Section 5: Chapter 11: Photosynthesis

Question 1

Where does photosynthesis take place (it’s site)?

Answer 1

Leaf - chloroplasts.

Question 2

How are leaves adapted to bring together the 3 materials used in photosynthesis? (9 points)

Answer 2

• Large SA for more sunlight.
• Leaves arranged to not overlap each other.
• Thin - short diffusion distance.
• Transparent cuticle and epidermis.
• Long mesophyll cells w/ chloroplasts to collect sunlight.
• Lots of stomata - only a short distance from mesophyll cells.
• Stomata open and close depending on light intensity.
• Air spaces - quick diffusion.
• xylem carries water, phloem carries sugars (produced in photosynthesis).

Question 3

What is the equation for photosynthesis?

Answer 3

6CO2 + 6H2O → C6H12O6 + 6O2

Question 4

What are the 3 main parts of a chloroplast?

Answer 4

• Thylakoids (LDR)
• Grana (stacks of thylakoids).
• Stroma (fluid matrix - LIR)

Question 5

What is oxidation?

Answer 5

Gaining oxygen or losing hydrogen.

Question 6

What is reduction?

Answer 6

Losing oxygen or gaining hydrogen.

Question 7

What is photolysis? (LDR)

Answer 7

• Light absorbed in photosystem II and splits water into 1/2 oxygen, 2 protons (H+) and 2 e-.
• Protons (H+) used by NADP to form NADPH (for LIR) or passed through ATP synthase.
• e- passed along chain of electron carrier proteins.

Question 8

What is photoionisation? (LDR)

Answer 8

Light ionised chlorophyll.

• Light energy absorbed.
• Energy → exciting electrons so they can leave chlorophyll.

Question 9

What is chemiosmosis? (LDR)

Answer 9

• excited electrons leave chlorophyll and move along proteins in thylakoid membrane.
• Release energy as they move - used to pump protons from photolysis across chloroplast membrane.
• Protons (H+) pass through ATP synthase → ATP produced.
• Protons (H+) combine with NADP to become NADPH.
• Protons (H+) move from high → low conc.

Question 10

What are the 3 stages of the light dependent reaction?

Answer 10

1) Photolysis.
2) Photoionisation.
3) Chemiosmosis.

Question 11

Where does the light dependent reaction take place?

Answer 11

Thylakoid membranes in the grana.

Question 12

What is the purpose of the light dependent reaction?

Answer 12

To create ATP and NADPH for the LIDR.

Question 13

What is the light-Independent reaction also known as?

Answer 13

The Calvin cycle.

Question 14

Describe the Light-Independent reaction. (5 steps)

Answer 14

1) CO2 and RuBP combine to make a 6C using enzyme rubisco.
2) 6C split into 2 GP mols.
3) GP reduced into TP. Uses ATP and NADPH.
4) Some TP used to make glucose.
5) Some TP used to regenerate RuBP using ATP.

Question 15

What is the Calvin Cycle also known as?

Answer 15

The light-independent reaction.

Question 16

What enzyme catalyses CO2 and RuBP bonding together?

Answer 16

Rubisco.

Question 17

How many carbons does RuBP contain?

Answer 17

5.

Question 18

How many carbons do GP and TP contain?

Answer 18

3.

Question 19

What 2 things is TP used for? (LIR)

Answer 19

• To make sugars eg/ glucose.

- TO regenerated RuBP, using ATP.

Question 20

Where does the light-independent reaction take place?

Answer 20

Chloroplast - stroma.

Question 21

How is the chloroplast adapted to carry out the light-independent reaction? (3 points)

Answer 21

• Fluid of storm contains all the needed enzymes.
• Stroma surrounds grana - produce of LDR can quickly diffuse into stroma.
• Contains DNA and ribosomes to manufacture proteins needed.

Question 22

What are the 3 limiting factors of photosynthesis?

Answer 22

• Temperature.
• Carbon dioxide conc.
• Light intensity.

Question 23

What apparatus is needed to measure photosynthesis?

Answer 23

Photosynthometer.

http://botanystudies.com/how-to-measure-photosynthesis/photosynthometer/

Question 24

Explain how a photosynthometer is used to measure photosynthesis at different light intensities.

Answer 24

• Water bath needed to keep temp constant.
• Source of CO2 needed.
• Source of light that can be moved to different distances.
• Kept in dark for 2hrs.
• Light switched on and plant left for 30mins.
• Oxygen released collected at end of capillary tube - amount measured with mm³ scale.
• Repeat at different light intensity and record vol of oxygen.

Question 25

How did Melvin Calvin discover the light-independent reaction?

Answer 25

Lollipop experiment.

• Radioactive hydrocarbonate supplied to algae.
• Algae put in methanol to stop reactions.
• Compounds of algae separated out.
• GP, TP and RuBP found.