photosynthesis

Question 1

how does PS produce glucose

Answer 1

light trapped by chlorophyll molecules

this energy used to drive synthesis of glucose from H2O and CO2

Question 2

briefly explain what happens during respiration

Answer 2

energy stored within binds used to synthesise ATP

biomass broken down to produce ATP for metabolic reactions

Question 3

what determines if reactions are exothermic or endothermic

Answer 3

total N and strength of bonds broken/formed

Question 4

describe bonding in small inorganic mol.s

Answer 4

strong bonds

release lots of energy when broken

Question 5

describe hydrogen- carbon bonds

Answer 5

in organic mols (glucose)
C+ H share electrons
non-polar
don’t require much energy to break

Question 6

why do living organisms need energy

Answer 6

find/produce food
respond to changes in environment
deal with threats from other organisms
reproduce

Question 7

what is the difference between ATP production in PS and respiration

Answer 7

PS
-light energy used to form chemical bonds in ATP
-these broken to release energy to form bonds in glucose
R
-organic mol.s (glucose) broken down
-energy released to to synthesis ATP

Question 8

what is chemiosmosis

Answer 8

diffusion of protons from high conc to low conc

synthesises ATP

Question 9

how are electrons excitated (raised to higher energy levels)

Answer 9

electrons in pigment mols excited by light

high energy electrons released when chemical bonds broken in respiratory substrate mol.s

Question 10

how does an electron transport chain work

Answer 10

-made up of series of electron carriers with progressively lower energy levels
-as electrons move from on carrier to the next, energy is released
-energy used to pump membranes across membrane, creating a gradient
-membrane is impermeable to H+ ions
-protons move back through membrane down gradient through hydrophilic channels
providing energy to synthesise ATP

Question 11

define autotrophic and heterotrophic

Answer 11

autotrophic= organisms that can photosynthesise
heterotrophic= obtain molecules through eating other organisms

Question 12

describe the structure of chloroplasts

Answer 12

• network of membranes create large SA to maximise light absorption
• form flattened sacs called thylakoids
• stacked to form grana
• grana joined by membranous channels called lamellae

Question 13

name 3 chlorophyll pigments

Answer 13

chlorophyll a (primary)
chlorophyll b
carotenoids

Question 14

where does LI PS take place

Answer 14

storm (fluid surrounding grana)

Question 15

describe the Calvin cycle

Answer 15

enzymes controlled reaction
each ‘turn’ produces 1 carbon
CO2 combines with 5-carbon mol RuBP
catalysed by enzyme RuBisCO
enzyme is competitively inhibited by oxygen
produces unstable 6-carbon mol which immediately breaks down into 2 3-carbon glycerate phosphate mol.s
GP mol.s converted into 3-carbon triode phosphates using H+ atoms from NADPH + ATP from LD PS
most triode phosphates regenerated to produce RuBP

Question 16

how many CO2 moles must enter Calvin cycle to produce 1 glucose mol

Answer 16

6

Question 17

describe non-cyclic photophosphorylation

Answer 17

• 2 electrons at photosystem || are excited when stimulated by light
• move down electron transport chain providing it with energy to form ATP
• electrons reach PS |, are excited and released onto another electron transport chain
• electrons reduce NADP to NADPH
• electrons at PS || replaced with ones from water
• O2 is a waste product

Question 18

what is photolysis

Answer 18

splitting of water by light

protons released into lumen of thylakoids increasing conc grad across membrane

Question 19

what is cyclic photophosphorylation

Answer 19

electrons leaving PS | return after electron transport chain
no NADPH produced
produces ATP without electrons from PS||