Respiration - Finished Flashcards
Why do organisms respire?
To provide energy for their cells
What is respiration?
The process by which ATP is synthesised using energy from glucose and other organic molecules
What are the four main stages of respiration?
Glycolysis
Link Reaction
Krebs Cycle
Electron Transport Chain
Where does Glycolysis take place?
The cytoplasm
What happens in Glycolysis?
Glucose (6c) phosphorylated by ATP (using 2 ATP) to make hexose phosphate (6c)
Hexose phosphate splits into 2 molecules of triose phosphate (3c)
Triose Phosphate is oxidised to form 4ATP and 2 reduced NAD and 2 molecules of pyruvate
What is the NETT amount of ATP, NADH2 produced in glycolysis?
2 ATP
2 reduced NAD
Where does the Link Reaction take place?
Mitochondrial matrix
What happens in the Link Reaction?
2 molecules of Pyruvate (3c) lose a molecule of CO2 each followed by the removal of H2 by the reduction of NAD to form 2 molecules of acetate (2c)
Acetate combines with coenzyme A to form acetyl coenzyme A
What is the NETT amount of ATP and NADH2 produced in the link reaction?
0 ATP
2 reduced NAD
Where does the Krebs Cycle take place?
Mitochondrial Matrix
What happens in the Krebs Cycle?
Coenzyme A is regenerated and the acetate fragment is picked up by a 4C acceptor molecule to make a 6C molecule
The 6C molecule is reduced by NAD and loses CO2 to form a 5C molecule
The 5C molecule is reduced by NAD, loses CO2 and forms a molecule of ATP to form a 4C molecule
The 4C molecule donates a H to FAD to form reduced FAD and donates another H to NAD to form reduced NAD
What is the NETT amount of ATP, reduced NAD and reduced FAD produced in the Krebs Cycle?
Per Glucose molecule = 2ATP, 6 reduced NAD, and 2 reduced FAD
Per turn = 1ATP, 3 reduced NAD, and 1 reduced FAD
What is the removal of hydrogen called?
dehydrogenation
What is the removal of carbon called?
decarboxylation
What enzyme is used in dehydrogenation?
dehydrogenase
What enzyme is used in decarboxylation?
decarboxylase
What is the function of the Krebs cycle?
Liberates energy from Carbon bonds to provide ATP and reduced NAD and FAD
Reduced NAD and FAD act as triggers for the next stage (ETC) by delivering electrons and hydrogen
Where is the Electron transport chain?
Inner membrane of the mitochondria
What happens in the electron transport chain?
High energy electrons are donated from reduced NAD and FAD
The electrons are transferred from one proton pump to another in the inner membrane (NAD 3 pumps, FAD 2 pumps)
Someof the energy from the elctrons are used to drive the proton pumps that move the H+ from the matrix into the intermembrane space. Therefore an electrochemical gradient of H+ ions is set up
The protons flow down the electrochemical gradient through ion channels and their associated ATP synthetase back inot the matrix
THis provides enough energy to make ATP
Known as Chemiosmotic theory
At the end of the ETC, electrons combine with O2 and H= ions to form water
How much ATP is made in the electron transport chain?
Each NAD can drive 3 proton pumps 10 NAD (2 glycolysis, 2 link, 2 krebs) = 30 ATP Each FAD can drive 2 proton pumps 2 FAD (Krebs cycle) = 4 ATP = 34 ATP molecules
How many ATP molecules are made over all per glucose molecule?
38
What is Substrate Level Photophosphorylation?
ATP production in Glycolysis and Krebs
What is Oxidative Photophosphorylation?
ATP production from the electron transport chain
Not all of the enery in glucose is captured in ATP. Where does the rest go?
There is a loss of energy in the form of heat energy
What are the similarities of ATP synthesis in Mitochondria and Choroplasts?
- Involves the transport of high energy electrons
- Electrons are pased from one carrier to another located in a membrane
- The energy released from the transfer of electrons is used to pump hydrogen ions (protons) from one side of the membrane to the other
- A proton gradient is created across a membrane
- Protons diffuse down the proton gradient through stalked particles consisting of a protein channel and the enzyme ATPsynthetase
What are the differences between ATP synthesis in Mitochondria and Chloroplasts?
M: High Energy Electrons derived from reduced NAD/FAD
C: High energy electrons derived from chlorophyll A
M: Oxygen is the final electron acceptor
C: NADP is the final electron acceptor
M: 3 types of proton pump
C: 1 type of proton pump
M: Water is formed
C: Water is broken down
What are the alternatives to aerobic respiration of glucose?
anaerobic respiration of glucose
Use of alternative respiratory substrates (fats and proteins)
What happens to repiration in anaerobic conditons?
Without oxygen (the terminal electron and hydrogen acceptor of the ECT) reduced NAD and FAD cannot be reoxidised by the ETC. Therefore NAD and FAD molecules are not able to pick up more hydrogen from the krebs cycle or link reaction - so these two stages of respiration cannot take place ONLY GLYCOLYSIS CAN TAKE PLACE
How can Glycolysis take place in the absence of oxygen?
Glycolysis can take place but the reduced NAD has to be re-oxidised in a different way as it cannot donate it’s hydrogens to oxygen
This MUST happen so that the cell does not run out of NAD otherwise ATP production by glycolysis would stop
How is reduced NAD re-oxidised in animals?
The hydrogen is given to pyruvate to form lactate. This re-oxidises NAD and therefore allows glycolysis to continue
How is reduced NAD re-oxidised in yeast?
Pyruvate loses a CO2 to create Ethanal. Ethanal then accepts the hydrogen from reduced NAD creating Ethanol - This reoxidised NAD and therefore allows glycolyis to continue
How are lipids used as an alternative to glucose?
Lipids are split into Glycerol and Fatty Acids
Glycerol = Converted into a 3 carbon sugar (an intermediate in glycolysis) which is modified and then enters the krebs cycle
Fatty Acids = Split inot 2C fragments which combine woth Coenzyme A to make acetyl coenzyme A which then enters the krebs cycle
How are proteins used as an alternative to glucose?
Proteins are broken down into amino acids
Amino acids are deaminated in the liver - the amine group is removed from the rest of the amino acid
Left with an organic acid which can be fed inot the Krebs cycle
