Module 5: Respiration Flashcards
Where does respiration occur in eukaryotes?
Cytoplasm and mitochondria
Where does respiration occur in prokaryotes
Cytoplasm and cell surface membranes
Where does anaerobic respiration occur?
The cytoplasm
Glycolysis: location
Cytoplasm
Link reaction: location
Matrix of mitochondria
Krebs Cycle: location
Mitochondria
Electron transport chain: location
Mitochondrial Cristae/ intermembrane space
Structure of mitochondria:
Outer membrane inner membrane Cristae intermembrane space matrix
What is the purpose of the outer membrane?
Contains transport proteins that enable the shuttling pyruvate from cytosol.
What is the purpose of the inner membrane?
Contains THE electron transport chain and ATP synthase
What is the purpose of of the cristae?
Inner membrane is arranged into folds to increase SA:VOL ratio
What is the purpose of of the Intermembrane Space:
Membranes maximise hydrogen gradient upon proton accumulation.
What is the purpose of the matrix:
Cavity contains enzymes for Krebs cycle and the link reaction
Why is respiration needed?
Plants and animals need to respire to provide chemical energy for active transport and metabolic reactions (Synthesis of molecules, transport of molecules, Cellular movement, synthesis of sugar by photosynthesis)
Growth + lots of things
What are 4 stages of aerobic respiration:
Glycolysis, Link Reaction, Krebs Cycle, the electron transport
Glycolysis: Steps
Phosphorylation - Hexose is phosphorylated by 2 ATP molecule. Reactive Hexose bisphosphate is formed.
Lysis - The hexose is split further forming two 3C sugars
Oxidation - Hydrogen is removed from the 3C sugars to reduce NAD into NADH.
ATP formation - ATP synthesised from sugar intermediates. Forming Pyruvate. Substrate Phosphorylation.
Link Reaction Stages:
Decarboxylation of pyruvate -> forms a CO2 molecule.
2C compound forms an acetyl compound via oxidation (Reducing NAD into NADH)
The acetyl compound combines with coenzyme A to form acetyl coenzyme A (Which delivers the acetyl group to the krebs cycle)
Link Reaction: What is actively transported from the cytosol into the mitochondrial matrix via carrier proteins.
Pyruvate
What stages of Respiration occur twice per glucose?
Link Reaction + Krebs Cycle + (With products formed from both halves) Electron Transport Chain.
What is the phrase that summarises the process of the link reaction?
Oxidative Decarboxylation.
How much ATP is produced during the link Reaction per glucose?
0 ATP molecules
How much ATP is produced during the Krebs Cycle per glucose:
2ATP molecules
Where does Krebs Cycle occur?
The matrix of the mitochondria
Where does Acetyl CoA transfer its acetyl group at the start of the Krebs Cycle:
To a 4C compound (oxaloacetate) to make a 6C compound.
What are the 3 types of reactions during krebs cycle?
Decarboxylation
Oxidation
Substrate level phosphorylation
Per glucose what does the krebs cycle produce?
4x CO2
2 x ATP
6 x NADH
2 x FADH
At which stage of the krebs cycle is ATP produced?
The 5C carbon intermediate is oxidised, undergoes decarboxylation and then phosphorylates ATP before undergoing further oxidisation until forming OAA (4C)
What are the different coenzymes in respiration?
NAD/H
FAD/H
Coenzyme A
Differences between NAD and FAD:
NAD is used in all stages of respiration, FAD only used in krebs cycle.
NAD accepts 1 H, FAD accepts 2H.
NAD is oxidised at the start of ETC, FAD oxidised further down ETC.
NAD produces 3 ATP, FAD produced 2 ATP.
How much NADH is produced by glycolysis for one glucose molecule?
2NADH
What is chemiosmosis?
The establishment of a proton gradient so protons diffuse through ATP synthase.
What is a general role of coenzymes in respiration?
Transport of protons and electrons between reactions.
What is the type of phosphorylation that occurs in the ETC?
Oxidative phosphorylation.
What is oxidative phosphorylation?
Hydrogen carrier molecules (FADH and NADH) are oxidised and the energy liberated from this allows for ATP to be synthesised via chemiosmosis.
Where is the ETC located?
Mitochondrial Cristae
What is the mitochondrial cristae?
The inner mitochondrial membrane arranged into folds to increase SA:VOL ratio
What accepts electrons and protons at the end of ETC?
Oxygen to form H2O (water)
What is the role of cytochrome C in the ETC:
To transfer electrons from the bc1 complex to the complex IV (4)
Where are protons actively pumped to during the ETC?
The intermembrane space.
What releases high energy electrons into the ETC?
The oxidisation of hydrogen carriers.
What type of protein actively pumps hydrogen into the intermembrane space?
Transmembrane carrier proteins.
What is the proton motive force?
The electrochemical gradient produced by the ETC.
How does oxygen maintain the electrochemical gradient at the end of the ETC?
The oxygen accepts two H+ ions from the matrix , reducing H+ accumulation in the matrix.
Why is oxygen vital for the ETC?
Oxygen removes de-energised electrons at the end of the ETC, preventing the chain from becoming blocked.
Why does aerobic respiration often not yield the maximum amount of ATP?
Some H+ does not move via ATP synthase and-so are not used to generate ATP.
Not all NADH is used in ETC, some is used for cell signalling.
Some ATP is released but is used to release heat.
Why would parasites living in the blood respire anaerobically?
- Most oxygen is bound to haemoglobin in erythrocytes, this is bound with a greater affinity than the parasites.
- The parasites would reside in the plasma with a very low oxygen supply.
Obligate Anaerobes
Cannot survive in oxygen
Facultative Anaerobes
Use both aerobic and anaerobic respiration. e.g yeast
Obligate Aerobics
- Only generate ATP in presence of O2.
- Some cells facultative.
e. g mammals
Fermentation:
Complex organic molecules are incompletely broken down into simpler inorganic compounds. This results in less ATP produced via substrate level phosphorylation.
What is the benefit of fermentation?
Survival without the presense of O2
Industrial use and production of alcohols.
Outline the effects of a lack of O2 which lead to anaerobic respiration:
Lack of O2 means there’s no electron acceptor of the ETC, therefore the ETC cannot continue. This prevents NADH and FADH from being oxidised and-so NAD and FAD cannot be regenerated. This means that no coenzymes can accept hydrogen in link reaciton and krebs cycle. This would lead to glycolysis ceasing, however it continues due to fermentation.
Where is lactate metabolised?
Liver.
Lactate fermentation in mammals:
2 pyruvate is reduced into 2 lactate in a reversible reaction where no atoms are lost. This can later be restored in the presence of oxygen.
Why is lactate fermentation useful?
The conversion of pyruvate into lactate regenerates NAD, allowing for continued glycolysis and substrate-level phosphorylation.
Why is lactate fermentation not sustainable?
Only 2ATP are produced per glucose
Alcoholic fermentation in Yeast:
Pyruvate is converted in Ethanal by Pyruvate decarboxylase, releasing two CO2. The ethanal is then reduced by NADH to form Ethanol. This regenerates NAD to allow it to continue as an electron acceptor for continued glycolysis.
What type of organic compound has the greatest energy yields?
Triglycerides.
What is a respiratory substrate?
A molecule which energy can be liberated from to synthesise ATP in a living cell. e.g Carbohydrates, lipids and proteins.
Carbohydrate hydrolysis:
Carbohydrates are hydrolysed into monosaccharides and enter glycolysis.
Triglyceride hydrolysis:
Triglycerides are hydrolysed into glycerol and fatty acids, which are able to be converted into Acetyl CoA and used in Krebs Cycle. Glycerol undergoes decarboxylation into pyruvate, which goes through the link reaction.
Protein Hydrolysis:
Proteins are hydrolysed into amino acids and can enter Krebs cycle and used in aerobic respiration.
How are fatty acids transported through the blood?
Fatty acids are bound to albumin.
What determines a respiratory substrate energy value?
The relative number of hydrogen atoms compares to carbon. More relative hydrogens leads to a greater energy value, because there are more Hydrogens to be oxidised.
Which type of respiratory substrate has the greatest energy value per mass?
Lipids
Why is glucose respired rather than higher yielding subtrates?
- Lipids take longer to be broken down and enter the Krebs cycle
- Carbohydrates contain more oxygen so require less to be oxidised.
- Carbohydrates can enter oxidisation more quickly and provide energy more rapidly.
What is the respiratory quotient?
A measure of the ratio of CO2 produced and oxygen consumed by an organism in a given time. This is used to compare different respiratory substrates.
RQ formula:
Vol. of CO2 produced / Vol. of O2 consumed
Carbohydrate RQ value:
1 -> (O2 = CO2)
Lipid RQ value:
0.7 - more oxygen is required to oxidised hydrogens.
Protein RQ value:
~0.8 - Contains oxygen but not as many as Carbohydrates.
What is the RQ value when Anaerobic respiration is occuring?
RQ >1
What is used to determine energy values of respiratory substrates?
Bomb Calorimeter.
How is the energy value of respiratory measured?
A weighed sample is places into an insulated sealed container. The sample is then burned under an oxygen atmosphere in a closed vessel, surrounded by water under controlled conditions. A thermometer is used to measure the temperature change of the water and the SHC of water is used to calculate the energy produced.
Why do proteins have a lower net energy yield?
Proteins require ATP to alter the structure of amino acids, reducing NET yield.
When are proteins used as energy sources?
When protein intake is high or if glucose and fat sources are depleted.
Explain the advantages of storing lipids as an energy resource:
Lipids have a high number of carbon-hydrogen bonds and-so have a very high energy yield.
Lipids form insoluble globules which and-so are less likely to be accidentally hydrolysed.
