3.3 Respiration Releases Chemical Energy In Biological Processes Flashcards
Overall equation for aerobic respiration
Glucose + 6oxygen atoms –> 6carbon dioxide + 6water molecules + 38ATP
What is the theoretical and usual range of ATP yielded during aerobic respiration of 1 glucose molecule?
Theoretical- 38 ATP
Usual - 32-38 ATP
Name 4 stages of aerobic respiration in order
Glycolysis
Link reacion
Krebs cycle
Electron transport chain
Where does glycolysis occur?
Cytoplasm
Does glycolysis require oxygen
No
Define aerobic respiration
Release of large amounts of energy as ATP from the breakdown of molecules where oxygen acts as the terminal election acceptor
Define anaerobic respiration
Release of relatively little energy as ATP from the breakdown of molecules in the absence of oxygen by substrate level phosphorylation.
Steps during glycolysis
• glucose is phosphorylated to produce glucose diphosphate by the use of 2 ATP
• Glucose diphosphate splits to 2 triose phosphate
• each triose phosphate is dehydrogenated as 2 NADs are reduced to NADH
• 4 ATP are produced by substrate-level phosphorylation
• 2 pyruvate molecules are produced
How many C in glucose diphosphate
6
How many C in triose phosphate
3
How many C in pyruvate
3
Define dehydrogenation
the removal of hydrogen atoms, performed by dehydrogenase enzymes.
Net yield of ATP during glycolysis and how
2 ATP
•4 produced but 2 are used to phosphorylate glucose
Where does Link reaction occur
Mitochondrial matrix
What does pyruvate have to do in order so undergo link reaction
Diffuse into the mitochondria
Does link reaction require oxygen?
Yes
Steps of the Link reaction
• pyruvate diffuses into the mitochondrial matrix
• pyruvate is dehydrogenated - the hydrogen released reduced NAD
• pyruvate is decarboxylated and so carbon dioxide is removed and acetyl is produced
• Coenzyme A is added to form acetyl CoA
Why does glucose have to be broken down to pyruvate before it enters the mitochondrion?
• glucose is too big to diffuse into the mitochondrion
• mitochondrion don’t possess the enzymes needed for glycolysis
Define decarboxylation
the removal of carbon dioxide, performed by decarboxylase enzymes.
Does krebs cycle require oxygen
Yes
Describe 1 cycle of Krebs cycle
• Acetyl CoA joins to [4C] acid to produce [6C] acid
• the [6C] acid is decarboxylated releasing 1 molecule of CO2 and dehydrogenated, reducing 1 NAD molecule
• the resulting [5C] acid is decarboxylated releasing 1 molecule of CO2 and dehydrogenated, reducing 2NAD AND 1FAD molecules, ATP is produced directly by substrate level phosphorylation
• resulting [4C] acid combines with acetyl CoA and the cycle continues
Does the electron transport chain require oxygen?
Yes
Where does the Electron Transport Chain occur?
Cristae - inner membrane of mitochondrion
Describe what happens in the Electron Transport Chain
• reduced NAD carries hydrogen atoms to the Electron Transport Chain
• the NADH is then oxidised and the hydrogen atoms split into protons and electrons
• the electrons are donated to the first electron carrier in the Electron Transport Chain and the protons remain in the matrix
• the electrons provide energy for the first proton pump - this energy is used to pump protons into the inter-membrane space
• the electrons pass along the chain of carrier molecules providing energy for each pump in turn
• the protons accumulate in the inter-membrane space as the inner membrane is impermeable to protons
• the concentration of protons becomes higher in the inter-membrane space and an electrochemical gradient is built up
• stalked particles contain the enzyme ATP synthetase
• protons diffuse back into the matrix through the stalked particle and their electrical potential energy is used to create ATP
• at the end of the chain the electrons combine with the protons and oxygen to form water - oxygen is the final electron acceptor
What else can the Electron Transport Chain be referred as
Chemiosmotic theory
How does cyanide affect the Electron Transport Chain
It is a non-competitive inhibitor of the final carrier
Electrons cannot pass to the terminal electron acceptor
The electrons are no longer moving which prevents the proton pumps from functioning
ATP synthesis soon stops
Explain the role of oxygen in the electron transport chain
It acts as the final electron acceptor
Without it electrons cannot leave the last proton pump and so no electrochemical gradient is created
What is the advantage of the highly folded cristae in mitochondria?
Increases surface area for the attachment of enzymes eg ATP synthetase
Products of respiration per molecule of glucose during glycolysis
2 ATP
2 NADH
Products of respiration per molecule of glucose of link reaction
2 NADH
2 CO2
Products of respiration per molecule of glucose of krebs cycle
2 ATP
6 NADH
2 FADH
4 CO2
Products of respiration per molecule of glucose of the Electron Transport Chain
34 ATP (10 NADHx3=30 and 2FADHx2=4)
6 H2O
What respiration stages occur during anaerobic respiration?
Glycolysis
Major consequence of only glycolysis occurring during anaerobic respiration
NADH is not oxidised in the Electron Transport Chain
NAD is not regenerated and so the lack of NAD stops ATP production as dehydrogenation occurs before production of the final 4 ATPs in glycolysis
What do animals do to overcome the issues of anaerobic conditions
For a short tome they can reduce pyruvate to lactate using hydrogen from NADH which regenerates NAD
This allows glycolysis to continue
How does yeast overcome the issues of anaerobic conditions
The pyruvate is first decarboxylated to ethanal and then reduced to ethanol using hydrogen from NADH
Why cant anaerobic respiration be sustained indefinitely
Lactate and ethanol quickly build up
Toxic
What does anaerobic conditions lead to in animals
An oxygen debt which requires lactate to be oxidised later in the liver
This releases further energy
Where does lactate build up in animals and what is the consequence
Builds up in the muscles
As it is toxic it causes cramp
What does anaerobic respiration lead to in yeast
As ethanol cannot be broken down later it can accumulate and reach toxic concentrations
How much ATP is produced during anaerobic respiration
2 ATP
Energy liberated from the hydrolysis of ATP
30.6 KJ per mole
Equation for efficiency of aerobic respiration
Energy from ATP/ energy in glucose
Efficiency of aerobic conditions
(30.6x38/2880) x 100 = 40.4%
Efficiency of anaerobic conditions
(30.6x2/2880) x 100 =2.1%
Energy in 1 mol glucose
2880 kJ
When can lipids be respired?
When carbohydrate supplies are low
What happens to triglycerides when they’re respired?
Hydrolysed into glycerol and fatty acid chains
How does glycerol enter the respiratory pathway
It is converted into triose phosphate
How do the fatty acid chains enter the respiratory pathway
They are split into 2C fragments which enter the Krebs cycle as acetyl co-enzyme A
What do longer fatty acid chains have and what are the effects of this during aerobic respiration using lipids?
• more C atoms - more CO2 produced
• more H atoms - more NAD is reduced
• more H atoms - more metabolic water produced
When can proteins be metabolised?
When fats and carbohydrates are unavailable- diet is lacking them or when diet contains a high proportion of protein
What happens when proteins are broken down as an alternative respiratory substrate
The proteins are hydrolysed into their constituent amino acids
These are deaminated in the liver which forms keto acid and ammonia
Some keto acids are fed into glycolysis (pyruvate) and some others are fed into the krebs cycle
Why does NADH2 and FADH2 lead to the synthesis of different numbers of ATP molecules
NADH2 delivers hydrogen to the first proton pump whilst FADH2 to the second proton pump
More protons pass into the inter-membrane space due to NADH2 than FADH2
More H+ means more ATP can be synthesised
Describe the role of oxygen in aerobic respiration
It acts as the final electron acceptor
It maintains the flow of electrons along the Electron Transport Chain and combines with H+ to maintain the proton concentration gradient
Respiration of triglycerides produces nearly double the amount of ATP as the respiration of glucose. Suggest and explain why glucose is used in muscles as the respiratory substrate rather than triglycerides
Respiration of triglycerides requires a large number of oxygen molecules and produces a large number of CO2 molecules
The circulatory system cannot deliver oxygen or remove carbon dioxide fast enough for muscles to respire
Explain the advantages of collecting results from the whole class
Increases reliability of the mean
Increases confidence
Can help identify anomalous results
