16) Photosynthesis

Question 1

Why do plants need energy for biological processes

Answer 1

Photosynthesis , active transport , DNA Replication , cell dicision and protein synthesis

Question 2

Why do animals need energy for biological processes

Answer 2

Muscle contraction , body temperature ,active transport , DNA Replication , cell division , protein synthesis

Question 3

What is phosphorylation , Photophosphorylation , Photolysis

Answer 3

Adding phosphate to a molecule

Adding phosphate to a molecule using light

Splitting a molecule using light energy

Question 4

Explain a coenzyme involved in photosynthesis

Answer 4

NADP - transfer hydrogenfrom one to another , mean it can readuce or axidise a molecule

Question 5

Describe the structure of the chlorplast

Answer 5

Thylakoids Fluid filled stacks
Grana Stacked up thylakoids
Lamellae bits of thylakoid membrane that links grana

Question 6

Summarise Photosystem 1

Answer 6

Absorb light at 700nm wavelengths

Question 7

Summarise Photosystem 2

Answer 7

Absorb light at 680 nm

Question 8

What happens in the Light-dependent reaction

Answer 8

Light energy is absorbed by photosynthetic pigments ( eg , chlorophyll a / b ) in photosystems are converted to chemical energy

Light used to add phosphate group to ADP to form ATP and to reduce NADP to form reduced NADP

NADP transfer hydrogen to light-indepenent reaction .

Question 9

What happens in the light-independent reaction

Answer 9

Called the calvin cycle
Rely on products from light-dependent reaction
Takes place in stroma
Atp + reduced NADP supply energy and hydrogen to make glucose from cO2

Question 10

How are photo systems linked

Answer 10

Photosystems linked by electron carriers

Question 11

WHat are electron carriers

Answer 11

Proteins (H+) that transfer electrons

Question 12

What do photosystems and electron carriers form?
What is this?

Answer 12

Electron transport chain
-Chain of proteins through which excited electrons flow

Question 13

What happens in the First stage of Non-cyclic Photophosphorylation

Answer 13

1) Light energy excites electrons in chlorophyll

Light is absorbed by PS2
Electron excite and move to a higher energy level
These high-energy electrons move along the electron transport chain to PS1

Question 14

What happens in the 2nd stage of Non-cyclic photoposhporylation

Answer 14

2) Photolysis of water produces proton ( H+ ions ) , electrons and O2

Electrons move from chloryphyll leave PS2 and move along electron transport chain , these are replaced
Light energy splits water into Hydrogen ions and electrons and oxygen

Question 15

What is the 3rd stage of Non-Cyclic Photophosphorylation

Answer 15

3) Energy from the excited electrons make ATP

Excited electrons lose energy and move along Electron transporter chain

ENergy used to transport protons into thylakoid by proton pumos
High conc of proton cause *Proton gradient *

Protons movw down gradient into stroma by ATP Synthase energy from this combines ADP and phosphate into ATP

Question 16

What happens in the 4th datge of Non-cyclic Photophosphorylation

Answer 16

4) Generates reduced NADP

Light is absorbed by PS1 which excites electrons again to an even higher energy level
Electrons transfered to NADP along with reduced NADP

Question 17

What is produced in cyclic photophosphorylation

Answer 17

Only produces ATP
Uses Ps1 , electrons are recycled and aren’t passed onto NADP so NADP or O2 is not made only ATP

Question 18

What products are made / done in the light-dependent reaction

Answer 18

Atp from photophosphorylation
Reduced NADP from NADP + H ions
Splitting of water = > protons , electrons , oxygen by photolysis

Question 19

What is the light independent reaction

Answer 19

Calcin cycle
Takes place in the stroma of the chloropasts
Camke triose phosphate from co2 , ribulose biphosphate.
Needs ATP an H+ ions

Question 20

WHat is the first stage of the Calvin Cycle

Answer 20

1) Carbon dioxide is combined with ribulose biphosphate to form 2 molecules of glycerate 3-phosphate

CO2 enters leaf and diffuse into stroma
COmbines with Ribulose bisphosphate ** which breakks down by enzyme *rubisco into *Glycerate 3-phosphate

Question 21

What happens in the 2nd stage of the Calvin Cycle

Answer 21

2) ATP and reduced NADP are required for the reduction of GP to triose phosphate

ATP from lDR provide energy to turn 2 Glycerate into 2 triose phosphate

Requite H+ ions and come from reduced NAFP .
NADP recycled to NADP

Triose phosphate converted into many useful organic compounds

Question 22

What happens in the 3rd stage of the Calvin Cycle

Answer 22

3) Ribulose biphosphate is regenerated
Five out of 6 TP molecules arent made to make sugar but regenerate RuBP

Uses the rest of ATP by the light-depenedent reaction

Question 23

What useful organic substances are produced by converting TP and GP

Answer 23

Carbohydrates
Lipids
AMino acids

Question 24

How much of each product is made t make 1 hexose sugar

Answer 24

6 cycles
to make 2 molecules of TP
18 ATP
12 Reduced NADP

Question 25

Describe the optimum conditions needed for photosynthesis

Answer 25

1) High light intensity of a certain wavelength
Light provide energy for LDR.
Higher intensity - more enrgy provided
Certain wavelength used , absorb red and blue , reflect green hence look green

**2) Temp around 25 **
Invlve enxymes , inactive when too low , denature when too high
Stomata closes at high
Thylakoid membranes may be damaged
Membrane around chloroplast damage - enzymes to be released into cell , reduce ror
Chlorophyll affected - red amount of light energy absorbed

3) Carbon dioxide at 0.4%

CO2 make up 0.04% of gas
Increases up to 0.4% give high rate of photosyntheses

Question 26

How does light intensity affect levels of GP , RuBP and TP

Answer 26

reduced NADP , ATP will be in short supply

Conversion of GP to TP amd RuBP is slow
GP level will rise , levels of TP and RuBP will fall

Question 27

How does temperature affect the levels of GP , RuBP and TP

Answer 27

Low temp , enzymes work slow
Levels of RuBP , GP , TP will fall
AFfect same way at high temp - denature

Question 28

How does Carbon Dioxide affect the levels of GP , RuBP and TP

Answer 28

Low CO2 , Coversion of RuBP to GP is slow
Level of RuBP will rise and level of GP and TP will fall.

Question 29

what are autotrophs

Answer 29

can make organic molecules from inorganic molecules

Question 30

what are heterotrophs

Answer 30

relies on organic molecules made from another organism

Question 31

Describe how light is absorbed in the chloroplast

Answer 31

There are different primary and accessory pigments in a photosystem.
For eg. Chlorophyll A and Chlorophyll B
Photon energy is absorbed by the pigments.
Cause an electron to be excited.
Electron is passed to different pigments
Accessory pigments can absorb a range of wavelengths.

Question 32

where are photosynthetic pgiments found

Answer 32

photosystems in the thylakoid