PHOTOSYNTHESIS

Question 1

ANTENNA COMPLEX

Answer 1

Composed of a cluster of chlorophyll molecules and accessory pigments
Embedded in the thylakoid membrane
Absorbs a photon and transfers the energy from pigment to pigment until it reaches the reaction center

Question 2

REACTION CENTER

Answer 2

Protein complex
Contains a chlorophyll-A molecule
Electrons of chlorophyll absorbs energy and begin photosynthesis

Question 3

Light dependent reactions PROCESS

Answer 3

Photoexcitation
Absorption of a photon by an electron of chlorophyll
Electron Transport
Transfer of excited electrons through a series of membrane-bound electron carriers, resulting in the pumping of a proton through the photosynthetic membrane, which creates a H+ reservoir and eventually reduces an electron acceptor
Chemiosmosis
The movement of protons through ATPase complexes to drive the phosphorylation of ADP to ATP

Question 4

Photo excitation

Answer 4

Photon strikes PS2 and excites an e- of chlorophyll P680. This electron is captured by a primary electron acceptor
Whenever photon strikes

Question 5

Electron Transport

Answer 5

• Electron is transferred to the first electron mobile carrier (PQ). This process occurs twice, causing 2 electrons to pass through the ETC
• A “Z” protein (enzyme) associated with PS2 facing the lumen splits water into O2, Protons and Electrons
• The 2 electrons replace the missing electrons in chlorophyll 680
• O2 leaves as by-product
• The protons remain in the thylakoid space (lumen). Helps create the H+ gradient that will power chemiosmosis
• The electrons that leave photosystem 2 pass through PQ, which transports protons from the stroma into the thylakoid lumen
• Helps create H+ gradient for chemiosmosis
• 4 protons are translocated from the stroma into the lumen for every pair of electrons

-The electrons move to b6-f complex, then to Pc, then to PS1 (by this time, the energy of the electrons has dissipated

• A photon of light strikes PS1 and excites the electrons of chlorophyll P700
  Electrons then pass through another ETC containing an iron-containing protein called Fd
• They then move to the enzyme NADP reductase that uses the 2 electrons and H+ ions from the stromA to reduce NADP+ to NADPH

Question 6

Chemiosmosis

Answer 6

Protons that accumulate in the thylakoid lumen contribute to an electrochemical gradient that drives the phosphorylation of ADP to ATP

Question 7

Light reactions purpose

Answer 7

using light energy and water to make ATP and NADPH for calvin cycle

Question 8

Light reactions LOCATION

Answer 8

in between the thylakoid lumen and the stroma (aka the thylakoid membrane)

Question 9

Light reactions REACTANTS:

Answer 9

NADP+, ADP + P, H2O, light energy

Question 10

Light reactions PRODUCTS:

Answer 10

NADPH, ATP, O2, H+,

Question 11

Light-independent reactions Carbon Fixation

Answer 11

3 CO2 molecules are added to RuBP and is catalyzed by the enzyme Rubisco
Produces 3 BPG (6 carbon with 1 phosphate group at each end)
Unstable so it splits

Question 12

Light-independent reactions Reduction reactions

Answer 12

6 ATP → 6 ADP + 6 P
6 NADPH → 6 NADP+ + 6 H+
6 three carbon-phosphate G3P are made
One G3P leaves the cycle (acts as a raw material in the production of other carbohydrates that the cells use for various structural and functional processes (ex. Glucose, starch, cellulose)

Question 13

Light-independent reactions RuBP regeneration

Answer 13

5 G3P molecules rearranges and becomes RuBP

3 ATP → 3 ADP + 3 Pi

Question 14

Light-independent reactions PURPOSE

Answer 14

the reactions that convert CO2 into carbs molecules

Question 15

Light-independent reactions Location

Answer 15

stroma of chloroplast

Question 16

Light-independent reactions reactants

Answer 16

3 CO2, 3 RuBP, 9 ATP, 6 NADPH

Question 17

Light-independent reactions products

Answer 17

9 ADP + 8 P, 6 NADP+, 6 H+, 1 G3P, 3 RuBP

Question 18

Why is RUBISCO so inefficient?

Answer 18

It is a large enzyme and works VERY slowly
It processes 3 substances/sec
Lacks specificity
Binds to CO2 as easily as it binds to O2
O2 is an inhibitor; it takes CO2 into another pathway that does not produce ATP or sugar
Plants need to use energy to reverse this

Question 19

ENGELMANN’S EXPERIMENT

PURPOSE:

Answer 19

to determine which wavelengths of light optimize photosynthesis
To determine whether all colours of the visible spectrum carried out photosynthesis equally well

Question 20

ENGELMANN’S EXPERIMENT RESULTS

Answer 20

Bacteria accumulated in areas where the filament was exposed to red and blue-violet light, with very few bacteria gathering in green light

Question 21

Absorption spectrum

Answer 21

How much wavelength of light is being absorbed by a specific pigment
A graph illustrating the wavelength of light absorbed by a pigment

Chlorophyll a 
Reflects blue-green 
Absorbs more red than chlorophyll b 
Chlorophyll b  
reflects yellow-green
Absorbs more blue than chlorophyll a

Question 22

Action spectrum

Answer 22

The amount of photosynthesis that occurs by a specific wavelength
A graph of the rate of a physiological activity (such as photosynthesis) plotted against wavelength of light.

Question 23

Green light

Answer 23

Chlorophyll a and b absorbs almost no green light however looking at the action spectrum, green light does contribute to photosynthesis
Therefore, since chlorophyll a and b does not meet the requirements of absorbing green, there are different pigments that contribute to absorption of green light and so green light is still able to be utilized by plants to create food via

Question 24

WHY ARE THE LEAVES OF PLANTS NOT GREEN IN THE FALL

Answer 24

Cold temp. result in the plants stopping production of chlorophyll molecules and disassembling the existing chlorophyll a and b pigments
The only pigments the human eye can see is the accessory pigments
Yellow and yellow-orange are located in the thylakoid membrane
Red, violet and blue are located in the vacuoles (not chloroplast) of the cell
The accessory pigment that reflect violet is less abundant

Question 25

Accessory Pigment

Answer 25

Accessory pigments bounce/transferring energy until it reaches chlorophyll
Chlorophyll are more abundant and more dominant in the case that they can actually being in redox reaction