Bell work

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Bell work

• Do you think photosynthesis could be considered
  the primary source of energy for life? Explain
  your answer.

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7.1 Sunlight powers life

• Life on earth is solar-powered.
• Biologists classify organisms according to how
  they obtain food.
• Autotrophs
• self-feeder, also name producers
• They convert inorganic compounds to organic
  compounds.
• Plants use the suns energy to convert water and
  carbon dioxide into sugars.
• Heterotrophs
• Organisms that cannot make their own food
• Also known as consumers
• Depend on producers

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7.2 Food stores chemical energy

• Energy is the ability to perform work.
• There are different forms of energy
• Kinetic energy
• Potential energy
• Thermal energy
• Chemical energy depends on the structure of
  molecules energy stored in bonds

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Energy

• Endergonic or endothermic reactions
• Photosynthesis CO2 H2O glucose
• Absorbs energy
• Feels cold to the touch
• Exergonic or exothermic reactions
• Cellular respiration glucose CO2 H2O
• Release energy
• Feels warm to the touch

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Calories

• The amount of energy required to raise the
  temperature of 1 gram (g) of water by 1 degree
  Celsius (C).
• 1 kilocalorie 1000 calories 1 Calorie
• food calorie

25 C 1 gram
Energy required to raise the temperature to 26
C
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Photosynthesis
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Figure 8-2Photosynthesis takes place in cellular
organelles called chloroplasts. In this
sunflower, the greatest numbers of chloroplasts
are located in the leaves. Chlorophylls give the
chloroplastsand in turn the leavestheir green
color.
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Chloroplast

• Disc-shaped structures are called grana, which
  are surrounded by the stroma.
• Each disc-shaped structure is called a thylakoid.
  
• In the thylakoid is the chlorophyll and other
  pigments needed for photosynthesis

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Chlorophyll

• Pigment
• Photoreceptor
• Absorbs the energy from the sun

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Electromagnetic Spectrum
Figure 8-5Different forms of electromagnetic
energy have different wavelengths. Shorter
wavelengths have more energy than longer
wavelengths.
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Types of Chlorophyll

• These two kinds of chlorophyll complement each
  other in absorbing sunlight.
• Plants can obtain all their energy requirements
  from the blue and red parts of the spectrum,
  however, there is still a large spectral region,
  between 500-600nm, where very little light is
  absorbed.
• This light is in the green region of the
  spectrum, and since it is reflected, this is the
  reason plants appear green.

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Figure 8-7The laboratory technique of paper
chromatography can be used to analyze the
pigments in a leaf.
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Figure 8-4This "road map" shows the two main
stages of photosynthesis the light reactions,
which occur in the thylakoids, and the Calvin
cycle, which occurs in the stroma.
Double membrane Stroma Grana Thylakoid
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Light-dependent Reactions Photosystems I and II
Figure 8-8When light strikes the chloroplast,
pigment molecules absorb the energy. This energy
jumps from molecule to molecule until it arrives
at the reaction center.
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Excited electrons

• http//earthguide.ucsd.edu/earthguide/diagrams/abs
  orption/absorption.html

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Light-dependent reactions

• Hydrolysis
• Break water
• Steps of e-
• Water
• Photosystem I
• Electron Transport Chain
• Photosystem II
• NADPH
• Movement of e- powers ATP formation

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Figure 8-11In this "construction analogy" for
the light reactions, the input of light energy is
represented by the large yellow mallets. The
light energy boosts the electrons up to their
excited states atop the platform in each
photosystem. The energy released as the electrons
move down the electron transport chain between
the photosystems is used to pump hydrogen ions
across a membrane and produce ATP.
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Light-dependent Reactions Overview

• What do I need?
• water, sunlight
• What do I get?
• ATP, NADPH (energy molecules)
• oxygen

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Light-independent reaction Calvin Cycle
3PGA 3-phosphoglyceric acid G3P
glyceraldehyde phosphate
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Calvin Cycle

• NADPH and ATP give the energy to be stored in
  glucose.
• What do I need?
• ATP, NADPH and 6 carbon dioxide molecules
• What do I get?
• Glucose (1 glucose for every 6 CO2)

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Photosynthesis Overview
C6H12O6
Figure 8-14The light reactions and the Calvin
cycle together convert light energy to the stored
chemical energy of sugar. The plant can use the
sugar to build other organic molecules.
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Photosynthesis Chemical Reaction

• Overall formula
• 6CO2 6H2O sunlight ? C6H12O6 6O2