5.2.2 Respiration Flashcards
What does ATP stand for?
Adenosine triphosphate
Why is ATP used in respiration?
- Small molecules
- Solubble
- Easily rephosphorylated
- Immediate energy source
- Released in small quantities
What is phosphorylation?
- Addition of a phosphate group to an organic molecule
What type of reaction is phosphorylation?
Condensation-reaction which requires lots of energy
Where does glycolysis take place?
In cytoplasm
What is the product of glycolysis?
- Glucose broken often into 2x3c Pyruvate
What happens in stage 1 phosphorylation in glycolysis?
- Glucose is turned into Hexose bisphosphate
- 2ATP become 2ADP + Pi
What happens in stage 2:lysis of glycolysis?
- Hexose biphosphate becomes 2x Triose phosphate
What happens in stage 3: phosphorylation and stage 4: dehydrogenation and substrate level phosphorylation in glycolysis?
- Pi is added forming Triose bisphosphate
- 2 ADP + Pi -> 2ATP
- NADox -> NADred
What is substrate level phosphorylation?
- Synthesis of ATP by transfer of a phosphate group from another molecule
Where does the link reaction take place?
- In the matrix of the mitochondria
What is the mitochondrial matrix?
- Space inside the mitochondrial membrane- Contains enzymes for Krebs cycle and link reaction
What happens during the link reaction?
- Pyruvate enters mitochondria in exchange for OH-
What are the products of the link reaction per molecule of glucose?
- 2x Acetyl COA
- 2x NADred
-2x CO2
What are the enzymes involved in the link reaction?
- Pyruvate dehydrogenase
- Pyruvate decarboxylase
Where does the Krebs cycle take place?
- Mitochondrial matrix
What occurs during the Krebs cycle?
- Acetyl COA is oxidised to oxaloacetate,yielding CO2
Why does the Krebs cycle need to be in the presence of oxygen despite not needing it directly?
- E- transport chain will not function
- Hydrogen carriers cannot offload Hydrogen
- Causes Kreb cycle to stop
What is the yield of the Krebs cycle per turn of the cycle?
- 2 Molecules CO2
- 1 ATP
- 3 NADred
- 1 FAD red
Where is most of the energy stored in the Krebs cycle?
In Hydrogen carriers such as NADox
What does Acetyl COA first turn into in the Krebs cycle?
A 6C compound called citrate and CO2
Why is the Krebs cycle cyclical?
Because the products feed into the reactants
What type of molecule are NAD and FAD besides Hydrogen carriers?
Coenzymes
What is the process of ADP + Pi -> ATP called?
Substrate level phosphorylation (NOT JUST PHOSPHORYLATION)
Where does oxidative phosphorylation take place?
Inner mitochondrial membranes
What does oxidative phosphorylation require?
- Oxygen
What is the sequence of events in the Electron Transport Chain?
- NADred and FADred delivered to electron transport chain
- H atoms split into H+ and e-
- Energy released as e- pass along chain
- Energy used to create a proton gradient between mitochondrial matrix and intermembrane space
What is chemiosmosis?
The diffusion of H+ ions from intermembrane space into mitochondrial matrix
Where does chemiosmosis occur in the electron transport chain?
- Via ion channels associated with ATP synthase
What is ATP synthase and why are its features good for the use in the electron transport chain?
- Two subunits
- Polypeptide with three binding sites- 1x to bring Pi,1x to bind Pi, 1x to release ATP
- Contains proton pores for H+ to flow through
How is water formed in relation to the electron transport chain?
Electrons and protons from the transport chain reacts with oxygen present to form H2O which creates an proton gradient so chemiosmosis can occur
What is the overall yield of ATP from respiration?
- 10 NADred = 30 ATP
- 2 FADred= 4 ATP
- 4 ATP from substrate level phosphorylation
Estimated yield= 38
Why is the estimated yield of ATP higher than the actual yield?
- Active transport into mitochondrial matrix of Pyruvate (uses ATP)
- Movement of H+ does not use all of the energy as some is released as heat
- NAD for active transport
- H+ ions leak back through membrane into matrix
Why does FAD carry less ATP than NAD?
FAD joins the electron transport chain later than NAD
What properties of the mitochondrial inner membrane allow chemiosmosis to occur?
- ATP Synthase so H= can flow through proton pores
- Impermeable to H+ ions
- Large surface area
What are two quantative changes in the intermembrane space due to oxidative phosphorylation?
- Greater positive charge of space
- Lower ph
What is the final electron acceptor of oxidative phosphorylation?
Oxygen
What is anaerobic respiration?
The release of energy in the absence of oxygen
Glycolysis used to produce ATP
Where does anaerobic respiration occur in mammals?
IN muscle tissue
What happens in anaerobic respiration in muscles?
Triose phosphate is turned into Pyruvate via an intermediate compound which forms 2x ATP and 1x NADred
Pyruvate is then dehydrogenised by lactate dehydrogenase forming Lactate, releasing energy
What occurs in anaerobic respiration in yeast?
- Glycolysis occurs as usual
- Pyruvate decarboxylated to ethanal
- Ethanal acts as H acceptor forming ethanol
What are the products of anaerobic respiration in yeast?
1x CO2
1x NADred which is oxidised again
2x ATP
What are the two enzymes involved in anaerobic respiration of yeast?
- Pyruvate decarboxylase
- Ethanol dehydrogenase
What are some alternative respiratory substrates rather than glucose?
- Glycogen- Broken down into glucose
- Triglycerides
- Fatty acids
- AMino acids
- LActate
- Ketone bodies
What is the definition of respiratory substrates?
- An organic substance that can be used for respiration
What cells can only respire glucose?
- Red blood cells
- Brain cells
What occurs during starvation?
- Proteins hydrolysed into amino acids then respired
- Some amino acids converted into Pyruvate
- ## SOme amino acids enter Krebs cycle directly
How do proteins differ from glucose in terms of respiration?
More hydrogen atoms
- Releases slightly more energy
How are triglycerides used in respiration?
- Hydrolysed to fatty acids and glycerol
Glycerol is then converted to glucose in the liver (glucoseneogenesis) - Fatty acids a=have long H chains so good source of ATP
1
