Photosynthesis- Topic 5

Question 1

What is the word equation for photosynthesis?

Answer 1

Carbon dioxide + water (light energy) —> oxygen + glucose

Question 2

What is the symbol equation for photosynthesis?

Answer 2

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

Question 3

Why do plants photosynthesise?

Answer 3

1. Energy for biological processes
2. Organic molecules needed for growth
3. Respiration (O2 is a product)

Question 4

What else does photosynthesis benefit?

Answer 4

1. If the plant is consumed organic molecules provide energy

2. Oxygen produced is released into the atmosphere and is available for other organisms

Question 5

The structure of a leaf: waxy cuticle

Answer 5

Prevents water loss and allows the light needed for photosynthesis through

Question 6

The structure of a leaf: upper epidermis

Answer 6

Protective layer that reduces water loss

Question 7

The structure of a leaf: palisade cells

Answer 7

Packed with chloroplasts containing chlorophyll that trap light

Question 8

The structure of a leaf: spongy mesophyll

Answer 8

Gas exchange

Question 9

The structure of a leaf: lower epidermis

Answer 9

Guard cells that allow water and gases in and out

Question 10

What is a photosynthetic pigment?

Answer 10

A coloured biological compound that is present in chloroplasts and photosynthetic bacteria which captures light energy for photosynthesis

Question 11

What are the two types of photosynthetic pigments?

Answer 11

Chlorophyll and carotenoid

Question 12

What is the absorption spectrum?

Answer 12

The range of amount of light of different wavelengths absorbed(Rate of absorption against wavelength)

Question 13

What is the action spectrum?

Answer 13

The rate of photosynthesis against the wavelength of light

Question 14

The structure of a chloroplast: double membrane

Answer 14

Controls what gets in and out of the cell

Question 15

Structure of a chloroplast: inner membrane

Answer 15

Folded to form thylakoids

Question 16

The structure of a chloroplast: thylakoids

Answer 16

Contains pigment. The first part of photosynthesis the light dependent reaction takes place here

Question 17

The structure of a chloroplast: inter-granal thylakoid

Answer 17

Extensions of the membrane. Also used for light dependent reaction

Question 18

The structure of a chloroplast: Granum

Answer 18

Stacks of thylakoids which increase surface area

Question 19

Structure of a chloroplast: stroma

Answer 19

Jelly like material that contains enzymes the second part of photosynthesis the light independent reaction takes place here

Question 20

Name 3 molecules involved in photosynthesis

Answer 20

Adenosine triphosphate (ATP) 
Adenosine diphosphate (ADP)
Nicotinamide adenine dinucleotide phosphate (NADP)

Question 21

What happens with ATP in the light dependent reaction?

Answer 21

ATP is synthesised from ADP + P- this is called phosphorylation. Since light energy is used here it is called photophosphorylation.

Question 22

What happens to ATP in the light independent reaction?

Answer 22

ATP is hydrolysed into ADP + P- when this bond is broken energy is released

Question 23

What are the nucleotides joined by in NADP?

Answer 23

Phosphate groups

Question 24

What can NADP accept? What does this cause?

Answer 24

NADP can accept electrons to be reduced NADP. (NADPH) this reduced NADP can be oxidised back to NADP releasing electrons.

Question 25

What is OILRIG?

Answer 25

``` Oxidation Is Loss of electrons Reduction Is Gaining electrons ```

Question 26

What is the location of the light dependent stage of photosynthesis?

Answer 26

Thylakoids membrane

Question 27

What is situated in the thylakoids membrane?

Answer 27

Light harvesting Photosystems (I) (II) that have chlorophyll at their centres

Question 28

What are the products of the light dependent reaction that pass on to the light independent reaction?

Answer 28

1. Reduced NADP | 2. ATP

Question 29

What are the products of the light dependent reaction that leave the plant?

Answer 29

Oxygen molecule

Question 30

What are the products of the light dependent reaction that are reused in another part of the light dependent reaction?

Answer 30

1. H+ ions | 2. Electrons

Question 31

What is the location of the light independent stage of photosynthesis?

Answer 31

Stroma

Question 32

What are the products of the light independent reaction the pass back into the light dependent reaction?

Answer 32

1. NADP 2. ADP 3. Inorganic phosphate

Question 33

What are the products of the light independent reaction that are used in other processes?

Answer 33

GALP is used to build carbohydrates, amino acids and lipids

Question 34

Using the products-GALP

Answer 34

1. Used directly in glycolysis 2. Some is converted to acetyl coenzyme A and used to synthesise lipids 3. Gluconeogenesis- converted to glucose which can be further used to build up more complex carbohydrates.

Question 35

Alternative routes- what happens to plants in hot weather?

Answer 35

- in hot conditions plants will close the stomata so less water is lost - this means less CO2 can get in and more O2 is trapped - O2 inhibits Rubisco

Question 36

Alternative routes- C4 pathway

Answer 36

An extra stage before photosynthesis which synthesises more carbon dioxide. It takes place in specialised cells near the surface.

Question 37

Alternative routes- CAM plants

Answer 37

Open stomata at night to allow CO2 through then uses a CO2 producing mechanism.

Question 38

Factors affecting the rate of photosynthesis- light intensity

Answer 38

- as light intensity increases the rate of photosynthesis increases. - until a plateau where a further increase in light intensity will not increase the rate of photosynthesis - this means something else is limiting it (probably CO2 concentration)

Question 39

What does light intensity affect?

Answer 39

-light intensity affects GALP- less reduced NADP and ATP from LD reaction= less GALP and more GP.

Question 40

Factors affecting the rate of photosynthesis- temperature

Answer 40

- increasing the temperature increases the kinetic energy - this increases the successful collisions of enzyme and substrate - which increases the rate of photosynthesis - until the enzyme denatures with further temperature increase

Question 41

What does temperature effect?

Answer 41

Rubisco- no CO2 fixing= build up of RuBp

Question 42

Factors affecting the rate of photosynthesis- CO2 concentration

Answer 42

- as CO2 concentration increases so does the rate of photosynthesis - until plateau - something else is limiting it (probably light intensity)

Question 43

What does CO2 concentration affect?

Answer 43

RuBp- less carbon fixing= more RuBp

Question 44

What is the compensation point?

Answer 44

When a plants photosynthesis rate= respiration rate (no oxygen will be released into the atmosphere)