Photosynthesis

1
Photosynthesis

• 6CO2 6H2O C6H12O6
  6O2
• Carbon dioxide water
  glucose oxygen

2
Photosynthesis

• Last week we saw yeast convert sugar (glucose)
  into ATP (energy), ethanol, and CO2
• Photosynthesis is another form of respiration
  (making ATP)
• Use sunlight to make carbohydrates that are
  further processed into ATP (cellular respiration)
  
• Produces glucose (for cell respiration) and
  oxygen (O2)
• Occurs in the leaf which work as solar panels

3
Anatomy of a Leaf

• Work as natural solar panels by absorbing light
  rays
• Cells within a leaf are filled with chloroplasts
• Within each chloroplast are thousands of
  chlorophyll which are molecules that absorb the
  light needed for photosynthesis
• We will do Activity 1 on pg. 131 and label the
  parts on drawing on pg. 132

4
Anatomy of a Leaf

• Prepared slides showing cross sections of a leaf
• Locate following structures
• Xylem large thick-walled cells that are part of
  the vein of the leaf
• Phloem smaller cells in the vein
• Mesophyll regions composed of a tightly packed
  palisades or spongy portions
• Upper and lower epidermis
• Guard cells in lower epidermis
• Stoma opening between two guard cells
• Cuticle covers the epidermis

Veins
5
Anatomy of a Leaf
6
Photosynthesis

• The reactants (NOT PRODUCTS!) of photosynthesis
  are CO2 and H2O
• How do these two reach the mesophyll area (where
  photosynthesis occurs) of the leaf?
• The densely packed palisade mesophyll cells
  maximize space efficiency for absorption of light
  and the process of photosynthesis
• The loosely packed spongy mesophyll cells
  facilitate diffusion of carbon dioxide to the
  cells

7
Photosynthesis in Spinach Leaves

• We are going to determine the rate of
  photosynthesis in spinach leaves
• Take 30 discs of spinach leaves and place in
  solution of NaHCO3 (sodium bicarbonate or soda
  water)
• Create a vacuum to draw out all oxygen (discs
  will sink to the bottom (I have done this for
  you)
• Remember Spaces among the spongy mesophyll are
  filled with air causing the leaf to float. The
  NaHCO3 replaces the air with soda water causing
  it to sink
• As photosynthesis occurs, oxygen is produced in
  the spongy mesophyll causing the disc to rise

8
Photosynthesis in Spinach Leaves

• Pour NaHCO3 into 3 Petri dishes (about ½ way
  full) and mark them Dark, Room, and Light
  along with a group name
• Take 30 spinach discs that are at the bottom of
  the bowl (NOT floating) and put 10 discs into
  each Petri dish
• Place the Petri dish marked Dark into the black
  plastic tub
• Place the petri dish marked light under the
  beaker of water that is under the lamp (water
  acts as a heat sink)
• Place the Petri dish marked Room on the desktop

9
Photosynthesis in Spinach Leaves

• After 20 minutes, we will check the rate of
  photosynthesis
• HOW?
• Since we took out all the oxygen from the spinach
  leaves via the vacuum the only oxygen they
  present after 20 minutes is the oxygen they
  produce during photosynthesis
• We will be counting the number of floating discs
  to stand for the amount of oxygen produced (the
  discs sunk to the bottom of the NaHCO3 because we
  took away their oxygen, as they make oxygen
  through photosynthesis they will again rise to
  the top of the NaHCO3 solution)
• Put the number of discs in the appropriate box of
  the chart on the handout

10
Other Activities

• Make sure to see leaf slides and label the parts
  on pg. 132
• Look at onion cells
• No chloroplasts present (WHY?)
• Notice cell wall
• Look at Elodea and notice the chloroplasts
• LET ME SEE THE HANDOUT AT END OF CLASS FOR
  INCLASS HOMEWORK GRADE (IF I DONT SEE IT, YOU
  DONT GET CREDIT!)