Respiration ( populations in ecosystems ) Flashcards
Describe how acetylcoenzyme A is formed in the link reaction.
- Oxidation of pyruvate
- Carbon dioxide is released
- Addition of coenzyme A
In the Krebs cycle, acetylcoenzyme A combines with four-carbon oxaloacetate to form six-carbon citrate.
This reaction is catalysed by the enzyme citrate synthase.
Oxaloacetate is the first substrate to bind with the enzyme citrate synthase.
This induces a change in the enzyme, which enables the acetylcoenzyme A to bind.
Explain how oxaloacetate enables the acetylcoenzyme A to then bind to the enzyme.
- There’s a change in the shape of the active site
- Substrate is now complementary to the active site
Another substance in the Krebs cycle is called succinyl coenzyme A. This substance has a very similar shape to acetylcoenzyme A.
Suggest how production of succinyl coenzyme A could control the rate of the reaction catalysed by citrate synthase.
( In the Krebs cycle, acetylcoenzyme A combines with four-carbon oxaloacetate to form six-carbon citrate.
This reaction is catalysed by the enzyme citrate synthase. )
- Succinyl coenzyme A is a competitive inhibitor
- It reduces the amount of enzyme substrate complexes
In muscles, pyruvate is converted to lactate during anaerobic respiration.
Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration.
( In the Krebs cycle, acetylcoenzyme A combines with four-carbon oxaloacetate to form six-carbon citrate.
This reaction is catalysed by the enzyme citrate synthase. )
- Regenerates NAD
- NAD is used in glycolysis
In muscles, some of the lactate is converted back to pyruvate when they are well supplied with oxygen.
Suggest one advantage of this.
- Lactic acid is toxic
Researchers investigated the effect of cyanide on oxygen uptake by mitochondria.
They prepared a suspension of mitochondria from animal cells and a suspension ofmitochondria from plant cells.
They placed the suspensions in separate flasks containing
isotonic solution, started the timer and began recording the concentration of oxygen in each flask.
- After 5 minutes, they added a respiratory substrate and ADP to each flask.
- After 13 minutes, they added cyanide solution to each flask.
The graph below shows their results.
From P to R the curves for animal and plant mitochondria overlap.
( Figure shows one line graph which splits into two towards the end )
( Y-axis represents “ Oxygen concentration “ )
( X-axis represents “ Time / minutes “ )
( The line graph is labelled with points P, Q, R, S and T )
( P and Q are parallel to eachother, basically just a straight line at the start of the graph )
( At Q, it is labelled “ Respiratory substrate and ADP added “ )
( R is after Q, which is lower than Q, a diagonal line going downwards )
( R is labelled “ Cynanide solution added “ )
( S is parallel to R, the line is dotted and labelled “ Animal mitochondria “ )
( T is diagonally lower than S, however less diagonal than Q to R )
( The line is dotted and is labelled “ Plant mitochondria “ )
Explain the line between P and Q.
- No aerobic respiration
- Because there’s no respiratory substrate
Explain the line between Q and R.
( Figure shows one line graph which splits into two towards the end )
( Y-axis represents “ Oxygen concentration “ )
( X-axis represents “ Time / minutes “ )
( The line graph is labelled with points P, Q, R, S and T )
( P and Q are parallel to eachother, basically just a straight line at the start of the graph )
( At Q, it is labelled “ Respiratory substrate and ADP added “ )
( R is after Q, which is lower than Q, a diagonal line going downwards )
( R is labelled “ Cynanide solution added “ )
( S is parallel to R, the line is dotted and labelled “ Animal mitochondria “ )
( T is diagonally lower than S, however less diagonal than Q to R )
( The line is dotted and is labelled “ Plant mitochondria “ )
- Oxygen concentration falls due to aerobic respiration
- Oxygen is a terminal electron acceptor
The respiratory substrate and ADP added after 5 minutes ( Q ) were part of a buffered isotonic solution.
What other substance would the buffer or solution have to contain?
( Figure shows one line graph which splits into two towards the end )
( Y-axis represents “ Oxygen concentration “ )
( X-axis represents “ Time / minutes “ )
( The line graph is labelled with points P, Q, R, S and T )
( P and Q are parallel to eachother, basically just a straight line at the start of the graph )
( At Q, it is labelled “ Respiratory substrate and ADP added “ )
( R is after Q, which is lower than Q, a diagonal line going downwards )
( R is labelled “ Cynanide solution added “ )
( S is parallel to R, the line is dotted and labelled “ Animal mitochondria “ )
( T is diagonally lower than S, however less diagonal than Q to R )
( The line is dotted and is labelled “ Plant mitochondria “ )
- Phosphate ions
Describe and explain the difference between line R to S ( animal mitochondria ) and line R to T ( plant mitochondria ).
( Figure shows one line graph which splits into two towards the end )
( Y-axis represents “ Oxygen concentration “ )
( X-axis represents “ Time / minutes “ )
( The line graph is labelled with points P, Q, R, S and T )
( P and Q are parallel to eachother, basically just a straight line at the start of the graph )
( At Q, it is labelled “ Respiratory substrate and ADP added “ )
( R is after Q, which is lower than Q, a diagonal line going downwards )
( R is labelled “ Cynanide solution added “ )
( S is parallel to R, the line is dotted and labelled “ Animal mitochondria “ )
( T is diagonally lower than S, however less diagonal than Q to R )
( The line is dotted and is labelled “ Plant mitochondria “ )
- Oxygen concentration continues to fall in plants but stays constant in animals
- Oxygen concentration falls more slowly in plants than before cyanide is added
- Because aerobic respiration continues in plant mitochondria
- Electron transfer continues in plant mitochondria
The figure below shows the apparatus used for measuring the rate of oxygen consumption in aerobic respiration by seeds.
( Diagram shows a big beaker containing two tubes, A and B )
( The beaker is a water bath at 20 Celsius )
( In between them is a “ Capilarry U-tube containing coloured liquid “, a block with a U-shaped tube in it )
( Tube A contains “ Potassium hydroxide solution plus water to equal the volume of the seeds and cage in the other tube “ )
( Tube B has a “ 1cm^3 syringe “ attached to it )
( Indie tube B contains a “ plastic cage with seeds in it “ and at the bottom is “ Potassium hydroxide solution to absorb carbond dioxide “ )
( Both tubes contain bungs and taps on them )
For the first 10 minutes, the tap attached to tube A was left open and the syringe from tube B was removed.
Suggest three reasons why the apparatus was left for 10 minutes.
- To allow equilibrium to be reached
- Allow for pressure change in the appratus
- To allow rate of respiration of seeds to stabalise
Suggest and explain why the chosen temperature was 20 °C for this experiment.
( The figure below shows the apparatus used for measuring the rate of oxygen consumption in aerobic respiration by seeds.
( Diagram shows a big beaker containing two tubes, A and B )
( The beaker is a water bath at 20 Celsius )
( In between them is a “ Capilarry U-tube containing coloured liquid “, a block with a U-shaped tube in it )
( Tube A contains “ Potassium hydroxide solution plus water to equal the volume of the seeds and cage in the other tube “ )
( Tube B has a “ 1cm^3 syringe “ attached to it )
( Indie tube B contains a “ plastic cage with seeds in it “ and at the bottom is “ Potassium hydroxide solution to absorb carbond dioxide “ )
( Both tubes contain bungs and taps on them ) )
- 20 Celsius is the optimum temperature for the seeds to grow
- It is also the optimum temperature for enzymes involved in respiration
After 10 minutes, the tap attached to tube A was closed and the syringe was attached to tube B.
Every minute, the syringe plunger was moved until the levels in
the U-tube were the same.
The reading on the syringe volume scale was then recorded.
The results are shown in the table below.
Time / minutes:
1 ) 0
2 ) 1
3 ) 2
4 ) 3
5 ) 4
6 ) 5
7 ) 6
8 ) 7
9 ) 8
10 ) 9
11 ) 10
Reading on syringe volume scale / cm^3:
1 ) 0.84
2 ) 0.81
3 ) 0.79
4 ) 0.76
5 ) 0.73
6 ) 0.70
7 ) 0.68
8 ) 0.66
9 ) 0.63
10 ) 0.62
11 ) 0.58
During the experiment, the coloured liquid in the tubing moved towards tube B.
Explain what caused this.
- The oxygen is used by the seeds
- CO2 is given out and absorbed by the potassium hydroxide solution
- Volume in B decreases
The mass of the seeds was 1.6g.
Use the information in the table above to calculate the rate of oxygen consumption in cm^3 g^-1 hour^-1 by the seeds.
Show your working.
( Time / minutes:
1 ) 0
2 ) 1
3 ) 2
4 ) 3
5 ) 4
6 ) 5
7 ) 6
8 ) 7
9 ) 8
10 ) 9
11 ) 10
Reading on syringe volume scale / cm^3:
1 ) 0.84
2 ) 0.81
3 ) 0.79
4 ) 0.76
5 ) 0.73
6 ) 0.70
7 ) 0.68
8 ) 0.66
9 ) 0.63
10 ) 0.62
11 ) 0.58 )
- 0.98
- Units = cm^3 g^-1 hour^-1
- ( So we do the maximum - minimum value of reading on syringe )
- 0.84 - 0.58 = 13 / 50
- ( Divide this by the mass ( g^- 1 ) )
- 13 / 50 / 1.6 = 13 / 80
- ( Divide this by the time in hours, ( hour^- 1 ) )
- 13 / 80 / 10 / 60
- = 39 / 40, = 0.975 = 0.98
A student investigated the rate of anaerobic respiration in yeast. She put 5 g of yeast into a glucose solution and placed this mixture in the apparatus shown in the figure below.
She then recorded the total volume of gas collected every 10 minutes for 1 hour.
( Diagram shows a typical way to measure the volume of gas produced )
( A conical flask with a bung on it which is attached to a gas syringe )
( Yeast is in glucose solution )
( With a layer of oil on top )
Explain why a layer of oil is required in this investigation.
- To prevent oxygen being taken up
The student’s results are shown in the following table.
Time / minutes:
1 ) 10
2 ) 20
3 ) 30
4 ) 40
5 ) 50
6 ) 60
Total volume of gas collected / cm^3:
1 ) 0.3
2 ) 0.9
3 ) 1.9
4 ) 3.1
5 ) 5.0
6 ) 5.2
Calculate the rate of gas production in cm^3 g^-1 min^-1 during the first 40 minutes of this investigation.
Show your working.
- 0.016
- Units = cm^3 g^-1 min^-1
- ( Divide the volume of gas collected at 40 mins by the mass of the seeds ( cm^3 g^-1 ) )
- 3.1 / 5 = 31 / 50
- ( Then divide this by the time in minutes )
- 31 / 50 / 40
- = 0.0155 = 0.016
