Respiration- module 5 Flashcards
what are the adaptations of mitochondria
-Folded inner membrane (cristae)- increase surface area to maximise respiration
-Matrix- contains enzymes for Krebs cycle and link reaction
-Inner mitochondrial membrane contains electron transport chains and lots of ATP synthase
4 stages of respiration
1)Glycolysis
2)Link reaction
3)Krebs cycle
4) Oxidative phosphorylation
The hydrolysis of ATP
Energy can be immediately available to cells by the hydrolysis of ATP to ADP and Pi
ADP is also hydrolysed into AMP and then hydrolysis can occur again to produce adenosine
Energy is released with each hydrolysis
glycolysis
-function is to produce Pyruvate from glucose
-Takes place in cytoplasm as glucose can’t cross outer mitochondrial membrane
-Doesn’t require oxygen so takes pklace in anaerobic respiration
-Involves a sequence of reactions catalysed by different enzymes and a coenzyme NAD
what is NAD
coenzyme derived from vitamin B3
responsible for transfer of hydrogen to hydrogenase enzyme
what are the 2 stages of glycolysis
Phosphorylation
Oxidation
Process of phosphorylation
1)ATP molecule is hydrolysed to release phosphate group
2)Phosphate group attached to glucose at carbon 6
3)molecule is now called hexose phosphate
4)Another ATP molecule is hydrolysed
5)phosphate is attached to hexose phosphate
6)molecule now called hexose bisphosphate
7)This addition activates the hexose sugar, but also prevents it from being transported out of the cell
8) Each molecule of hexose 1,6-bisphosphate is now split into two molecules of triose phosphate
Process of Oxidation (glycolysis)
1)triose phosphate molecules are dehydrogenated (2 hydrogen atoms removed)
2)they now have been oxidised
3)This is catalysed by dehydrogenase enzymes
4)require coenzyme NAD to combine with hydrogen atoms to become reduced NAD or NADH
Two molecules of NAD are produced per glucose molecule
Two ATP molecules are also produced in phosphate-level phosphorylation
Enzyme catalysed reactions convert triose phosphate into pyruvate (3C compound)
Two more ATP molecules are produced by phosphorylation of ADP
Link reaction does
Links anaerobic glycolysis to the aerobic steps of respiration
Pyruvatev is actively transported to the Matrix of the mitochondria via special carrier proteins
The pyruvate is converted into acetyl coenzyme A (acetyl Coa)
Products of link reaction per glucose
-2 acetyl CoA
- 2CO2
- 2NADH
Process of link reaction
-pyruvate actively transported into matrix of mitochondria
-pyruvate decarboxylated (CO2 removed)
-then dehydrogenated by NAD to produce NADH
THIS produces Acetate
Coenzyme A forms with Acetate to form acetyl coenzyme A
This is then transported to the krebs cycle
Process of Krebs cycle
1)Acetyl CoA (2C) combines with oxaloacetate (4C) to form Citrate (6C) - > CoA goes back to the link reaction
2) Citrate is converted to a 5C compound by decarboxylation + dehydrogenation forming reduced NAD
3) Regeneration of Oxaloacetate forms 5C compound by decarboxylation, dehydrogenation forming 2 x reduced NAD, reduced FAD and substrate - level phosphorylation to make ATP
Respiratory quotients
When an organism respires a specific respiratory substrate, the respiratory quotient (RQ) can worked out.
This is the volume of CO2 produced when that substrate is respired divided by the volume of O2 consumed in a set time.
The answer tells us which molecule is being respired.
average energy value of the respiratory substrate carbohydrates (KJ g^-1)
15.8
average energy value of the respiratory substrate Lipids (KJ g^-1)
39.4
average energy value of the respiratory substrate proteins (KJ g^-1)
17.0
RQ value of Lipids
0.7
RQ of amino acids and proteins
0.9
RQ of carbohydrates
1
Fermentation
A form of anaerobic respiration in which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of the ETC.
Lactate fermentation
Occurs in the cytoplasm of mammals and bacterial cells.
Produces lactate (lactic acid).
Only 2ATP molecules produced in glycolysis.
NADH from glycolysis transfers hydrogen atoms to pyruvate to form lactate & NAD.
Catalysed by the enzyme lactate dehydrogenase.
Regenerated NAD can be reused in glycolysis.
Why can’t this continue?b lactic acid build up- enzymes denature, not enough ATP for vital processes
Lactate, less stages
ethanol fermentation
Occurs in the cytoplasm of yeast and plant cells.
Produces ethanol.
CO2 is removed from pyruvate to form ethanal. This is catalysed by pyruvate decarboxylase.
Reduced NAD transfers hydrogen atoms to ethanal to form ethanol and NAD.
NAD goes back to be used in glycolysis.
Only 2ATP molecules produced in glycolysis.
Only 2ATP molecules produced in glycolysis.
Can continue in the absence of oxygen
Why does Anaerobic respiration yield less energy than aerobic? (3 marks)
Only producing ATP during glycolysis
Net gain of 2 ATP produced during glycolysis
No link reaction/Krebs cycle
No oxidative phosphorylation
respirometer use
Used to indicate the rate of aerobic respiration by measuring the amount of oxygen consumed in a set period of time
how to Calculating rate of respiration using a respirometer
Leave the respirometer for a set amount of time
Distance moved by the liquid in the manometer is read
Would also need to know diameter of capillary tube to calculate volume
To calculate the rate of respiration (mm3 min-1)
Volume of oxygen used/
time taken
Data logging using respirometer
Respirometers can be set up with electronic oxygen sensors to measure the oxygen concentration inside the respirometer chamber.
Reduce the chance of human error- make results more precise
use of Manometer containing coloured liquid and a calibrated scale
in respirometer
Moves towards tube with organism in due to pressure changes when oxygen used up
use of KOH in respirometer
absorbs CO2
use of tap in respirometer
Stops gases escaping to ensure a closed system
use of scale in respirometer
To measure movement of liquid, to calculate rate
use of syringe in respirometer
To reset liquid in manometer to a set level for repeats
use of glass beads in respirometer
Equal mass to organism
act as a control
Oxidative phosphorylation process
1)Hydrogen atoms released from NADH and FADH2 as they are oxidised to NAD and FAD. Hydrogen atoms split into protons (H+) and electrons (e-).
2)Electrons move along the electron transport chain (located at the inner mitochondrial membrane), losing energy at each carrier.
3)This energy is used to pump protons from the matrix into the intermembrane space (the space between the inner and outer membrane).
4)The concentration of protons is now higher in the intermembrane space than the mitochondrial matrix. This forms an electrochemical gradient-a concentration gradient of ions.
5)Protons move down the electrochemical gradient back to the matrix via ATP synthase.
6)The movement of protons drives the synthesis of ATP from ADP and inorganic phosphate.
7)The process of ATP production driven by the movement of H+ ions across a membrane (due to the electrons moving down the electron transport chain) is called chemiosmosis.
8)In the mitochondrial matrix, at the end of the ETC, protons, electrons and oxygen combine to form water. Oxygen is said to be the final electron acceptor.
Chemiosmosis
Chemiosmosis is the synthesis of ATP driven by the flow of protons through a partially permeable membrane, specifically the flow of hydrogen ions through the inner mitochondrial membrane.
oxidative phosphorylation definition
Oxidative phosphorylation is the formation of ATP by adding a phosphate group to ADP, using energy from electrons moving down an electron transport chain and in the presence of oxygen, the final electron acceptor.
How to measure rate of respiration in yeast
Anaerobic
1)Place 100ml of 5% glucose solution in conical flask
2)Add 5g of yeast to the glucose solution and stir with glass rod for 2 minutes
3)Once the yeast has been added and stirred, carefully trickle some oil down the inside of the conical flask so it settles on and completely covers the surface of the solution. This will force yeast to respire anaerobically
4) Place conical flask in water bath at 40 degrees Celsius for 10 mins to allow yeast to begin to respire
5)Clamp a gas syringe in place and place the bung on top of the conical flask.
6) Record the volume of gas in the syringe every minute for 10 mins
7)Repeat the experiment 3 times and calculate a mean rate of CO2 production
(For aerobic, do the same but don’t add oil)
GLYCOLYSIS
Phosphorylation of glucose- uses 2 ATP, the two phosphates released join to glucose to make hexose bisphosphate
This destabilises the molecule so its splits into 2 TP molecules
Two TP molecules are oxidised by the removal of 2 hydrogen atoms ( dehydrogenation catalysed by dehydrogenase enzymes) to form 2 pyruvate molecules. NAD+ accepts the hydrogens forming 2 reduced NAD molecules (NADH). 4 ATP molecules are produced by substrate-level phosphorylation.
Overall net yield of 2 ATP.
2NADH are also formed
why is it important for that NAD is converted into NADH in anaerobic respiration
For glycolysis to take place, NAD is needed.
There is a limited amount of NAD in the cell
formation of NAD allows glycolysis to continue / some ATP to be formed
what properties of the mitochondrial inner membrane allow chemiosmosis to occur?
(mostly) impermeable to H+ ions/protons.
Large SA
Presence of ATP synthase/stalked particles
How many ATP made per glucose molecule in aerobic respiration
32
How many ATP made per FADH2
1.5 ATP
How many ATP made per NADH
2.5
products of krebs cycle per glucose
2 ATP
4 CO2
2FADH2
6 NADH
