Photosynthesis 5.1

Question 1

What is meant by oxidation?

Answer 1

-loss of electrons or hydrogen

Question 2

What is meant by reduction?

Answer 2

-gain of electrions or hydrogen

Question 3

What is the chemical equation for photosynthesis?

Answer 3

6CO2 + 6H2O —-> C6H1206 + 6O2

Question 4

Names the structure in the chloroplast and describe how they are adapted for photosynthesis: 9 structures

Answer 4

-70s Ribosomes
Synthesise protiens and enzymes for photosynthesis
-Stroma
Contains enzymes for light independent reaction
-Outer membrane
-Inner membrane
-Circular DNA
codes for protiens and enzymes for photosynthesis
-lamellae
-Thylakoid membranes
Contain chlorophyll for absorption of light for light dependent reaction
-Granum/grana
increased surface area for absorption of light

Question 5

What are the 2 stages of photosynthesis?

Answer 5

Light dependent reaction
Light independent reaction

Question 6

Describe the detailed steps in the light dependent reaction? (to make ATP not including water)

Answer 6

-Chlorophyll is found in the thylakoid membrane
-Chlorophyll absorbs light energy which excites electrons in the chlorophyll (PHOTOIONISATION)
-Electrons leave chlorophyll and pass down electron transfer chain (in the thylakoid membrane) in a series of redox reactions
-Electrons loose energy at each level which is used to pump hydrogen ions across the thylakoid membrane
-This increases concentration in the thylakoid membrane
-Hydrogen ions diffuse out the thylakoid membrane through ATP synthase down their electrochemical gradient (chemiosmotic theory)
-This releases energy to synthesis convert ADP+Pi into ATP
-(use of water is on a different flashcard)

Question 7

How is water used in the light dependent reaction?

Answer 7

-Water is split using photolysis-O2 is used in respiration or released
-Electrons released are used to replace electrons in chlorophyll
-protons released are used to combine with electrons at the end of the transfer chain to produce hydrogen
-Hydrogen is used to reduce NADP to NADPH

Question 8

What products from the light dependent reaction are used in the light independent reactions

Answer 8

ATP
NADPH

Question 9

Where does the light independent reaction occur

Answer 9

The stroma

Question 10

What are the detailed steps of the Light independent reaction?

Answer 10

-CO2 reacts with ribulose phosphate RuBP (5C) to form two molecules of GP (2X3C)
-Reaction catalysed by enzyme rubisco
-Energy from hydrolysis of ATP and NADPH from the light dependent reaction are used to reduce the GP to 2 triose phosphate (2x3C)
-(NADP reformed to be used in the light dependent reaction)
-1/6 of triose phosphate is converted into useful organic substances eg glucose
-5/6 is used to regenerate RUBP in the light independent reaction using energy from the hydrolyisis of ATP

Question 11

What is the role of NADP in the light dependent and light independent reaction

Answer 11

In the light dependent reaction
-NADP is reduced to NADPH by hydrogen from the photolysis of water
In the light independent reaction
-NADPH with energy from the hydrolysis of ATP is used in the light dependent reaction to reduce GP to 2 triose phosphate
-NADP is reformed to be reused in the light dependent reaction

Question 12

What reaction of photosynthesis is similar to respiration

Answer 12

Light dependent reaction and oxidative phosphorylation
-energy from electron transfer chain used to pump hydrogen ions across membrane to a high concentraion
-Electrons diffuse back through membrane through ATP Synthase down and electrochemical gradient
-Energy released is used to combine ADP and Pi to form ATP

Question 13

What are the limiting factors of photosynthesis what do they cause less of?

Answer 13

-Carbon dioxide conc-> less GP
-Light intensity less -> excited electrons
-Temperature->less energy for rubisco to form enzyme substrate complexes