Photosynthesis - Light Dependent Reaction

Question 1

What are the 2 stages of photosynthesis?

Answer 1

Light dependent reaction
Light independent reaction (Calvin cycle)

Question 2

Where does photosynthesis happen?

Answer 2

In the chloroplasts of plant cells

Question 3

What are chloroplasts?

Answer 3

Small, flattened organelles surrounded by a double membrane

Question 4

What are thylakoids?

Answer 4

Fluid filled sacks stacked up in ten chloroplast into structures called grana

Question 5

How are grana linked together?

Answer 5

By bites of thylakoid membrane called lamellae

Question 6

What are photosynthetic pigments?

Answer 6

Coloured substances that absorb the light energy needed for photosynthesis

Question 7

Where are photosynthetic pigments found?

Answer 7

In the thylakoid membranes of chloroplasts that are attached to proteins called photosysyem

Question 8

How does photosystem 1 absorb light?

Answer 8

Absorbs light best at a wavelength of 700nm

Question 9

How does photosysyem 2 absorb light?

Answer 9

Best at 680nm

Question 10

What are stroma

Answer 10

Gel-like substance in the inner membrane of the chloroplast called stroma

Question 11

What does the stroma contain?

Answer 11

Enzymes, sugars and organic acids

Question 12

Where are carbohydrates made in photosynthesis stored?

Answer 12

As starch grains in the stroma

Question 13

Label the chloroplast

Answer 13

Question 14

What is a coenzyme?

Answer 14

A molecule that aids the function of an enzyme

Question 15

How do coenzymes work?

Answer 15

By transferring a chemical group from one molecule to another

Question 16

What is an example of a co enzyme used in photosynthesis?

Answer 16

NADP

Question 17

What does NADP do?

Answer 17

Transfers hydrogen from 1 molecule to another - so it can reduce or oxidise a molecule

Question 18

Where does the light dependent reaction happen? (LDR)

Answer 18

In the thylakoid membranes of the chloroplasts

Question 19

What happens in the LDR?

Answer 19

-Light energy is absorbed by chlorophyll in the photosystems
-The light energy excites the electrons in the chlorophyll, giving them more energy
-This causes them to eventually be released from chlorophyll
—> called photionisarion
-Chlorophyll is now positively charged ion

Question 20

What is some of the energy from the electrons in the LDR used for?

Answer 20

-Used to add a phosphate group to ADP and Pi to form ATP (phosphorylation)
-Used to reduce NADP to form reduced NADP
-Splitting water into protons, electrons and oxygen (photolysis)

Question 21

What is transferred to the light dependent reaction from where?

Answer 21

-ATP transfers energy and reduced NAPD transfers hydrogen
-So water is oxidised to oxygen

Question 22

Where does the light independent reaction occur?

Answer 22

In the stroma of the chloroplast

Question 23

What happens in light independent reaction?

Answer 23

ATP and reduce NADP from the light dependent reaction supply the energy and hydrogen to make glucose from CO2

Question 24

LDR and LIDR diagram

Answer 24

Question 25

What are the 3 products of LDR?

Answer 25

-ATP -NADPH (reduced NAD) -Oxygen (waste) —> all needed for Calvin cycle

Question 26

Ultrastructure of thylakoid

Answer 26

Question 27

What is photolysis simply and equation

Answer 27

Replenishing electrons

Question 28

Describe LDR exam q

Answer 28

1) Light energy enters the thylakoid 2) and excites electrons in chlorophyll 3) electrons are emitted 4) and the energy is released 5) as they move along the ETC (electron transport chain) 6) via a series of redox reactions 7) An electrochemical gradient of protons is formed 8) Protons diffuse through ATP synthase via chemiosmosis 9) ADP + Pi —> ATP 10) NADP is reduced 11) Photolysis of water replenishes the electron of chlorophyll

Question 29

What are electron carries

Answer 29

Proteins that transfer electrons

Question 30

What is an electron transport chain?

Answer 30

A chain of proteins through which excited electrons flow

Question 31

What does non-cyclic photophosphorylation make?

Answer 31

ATP, reduced NADP and oxygen

Question 32

Explain how non-cyclic photophosphorylation occurs?

Answer 32

1) Light energy absorbed by PSII 2) This excited electrons in chlorophyll 3) Electrons move to a higher energy level 4) These r released from chlorophyll, move down electrons transport chain to PSI 5) these r replaced when light energy splits water into protons, electrons and oxygen (photolysis) 6) The electrons lose energy as they go down the ETC 7) This energy is used to transport protons into the thylakoid so thylakoid has a higher conc of protons in the stroma 8) This forms a proton gradient across the thylakoid membrane 9) Protons then move down their conc grad into the stroma, via ATP synthase 10) energy from this movement forms ATP from ADP and Pi 11) Ligjt energy is absorbed by PSI, exciting electrons to a higher energy level 12) Electrons are transferred to NADP, with a proton from the stroma to form reduced NADP

Question 33

What is the chemiosmotic theory?

Answer 33

The process of electrons flowing down the ETC and creating a proton gradient across the membrane to drive ATP synthesis

Question 34

What does cyclic phosphorylation make and using what?

Answer 34

Only ATP made using PSI