Chapter 9.4 - Photosynthesis

Question 1

Photosynthesis

Answer 1

The process by which plants, algae and some bacterias use the energy of sunlight to derive the synthesis of organic molecules, usually from carbon dioxide and water

Question 2

Chloroplast

Answer 2

• Two membranes known as the envelope (inner and outer membranes)
• Contains a series of membranes called the thykaloid membranes, where all light reactions in photosynthesis occur.
• The space enclosed in the thykaloid membrane is the thykaloid lumen.
• Outside the thykaloid membrane is the stroma (in between thykaloid and envelope where carbon fixation reactions occur.

Question 3

Photosynthesis continued (3) diagram

Answer 3

1. Chloroplasts are semi-autonomous, meaning they have DNA to produce some of their proteins but not all (Calvin Cycle). Chloroplasts evolved from cyanobacteria, by a process called endosymbiosis.
2. Water doesn’t give up electrons and insead gets oxidized to release sugars
3. Electrons from water drive an ETC (light RXNs)
   * *ATP and NADPH will drive the reduction of CO2 to form sugars.

Question 4

NADPH

Answer 4

Functions exactly like NADH only with an added phosphate group.
-NADPH uses anabolic reactions rather than catabolic like NADH.

Question 5

Chlorophyll

Answer 5

A conjugated double bond system of porphyrin ring responsible for light absorption. Its hydrophobic tail keeps it in the membrane DIAGRAM

Question 6

Carotenoids

Answer 6

Can absorb light and help to release the energy as heat

Question 7

Alternative Effects of Light Absorbed by a pigment molecule

Answer 7

DIAGRAM

Question 8

Fate #1

Answer 8

Electrons will return to ground state, but the energy is lost as light (energy = excited) Also known as fluorescence

Question 9

Fate #2

Answer 9

Electrons will return to groud state but the energy will be passed to another (usually)

• only occurs within a very short distance (chlorophylic) so pigment molecules need to be in very close proximity if one another.
• energy ultimately transfers to the reaction centre.

Question 10

Fate #3

Answer 10

Loss of electrons a.k.a OXIDATION.

• usually only occurs in reaction centre and not the antennae (light harvesting complexes)
• there is a special pair of chlorophylls in the reaction centre.

Question 11

A Photosystem

Answer 11

There are two systems: 1 & 2.

• Light harvesting Reactions:
  
  • bind chlorophyll and carotenoids
  • absorbs light
  • directs excitation energy into reaction centres
• Reaction Centres:
  
  • has “special pair” of chloroplasts
  • loses electron when it absorbs excitation energy
  • stong oxidant

Question 12

P700

Answer 12

Special pair of chlorophylls in PS1 (refers to wavelength absorbed)

Question 13

P680

Answer 13

Special pair of chlorophylls in PS2

Question 14

The “photo” part of photosynthesis

Answer 14

• Plants have two photosystems connected by an ETP
• Function of creating an ETC: creating a chemical gradient for protons
• You need to have a source of electrons and an acceptor
• *diagram**

Question 15

The “synthesis” part of photosynthesis

Answer 15

-Products of light reactions diagram

Question 16

Calvin Cycle pt.1

Answer 16

1. Carbon Fixation:
   - CO2 is fixated into an organic carbon molecule
   - RUBISCO: the enzyme responsible for carbon fixation made of carboxylase and oxygenase.
   * diagrams*

Question 17

Calvin Cycle pt. 2

Answer 17

2. Reduction of 3-PGA:
   - Cycle:
   
   • Reduction-> G3P-> (Glycolysis - synthesis - glucose/sugars)

Question 18

Calvin Cycle pt. 3

Answer 18

3. Some G3P regenerate

- this “starts production”

Question 19

Plant Cells in daylight- 7 Steps (diagram required)

Answer 19

• plants have mitochondria*
  1. Derive photosystem E.T.C
  2. Proton gradient, NADH Acceptor
  3. ^pH used to make ATP
  4. ATP and NADPH drive fixation of CO2 (requires a lot of energy)
  5. G3P (used for regeneration of cycle and metabolism)
  6. Makes starch (storage molecule). Exports G3P to the cytoplasm
  7. G3P can be used to make sucrose (transport sugar) and can also enter glycolysis, mitochondria and ATP synthesis

Question 20

Plant Cells After Dark - 2 Steps (Diagram required)

Answer 20

• mitochondria*
  1. Break down starch -> ultimately go down to G3P
  2. Exported from chloroplast: ultimately makes pyruvate>mitochondria>make ATP>provide energy for plant