Respiration Flashcards
what is aerobic respiration
the process of breaking down a respiratory substrate (glucose) in order to produce ATP using oxygen
equation for aerobic respiration
C6H1206 + 6 O2 → 6 CO2 + 6 H20 + 2870kJ
what is the energy released during the process of aerobic respiration used for
used to phosphorylate (add a phosphate) ADP to form ATP
what are the four stages of aerobic respiration
state where each stage occurs
Glycolysis (cytoplasm)
Different parts of mitochondria:
The Link reaction (matrix of mitochondria)
The Krebs cycle (matrix of mitochondria)
Oxidative phosphorylation (inner membrane of mitochondria)
what is a coenzyme
non protein molecule that helps enzyme carry out function without being used in the reaction itself
what are the roles of NAD and FAD
the coenzymes responsible for transferring hydrogen between molecules hence being able to reduce or oxidise a molecule
what is Coenzyme A responsible for
transfer of acetate from one molecule to another
what are the four main structures of the mitochondira
and describe each one
The outer membrane
Smooth
Permeable to several small molecules
The inner membrane
Folded (cristae)
Less permeable
The site of the electron transport chain (used in oxidative phosphorylation)
Location of ATP synthase enzymes (used in oxidative phosphorylation)
The intermembrane space
Has a low pH due to the high concentration of protons
The concentration gradient across the inner membrane is formed during oxidative phosphorylation and is essential for ATP synthesis
The matrix
Is an aqueous solution within the inner membranes of the mitochondrion
Contains ribosomes, enzymes and circular mitochondrial DNA necessary for mitochondria to function
what ensures that the energy trapped within the chemical bonds of the glucose molecule is released gradually and not all at once
These chemical reactions are controlled by intracellular enzymes
why is a sudden release of a large amount of energy bad
would result in an increase in body temperature to levels that would denature enzymes
why is glycolysis the first step for both aerobic and anaerobic respiration
It does not require oxygen to take place
where does the partial oxidation of glucose occur during glycolysis and what does it involve
takes place in the cytoplasm
Trapping glucose in the cell by phosphorylating the molecule
Oxidising triose phosphate (by losing hydrogen)
what is produced in glycolysis during anaerobic conditions
produces lactic acid or lactate instead of pyruvate
what happens during the phosphorylation of glucose
Two molecules of ATP are required to provide the two phosphates needed for the phosphorylation of glucose producing two molecules of triose phosphate and two molecules of ADP
what happens during the oxidation of triose phosphate
After triose phosphate loses hydrogen, it forms two molecules of pyruvate
The hydrogen ions are collected by NAD which reduces the coenzyme
This forms two reduced NAD or NADH
Even though a total of four ATP molecules were produced during glycolysis, two of them were used to phosphorylate glucose
There was therefore a net gain of two ATP molecules
Draw the process of glycolysis
what is the end product of glucolysis
pyruvate
what does pyruvate contain
substantial amount of chemical energy that can be further utilised in respiration to produce more ATP
where are the enzymes and coenzymes required for the link reaction found
in the mitochondrial matrix
when oxygen is available where does the pyruvate go
pyruvate will enter the mitochondrial matrix and aerobic respiration will continue
Pyruvate moves across the double membrane of the mitochondria via active transport
Once in the mitochondrial matrix pyruvate takes part in the link reaction
what does pyruvate require to move across double membrane of the mitochondria
It requires a transport protein and a small amount of ATP
where does the pyruvate enter the mitochondrial matrix from
from the cytosol (cytoplasm) by active transport
why is it referred to as the link reaction
because it links glycolysis to the Krebs cycle
what are the steps of the link reaction
Pyruvate is oxidised (hydrogen is removed) by enzymes to produce acetate, CH3CO(O) (also known as acetic acid)
Pyruvate is also decarboxylated (carbon is removed) in the form of carbon dioxide
Reduction of NAD to NADH or reduce NAD by collecting hydrogen from pyruvate
Acetate combines with coenzyme A to form acetyl coenzyme A (acetyl CoA)
is ATP produced during the link reaction and what is produced
No ATP is produced
Acetyl coA
CO2
NADH
equation of Link reaction
DRAW THIS
pyruvate + NAD + CoA → acetyl CoA + carbon dioxide + reduced NAD
why will the link reaction and Krebs cycle occur twice for every molecule of glucose
Every molecule of glucose produces two pyruvate molecules
Hence, each molecule of glucose will produce:
Two molecules of acetyl CoA
Two molecules of CO2
Two molecules of reduced NAD
What does the Krebs cycle consist of
a series of enzyme-controlled reactions
2 carbon (2C) Acetyl CoA enters the circular pathway from the link reaction in glucose metabolism
4 carbon (4C) oxaloacetate accepts the 2C acetyl fragment from acetyl CoA to form the 6 carbon (6C) citrate
Coenzyme A is released in this reaction to be reused in the next link reaction
Citrate is then converted back to oxaloacetate through a series of oxidation-reduction (redox) reactions
Draw Kreb cycle
when can Acetyle CoA be entered directly into the Krebs Cycle
Acetyl CoA formed from fatty acids (after the breakdown of lipids) and amino acids enters directly into the Krebs Cycle from other metabolic pathways
where is Oxaloacetate regenerated
regenerated in the Krebs cycle through a series of redox reactions
Describe process of regeneration of oxaloacetate
Decarboxylation of citrate
Releasing 2 CO2 as waste gas
Oxidation (dehydrogenation) of citrate
Releasing H atoms that reduce coenzymes NAD and FAD
These will be used during oxidative phosphorylation
3 NAD and 1 FAD → 3NADH + H+ and 1 FADH2
Substrate linked phosphorylation
A phosphate is transferred from one of the intermediates to ADP, forming 1 ATP to supply energy
why are two cycle required per glucose molecule during the regeneration of oxaloacetate
Because two acetyl-CoA molecules are produced from each glucose molecule
Therefore, at the end of two cycles, the products are:
Two ATP
Six NADH (reduced NAD)
Two FADH2 (reduced FAD)
Four CO2
where does oxidative phosphorylation occur and what does it produce
it takes place at the inner mitochondrial membrane
It results in the production of many molecules of ATP and the production of water from oxygen
explain the chemiosmotic theory of oxidative phosphorylation
energy from electrons is passed through a chain of proteins in the membrane, known as the electron transport chain
This energy is used to pump protons (hydrogen ions) against their concentration gradient into the intermembrane space
The protons are then allowed to flow by facilitated diffusion through a channel enzyme called ATP synthase into the matrix
The energy of the protons flowing down their concentration gradient resulting in the phosphorylation of ADP into ATP by ATP synthase
where are hydrogen atoms donated from and what do the hydrogen atoms do (outline of oxidative phosphorylation)
by reduced NAD (NADH) and reduced FAD (FADH2) from the Krebs Cycle
Hydrogen atoms split into protons (H+ ions) and electrons
The high energy electrons enter the electron transport chain and release energy as they move through the electron transport chain
The energy released is used to transport protons across the inner mitochondrial membrane from the matrix into the intermembrane space
A concentration gradient of protons is established between the intermembrane space and the matrix
The protons return to the matrix via facilitated diffusion through the channel enzyme ATP synthase
The movement of protons down their concentration gradient provides energy for ATP synthesis
Oxygen acts as the ‘final electron acceptor’ and combines with protons and electrons at the end of the electron transport chain to form water
structure of electron transport chain
a series of membrane proteins/ electron carriers
They are positioned close together which allows the electrons to pass from carrier to carrier
The inner membrane of the mitochondria is impermeable to hydrogen ions so these electron carriers are required to pump the protons across the membrane to establish the concentration gradient
what does oxidative phosphorylation use energy for from the reduced NAD and FAD
Oxidative phosphorylation uses energy from reduced NAD and FAD to produce ATP
3 ATP molecules for every reduced NAD molecule
2 ATP molecules for every reduced FAD molecule
how many ATP molecules produced during aerobic respiration for every molecule of glucose
38 ATP molecules
why is oxygen important for aerobic respiration
Oxygen acts as the final electron acceptor. Without oxygen the electron transport chain cannot continue as the electrons have nowhere to go. Without oxygen accepting the electrons (and hydrogen ions) the reduced coenzymes NADH and FADH2 cannot be oxidised to regenerate NAD and FAD, so they can’t be used in further hydrogen transport.
method for investigating the rate of respiration
Measure oxygen consumption: set up the respirometer and run the experiment with both tubes for a set amount of time (e.g. 30 minutes)
As the seeds consume oxygen, the volume of air in the test tube will decrease (CO2 produced during respiration is absorbed by soda lime or KOH)
This reduces the pressure in the capillary tube and manometer fluid will move towards the test tube containing the seeds
Measure the distance moved by the liquid in a given time
Use this measurement to calculate the change in gas volume within a given time
Reset the apparatus: Allow air to re-enter the tubes via the screw cap and reset the manometer fluid using the syringe
Repeat experiment several times and calculate the average volume of oxygen consumed
how can the volume of oxygen consumed be worked out
The diameter of the capillary tube r (cm)
The distance moved by the manometer fluid h (cm) in a minute using the formula
πr2h
consequences of not enough oxygen available for respiration
There is no final acceptor (oxygen) of electrons from the electron transport chain
The electron transport chain stops functioning
No more ATP is produced via oxidative phosphorylation
Reduced NAD and FAD aren’t oxidised by an electron carrier
No oxidised NAD and FAD are available for dehydrogenation in the Krebs cycle
The Krebs cycle stops
The link reaction also stops
what are the anaerobic pathways
Some cells are able to oxidise the reduced NAD produced during glycolysis so it can be used for further hydrogen transport
This means that glycolysis can continue and small amounts of ATP are still produced
Certain types of micro-organisms and mammalian muscle cells use lactate fermentation
explain lactate fermentation
In this pathway reduced NAD
transfers hydrogen to pyruvate to form lactate
NAD can now be reused in glycolysis
Pyruvate is reduced to lactate by enzyme lactate dehydrogenase
Pyruvate is the hydrogen acceptor
The final product lactate can be further metabolised
A small amount of ATP is produced
what two things happen after lactate is produced
It can be oxidised back to pyruvate which is then channelled into the Krebs cycle for ATP production
It can be converted into glucose by the liver cells for use during respiration or for storage (in the form of glycogen)
why do animals breathe deeper and faster after exercise
The oxidation of lactate back to pyruvate needs extra oxygen
This extra oxygen is referred to as an oxygen debt
why is ATP used in the start of glycolysis
to make glucose more reactive and reduce activation energy
importance of outer mitochondrial membrane being impermeable to hydrogen ions
to stop H* diffusing out (of mitochondrion) / into cytoplasm (1)
* (therefore) maintaining a high concentration (of H* in the intermembrane space (1)
so {hydrogen ions / protons / H*) can move down (concentration / electrochemical gradient (1)
* (by) chemiosmosis (1)
* to synthesise ATP (1)
explain why some ATP is broken down during glycolysis
(because the breakdown of ATP) (donates phosphate to / phosphorylates} the glucose (1)
* (ATP) supplies energy to break down the glucose (1)
to produce (phosphorylated) 3-carbon compounds (1)
explain the role of carrier molecules in the electron transport chain
receive hydrogen from reduced NAD AND FAD
split hydrogen into electron and H+ and protons
the electrons are transferred down the electron transport chain via redox reactions
energy released is used to pump protons into the intermembrane space
why is ATP required to convert F6P to F26BP
hydrolysis of ATP (1)
provides energy for the reaction (1)
provides phosphate group for phosphorylation of
F-6-P
what is the need for reduced NAD to be oxidised in the mitochondira
so that hydrogen can be delivered to the electron transport chain (1)
to allow { ATP synthesis / chemiosmosis } (1)
to regenerate NAD (1)
