Module 5.7 - Respiration Flashcards
Stages of glycolysis
Phosphorylation of glucose to hexose bisphosphate (2 ATP molecules hydrolysed, each phosphate group added to glucose on 1C and 6C to form hexose bisphosphate, energy released from hydrolysed ATP activates hexose sugar to prevent it being transported outside of the cell)
Splitting each hexose bisphosphate molecule into two triose phosphate molecules (each molecule of hexose bisphosphate is split into 2 3C molecules of triose phosphate)
Oxidation of triose phosphate molecules to pyruvate (dehydrogenase enzymes, aided by NAD, remove H from triose phosphate, producing 2 molecules of pyruvate, 2NAD accept H and are reduced to NADH)
4ATP produced for every 2TP molecules
Net gain of ATP in glycolysis
2 as 2 are used for splitting glucose into hexose bisphosphate
Fates of pyruvate
Actively transported into mitochondria for link reaction (aerobic conditions)
Converted into lactate (anaerobic conditions)
Converted into ethanol (anaerobic conditions)
Properties of outer membrane of mitochondria
Contains protein channels or carriers to allow pyruvate to pass through
Has a similar composition to other organelle membranes
Properties of inner membrane of mitochondria
Different membrane structure
Much less permeable to small ions than outer membrane
Folded into cristae to give large surface are
Contains electron carriers and ATP synthase enzymes
Contents of the mitochondrial matrix
Enzymes Molecules of coenzymes NAD Oxaloacetate Mitochondrial DNA Mitochondrial ribosomes
Stages of the link reaction
Pyruvate transported across mitochondrial envelope using a transport protein called the pyruvate-H+ symport
Pyruvate is decarboxylated (carboxyl group removed), which causes some CO2 production
It is also dehydrogenated (H atoms removed) to produce an acetyl group
These reactions are catalysed by a multi-enzyme complex called pyruvate dehydrogenase
The acetyl group combines with coenzyme A to become acetyl CoA
The coenzyme NAD becomes reduced
Krebs cycle stages
The acetyl group from CoA combines with oxaloacetate (4C) to form citrate (6C)
Citrate is is decarboxylated and dehydrogenated, producing a 5C molecule, one molecule of CO2 and one molecule of NADH
This is repeated to form a 4C molecule
Substrate level phosphorylation occurs between the 4C compound and coenzyme A, producing one molecule of ATP
The 4C compound is dehydrogenated, producing a new 4C compound and FADH
The new 4C compound is rearranged by an isomerase enzyme, further dehydrogenation occurs, producing one molecule of NADH and oxaloacetate
How can other molecules be respired (other than glucose)?
Fatty acids - produce acetate
Glycerol - produces pyruvate
Amino acids - deaminated or can be changed into pyruvate or acetyl CoA
How many turns of the Krebs cycle per molecule of glucose?
2
Oxidative phosphorylation stages
NADH binds to complex I
Releases H atom as H+ and e-
NADH oxidised to NAD
A total of 10H+ can be pumped from matrix to intermembrane space using energy from e- passing along the electron transport chain
FADH binds to complex II
Releases H atom as H+ and e-
FADH oxidised to FAD
A total of 6H+ can be pumped from matrix to intermembrane space using energy from e- passing along the electron transport chain
As protons accumulate in the intermembrane space, a proton gradient forms across the inner membrane
Protons diffuse down the concentration gradient by chemiosmosis through ATP synthase, causing a conformational change in the enzyme, allowing ADP and Pi to combine, forming ATP
Oxygen is the final electron acceptor, combining with electrons coming off the electron transport chain and with protons through ATP synthase, forming water
Net gain of ATP in the Krebs cycle
2 as there are 2 turns of the cycle per molecule of glucose
Net gain of ATP in oxidative phosphorylation
28
Net gain of ATP in total
32
Define chemiosmosis
The flow of protons down their concentration gradient across a membrane through a channel associated with ATP synthase
