9 Cellular Respiration and Fermentation Flashcards
Note:
Generally speaking, this set of cue cards will use simply ‘respiration’ to refer to ‘anaerobic respiration’
What does cellular respiration include?
Technically both aerobic and anaerobic (and excludign glycolysis) but it often just refers to aerobic.
What is reduction?
A gain of electrons (/hydrogen)
What is oxidation?
A loss of electrons (/hydrogen)
In redox reactions what do electrons typically travel with?
Protons i.e to form a hydrogen atom
How is energy from ATP carried?
By electron carriers
What electron carrier is typically used in respiration and why?
NAD+ because it can easily cycle between its oxidised (NADH) and reduced (NAD+ states)
What class of chemical is NAD+?
A coenzyme.
What does NAD stand for in NAD+?
nicotinamide adenin dinucleotide
How do electron carries collect electrons?
Enzymes called dehydrogenases remove two hydrogen atoms (2 electrons and 2 protons) from glucose etc. and thereby oxidise it.
One proton is released as H+. This leaves the electron carrier with an extra hydrogen (NAD–>NADH) and an electron which cancel the charge.
Why are electron carriers important?
They allow a controlled release in energy from glucose, not a brief explosion where little energy could be collected.
What is the highest energy form of NAD?
NADH
What are the stages of respiration?
Glycolysis, pyruvate oxidation & citric acid cycle and oxidative phosphorylation.
Where does glycolysis occur?
In the cytosol.
By what basic ways is ATP synthesised?
Oxidative phosphroylation and substrate-level phosphorylation.
What is oxidative phosphorylation?
The regeneration of ATP using the energy of an electron transport chain.
Note that it uses inorganic phosphates from the use of ATP.
What is substrate level phosphorylation?
The regeneration of ATP through the transfer of a phosphate molecule from a substrate to an ADP molecule.
What phases can glycolysis be divided into?
Energy investement phase and energy payoff phase
What is the net gain of ATP thorugh the glycolysis of one glucose molecule?
2 ATP
Per glucose molecule, how much ATP is used during the energy investement phase of glycolysis?
2 ATP molecules
Per glucose molecule, how much ATP is yielded during the energy payoff phase of glycolysis?
4 ATP molecules (net of 2)
In order, what are the substrates of the energy investement phase of glycolysis?
Glucose, Glucose 6-phosphate, Fructose 6-phosphate, Fructose 1,6-bisphosphate and Dihydroxyacetone/Glyceraldehyde 3-phosphate.
In order, what are the enzymes of the energy investement phase of glycolysis?
Hexokinase, Phosphoglucoisomerase, Phosphofructokinase, Aldolase and Isomerase
How many stages are there of the energy investement phase of glycolysis?
5.
What is Step 1 of Glycolysis?
ATP is added to Glucose by Hexokinase, turning it into Glucose 6-phosphate.
What is Step 2 of Glycolysis?
Phosphoglucoisomerase converts Glucose 6-phosphate to its isomer Fructose 6-phosphate.
What is Step 3 of Glycolysis?
Fructose 6-phosphate is converted to Fructose 1,6-biphosphate using phosphofructokinase and ATP.
What is Step 4 of Glycolysis?
Aldolase cleaves Fructose 1,6-biphosphate into two 3 carbon sugars: dihydroxyacetone and glyceraldehyde 3-phosphate.
What is Step 5 of Glycolysis?
Isomerase catalyses the conversion of Dihydroxyacetone phosphate to its isomer glyceraldehyde 3-phosphate. Which is later used to the energy payoff phase.
When does the actual sugar splitting of Glycolysis occur and what does this mean?
In the 4th step of glycolysis in which Adolase cleaves Fructose 1,6-biphosphate into dihydroxyacetone and glyceraldehyde 3-phosphate.
The significance of this is that the energy payoff stage occurs twice per glucose molecule and thus yields ATP in units of 2.
In order, what are the substrates of the energy payoff phase of glycolysis?
Glyceraldehyde 3-phosphate → 1,3-Biphosphoglycerate → 3-Phosphoglycerate → 2-Phosphoglycerate → Phosphoenol pyruvate (PEP) → Pyruvate
In order, what are the enzymes of the energy payoff phase of glycolysis?
Triose phosphate dehydrogenase, Phosphoglycerokinase, Phosphoglyceromutase, Enolase, Pyruvate kinase
How many steps are there of glycolysis?
10
At what step does the energy payoff phase of glycolysis begin?
Step 6
What is Step 6 of Glycolysis?
Triosephosphatedehydrogenase oxides the Glyeraldehyde 3-phosphate by transfering electrons from it to NAD+, forming 2 molecules of NADH (per. gluc.)
The energy release from this reaction is used to add a phosphate to the substrate, formign 1,3 biphosphoglycerate
What is Step 7 of Glycolysis?
Phosphoglycerokinase removes a phosphate group from 1,3-biphosphoglycerate, yielding 3-phosphoglycerate and 2 ATP (per. gluc.)
What is step 8 of glycolysis?
Phosphoglyceromutase converts 3-phosphoglycerate to its isomer 2-phosphoglycerate.
What is Step 9 of Glycolysis?
Enolase converts 2-phosphoglycerate to Phosphoenol pyruvate (PEP) and H2O
During what phase of respiration is water formed?
Glycolysis (step 9: 2-phosphoglycerate to phospoenol-pyruvate(PEP) and water) and Oxidative phosphorylation
What is Step 10 of Glycolysis?
Phophoenol-pyruvate (PEP) is converted by pyruvate kinase to pyruvate and 2 ATP (per gluc.)
What is the end product of glycolysis?
Pyruvate.
In what steps of glycolysis is ATP used?
Step 1 (Glucose → Glucose 6-phosphate) and Step 3 (Fructose 6-phosphate → Fructose 1,6-biphosphate)
In what stages of glycolysis is ATP released?
7 (1,3-Biphosphoglycerate → 3-Phosphoglycerate) and 10 (Phosphoenol-pyruvate → Pyruvate)
What stages of Glycolysis involve the addition or release of chemicals other than ATP and substrates?
Step 6 (Glyceraldehyde 3-phosphate → 1,3-Biphoglycerate uses 2NAD+ to form 2NADH + 2H+; and it uses 2 phosphate groups) and Step 9 (2-Phosphoglycerate → Phosphoenol pyruvate (PEP) and H2O)
What occurs after glycolysis?
THe oxidation of Pyruvate to Acetyl CoA
What is the net input of glycolysis?
Glucose → 2 Pyruvate + 2H2O
2 ADP → 2 ATP
2 NAD+ + 2 H+ → 2 NADH
(per gluc.)
What does S-CoA represent?
Acetyl CoA (it is often found bound to a sulphur atom)
How many stages are there of Pyruvate oxidation?
3
What occurs during Step 1 of Pyruvate oxidation?
The pyruvate is actively transported into the mitochondrion where two oxygen atoms and a carbon atom are cleaved off, forming CO2
What occurs during Step 2 of Pyruvate oxidation?
The remaining two-carbon fragment is oxidised to form acetate. This converts NAD+ → NADH + H+
What occurs during Step 3 of Pyruvate oxidation?
Coenzyme A is added to the Acetate, forming Acetyl CoA.
Per pyruvate, what are the net inputs/outputs of pyruvate oxidation?
Input:
1 pyruvate, 1 NAD+, 1 CoA
Output:
1 Acetyl CoA, 1 NADH + H+
How does pyruvate enter the mitochondrion and why?
Active transport because it is a charge molecule.
What catalyses Pyruvate oxidation?
An enzyme complex named the ‘pyruvate dehydrogenase complex’
Per Pyruvate molecule, what are the net outputs of the citric acid cycle?
1 CoA, 2 CO2, 3 NADH + 3H+, 1 ATP and 1 FADH2
Per Pyruvate molecule, what are the net inputs of the citric acid cycle?
1 NAD+, 1 ADP + 1 Pi, 1 FAD
What is the citric acid cycle also known as?
The Krebs cycle
How many steps does the citric acid cycle have?
8
What are the substrates, in order, of the citric acid cycle?
Acetyl CoA → Citrate → Isocitrate → α-Ketoglutarate → Succinyl CoaA→ Succinate → Fumarate → Malate → Oxaloacetate
What is Step 1 of the citric acid cycle?
Oxaloacetate and Acetyl CoA are combined to form citrate, with the release of CoA-SH (CoA + sulphur + hydrogen)
What is step 2 of the citric acid cycle?
Citrate is converted into its isomer Isocitrate by removing a water molecule then adding it elsewhere.
What is step 3 of the citric acid cycle?
Isocitrate is converted to α-ketoglutarate. This releases CO2 and converts NAD+ to NADH and H+.
What is step 4 of the citric acid cycle?
α-ketoglutarate is combined with the CoA-SH from Step 1 to form Succinyl CoA. This releases a CO2 and converts a NAD+ to NADH and H+.
What is step 5 of the citric acid cycle?
Succinyl CoA is converted to Succinate. This releases CoA-SH
What is step 6 of the citric acid cycle?
Succinate → Fumarate, causing FAD → FADH2
What is step 7 of the citric acid cycle?
fumarate + H2O → Malate
What is step 8 of the citric acid cycle?
malate → oxaloacetate causing NAD+ → NADH + H+
How many carbon atoms does acetyl CoA have?
2+CoA
How many carbon atoms does citrate have?
6
How many carbon atoms does isocitrate have?
6
How many carbon atoms does α-ketoglutarate have?
5
How many carbon atoms does succinyl CoA have?
4 + CoA
How many carbon atoms does succinate have?
4
How many carbon atoms does fumarate have?
4
How many carbon atoms does malate have?
4
How many carbon atoms does oxaloacetate have?
4
Per ACETYL CoA molecule, what are the net inputs and outputs of the citric acid cycle?
Input:
1 Acetyl CoA, 3 NAD+, 1 ADP + Pi, 1 FAD
Output:
1 CoA-SH, 2 CO2, 3 NADH + 3 H+, 1ATP, 1 FADH2
During which stages of the citric acid cycle is CoA-SH released?
Step 1 (Oxaltoacetate + Acetyl CoA to Citrate) and Step 5 (Succinyl CoA to succinate)
During which stages of the citric acid cycle is NAD+ turned to NADH and H+?
Step 3 (Isocitrate to a-ketoglutarate), Step 4 (a-ketoglutarate to succinyl CoA) and Step 8 (malate to oxaloacetate)
During which stages of the citric acid cycle is CO2released?
Step 3 (isocitrate ot a-ketoglutarate) and Step 4 (a-ketoglutarate to succinyl to succinate)
During which stages of the citric acid cycle is GDP + P converted to GTP?
Step 5 (succinyl CoA to succinate)
During which stages of the citric acid cycle is FAD converted to FADH2?
Step 6 (succinate to fumarate)
During which stages of the citric acid cycle is water taken in?
Step 7 (fumarate to malate)
Where is ATP generated during the citric acid cycle?
Step 5 (succinyl CoA to succinate) converts a GDP to GTP. This GTP can then be used to convert ADP to ATP.
Where are the enzymes that perform the citric acid cycle?
They are all in the mitochondrial matrix with the exception of the one which catalyses step 6 (succinate to fumarate) which is located in the mitochndrial membrane.
What occurs after glycolysis?
oxidative phosphorylation
What is oxidative phosphorylation divided into?
Electron transport chain and chemiosmosis
What is the purpose of the electron transport chain?
To convert the energy of electrons in electron carriers to chemiosmotic potential.
What is the electron transport chain broken down into?
4 protein complexes of electron carriers and 2 mobile carriers
Where does oxidative phosphorylation occur?
In the inner membrnae of the mitochondria in eukaryotes. In prokaryotes it occurs in the plasma membrane.
What is the structure of the electron transport chain in term of protein complexes?
Complex I and Complex II → Q → Complex III → Cyt c → Complex IV → oxygen
What does ‘Q’ stand for interms of the electron transport chain?
ubiquinone
What does cyt a stand for in the electron transport chain?
cytochrome a
What are many of the electron carriers in the electron transport chain?
Cytochromes.
How does hte electron transport collect energy from the electrons as they move from high energy to low energy?
As they pass through complex I, complex III (not II) and complex IV H+ ions are pumped outside the membrane as a form of potential energy.
Where does NADH enter the electron transport chain?
At complex I
Where does FADH2 enter the electron transport chain?
At complex II
What provides the electrons for the electron transport chain?
NADH and FADH2
Which electron carrier provides the most energy through the electron transport chain?
NADH as the complex II FADH2 enters does not pump H+ ions.
What is the final step of the electron transport chain and what does it cause?
The electrons are added to oxygen causing it to bond with H+ ions to form H2O
What causes a flow of electrons through the electron transport chain?
The final electron accepter (oxygen) is highly electrongeative so ‘pulls’ electrons thorugh the chain.
During the electron transport chain, where are H+ ions pumped to and where are they from?
They are pumped from the mitichondrial matrix to the intermembrane space.
Which stage of oxidative phosphorylation produces ATP?
Chemiosmosis
Describe chemiosmosis.
The pumpin of H+ ions during the electron transport chain has left a high concentration of H+ ions in the intermembrane space (or extracellular if prokaryote).
These ions then passively move back through a protein named ATP synthase causing its rotors to spin and thus providing the energy for ADP → ATP
Where does oxygen receive electrons from the electron transport chain?
In complex IV
How does ATP synthase work?
H+ molecules pass through the stator (region which supports it) and onto the rotor, causing it to spin. This spining is transferred to an internal rod which carries it to the catalytic knob where ADP → ATP
What organism can undergoe anaerboic respiration?
Only prokaryotes (note that it does not occur in humans etc.: this is fermentation)
What adaptation is needed to perform anaerobic respiration, what is an example of this?
An alternative as oxygen to act as an electronegative final electron receptor.
For example some saltmarsh bacteria use SO42- resulting in H2S instead of water (and leading to a smell)
What is the difference between anaerobic respiration and fermentation?
In anaerobic respiration an electron transport chain is still present but has a chemical other than oxygen.
Fermentation is simply glycolysis with an way of regenerating the NAD+.
After glycolysis what general step must occurs in fermentation and why is it important?
Glycolysis converts NAD+ to NADH. After glycolysis this NADH must be recycled back to NAD+ to allow glycolysis to continue.
What stage of fermentation yields ATP and how much?
Glycolysis provides 2 ATP molecules.
How much ATP does each stage of aerobic respiration provide and thus how much is yielded in total per molecule of ATP?
Glycolysis: 2
Citric acid cycle: 2
Oxidative Phosphorylation: 26 or 28
Total: 30 or 32
What forms of fermentation are there?
Alcohol fermentationa dn lactic acid fermentation
What is the process of alcohol fermentation?
Glucose-glycolysis->2 Pyruvate→2 Acetaldehyde(ethanal)+2 CO2→2 ethanol
What is the process of lactic acid fermentation?
Glucose-glycolysis-> 2 pyruvate → lactate
What organisms perform lactic acid respiration and which perform alcohol fermentation?
Alcohol: prokaryotes and yeast etc.
Lactic acid: human muscle cells etc.
What happens to the lactic acid produced by anerabically fermenting muscle cell?
Some of it lingers and causes cramps
However it is slowly brought to the liver where it is converted to pyruvate to be used for full respiration when oxygen is avaliable.
How can fats be used for respiration?
The glycerol in lipids can be converted to G3P for use in glycolysis
The fatty acids can be converted to acetyl CoA which also generates NADH and FADH2 for oxidative phosphorylation
How is the rate of cellular respiration controlled?
By feedback regulation. This occurs because ATP and citrate inhibit Phosphofructokinase from continuing glycolysis and thus decreases the rate of respiration. High AMP (adenosine monophosphate) levels stimulate this enzyme when they are formed from ATP.
What is the molecular formula of Acetyl CoA?
C23H38N7O17P3S
