in this bubble there will be more than 5000 a level biology questions- if you do them all and master the mark scheme you will get an A* in biology without a doubt- all questions come with mar schemes which will help you get that A grade
1. The diagram shows the flow of energy through a marine ecosystem.
–2 –1
The units are kJ m year .
L ig h t e n e rg y m e a s u re d a t se a su rfa c e
1 2 .5 × 1 0 5
6250
1000 R e s p ir a tio n 1 2 5 0
P ro d u c e rs
4000
500 R e s p ir a tio n 2 8 0 0
P rim a ry c o n s u m e rs
700
100 R e s p ira tio n 5 5 0
S e c o n d ary c o n su m e rs
50
E n e rg y in fa e c e s
a n d d e a d o rg a n is m s
w h ic h fa ll to th e b o tto m
(a) (i) Calculate the percentage of the light energy at the sea surface which is converted
into chemical energy in the producers. Show your working.
(2)
(ii) The percentage of the light energy at the sea surface which is converted into
chemical energy in the producers is very small. Give two reasons for this.
(2)
(b) Use the information in the diagram to explain why marine ecosystems such as this rarely
have more than five trophic levels.
(2)
(c) What happens to the energy in faeces and dead organisms which fall to the bottom of the
sea?
(2)
1
,(d) Light energy is important in the light-dependent reaction of photosynthesis. The energy
changes which take place in the light-dependent reaction are shown in the diagram.
C h a in o f
e le c tro n
c a rrie rs
C h a in o f
e le c tro n
c a rrie rs
E n e rg y R educed
L evel N A D P N A D P
ATP
L ig h t
A D P + Pi
C h lo ro p h y ll
L ig h t
C h lo ro p h y ll
(i) Describe what happens to the chlorophyll when it is struck by light.
(2)
(ii) The weedkiller DCMU blocks the flow of electrons along the chains of electron
carriers. Describe and explain the effect this will have on the production of triose
phosphate in the light-independent reaction.
(3)
(e) Living organisms release energy from organic molecules such as glucose during
respiration.
Much of this energy is used to produce ATP.
Explain why ATP is better than glucose as an immediate energy source for cell
metabolism.
(2)
(f) The production of ATP is said to be coupled to the transport of electrons along the carrier
chain. Normally, electrons are only passed along the carrier chain if ADP is being
converted to ATP at the same time. When the amount of ADP in a cell is low, electrons do
not flow from reduced coenzyme to oxygen.
(i) Suggest how the rate of respiration is linked to the needs of the cell.
(3)
(ii) DNP is a substance which allows electron transport to take place without the
production of ATP. When DNP is given to rats, their body temperatures rise.
Explain why.
(2)
(Total 20 marks)
2
, 2. The diagram gives an outline of the process of aerobic respiration.
G lu c o s e
2 ATP
S ta g e C
S ta g e A 2 re d u c e d N A D 6 ATP
4 ATP
2 P y ru v a te
2 C O 2
2 re d u c e d N A D 6 ATP
2 A c e ty lc o e n z y m e A
2 C oenzym e A
6 re d u c e d N A D 18 AT P
S ta g e B 2 re d u c e d N A D 4 ATP
2 ATP
4 C O 2
H + io n s a n d e le c tro n s
(a) (i) Complete the table by naming stages A and B and giving the location of each stage
in a cell such as a liver cell.
Stage Name of stage Location in cell
A
B
(2)
(ii) How many carbon atoms are there in each pyruvate ion? ...............................(1)
3
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