Photosynthesis and Respiration- Photosynthesis

Question 1

What are chloroplasts?

Answer 1

Flattened organelles surrounded by a double membrane that are found in plant cells

Question 2

What are thylakoids?

Answer 2

Fluid-filled sacs

Question 3

What are grana?

Answer 3

Structures in the chloroplast that are made from stacked up thylakoids

Question 4

How are the grana linked together?

Answer 4

By bits of the thylakoid membrane called lamellae

Question 5

What are photosynthetic pigments?

Answer 5

Coloured substances that absorb the light energy needed for photosynthesis

Question 6

Where are photosynthetic pigments found?

Answer 6

In the thylakoid membrane attached to proteins

Question 7

What is a photosystem?

Answer 7

The protein and pigment

Question 8

Which photosystem absorbs light best at 700nm?

Answer 8

Photosystem I

Question 9

Which photosystem absorbs light best at 680nm?

Answer 9

Photosystem II

Question 10

What is the stroma?

Answer 10

A gel-like substance contained within the inner membrane of the chloroplasts and surrounding the thylakoids

Question 11

What does the stroma contain?

Answer 11

Enzymes, sugars and organic acids

Question 12

What happens to carbohydrates that are produced by photosynthesis and not used straight away?

Answer 12

They are stored as starch grains in the stroma

Question 13

What are the two stages that make up photosynthesis?

Answer 13

The light-dependent reaction and the light-independent reaction

Question 14

Where does the light-dependent reaction take place?

Answer 14

In the thylakoid membranes of the chloroplast

Question 15

What is the process of the light-dependent reaction?

Answer 15

1. Light energy is absorbed by chlorophyll in the photosystems
2. The light energy excites the electrons in the chlorophyll, leading the their eventual release from the molecule
3. The chlorophyll has been photoionised
4. Some of the energy from the released electrons is used to add a phosphate group to ADP to form ATP, and some is used to reduce NADP to form reduced NADP
5. ATP transfers energy and reduced NADP transfers hydrogen to the light-independent reaction
6. During the process H2O is oxidised to O2

Question 16

What is the light-independent reaction also called?

Answer 16

The Calvin cycle

Question 17

Where does the light-independent reaction take place?

Answer 17

In the stroma of the chloroplast

Question 18

What happens in the light-independent reaction?

Answer 18

The ATP and reduced NADP from the light-dependent reaction supply the energy and hydrogen to make simple sugars from CO2

Question 19

What are electron carriers?

Answer 19

Proteins that transfer electrons

Question 20

What is an electron transport chain?

Answer 20

A chain of proteins through which excited electrons flow

Question 21

What happens when light energy excites electrons in chlorophyll?

Answer 21

The electrons move to a higher energy level

Question 22

What happens to the high-energy electrons?

Answer 22

They are released from the chlorophyll and move down the electron transport chain

Question 23

What happens after the excited electrons move down the electron transport chain?

Answer 23

Light energy splits water into protons (H+ ions), electrons and oxygen- photolysis

Question 24

What is the reaction for photolysis?

Answer 24

H2O —> 2H+ + 1/2O2

Question 25

What happens to the excited electrons as they move down the electron transport chain?

Answer 25

They lose energy

Question 26

How is the energy from the excited electrons used?

Answer 26

To transport proteins into the thylakoid so that the thylakoid has a higher concentration of protons than the stroma which forms a proton gradient across the thylakoid membrane

Question 27

How do protons move down their concentration gradient?

Answer 27

Into the stroma via ATP synthase, which is embedded into the thylakoid membrane

Question 28

How is the energy from the protons moving down their concentration gradient used?

Answer 28

To combine ADP and inorganic phosphate to form ATP

Question 29

How is reduced NADP formed?

Answer 29

Electrons are transferred to NADP along with a proton from the stroma

Question 30

What molecule does the light-independent reaction make?

Answer 30

Triose phosphate from CO2, and ribulose biphosphate

Question 31

How can triose phosphate be used?

Answer 31

To make glucose and other useful organic substances

Question 32

How does the light-independent reaction start?

Answer 32

CO2 enters the leaf through the stomata and diffuses into the stroma of the chloroplast

Question 33

What happens once CO2 has entered the leaf?

Answer 33

It is combined with ribulose biphosphate (RuBP), a 5-carbon compound, and the reaction is catalysed by the enzyme rubisco

Question 34

After RuBP has combined with CO2, what is produced?

Answer 34

A 6-carbon compound, which is unstable, so is quickly broken down into two molecules of a 3-carbon compound called glycerate 3-phosphate (GP)

Question 35

What does the hydrolysis of ATP do?

Answer 35

Provides energy to turn GP into a different 3-carbon compound called triose phosphate (TP)

Question 36

What does the reaction that turns GP to TP require?

Answer 36

H+ ions which come from reduced NADP which is recycled to NADP

Question 37

What is some TP then converted into?

Answer 37

Useful organic compounds and some continues to regenerate RuBP

Question 38

How many times does the Calvin cycle need to turn to make one hexose sugar?

Answer 38

Six