Respiration Flashcards
Describe the structure of the mitochondria
Outer membrane- separates the contents of the mitochondria from the rest of the cell to create ideal conditions for respiration (compartmentalisation)
Inner membrane- contains the ETC and ATP synthase
Cristae- projections of the inner membrane to increase the surface area available for oxidative phosphorylation
Inter membrane space- where protons are pumped into to create a proton gradient
Matrix- contains essential enzymes for the link reaction and Krebs cycle and contains mitochondrial DNA
Describe the process of glycolysis
Two ATP molecules donate their Pi to a glucose, phosphorylating the glucose to form hexose bisphosphate
This splits up into 2 triose phosphate
A free Pi from the cytoplasm attaches to each triose phosphate, forming triose bisphosphate
This molecule is oxidised, by losing a hydrogen atom each, which is accepted by NAD and it turns into reduced NAD x2
Triose bisphosphate loses its 2 pi, ADP turns into ATP x4
This forms two molecules of pyruvate (3C)
What is substrate level phosphorylation and give and example
The production of ATP without the need for an electron transport chain
Glycolysis
What are the final products of glycolysis and what is their fate?
Net gain of 2 ATP
2 pyruvate- goes to link reaction
2 reduced NAD- oxidative phosphorylation
What are the sites of the different stages of aerobic respiration
Glycolysis- cytoplasm (only stage that is anaerobic)
Link reaction- mitochondrial matrix
Krebs cycle- mitochondrial matrix
Oxidative phosphorylation- cristae of the inner mitochondrial membrane
Describe oxidative decarboxylation (the link reaction)
Pyruvate molecule is actively transported from cytoplasm to mitochondrial matrix through carrier proteins
Decarboxylation- carbon dioxide removed
Oxidation of pyruvate- losing a H atom which NAD accepts to become reduced NAD
Results in a 2C acetyl group, which joins with coenzyme A forming acetyl coA
acetyl coA delivers acetyl group to Krebs cycle
Describe the Krebs cycle
2C acetate combines with 4C oxaloacetate to form 6C citrate
Citrate undergoes oxidation decarboxylation twice, to form a 4C molecule ( 2 CO2 and 2 NADH produced)
An ATP molecule produced by substrate level phosphorylation
FAD reduced to red FAD
NAD reduced to red NAD
What are the differences between NAD and FAD
NAD can produce 3 ATP molecules whereas FAD can only produce 2 ATP molecules
NAD takes part in all the stages of respiration whereas FAD only takes part in the Krebs cycle
NAD accepts one hydrogen whereas FAD accepts 2 hydrogens
What are the end products of the Krebs cycle
3 NADH
1 FADH2
1 ATP
2 Co2
Describe oxidative phosphorylation
NADH and FADH dissociate to release the hydrogen atoms that they collected
Hydrogen atoms dissociate into hydrogen ions and electrons
Electrons can enter the electron transport chain, losing energy as they move through each successive electron carrier
This energy is used to drive the active transport of hydrogen ions into the intermembrane space
This creates a proton concentration gradient, so the hydrogen ions diffuse down the electrochemical gradient, through ATP synthase
This produces ATP (ADP+ Pi= ATP)
Why is oxygen described as the final electron acceptor ?
At the end of the electron transport chain, electrons combine with hydrogen ions and oxygen to form water
What is chemiosmosis
Diffusion of protons down the electrochemical gradient through ATP synthase
What happens if there is no oxygen available
Oxygen cannot act as the final electron acceptor
Flow of electrons down the electron transport chain stops
Synthesis of ATP by chemiosmosis stops
Reduced NAD and FAD can no longer be oxidised
NAD and FAD can no longer be regenerated
Link reaction and Krebs cycle stops
Lactate fermentation
Occurs in mammals
Pyruvate— Lactate
Using a H from reduced NAD- which turns into NAD and can be used to continue glycolysis so some ATP can still be generated
Reaction catalysed by lactate dehydrogenase
Lactate can be converted into glucose in the liver- requires oxygen
Alcoholic fermentation
Occurs in plants/ yeast
Pyruvate— ethanal
Pyruvate loses a Co2 (decarboxylation)
Reaction catalysed by pyruvate decarboxylase
Ethanal— ethanol
Using a H from reduced NAD, which turns into NAD so glycolysis can continue
Irreversible process
