Photosynthesis (5.5-5.9)

Question 1

Calvin cycle

Answer 1

The group of light-independent reactions involved in photosynthesis
Produces GALP from CO2 and a 5C molecule

Question 2

Carbon fixation (Calvin cycle)

Answer 2

​The addition of CO2​ ​ to RUBP to form an unstable 6 carbon intermediate in the Calvin cycle catalysed by RuBisCO

Question 3

Chlorophyll

Answer 3

​The main photosynthetic pigment found in chloroplasts which is used to capture energy from light during photosynthesis.

Question 4

Chloroplast

Answer 4

​An organelle found in plants and algae which is the site of photosynthesis.

Question 5

Glyceraldehyde-3-phosphate (GALP)

Answer 5

The 3 carbon molecule produced by the reduction of GP by reduced NADP using the energy provided by the hydrolysis of ATP.

Question 6

G​lycerate ​3​-phosphate ​(GP)

Answer 6

The 3 carbon molecule produced by the spontaneous breakdown of the 6 carbon product of carbon fixation.

Question 7

Granum

Answer 7

A stack of thylakoids.

Question 8

Photolysis of water

Answer 8

Light energy splits water into protons, electrons and oxygen
Helps replace electrons in PS2

Question 9

Photophosphorylation of ATP

Answer 9

A phosphate group is added onto ADP to form ATP using light energy

Question 10

Photosynthesis

Answer 10

The process of using light energy to carry out the photolysis of water and store the hydrogen in organic molecules by combining it with carbon dioxide

Question 11

RuBisCO

Answer 11

The enzyme used to fix carbon dioxide in the Calvin cycle.

Question 12

Stroma

Answer 12

​The liquid portion of the chloroplasts where the light-independent reactions of photosynthesis take place.

Question 13

Thylakoids

Answer 13

​Flattened membrane-bound sacs found inside chloroplasts which are the site of the light-dependent reactions of photosynthesis.

Question 14

ATP synthase

Answer 14

Catalyses the phosphorylation of ADP to ATP by transporting hydrogens back down their concentration gradient

Question 15

Products of light dependent reaction

Answer 15

ATP (made from ADP and Pi in photophosphorylation)
reduced NADP (from NADP)
Protons, hydrogen and oxygen (from photolysis of water)

Question 16

Hydrolysis

Answer 16

The splitting of a molecule using water

Question 17

Photosynthesis equation

Answer 17

6CO2 + 6H2O + energy -> C6H12O6 + 6O2

Question 18

NADP

Answer 18

An enzyme which transfers hydrogen from one molecule to another

Question 19

Light dependent reaction stages

Answer 19

• Light energy causes photolysis of water, forming protons, electrons and oxygen
• Light strikes chlorophyl molecules in PS2, causing electrons to become excited and emitted
• Electrons pass down electron transport chain
• Energy lost at each transfer is used to pump protons from stroma into thylakoid lumen
• The protons then move back down their concentration gradient into the stroma via ATP synthase (chemiosmosis)
• ATP is formed in this process called photophosphorylation
• Light excites PS1 electrons which transfer to NADP to from reduced NADP with the help of a proton

Question 20

Role of photosystem 1

Answer 20

Absorbs light energy to excite electrons which convert NADP to reduced NADP with the help of a proton

Question 21

Role of photosystem 2

Answer 21

Absorbs light energy which excites electrons in the chlorophyl which then pass down an electron transport chain into PS1

Question 22

ATP synthase

Answer 22

An enzyme which allows protons to move down their concentration gradient from the thylakoid lumen to the stroma
Converts ADP and Pi into ATP

Question 23

Non cyclic photophosphorylation

Answer 23

Uses both photosystems to produce ATP, reduced NADP and O2

Question 24

Cyclic photophosphorylation

Answer 24

Only uses PS1 to only produce small amounts of ATP

The electrons are passed back to PS1 instead of onto NADP

Question 25

Light independent reaction stages

Answer 25

• CO2 diffuses into stroma and combines with RuBP (5c) to form 2 molecules of GP (3c) using enzyme RuBiSCo
• Both molecules of GP are phosphorylated by ATP and reduced by reduced NADP to form 2 molecules of GALP (3c)
• ADP + Pi and NADP are products
• Every 1 in 6 GALP molecules is used for products of photosynthesis, and the rest are regenerated into RuBP using energy from the hydrolysis of ATP

Question 26

Fixation of CO2 in Calvin cycle

Answer 26

CO2 diffuses from stroma and combines with RUBP (5C) with it being catalysed by enzyme Rubisco
The product is 2 GP (3C)

Question 27

Reduction of GP in Calvin cycle

Answer 27

Both molecules of GP are phosphorylated using ATP and reduced using reduced NADP
Forms 2 molecules of GALP (3C)

Question 28

Regeneration of RUBP in Calvin cycle

Answer 28

1/6 molecules of GALP are used to make products of photosynthesis
The rest are used to regenerate RUBP

Question 29

How many turns of the carbon cycle to produce a glucose

Answer 29

6

Question 30

Rubisco

Answer 30

Enzyme used to catalyse CO2 combining with RUBP (5C)

Question 31

GP

Answer 31

A 3 carbon molecule produced in the fixation of CO2

2 lots are produced each time

Question 32

Hydrolysis of ATP

Answer 32

Breaking down of ATP into ADP and Pi which provides an immediate supply of energy for biological processes

Question 33

How does Calvin cycle make carbohydrates

Answer 33

Joining of hexose sugars

Question 34

Adaptations of thylakoids for photosynthesis

Answer 34

Stacked into grana to increase surface area and maximise absorbance of light and contain lots of ATP synthase

Question 35

Adaptation of the membrane of the chloroplast

Answer 35

Double membrane to keep reactants close to the reaction sites

Question 36

PS1 wave absorption of light

Answer 36

700nm

Question 37

PS2 wave absorption of light

Answer 37

680nm