Photosynthesis

Question 1

what is an autotroph

Answer 1

an autotroph is an organism that uses an energy source to make complex carbohydrate

Question 2

what are the two main groups of autotrophs

Answer 2

-Chemoautotrophs (bacteria) make carbohydrates using chemical energy

Photoautotrophs-(plants + algae) use light energy to make carbohydrates

Question 3

what is the equation for photosynthesis

Answer 3

Carbon dioxide + water –> Glucose + Oxygen

on arrow- sunlight, chlorophyll

Question 4

What are the two stages of photosynthesis

Answer 4

Light dependent stage

Light independent stage

Question 5

where does photosynthesis take place

Answer 5

chloroplast

Question 6

what are the photosynthetic pigments found in chloroplasts

Answer 6

• Chlorophylls e.g chlorophyll a and chlorophyll b

- carotenoids e.g carotene and xanthophyll

Question 7

where in the chloroplast does the light dependent reaction happen

Answer 7

thylakoid membrane

Question 8

what is photoionisation

Answer 8

• photons of light excite the electrons in chlorophyl
• continued excitation causes the release of the electrons
• the e- can then be passed down electron transport chain

Question 9

explain the light dependent reaction

Answer 9

-chlorophyl A on photosystem II absorbs photon of light- this excites the electrons to higher energy levels
- electron passed down electron transport chain to plastoquinone B6F to Photosystem I
the electron is reexcited at PS I
-as the electron is passed down the chain, it drops down energy levels. this energy is used to pump H+ from the stroma into the thylakoid lumen
-NADP+ is the final electron acceptor –> NADPH
-the original e- is replaced through the oxidation of water to produce 2O2 + 4H+ + 4e-
-the H+ in the thylakoid lumen diffuse back into the stroma through ATP synthase to produce ATP

Question 10

what wavelength of light does photosystem II absorb

Answer 10

680nm

Question 11

what wavelength of light does photosystem I absorb

Answer 11

700nm

Question 12

what products are taken from the light dependent reaction to the light independent reaction

Answer 12

NADPH

ATP

Question 13

where does the light independent reaction take place

Answer 13

stroma

Question 14

what is another name for the light independent reaction

Answer 14

Calvin cycle

Question 15

explain how the light independent reaction happens

Answer 15

• Carbon dioxide reacts with Ribulose-1,5-biphosphate (RuBP) to form 2 molecules of Glycerate 3 phosphate through
• catalysed by Ru Bis Co
• energy from ATP and NADPH
• some Glycerate 3 phosphate recycled to RuBP- process uses ATP
• some Glycerate 3 phosphate can be converted to useful organic substances

Question 16

what reaction joins CO2 to Ribulose biphosphate

Answer 16

carbon fixation

Question 17

what is an electron transport chain

Answer 17

a series of complexes that transfer electrons between electron donors and electron acceptors through redox reactions

Question 18

in the light dependent reaction what are the 2 forms of photophosphorylation

Answer 18

Cyclic- electron from PS I recycled to PS II

non cyclic- NADPH as final acceptor and Water as donor

Question 19

what factors limit the rate of photosynthesis

Answer 19

light
water
carbon dioxide

Question 20

what happens if there is not enough magnesium

Answer 20

chlorosis

mg is in chlorophyll a- unable to make chlorophyll a