Unit 3.4.3 - Photosynthesis

Question 1

Where does photosynthesis take place?

Answer 1

In the chloroplast of plant cells.

Question 2

What is a redox reaction?

Answer 2

Reaction that involve simultaneous oxidation and reduction.

Question 3

Give two examples of redox reactions.

Answer 3

Photosynthesis and Respiration.

Question 4

What is reduction?

Answer 4

Gain of electrons/gaining a hydrogen.

Question 5

What is oxidation?

Answer 5

Loss of electrons - losing a hydrogen.

Question 6

What is a coenzyme?

Answer 6

A molecule that aids the function of an enzyme.

Question 7

How does a coenzyme work?

Answer 7

By transferring a chemical group from one molecule to another.

Question 8

Where does the light dependent reaction happen?

Answer 8

On the thylakoid membranes.

Question 9

In 5 steps describe what happens in the light dependent reaction?

Answer 9

1. Chlorophyll absorbs light energy, becomes excited and loses 2 electrons. 2. The excited electrons pass down an electron transport chain, energy is lost as they do this and it used to turn ADP into ATP. 3. Photolysis of water produces half an oxygen molecule, 2 electrons and 2 hydrogen ions. 4. The 2 hydrogen ions from the electron transport chain combine with the electrons and are attached to the NADP to form NADPH. 5. The 2 electrons formed from the water molecules splitting pass to the chlorophyll to replace the ones lost.

Question 10

What is photolysis?

Answer 10

Splitting of something using light energy.

Question 11

What is another name for the light independent reaction?

Answer 11

The Calvin cycle.

Question 12

Where does the light independent reaction take place?

Answer 12

The stroma of the chloroplast.

Question 13

Describe in 3 steps what happens during the light independent reaction.

Answer 13

1. A carbon dioxide fixes onto Ru Bp and forms 2 molecules of GP. 2. GP is reduced by the 2 NADPH to produce 2 TP, this reaction requires energy, also during this the NADPH is oxidised to form NADP. 3. The 2 TP is broken down and 5 of the carbon atoms go back to make RuBp and 1 goes to make a glucose molecule.

Question 14

What does Ru Bp stand for?

Answer 14

Ribulose Bisphospate.

Question 15

What does GP stand for?

Answer 15

Glycerate 3 - phosphate

Question 16

What does TP stand for?

Answer 16

Triose Phosphate

Question 17

How many carbons are in Ru Bp?

Answer 17

5

Question 18

How many carbons are in GP?

Answer 18

3

Question 19

How many carbons are in TP?

Answer 19

3

Question 20

How many does the light independent reaction have to happen to produce 1 glucose molecule?

Answer 20

6

Question 21

What is used and made at the start and end of the light independent reaction?

Answer 21

Ru Bp

Question 22

What provides energy for the light dependent reaction?

Answer 22

Light

Question 23

Does chlorophyll absorb all wave lengths of light?

Answer 23

No it only absorbs certain ones.

Question 24

How does absorption of light by chlorophyll change as wave length/colour changes?

Answer 24

They absorb it bet in violet/blue light in shorter wave lengths and in red light at longest wave lengths. Wave lengths in the middle of those two produce green light which is reflected by plants so absorption is low.

Question 25

What makes a plant look green?

Answer 25

It reflects green light.

Question 26

What 4 factors limit photosynthesis?

Answer 26

1. Light intensity 2. Wave length of light 3. Temperature 4. Carbon Dioxide

Question 27

How does light intensity affect the rate of photosynthesis and why?

Answer 27

As light intensity increases so does the rate of photosynthesis because it is needed to start the light dependent reaction.

Question 28

What is the point called on the graph against light intensity and rate of photosynthesis when it levels off and why does it do so?

Answer 28

Saturation point, light intensity is no longer a limiting factor.

Question 29

How does carbon dioxide concentration affect the rate of photosynthesis and why?

Answer 29

As concentration of carbon dioxide increases so does photosynthesis because it is a raw material needed for the process.

Question 30

How does temperature affect the rate of photosynthesis?

Answer 30

As temperature increases so does the rate of photosynthesis up to the optimum temperature after this point the rate of photosynthesis starts to decrease.

Question 31

Why does increase in temperature increase the rate of photosynthesis but only up to a point?

Answer 31

Photosynthesis has reactions that involve enzymes, higher temperatures mean the particles have more energy so are more likely to collide with the active sites with enough energy to react. However after the optimum temperature the temperature begins to interfere with the hydrogen bonds holding the enzymes together and so it active site changes shape. It can no longer form ES complexes and so is denatured meaning the rate of photosynthesis will decrease.

Question 32

Why do commercial growers of plants grow the plants in optimal conditions?

Answer 32

There are no limiting factors, this increases the growth which increases the yield.

Question 33

How do farmers stop carbon dioxide being a limiting factor?

Answer 33

They add carbon dioxide to the air by burning a small amount of propane in a carbon dioxide generator.

Question 34

How do farmers stop light intensity being a limiting factor?

Answer 34

The walls are glass in a green house so the light can get through during the day. Lamps provide light at night.

Question 35

Why do lights in green houses often use red or blue lights?

Answer 35

These colours produce the wave lengths that are best absorbed into the chlorophyll.

Question 36

How do famers stop temperature being a limiting factor?

Answer 36

Greenhouses trap heat energy from the sunlight to warm the air. Heating and cooling systems can be used to keep a constant optimum temperature.

Question 37

Why does increasing the rate of photosynthesis increase the yield in plants?

Answer 37

More photosynthesis means more glucose will be formed so they can produce ATP through respiration. Which can be used for DNA replication, cell division and protein synthesis allowing the plant to grow more increasing yield.

Question 38

Label this diagram.

Answer 38

Question 39

Draw a graph for wavelength against absorption.

Answer 39