1. Cell Energy: Photosynthesis
Chapter 8

2. Energy and life Energy- Ability to do work No energy = no life
Laws of thermodynamics
First law- energy cannot be created or destroyed, it can only be changed/converted.
Second law- entropy in a system is always increasing
Entropy: amount of disorder, energy not available to do work
Said simply: energy cannot be converted without the loss of useable energy (thermal energy/heat)
Example : Food chains

3. 10% Rule
Only 10% of energy from a trophic level is passed to next level Caused by 2nd law of thermodynamics

4. Forms of Energy
Energy comes in many forms:
Light
Heat
Electricity
. . . Energy can also be stored in the bonds of chemical compounds.

5. Autotrophs and heterotrophs
Autotrophs- organisms that make their own food from energy from the sun or other sources
Known as producers
Heterotrophs- organisms that need to ingest or consume food to obtain energy
Known as consumers
ALL organisms have to release the energy in sugars and other compounds to live.

7. Metabolism- all of the chemical reactions in a cell
Anabolism- Synthesis reactions in a cell
Example: photosynthesis
Catabolism- Decomposition reactions in a cell
Example: Cellular respiration

8. Photosynthesis- light energy from the sun is converted into chemical energy for use by the cell
Cellular respiration- Organic molecules are broken down to release energy for use by the cell.

9. Chemical Energy and atp
ATP- Adenosine Triphosphate- Energy for the cell
Made of adenosine, ribose and three phosphates
ATP releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate
ADP + P (or Pi)

10. CHEMICAL ENERGY AND ATP (Not in notes)
Storing energy- when bonds are formed, energy is stored
ADP- Adenosine diphosphate is similar to ATP, but with two phosphates instead of three
Energy is stored when another phosphate is added to ADP

12. Energy is released when bonds are broken
Releasing energy
Energy is released when bonds are broken
When a phosphate is removed from ATP, energy is released
As many as two phosphates can be removed from ATP
Remove one phosphate = ADP
Remove two phosphates = AMP (Adenosine Monophosphate)

13. Using biochemical energy
1. Cells use ATP for active transport, to move organelles in the cell, and to synthesize proteins and nucleic acids
2. Cells do not keep large amounts of ATP in the cell. The cell can regenerate ATP from glucose as needed
Cellular Respiration
3. ATP is great for transferring energy, but not for storing it.

14. Where do trees get their mass from? Veritasium Video
Video from:

15. Photosynthesis overview
Photosynthesis- The process by which plants use sunlight to convert water and carbon dioxide into sugar
The photosynthesis equation:
6 CO2 + 6 H20 + light  C6H12O6 + 6 O2
Carbon dioxide and water and light  sugar and oxygen
What are the products and the reactants?

16. photosynthesis requires light
Visible light is a mixture of wavelengths: ROY G BIV
Shorter waves: more energy
Longer waves: less energy
Wavelength corresponds to color

17. Pigments in photosynthesis
Pigments- light absorbing particles
There are different types of pigments
Chlorophyll- principal pigment that absorbs light in the blue-violet and red regions, but not the green
Chlorophyll is found in the chloroplasts of leaves
This is why chloroplasts and plants look green
There are accessory pigments: like carotenoids (think carrots)

18. Chlorophyll is best at absorbing ____________
Chlorophyll a & b
Chlorophyll is best at absorbing ____________
Does not absorb ______________________
Blue and red
Green and yellow

19. Photosynthesis Reactions
Site of photosynthesis
Pigment: chlorophyll
Organelle: Chloroplast
Double membrane
Contains Thylakoids, grana, stroma
Plant cell: mesophyll
Gas exchange: stomata

20. Organelles of photosynthesis
Thylakoids – membranes that form sacs in which pigments are embedded
Grana (granum, singular) – The stacks of thylakoids
Stroma – the space surrounding the thylakoids
Contains enzymes that catalyze the formation of sugar from carbon dioxide and water
Also contains the chloroplast’s DNA & RNA

21. Parts of the Chloroplast
Stroma –
Liquid inside the chloroplast. Surrounds the thylakoid membranes.
Grana – (granum plural)
Stacks of thylakoid membranes
Thylakoid –
Membranes containing photosystems
Photosystems –
Light capturing systems
Parts of the Chloroplast

22. Two Processes of Photosynthesis
1. Light Dependent Reaction 2. Calvin Cycle (Light Independent Reaction)

24. The light reaction Overview
Takes place in the membrane of the thylakoids
Chlorophyll absorb the light, light energy is converted into chemical energy needed to produce sugars
Water is split into Hydrogen and Oxygen in the process

25. Steps to the light reaction: Thylakoid membrane
Photons of light strike Photosystem (PS) II, one of two clusters of light absorbing pigments
Two electrons from PS II jump to an e- carrier
Electrons moves from PS II to PS I (other photosystem)
e- get re-excited in PS I

26. Steps of photosynthesis
At the same time, light energy is used to split a molecule of water into 2H+ , O2 and 2e-
2 H2O → 4 H+ + 4 e- + O2
O2 leaves out the stomata (pores)
H+ remain in the inside of the thylakoid
These e- replace those lost in PS II

27. Together they convert NADP+ to NADPH
The re-excited electrons in PS I combine with H+ from splitting of water
Together they convert NADP+ to NADPH
NADPH is an electron carrier that will take the electrons into the second phase (dark phase) of photosynthesis

29. Meanwhile, in the thylakoid
The H+ now in HIGH concentration in the thylakoid space travel down their membrane through ATP Synthase to the stroma
This energy adds a Pi to ADP to make ATP
The ATP and the NADPH now head to the Calvin Cycle to act as the energy to drive the reaction
Summary: Reactants- H20 and Light
Products – O2 (as waste), ATP and NADPH

31. Helpful animations
/metabolism/photosynthesis.swf step by step photosynthesis light reaction

33. The Calvin Cycle Overview
Takes place in the stroma (empty space)
ATP and NADPH from the light reaction are used to “fuel “ the Calvin Cycle
Saves chemical energy from light reaction in sugar

34. Steps to the Calvin cycle
CO2 enters through the stomata (pores in the leaf) and combines with RuBP
Catalyzed by RuBiCO, the most abundant enzyme on earth!
Series of reactions convert CO2 into glucose

35. Steps of Calvin cycle Carbon for Glucose comes from CO2
Hydrogen for Glucose comes from NADPH – from light reaction
Oxygen for glucose comes from CO2
Needs energy for reactions to occur – comes from Light reaction

37. What it really looks like

38. Summary of the Calvin cycle
Reactants- ATP, NADPH , and CO2 Products: Glucose

40. Summary of photosynthesis
Two step process
1. Light Dependent Reaction in the Thylakoid membrane
2. Light Independent Reaction (Calvin Cycle) in the Stroma
The reactants : CO2 and H2O
The products: C6H12O6 AND O2

41. What Affects the rate of photosynthesis?
Temperature
CO2
Light
Water