Photosynthesis

Question 1

What is the equation for photosynthesis?

Answer 1

6CO₂ + 6H₂O + light energy —> C₆H₁₂O₆ + 6O₂

Question 2

What is photosynthesis an example of?

Answer 2

A metabolic pathway

Question 3

What is a metabolic pathway?

Answer 3

The process occurs in a series of small reactions controlled by enzymes

Question 4

Where does photosynthesis take place?

Answer 4

In the chloroplasts of plant cells

Question 5

What is the structure of a chloroplast?

Answer 5

They are small, flat organelles surrounded by a double membrane.
Thylakoids are stacked up into structures called grana
Grana are linked together by bits of thylakoid membrane called lamellae

Question 6

What do chloroplasts contain?

Answer 6

Photosynthetic pigments

Question 7

What are some examples of photosynthetic pigments?

Answer 7

Chlorophyll a
Chlorophyll b
Carotene

Question 8

Where are photosynthetic pigments found in the chloroplast?

Answer 8

Thylakoid membranes

Question 9

What is the purpose of photosynthetic pigments?

Answer 9

To absorb the light energy needed for photosynthesis

Question 10

What are photosynthetic pigments attached to? What is this combination called?

Answer 10

A protein

A photosystem

Question 11

What are the two photosystems called and what wavelengths of light do they each absorb?

Answer 11

Photosystem ll comes first and absorbs light best at a wavelength of 680 nm
Photosystem l comes second and absorbs light best at a wavelength of 700nm

Question 12

What is the stroma?

Answer 12

Gel-like substance which contains enzymes, sugars and organic acids

Question 13

How are the carbohydrates produced by photosynthesis used?

Answer 13

They are stored as starch grains in the stroma

Question 14

What is a redox reaction?

Answer 14

A reaction which involves both reduction and oxidation

Question 15

What is OILRIG?

Answer 15

Oxidation is loss of electrons

Reduction is gain of electrons

Question 16

What is a coenzyme and how do they work?

Answer 16

A co-enzyme is a molecule that aids the function of an enzyme as they work by transferring a chemical group from one molecule to another

Question 17

Which co-enzyme is used in photosynthesis?

Answer 17

NADP

Question 18

What are the two stages of photosynthesis?

Answer 18

Light dependent

Light independent

Question 19

Where does the light-dependent reaction take place? Why?

Answer 19

The thylakoid membranes

This is where the photosynthetic pigments are

Question 20

What is the first stage of non-cyclic photophosphorylation?

Answer 20

Photoionisation

Question 21

Describe what happens during photoionisation.

Answer 21

The light energy is absorbed by the chlorophyll in the photosystems, causing an electron to become excited and be released from the chlorophyll molecule and the high energy electrons move down the electron transport chain to PSl

Question 22

What is the second stage during non-cyclic photophosphorylation?

Answer 22

Photolysis

Question 23

Describe what happens during photolysis.

Answer 23

The light energy splits up a water molecule at PSll into protons (H+ ions), electrons and oxygen

Question 24

What is the purpose of photolysis?

Answer 24

To replenish the lost electrons at PSll

Question 25

What is the equation for photolysis?

Answer 25

H₂O ---> 2H⁺ + 2e⁻ + 1/2O₂

Question 26

What is the third stage of non-cyclic photophosphorylation?

Answer 26

The excited electrons lose energy as they move along the electron transport chain. This energy is used to actively transport H+ ions across into the thylakoid. This creates a proton gradient across the thylakoid membrane.

Question 27

What role does ATP synthase play in non-cyclic photophosphorylation?

Answer 27

Protons move down their concentration gradient into the stroma through ATP synthase. This energy from the movement drives the synthesis of ATP from ADP and an inorganic phosphate

Question 28

What is the final stage in non-cyclic phosphorylation?

Answer 28

The electrons are transferred to NADP with an H+ ion to form reduced NADP

Question 29

What is the chemiosmotic theory?

Answer 29

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

Question 30

What is cyclic photophosphorylation?

Answer 30

It only uses PSl | The electrons aren't transferred to NADP but instead passed back to PSl via electron carriers

Question 31

What does cyclic photophosphorylation produce?

Answer 31

Doesn't produce reduced NADP or oxygen | Small amounts of ATP

Question 32

Where does the Calvin cycle take place?

Answer 32

In the stroma of the chloroplast

Question 33

What enzyme is involved in the Calvin cycle?

Answer 33

Rubisco

Question 34

What is the first stage of the Calvin cycle?

Answer 34

CO2 enters the leaf through the stomata Combines with 5 carbon ribulose biphosphate (RuBP) Catalysed by rubisco

Question 35

What is the second stage of the Calvin cycle?

Answer 35

Forms an unstable 6 carbon compound which quickly breaks down into 2 glycerate-3-phosphate molecules, a 3 carbon compound

Question 36

What is the third stage of the Calvin cycle?

Answer 36

The hydrolysis of 2 ATP molecules provides energy to reduce the 3-carbon compound. It is reduced again when 2 molecules of reduced NADP are oxidised. This forms 2 molecules of triose phosphate, a 3 carbon molecule

Question 37

How are useful substances formed from the Calvin cycle?

Answer 37

One carbon atom is from TP for every cycle of the Calvin cycle

Question 38

What is the fourth stage of the Calvin cycle?

Answer 38

5 out of every 6 molecules of TP produced go on to regenerate 5 carbon molecule RuBP. This also uses ATP, breaking it down to ADP and an inorganic phosphate

Question 39

How many times does the Calvin cycle have to repeat in order to formulate a glucose molecule?

Answer 39

6 times

Question 40

What useful substances are formed from the Calvin cycle?

Answer 40

Carbohydrates Lipids Amino acids

Question 41

What is the purpose of ATP in the light-independent reaction?

Answer 41

To provide energy for the conversion of glycerate-3-phosphate into triose phopshate

Question 42

What is the purpose of NADPH in the light-independent reaction?

Answer 42

To reduce glycerate-3-phosphate to triose phosphate