynthesis

• Non-light dependent (dark) reactions
• Takes place in the Stroma
• Includes the Calvin cycle
• Does not literally occur in the dark, but
  requires no light to occur
• Carbon dioxide is split,
• Carbon to make sugars
•  ATP NADPH2  CO2   C6H12O6

• Light dependent reactions
• Take place in the Thylakoid Membrane
• Depends on sunlight for activation energy
• Responsible for the absorbing of light in
  Photosynthesis
• Water is split,
• giving off oxygen
• H2O   O2  ATP NADPH2

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8-3 Reactions of Photosynthesis
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Carrier Molecule
8-3 Reactions of Photosynthesis

• Compound that can accept a pair of high energy
  electrons and transfer them along with most of
  their energy to another molecule
• Ex.) NADP

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8-3 Reactions of Photosynthesis
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Q What does this do?
8-3 Reactions of Photosynthesis

• NADP H NADPH

A this traps sunlight in chemical form
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Light Dependent Reactions
8-3 Reactions of Photosynthesis

• Uses energy from light to produce
• Oxygen gas
• ATP
• NADPH

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8-3 Reactions of Photosynthesis
Watch The Light Reaction Video
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8-3 Reactions of Photosynthesis
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8-3 Reactions of Photosynthesis
Watch The Light Reaction Video
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The Calvin Cycle
8-3 Reactions of Photosynthesis

• The ATP and NADPH formed by the light-dependent
  reactions contain an abundance of chemical
  energy, but they are not stable enough to store
  that energy for more than a few minutes.
• The Calvin cycle uses ATP and NADPH from light
  dependent reactions to produce high energy sugars

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The Calvin Cycle
8-3 Reactions of Photosynthesis

• These reactions dont require light, therefore
  these reactions are called
• Light independent reactions

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8-3 Reactions of Photosynthesis
Watch The Calvin Cycle Video
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8-3 Reactions of Photosynthesis
Watch The Calvin Cycle Video
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Factors Affecting Photosynthesis
8-3 Reactions of Photosynthesis

• Not enough water
• Temperature
• Light intensity

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Review Photosynthesis uses light energy to make
food molecules
8-3 Reactions of Photosynthesis
Sugar used for
? Cellular respiration
? Cellulose
? Starch
? Other organic compounds
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8-3 Reactions of Photosynthesis