respiration

Question 1

why does the aerobic respiration yield fewer molecules of ATP than the theoretical maximum

Answer 1

1 some ATP used to (actively) transport pyruvate
(into the mitochondrion) ;
2 some ATP used to (actively) transport
H
(+) from (reduced) NAD ,
formed in glycolysis / into the mitochondrion ;
3 some energy released in ETC ,
is not used to transport H+
(across inner membrane) /
is released as heat ;
4 not all the H+ movement (back across membrane) ,
is used to generate ATP /
is through ATP synth(et)ase ;
5 not all the, reduced NAD / red NAD / NADH ,
is used to feed into the ETC ;

Question 2

explain why the incomplete breakdown of glucose in anerobic respiration yields produces less ATP than aerobic respiration

Answer 2

explain why the incomplete breakdown of glucose in anerobic respiration yields produces less ATP than aerobic respiration

Question 3

Certain parasites live in the blood of mammals.

Suggest why, even though blood carries oxygen, these parasites are adapted to respire anaerobically.

Answer 3

1 idea that parasites have little access to oxygen ;
2 (inaccessible because)
little oxygen dissolved in plasma /
oxygen not very soluble (in plasma) ;
3 (inaccessible because) idea that oxygen is ,
combined with haemoglobin /
contained in red blood cells ;
4 idea that haemoglobin has greater affinity for oxygen
than parasite (pigment) ;

Question 4

The anaerobic respiration pathway in animal cells can be reversed, but the anaerobic respiration pathway in yeast cells cannot be reversed. Explain why, using your knowledge of the differences between the two pathways.

Answer 4

in animals
A1 pyruvate is , converted / reduced , to , 
lactate / lactic acid ; 
A2 can be reversed as no , 
atoms lost / other product formed ; 
A3 lactate dehydrogenase available 
to reverse the reaction ; 
in yeast 
Y1 pyruvate converted to ethanol (in 2 steps) and 
carbon dioxide / CO2 ; 
Y2 cannot be reversed as , 
carbon dioxide is / atoms are , lost 
; 
Y3 (de)carboxylase enzyme cannot 
reverse the reaction 
QWC 
pyruvate, lactate, 
lactate dehydrogenase carbon dioxide, 
ethanol 
(de)carboxylase / (de)carboxylation

Question 5

State precisely where in the cell glycolysis occurs.

Answer 5

cytoplasm (of cell) ;

Question 6

Outline the process of glycolysis.

Answer 6

1 phosphorylation of glucose ;
2 so forming hexose (1,6) bisphosphate ;
3 (then) splitting into / formation of ,
two / 2 , triose phosphate(s) / TP ;
4 (for formation of pyruvate) dehydrogenation /
oxidation / formation of reduced NAD ;
5 pyruvate produced (from , TP / (3C) intermediate) ;
6 total production 4 ATP / net production of 2 ATP
QWC
phosphorylation (or derived term) glucose
hexose (1,6) bisphosphate triose phosphate
dehydrogenation OR oxidation (or derived terms)
pyruvate

Question 7

State precisely where in the liver cell the excess reduced NAD can be re-oxidised.

Answer 7

crista(e) / inner mitochondrial membrane ; `

Question 8

Suggest the type of reaction that removes a phosphate group from an ATP molecule.

Answer 8

hydrolysis

Question 9

State the precise location of the electron transport chain in the cell.

Answer 9

crista(e) / inner mitochondrial membrane ;

Question 10

Explain why this anaerobic pathway is important for the plant cell.

Answer 10

1 releases NAD , to accept more H / to be reduced again /
so glycolysis can continue
or
allows (some) ATP to be generated (in glycolysis) ;
2 (some ATP available) for named cellular process ;

Question 11

State the stage or stages of aerobic respiration during which: carbon dioxide is produced

Answer 11

link reaction and Krebs cycle ;

Question 12

State the stage or stages of aerobic respiration during which: oxygen is used.

Answer 12

oxidative phosphorylation ;

Question 13

Suggest how a weak and irregular heart beat could result in fatigue.

Answer 13

1 idea of slow rate of / sluggish , blood flow
or
low(er) blood pressure ;
2 less / irregular amount of ,
oxygen (reaching cells) for ,
(aerobic) respiration / oxidative phosphorylation ;
3 less glucose (reaching cells) for respiration ;
4 (so) less ATP produced ;
5 idea of increased acidity (as CO2 / lactate builds up)
interfering with / affects ,
enzymes / respiratory metabolism ;

Question 14

It has been suggested that in cells of people with CFS, pyruvate may not be transferred into the mitochondria efficiently. Outline the consequences of an inefficient transfer of pyruvate into mitochondria and link this to the symptoms of CFS stated above.

Answer 14

1 less pyruvate for , link reaction / Krebs cycle
or
link reaction / Krebs cycle , cannot take place / reduced
or
only / mainly , glycolysis takes place ;
2 no / little , oxidative phosphorylation ;
3 less , energy / ATP ,
for muscle contraction /
resulting in muscle weakness /
for mental processes ;
4 anaerobic respiration takes place ;
5 lactate / decrease in pH , causing aching muscles ;

Question 15

people with CFS overproduce T lymphocytes and associated cytokines, but immune response still poor. Suggest a reason for the poor specific immune response in people with CFS.

Answer 15

1 idea that B lymphocytes do not respond to cytokines
 (that have been produced) ;
2 little , energy / ATP , for B cell ,
 mitosis / clonal expansion ;
3 little , energy / ATP , for ,
 production / release , of antibodies ;

Question 16

Explain how the three reaction pathways, glycolysis,calvin cycle and krebs cycle are able to work independently of each other in the same leaf cell.

Answer 16

1. take place in different , parts / organelles , of the cell
   or
   compartmentalisation
   reactions separated by membranes ;
2. glycolysis , in cytoplasm ;
3. Calvin cycle , in , chloroplast / stroma (of chloroplast) ;
4. Krebs cycle , in ,
   mitochondrion / matrix (of mitochondrion) ;

Question 17

State the products of oxidative phosphorylation.

Answer 17

ATP / adenosine triphosphate ;
water / H2O ;
(oxidised) NAD / FAD

Question 18

Explain the role of coenzymes in this leaf cell

Answer 18

1. NAD / FAD / NADP , can ,
accept hydrogen / accept H / be reduced ;
2. reduced , NAD / FAD ,
 supplies / carries , electrons ,
to the electron transport chain /
 for oxidative phosphorylation ;
3. reduced , NAD / FAD ,
supplies / carries , hydrogen ions for ,
chemiosmosis /
 oxidative phosphorylation ;
4. reduced NADP , supplies / carries , hydrogen to ,
light independent stage / Calvin cycle / X ;
5. coenzyme A / CoA , carries ,
 acetate / ethanoate / acetyl group ,
to , Krebs cycle / Y ;

Question 19

state and explain one way in which the basic aerobic respiration equation is an over-simplification.

Answer 19

glucose is not the only substrate / there are other substrates eg fats
or
ATP is produced / energy is released ;
(by) substrate level / oxidative, phosphorylation ;
or
ATP / energy, required ;
(for) phosphorylation / glycolysis ;
or
is not a single step reaction / other steps involved /
other products
or
enzymes are involved ;
dehydrogenation / decarboxylation / oxidative phosphorylation /
named (respiratory) enzyme ;
or
coenzymes / NAD, involved ;
oxidative phosphorylation / link reaction / Krebs cycle / glycolysis ;
or
glucose does not, combine / react , (directly) with oxygen ;
(oxygen) used in oxidative phosphorylation /
is final electron acceptor / is final hydrogen acceptor ;

Question 20

State precisely where in the cell glycolysis takes place.

Answer 20

cytoplasm

Question 21

Describe the fate of pyruvate during anaerobic respiration in an animal cell and explain the importance of this reaction.

Answer 21

1. pyruvate converted to lactate
2. pyruvate , accepts hydrogen from , reduced NAD
3. (catalysed by) lactate dehydrogenase
4. no oxygen to act as final hydrogen / electron, acceptor
5. so link reaction / Krebs cycle / ETC, cannot take place
6. NAD regenerated /able to be re-used ;
7. allows glycolysis to continue / pyruvate continues to be made ;
8. limited / small amount of / some, ATP can be produced ;

Question 22

Suggest how the seal is adapted to respire for such a long time underwater.

Answer 22

idea that seal , has low(er) metabolic rate /
has low(er) respiratory rate /
has low(er) energy requirements /
uses (relatively) little ATP ;
able to respire anaerobically for a long time / more glycolysis ;
large supplies of NAD (to accept H) ;
(this) prevents , build-up of lactate / lowering of pH ;
idea that (seal) tolerates lactate / removes lactate quickly ;
idea that (seal) tolerates high CO2 concentration ;
idea that (seal) tolerates low pH / has more pH buffers ;
synoptic / inference
idea that blood diverted from certain regions /
certain regions have reduced metabolic activity ;
idea that has plenty of , haemoglobin / red blood cells /
myoglobin (as oxygen source) ;
idea that haemoglobin has a higher affinity for oxygen /
dissociates less readily /dissociation curve shifted to left ;

Question 23

One effect of thyroid hormones is to increase the activity of mitochondria within cells.
Suggest how the metabolism of a person with the condition congenital hypothyroidism might differ from that of a person who does not have this condition.

Answer 23

1 low / less / no, thyroid hormones ;
2 less (aerobic) respiration ;
3 less, ATP produced / energy ;
4 slow(er) metabolism / low(er) (B)MR ;
5 low body temperature ;