Respiration Flashcards
What are the 4 stages of respiration?
Glycolysis
Link Reaction
Krebs Cycle
Electron Transport Chain
Where does glycolysis occur in the cell?
Cell cytoplasm
Which coenzyme/s are involved in glycolysis?
NAD+
What is the role of NAD+ in glycolysis?
Transferring of electrons between molecules
What are the four steps of glycolysis?
Phosphorylating glucose
Splitting phosphorylated glucose
Phosphorylation (second)
Oxidation to pyruvate
Explain the process of phosphorylation of glucose
2 ATPs hydrolysed into 2ADP + 2Pi provide the phosphates for a molecule of glucose (6C) to be converted into hexose bisphosphate (6C)
What is the point of phosphorylating glucose?
Makes it more reactive
Explain what happens in the lysis stage of glycolysis
Hexose bisphosphate is converted into two molecules of triose phosphate (3C)
What are triose phosphate molecules phosphorylated to?
Two triose bisphosphate molecules with the phosphate coming from free ions in the cytoplasm
Explain how triose bisphosphate molecules are oxidised to pyruvate
Two molecules of triose bisphosphate are oxidised to pyruvate
NAD+ ions accept the removed hydrogen ions to form r NADH
ATP is reduced by substrate level phosphorylation
Explain what substrate level phosphorylation is
The formation of ATP without he use of an electron transport chain
What is the net overall yield of ATP in glycolysis?
2 molecules of ATP
Is glycolysis aerobic or anaerobic?
Aerobic
Where does the link reaction occur?
Mitochondrial Matrix
How does pyruvate reach the mitochondrial matrix for the link reaction?
Actively transported from the cytoplasm via carrier proteins
Explain what occurs during the link reaction
Decarboxylation of pyruvate to release carbon dioxide
Pyruvate is oxidised
NAD+ into NADH
A molecule of acetyl Coenzyme A is produced
What is the name of the process of the link reaction?
Oxidative Carboxylation
Where does the NADH produced in the link reaction go?
Used in oxidative phosphorylation to synthesise ATP
What happens to the waste carbon dioxide produced in the link reaction?
Diffuse away
Removed as metabolic waste
Used as raw material in photosynthesis
Where does the Krebs Cycle take place?
The mitochondrial matrix
What two coenzymes does the Krebs Cycle involve?
NAD+ and FAD
Explain step 1 of the Krebs cycle
Acetyl CoA (2C) joins with oxaloacetate (4C) to form citrate (6C)
Explain step 2 of the Krebs cycle
Decarboxylation of citrate resulting in removal of carbon dioxide
Hydrogen removed from citrate which reduces NAD+
A five carbon compound is formed
Explain step 3 of the Krebs Cycle
Further decarboxylation and dehyradation to produce a 4 carbon compound
NAD+ is reduced to NADH
ATP produced via substrate level phosphorylation
Explain step 4 of the Krebs Cycle (regeneration)
Regeneration of oxaloacetate
FAD reduced to FADH2
NAD+ reduced to NADH
Where does oxidative phosphorylation take place?
In the cristae/inner membrane of the mitochondria
What is the role of NADH and FADH2 in respiration?
Carry H atoms to the electron transport chain where they dissociate into H+ ions and e-
Electrons are passed down electron transport chain
What type of reaction occurs in the electron transport chain?
Redox
What happens when electrons are passed down the transport chain?
Release energy
Energy is used to actively transport H+ ions into inter membrane space across inner mitochondrial membrane
Energy is released in stages in the electron transport chain. What is the advantage of this?
More efficient. Less energy is lost as heat
How is ATP synthesised in oxidative phosphorylation?
Protons accumulate in the inner membrane space creating a high concentration of protons
Protons diffuse back via ATP synthase channels
ATP is synthesised via chemiosmosis
Explain the process that occurs at the end of the electron transport chain
Oxygen acts as a terminal acceptor
Electrons combine with hydrogen ions and oxygen to form water
What is oxidative phosphorylation?
Phosphorylation of ADP to form ATP using energy released by electrons in the electron transport chain
Define the term ‘obligate anaerobes’
Organisms that cannot survive in the presence of oxygen
Define the term ‘facultative anaerobes’
Synthesis of ATP by aerobic respiration if oxygen is present, but can switch to anaerobic respiration in the absence of oxygen
Define the term ‘obligate anaerobes’
Can only synthesise oxygen in the presence of oxygen
Define the term ‘fermentation’
The process by which complex organic compounds are broken down into simpler inorganic compounds without the use of oxygen or the involvement of the electron transport chain
How is ATP produced in anaerobic respiration?
Substrate level phosphorylation
What are the two types of anaerobic respiration?
Alcoholic fermentation
Lactate fermentation
Where does alcoholic fermentation take place?
Yeast and some plant root cells
Where does lactate fermentation occur?
Animal cells
Explain the effects of a lack of oxygen on the process of respiration
No oxygen = no terminal electron acceptor in oxidative phosphorylation
Flow of electrons stop
Synthesis of ATP by chemiosmosis stops
NADH and FADH2 have nowhere for electrons to go
Oxidation of pyruvate and Krebs cycle stop
Explain the process of lactate fermentation
Pyruvate acts as a hydrogen acceptor for hydrogen from NADH
Catalysed by lactate dehydrogenase
Pyruvate converted into lactate
NAD is regenerated
How does glycolysis not stop despite lack of oxygen?
Fermentation regenerates NAD which is input into glycolysis
How is lactic acid stored in the body?
Converted to glucose in the liver
Oxygen needed for this process creating an oxygen debt
What are the two main reasons lactic acid cannot occur indefinitely?
Reduced quantity of ATP produced would not be enough to sustain vital processes for a long period of time
Accumulation of lactic acid causes a fall in pH leading to proteins denaturing. Respiratory enzymes and muscle filaments cease to function at low pH
Is lactate fermentation reversible?
Yes
Is alcoholic fermentation reversible?
No
Explain the process of alcoholic fermentation
Pyruvate converted to ethanal, catalysed by pyruvate decarboxylase
Ethanal accepts a hydrogen atom from reduced NAD forming ethanol
NAD acts as a coenzyme and glycolysis continues
How long can alcoholic fermentation last for?
Continue indefinitely
Ethanol is a toxic waste product to yeast cells and they are unable to survive if ethanol accumulates above 15%
Define respiratory substrate
Any biological molecule that can be broken down in respiration to release energy
Why does the energy each respiratory substrate release differ?
Depends on the different amounts of hydrogen in the molecules. The more hydrogen the more enzymes can be reduced to be used in the ETC
What is the name of the process of removing an amine group?
Deamination
How do proteins form respiratory substrates?
Proteins are hydrolysed to amino acids
Amino acids are deaminated in the liver
Enter respiratory pathway normally via pyruvate
How do fatty acids form respiratory substrates?
Triglycerides are hydrolysed into fatty acids and glycerol
Fatty acids form Acetyl CoA
Glycerol converted into pyruvate. Undergoes oxidative carboxylation forming acetyl. Picked up by co A to form acetyl CoA
What is the respiratory quotient a measure of?
The amount of CO2 produced in respiration relative to the levels of oxygen used in respiration
What is the purpose of the respiratory quotient?
Gives an indication of the type of respiratory substrate being produced
How is the respiratory quotient measured?
Using a respirometer
What is a normal respiratory quotient?
0.8-0.9
What levels does the respiratory quotient reach during anaerobic respiration?
Above 1
