Topic 5.2 Photosynthesis

Question 1

Where does the light dependent stage take place?

Answer 1

• Thylokoid membrane

Question 2

Where does the light independent stage take place?

Answer 2

• Stroma

Question 3

Autotroph

Answer 3

An organism which makes complex organic compounds eg. glucose from simple organic molecules eg. carbon dioxide and water

Question 4

Heterotroph

Answer 4

An organism that obtains complex organic compounds eg. glucose by feeding on other organisms or their dead remains

Question 5

Factors that effect the rate if photosynthesis (Temperature)

Answer 5

• Calvin cycle is enzyme controlled reaction
• Temperature increases the rate of reaction
• Enzyme will denature at high temperature
• Less kinetic energy, less collisions less enzyme substrate complexes forming

Question 6

Factors that effect the rate if photosynthesis (Light intensity)

Question 7

Factors that effect the rate if photosynthesis (Co2 conc)

Question 8

Is photosynthesis a end or exothermic ?

Answer 8

Endothermic

Question 9

Photophosphorylation

Answer 9

When energy from light allows a phosphate to be added

Question 10

Photolysis

Answer 10

When light energy splits water into H+ ions and OH-

Question 11

Chloroplast envelope

Answer 11

Double membrane permeable to glucose,oxygen,carbon dioxide and some ions

Question 12

Stroma

Answer 12

Matrix of the chloroplast. Site of light independent reactions

Question 13

Lipid droplet

Answer 13

Energy store made from sugars produced during photosynthesis

Question 14

Starch grain

Answer 14

The insoluble carbohydrate storage product of photosynthesis

Question 15

Stack of thylakoid membranes

Answer 15

Forming the grana, site of light dependent reactions

Question 16

Why is only 2% of the sun’s radiation landing on an area turned into sugar by photosynthesis?

Answer 16

• Some of the light misses the chloroplast
• Some of the light is reflected
• Some of the radiation is transmitted as heat
• Some of the light is the ‘wrong’ wavelength

Question 17

Action spectrum

Answer 17

The wavelengths of light
that affect the rate of
photosynthesis

Question 18

Absorption spectrum

Answer 18

The wavelengths of light
that pigments absorb

Question 19

Light independent reaction

Answer 19

• Co2 binds with RUBP in the presence of RUBISCO (an enzyme) to form a 6 carbon unstable intermediate.
• The unstable intermediate immediately breaks down into 2 GP’s
• These two GP molecules go through a series of reactions to form two GALP molecules
• The reactions are ATP → ADP + Pi
  NADPH → NADP
• ⅚ of them will reform RUBP using ATP → ADP + Pi and ⅙ will go off to form glucose, amino acids, Carbo-hydrates and lipids

Question 20

Light dependent reaction
(Cyclic photophosphorylation)

Answer 20

• Photons of light hit photosystem 1
• Electrons are excited to a higher energy level and leave the photosystem
• The excited electrons pass along the electron transport chain, releasing energy
• The energy released drives the process of chemiosmosis
• ATP is Produced
• At the end of the electron transport chain the electrons rejoin the photosystem in a cyclic cycle

Question 21

Light dependent reaction
(Non - cyclic photophosphorylation)

Answer 21

• Photons of sunlight hit the chlorophyll making the electrons excited
• Electrons leave the molecule
  and they go to the electron transport chain down electron acceptors
• Releasing little bits of energy between each one to form ATP
• The electron does not return to PS2 and goes to PS1
• PS2 is now unstable
• Photolysis of water releases H+ and OH- ions
• The H+ is used to reduced NADP to NADPH
• The OH- ions reform oxygen

Question 22

Rf values

Answer 22

• A smaller Rf value indicates the pigment is less soluble and larger in size
• A larger Rf value indicates the pigment is more soluble and smaller in size

Question 23

Calculating Rf values

Answer 23

Distance pigment travelled / Distance solvent travelled