Unit 5

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Unit 5 Cellular Energy

• Photosynthesis

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Early Investigations of Photosynthesis

• Belgium 1600s
• Jan van Helmont designed an experiment to
  determine how plants gain mass
• Grew a plant for 5 years
• Mass of soil unchanged
• Mass of plant gained 75 kg
• His conclusion increase in mass due to water

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• England 1700s
• Joseph Priestly curious about conditions needed
  to keep a candle burning
• Placed lit candle in upside down jar as flame
  died out he decided something in the air allowed
  it to burn
• Tried again with a plant in the jar let it sit
  for several days then lit candle
• Flame continued to burn decided that the plant
  produced something that allowed candle to burn

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• Holland 1779
• Jan Ingenhousz wanted to know conditions under
  which plants would produce oxygen
• Used aquatic plants
• Placed one tank in dark conditions no
  noticeable changes
• Placed another tank in light conditions observed
  bubble being released from plants

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Autotrophs

• Plants and other types of organisms (autotrophs)
  are able to use light energy from the sun to
  produce food

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Photosynthesis

• The use of light Energy to convert Water (H20)
  and Carbon Dioxide (CO2) into Oxygen (O2) and
  High Energy Carbohydrates
• Examples Sugars and Starches

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Energy

• Energy Takes Many Forms such as light, heat,
  electrical, chemical, mechanical
• Energy can be changed from one form to another
• Energy can be stored in chemical bonds then
  released later

Candles release energy as HEAT LIGHT
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• For photosynthesis to occur, light energy must be
  captured this is a job for
• THE
• CHLOROPLAST!!!!

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Light and Pigments

• The chloroplast contains pigments light
  absorbing molecules
• Chlorophyll is the primary light-absorbing
  pigment in autotrophs

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• So,Chlorophyll is found inside chloroplasts
• And chloroplasts are found in the cells of
  autotrophs

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• Energy From The Sun Enters Earths Biosphere As
  wavelengths
• Light Contains A Mixture Of Wavelengths
• Different Wavelengths Have Different Colors

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• Different pigments absorb different wavelengths
  of light
• Chlorophyll a absorbs red an violet wavelengths
• Chlorophyll b absorbs blue

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• The green wavelengths are reflected back
• This is why leaves are green!

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• Autotrophs also have other accessory pigments
  that help absorb orange and yellow,
• When it gets cold, these pigments stop working
  first
• This is why the leaves change color in the fall

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• So, back to
• THE CHLOROPLAST
• Think of them as tiny solar panels!

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• The chloroplasts are not just green sacs in the
  cells of a plant
• The inner structure has 2 areas that carry out
  the chemical reactions of photosynthesis
• Grana stacks of disks
• called thylakoids
• 2. Stroma fluid that
• surrounds grana

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• The chloroplast captures light energy and mixes
  it with H2O and CO2
• The water is supplied by the xylem bundles that
  bring water from the roots to the leaves

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• The CO2 enters the leaves through pores called
  stomata found on the underside of the leaf
• Each stoma is surrounded by a guard cell that
  opens/closes the stoma using osmotic pressure

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• The light energy blows apart the bonds between
  all the carbon, hydrogen and oxygen atoms
• New bonds form and
• TA-DAH!
• A glucose molecule (C6H12O6) is made!
• There is some leftover oxygen, so it is paired up
  and sent back out the stomata into the atmosphere
  as O2

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Photosynthesis Overview

• This happens in 2 stages
• The Light Dependent Reactions -Takes place in
  grana
• The Light Independent Reactions (aka The Dark
  Reactions or The Calvin Cycle)
• -Takes place in stroma

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The Photosynthesis Equation
6CO2 6H20
C6H12O6 6O2
Light Energy
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Factors Affecting the Rate of Photosynthesis

• Amount of available water
• Temperature
• Amount of available light energy

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Energy Flows and Cycles of Matter

• Laws of Conservation state that neither matter
  nor energy is created or destroyed
• They are transferred and transformed through
  chemical processes

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The Carbon Oxygen Cycles

• Carbon is
• One of the most abundant elements on Earth
• CO2 is found as a gas in the air and as a
  dissolved gas in bodies of water due to cellular
  respiration
• Stored in limestone and in reservoirs of crude
  oil/natural gas
• Taken up/stored by producers
• Transferred to the tissues of consumers

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• Oxygen is
• A waste gas provided by land water producers
  during photosynthesis
• Use by Aerobic organisms during some type of
  cellular respiration
• Also stored and transferred in body tissues
• Excess oxygen is bonded with carbon or hydrogen
  and excreted as CO2 or water vapor