Photosynthesis

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Photosynthesis
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Photosynthesis

• Involves concepts from

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Organisms exist because of chemical reactions
occurring within cells.

• Chemical reactions occur in all cells, tissues,
  organs, and organ systems.

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What is a chemical reaction?

• Atoms or ions are
• joined together by chemical bonds (forming a
  compound)
• OR
• compounds are broken apart
• All chemical reactions involve a rearrangement
  of atoms or ions AND

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Chemical Reactions

• Example of a reaction
• 2H2 O2 ? 2H2O
• A molecule of hydrogen is made up of 2 hydrogen
  atoms held together by high energy bonds.
• A molecule of oxygen is made of 2 oxygen atoms
  held together by high energy bonds.

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Chemical Reactions

• 2H2 O2 ? 2H2O
• Water is formed when molecules of hydrogen and
  molecules of oxygen are broken
• AND
• Atoms rearrange themselves into molecules of
  water held together with low energy bonds.

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Chemical Reactions
2H2 O2 ? 2H2O
HIGH ENERGY BONDS LOW ENERGY BONDS
REACTANTS PRODUCTS

All of the extra energy found on the reactant
side of the equation is released with the product
as heat or light.
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Law of Conservation of Energy

• Energy cannot be created or destroyed, however it
  can change forms.
• In our example If the reaction is reversed
• Energy must be added to water to break it down.
  This added energy ends up stored in chemical
  bonds of hydrogen and oxygen molecules.  
• 2H2O Heat ENERGY? 2H2 O2
•  Energy can be stored for later use.

Worksheet chemical reactions and energy
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Chemical Reaction-Formation of Water

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Forms

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Physics

• White light is made up of a spectrum of colors.

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Physics

• The spectrum is seen when the white light is
  broken up into its components by prisms or
  raindrops

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Light

• When all colors within white light are reflected
  back to our eyes ? we see WHITE!
• When all colors within white light are absorbed
  by an object ? we see BLACK!
• A surface appears a particular color because it
  contains a "pigment" that reflects that
  particular color and absorbs all other colors.
• Pigment light absorbing colored molecule

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Name the color

• What is the color of a sweater that absorbs blue,
  green and yellow light?

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What colors are absorbed by
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Green Plants

• Reflect green light
• Absorb all other colors of light

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Green Plants
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Biology

• Organisms make their own food and are called
  autotrophs

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Or

• Organisms EAT plants or animals and are called
  __________________________________

heterotrophs
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Biology

• Autotrophs use light energy from the sun (or
  chemical energy) to produce energy rich
  sugars/carbohydrates. Examples of autotrophs
  _____________________,________________,
• ____________________________

some protista
green plants
some bacteria

• Energy in most ecosystems on earth comes from

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Early Scientific Research on Photosynthesis

• 1643 Belgium
• Jan van Helmont

• With your group analyze van Helmonts
  experiment

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Conclusions from van Helmonts experiment

• 164 pounds of wood, bark, and roots had arisen
  from water alone. The mass of the tree did NOT
  come from the soil.
• Was van Helmont correct? _____________________

Partially correct

• The mass of a plant comes in part from waterNOT
  from soil (except for a tiny fraction)
• Plants are made of carbohydrates. The term
  hydrate water.

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Late 1700s EnglandJoseph Priestley

• Joseph Priestley discovered oxygen in 1774
• He continued to experiment with gases, plants and
  animals.

With your group analyze Priestleys experiment!
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Priestleys Photosynthesis Experiment

• Priestley concluded green plants produce the
  substance oxygen necessary for a fire to burn
  and for animals to breathe.

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Late 1700s Jan Ingenhouszs

• Jan Ingenhousz was born in 1730 in the
  Netherlands. He trained as a medical doctor.
• In 1779, Ingenhousz took a position in the same
  laboratory as Joseph Priestley.
• Ingenhousz carried out research on
  photosynthesis.

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Ingenhouszs Photosynthesis Experiment

• Ingenhousz placed a pond plant in a jar filled
  with water
• He placed the jar in bright sunlight and observed
  bubbles produced by the plant
• He placed the jar in low light conditions and
  observed no bubbles produced by the plant

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Ingenhouszs Conclusion

• Green plants only produce oxygen in the presence
  of _______________.

Sunlight
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Photosynthesis

• By the mid-1800s, it was understood that plants
  use carbon dioxide and water to produce glucose
  and oxygen using light energy from the sun.  
• Photosynthesis Reaction

Reactants energy source Products
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Photosynthesis

• CO2 enters plants through stomata (singular
  stoma) in leaves and stem.
• O2 and water exit the stomata

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Carbon Dioxide
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Water

• H2O enters plants through roots and is carried by
  the veins to leaves

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Products of Photosynthesis

• Glucose and Oxygen
• Glucose is carried from the leaves of the plant
  in phloem (downward veins) to the parts of the
  plant where photosynthesis does not occur (roots,
  flowers).
• Glucose is stored in fruits (apples, oranges,
  etc.) and roots (onions, potatoes, etc.)
• Oxygen is released from stomata.

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Photosynthesis

• Complete worksheet on Green Plants!

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What else is needed for Photosynthesis?

• Photosynthesis occurs in the chloroplasts of
  plant cells.

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Chloroplasts are made of

• thylakoids sac-like membranes containing
  molecules of chlorophyll, a pigment, which
  absorbs red and blue light.
• stroma space outside of the thylakoids

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If plants contain chlorophyll why do they turn
color in the fall?

• Some plants have leaves with multiple pigments
  for maximum absorption of light at different wave
  lengths.
• In the fall, the pigments begin to break-down.
• Chlorophyll breaks down first, revealing the
  other pigments below.

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Processes of Photosynthesis

• Two Stage process
• Light DEPENDENT reaction and
• Light INDEPENDENT reaction or CALVIN CYCLE

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LIGHT DEPENDENT REACTION

• Occurs only in light!
• Takes place in thylakoid (Overview)
• H2O enters chloroplast (through xylem)
• Bonds holding H2O together are broken and H ions
  and oxygen atoms are produced
• H ions are used in making glucose.
• O2 (waste product) is released through stomata.
  This is the oxygen we breathe.

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Light Dependent Reaction (cont)

• Light energy enters the thylakoid in the plants
  chloroplasts.
• This energy is converted into chemical energy and
  is stored in two chemical compounds through
  electron transport chains.
• ATP (Adenosine Triphosphate)
• NADPH (Nicotinamide Adenine Trinucleotide
  Phosphate)
• Electron transport chains are used for extracting
  energy from sunlight 

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Light Dependent Reaction

• The light energy hasnt been created or destroyed
  by the plant, but it has changed form.
• Light energy transformed into Chemical Energy
  (energy stored in the chemical bonds of ATP and
  NADPH)
• ADP P ? ATP NADP H ? NADPH

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Fact Check Light Dependent Reaction

• In which part of the chloroplast does the light
  dependent reaction occur?
• Which two high energy molecules are produced
  using the light energy from the sun?
• What is the waste product of the light
  dependent reaction?
• How does this waste product exit the plant cells?
• Which part of the water molecule is used to make
  a molecule of glucose?
• What is the role of sunlight in the process of
  photosynthesis?

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Light Independent Reaction or Calvin Cycle

• Occurs in stroma the space surrounding the
  thylakoid membranes
• Takes place in light OR dark

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Light Independent Reaction or Calvin Cycle

• CO2 enters chloroplasts through stomata.
• Energy stored during the light dependent reaction
  (ATP and NADPH) is used to convert carbon dioxide
  and H ions (from water) into glucose.
• Glucose can then be converted into molecules
  needed by the cell
• Inorganic carbon (CO2) has been converted into
  organic molecules carbon fixation.

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Light Independent Reaction or Calvin Cycle

Chemical Energy in ATP NADPH
H CO2 ? Glucose
Low energy bonds in CO2
High energy bonds in glucose
Low energy ADP NADP (Available for light
dependent reaction)
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Photosynthesis Equation!

• INORGANIC ORGANIC
• 6CO2 6H20 ? C6H1206 6O2
• Reactants Products

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Fact Check Light Independent Reaction

1. In which part of the chloroplast does the light
   independent reaction occur?
2. What is another name for the Light Independent
   Reaction?
3. Why is it called the Light Independent Reaction?
4. Which molecule is added to H- (from the light
   dependent reaction) to make glucose?
5. How does the molecule referred to in 4 enter the
   chloroplast?
6. Which molecule is used to provide the chemical
   energy for the high energy bonds holding glucose
   molecules together?

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Factors affecting Photosynthesis

1. Light - Absence of light ? no photosynthesis
2. Increase in light intensity increases rate of
   reaction (up to a pointthis point is dependent
   on the particular species of plant)
3. Water - Absence of water slows or stops the
   process
4. Temperature Occurs at ?0?C?? 35?C (dependent on
   the ecosystem)

Would you expect a shortage of CO2 to be a
problem for plant growth on earth? Why or why
not?
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Factors Affecting Photosynthesis
Carbon dioxide