ENVS 10

1
ENVS 10

• Lecture 4
• Cellular Respiration and Photosynthesis

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Energy Flow

• Sunlight converted to sugar via photosynthesis
• Animals eat plants
• Animals eat animals
• Animals and plants die
• Chemicals are recycled back into the environment

3
Energy

• Energy is defined as the ability to do work
• It exists in two states kinetic and potential

Potential Energy stored energy
Kinetic Energy energy of motion
4
Energy Converting Organelles

• Two organelles associated with energy conversion
  reactions in the cell
• Mitochondria
• Found in almost all eukaryotes
• Chloroplasts
• Found only in plants and algae

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Mitochondria

• Powerhouses of the cell
• Extract energy from organic molecules through
  oxidative metabolism

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Chloroplasts

• Energy-capturing centers
• Sites of photosynthesis in plants and algae
• Like mitochondria, they are surrounded by two
  membranes
• However, inner membrane much more complex

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Biochemical Reactions

• Biochemical reactions -- formation, breakdown,
  and rearrangement of molecules to provide
  organisms with essential energy and building
  blocks.
• Cellular Respiration
• C6H12O6 6O2 ? 6H2O 6CO2 Energy
• sugar oxygen ? water carbon
  dioxide
• Photosynthesis
• Energy 6CO2 6H2O ? C6H12O6 6O2
• carbon dioxide water ? Sugar
  oxygen

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Cellular Respiration

• Method for using the chemical energy that we
  intake as food
• Break down food into organic molecules
• Organic molecules taken into cells
• Chemical bonds of Organic molecules are broken in
  order to create energy that the cell can use to
  do work

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Cellular Respiration

• Series of chemical reactions
• Occurs in the Mitochondria
• Reactions yield cellular energy in the form of 38
  ATP molecules for each glucose molecule processed

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Redox Reactions

• Chemical reactions that transfer electrons from
  one substance to another are called
  oxidation-reduction reactions (redox reactions)
• Loss of electrons oxidation
• Glucose is oxidized (loses electrons to Oxygen)
• Gain of electrons reduction
• Oxygen is reduced (gains electrons and Hydrogen)

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Cellular Respiration
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THE BASICS OF PHOTOSYNTHESIS

• Almost all plants are photosynthetic autotrophs,
  as are some bacteria and protists

• They generate their own organic matter through
  photosynthesis

(c) Euglena
(d) Cyanobacteria
(b) Kelp

• (a) Mosses, ferns, and
• flowering plants

Figure 7.2
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Chloroplasts Sites of Photosynthesis

• Photosynthesis

• Occurs in chloroplasts

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• Chloroplasts

• Are found in the cells of the mesophyll
• Have a double membrane
• Contain stroma, a thick fluid inside the first
  membrane
• Contain thylakoids, membranous sacs arranged in
  stacks of discs

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Vein
Chloroplast
Meso- phyll
Inner membrane
Outer membrane
Stomata
Leaf cross section
Mesophyll cell
Grana
Stroma
Thylakoid
Thylakoid space
Figure 7.3
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The Overall Equation for Photosynthesis

• The reactants and products of the reaction

Light energy
Photo-synthesis
Glucose
Oxygen gas
Carbon dioxide
Water
Unnumbered Figure 7.1
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Increasing energy

• The full range of radiation is called the
  electro-magnetic spectrum

Gamma rays
Micro- waves
X-rays
UV
Infrared
Radio waves
Visible light
Wavelength (nm)
600 nm
Figure 7.5
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Chloroplast Pigments

• Chloroplasts contain several pigments

• Chlorophyll a
• Chlorophyll b
• Carotenoids

Figure 7.7
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How Photosynthesis Moderates the Greenhouse Effect

• Old-growth forests

• Are important for lumber
• Are important for moderating world climates

Figure 7.16
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• The Greenhouse effect

• Warms the atmosphere
• Is caused by atmospheric CO2

Sunlight
Atmophere
Radiant heat trapped by CO2
Figure 7.17
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• Destruction of forests may be increasing this
  effect
• Greenhouse gases are the most likely cause of
  global warming, a slow but steady rise in the
  Earths surface temperature