1. Photosynthesis

2. Energy balance of Respiration and Photosynthesis
Completely burning glucose yields 686 kcal per 180 g. That’s 4 kcal/g of sugar or carbohydrate that you eat.
Building glucose from CO2 in the air and H2O takes 686 kcal per 180 g (2,840 KJ/180 g). Sunlight is converted into electrical energy in the leaf. The glucose is then further assembled into cellulose, lignin, and starches.

3. First, a brief review of plant cells

4. The ‘power plant’ of the cell: Animal cells have mitochondria Plant cells have chloroplasts

5. Leaf Structure vascular bundle (vein) xylem (water) phloem (sugar)
cuticle
epidermis
palisades
layer
spongy
layer
epidermis
stomate
guard cells
cuticle

6. Function of Leaf Structures
Cuticle = ‘skin’ in Latin
waxy coating reduces water loss
Epidermis = ‘upon’ + ‘skin’ in Gk.
skin protecting leaf tissues
Palisades layer = ‘a fence of stakes’ in Latin
high concentration of chloroplasts
Spongy layer
air spaces
gas exchange
CO2 in for sugar production, remove waste O2

7. Transpiration Xylem = ‘wood’ xylem (water) stomate guard cells O2 H2O
CO2
stomate
guard cells O2
H2O
CO2

8. Transpiration Water evaporates from the stomates in the leaves
pulls water up from roots
water molecules stick to each other
more water is pulled up tree from ground

9. Stomates & Guard Cells Stoma = mouth guard cell stomate
Function of stomates
CO2 in
O2 out
H2O out
Function of guard cells
open & close stomates
guard cell
stomate

10. Guard cells & Homeostasis
Homeo = similar
Stasis = standing still
Guard cells & Homeostasis
Homeostasis
keeping the internal environment of the plant balanced
Stomates open
let CO2 in
needed to make sugar
let H2O out
so it gets to leaves
let O2 out
get rid of waste product
Stomates close
if too much H2O evaporating

11. Xylem
carry water up from roots
Xylem = ‘wood’

12. Phloem: food-conducting cells
“Phloem” means husk or bark
carry sugars around the plant wherever they are needed
new leaves
fruit & seeds
roots

13. Photosynthesis

14. The overall process has
2 phases – light dependent and light independent.
Light phase: energy harvesting
Dark phase: molecule building. The Calvin Cycle.

15. Stage 1. The light-dependent phase: energy conversion/ energy harvesting Takes place in the thylakoid membrane inside the chloroplast. Involves PS I and PS II systems.

16. ‘Light reactions’: The simple view

17. The ‘less simple’ view

18. The complex view

19. The light reactions actually happen in 2 steps, with slightly different pigments

20. The ‘antenna’ pigments capture a range of wavelengths and channel the (now electrical) energy to chlorophyll A

22. Greens and yellows are emitted

23. Now on to Stage 2, the
light-independent (dark) phase, also known as: ‘Glucose construction’
‘Carbohydrate assembly’
‘Carbon or CO2 fixation’
Takes place outside of the thylakoid membrane in the stroma inside the chloroplast

24. Again, the overall process

25. The Calvin Cycle. One of the greatest discoveries of modern science
The Calvin Cycle. One of the greatest discoveries of modern science. Melvin Calvin awarded the 1961 Nobel Prize in Chemistry.

26. Alternate view

27. Energy molecules: ATP and NADPH
Currency analogy
ATP = $.25
Glucose = $10.00 (38 ATP’s to build 1 glucose)
Battery analogy
ATP phosphate bond stores 30 KJ/mol (7kcal/mol)
NADPH/NADP+ stores ≈ 200 KJ/mol (50kcal/mol)
Glucose C6H12O6 bond energy = 2,840 KJ/mol (686 kcal/mol)
Each cell produces 10 million ATP molecules per second

28. ATP – the battery of the cell
The 3rd phosphate bond contains 30 KJ/mol (7kcal/mol)

29. ATP = charged battery ADP = depleted battery
This bond stores about 30KJ/mol

30. NADPH is the other energy molecule in photosynthesis.

31. NADP+ = oxidized form. Depleted battery.
NADPH = reduced form. Charged battery. The extra electron carries ≈ 7X the energy as an ATP molecule.
NADP+ = oxidized form. Depleted battery.
This bond stores about 200KJ/mol

32. Photosynthesis pigments
Discussion: which solvent, polar or non-polar, can be used to extract and dissolve each from leaves?

33. Chlorophyll B