Chapter 18 Respiration Flashcards
What are the 4 stages of respiration and where they take place?
Glycolysis- cytoplasm
Link Reaction- mitochondrial matrix
The Kreb’s Cycle- mitochondrial matrix
Oxidative phosphorylation- inner mitochondrial membrane
What is the purpose of glycolysis?
To generate some ATP by substrate-level phosphorylation
Breaks down molecules enough so that they are small enough to enter the mitochondria
What are the main steps of glycolysis?
Phosphorylation of glucose: 2 phosphate groups from ATP join the glucose molecule (isomerisation in between), forming a hexose-1,6-biphosphate sugar
Lysis- the hexose sugar splits into two smaller triose phosphates (DHAP and GALP)
Phosphate groups are added from free phosphates in the cytoplasm, forming two triose biphosphate molecules
Enzymes catalyse the dehydrogenation and formation of 2 ATP from each the biphosphates, forming 2 pyruvate molecules and total of 2 NADH
What is the yield from glycolysis?
2 Pyruvate molecules
Net of 2 ATP (4 ATP but 2 used in the start)
2 NADH
What is substrate level phosphorylation?
The direct exchange of phosphate, from one molecule to another, forming ATP
No electron transport chain needed
What is the process of the link reaction?
Pyruvate enters the mitochondrial matrix by active transport via carrier proteins
Undergoes oxidative decarboxylation, the removal of a CO2 and hydrogen, forming acetate (ethanoate) molecules, NADH, and CO2
Acetyl bound to coenzyme A, forming acetylCoA
What is the yield from the Link reaction?
2( 1x NADH)
2 (1 x CO2)- diffuses out
2 (1x AcetylCoA)
What is the process of the Krebs Cycle (OCR A) ?
AcetylCoA reacts with Oxaloacetate (2-oxobutanedioic acid) to form citrate
Citrate undergoes oxidative decarboxylation forming NADH and CO2 and alpha keto gluterate (5c). This is repeated forming a 4 carbon compound.
The 4 carbon compound is further modified, undergoing oxidation and forming further NADH, FADH2 and a small amount of ATP, and regenerating oxaloactetate
What is the full Citric Acid Cycle?
AcetylCoA —/ alpha ketogluterate + NADH + CO2
alpha ketogluterate + coA —/ succinylCoA + CO2 + NADH
Succinyl CoA —-/ succinate + coA, also forming ATP by substrate-level phosphorylation
Succinate —/ Fumerate + FADH2
Fumerate + Water—/Malate
Malate —-/Oxaloacetate + NADH
(Succinate, then alphabetical)
What is the net yield from the Krebs Cycle?
2(3 NADH)
2(FADH2)
2(ATP)
What is the process of oxidative phosphorylation?
NADH and FADH2 release hydrogen, which splits into protons and high energy electrons. The high energy electrons are passed to a series of carrier molecules called the electron transport chain
As the electrons pass down the chain, the redox reactions enable energy to be used to pump protons from the matrix to the intermembrane space. This establishes a proton gradient.
Protons will diffuse through the hydrophilic protein channel and enzyme ATP synthase, use the energy from the proton-motive force to synthesise ATP from ADP
The final electron acceptor is oxygen, which combines with protons to form water.
This is an example of chemiosmosis. The channels proteins are leaky so this is not 100% efficient
What is the theoretical yield for aerobic respiration for bacteria and multicellular organisms? Why?
38 for bacteria
36 for multicellular organisms, as some ATP used through the movement of molecules within the cell
What is the actual yield of aerobic respiration for multicellular organisms?
30 ATP
1) The membranes of the mitochondrial membrane are leaky, and some protons move back in from the intermembrane space to the matrix, decreasing the proton gradient
2) ATP is needed to actively transport pyruvate into the matrix
3) ATP is needed to actively transport NADH (from glycolysis) to the mitochondrial membrane
How many protons/electrons are donated by NADH/FADH2? How much ATP is generated per molecule?
NADH- 2 electrons, 1 Hydrogen, 3ATP
FADH2- 2 electrons, 2 Hydrogens, 2 ATP
Why is the yield of ATP higher for NADH than FADH2?
NADH delivers its high energy electrons at an earlier stage of the electron transport chain
This results in greater chemiosmosis , more ATP
What are the 3 types of classification for respiring eukaryotic organisms?
Obligate anaerobes- cannot survive in the presence of oxygen
Facultative anaerobes- can use O2 for aerobic but also anaerobic
Obligate aerobes- require oxygen to respire
What is the process of anaerobic respiration in humans?
Glycolysis as normal, producing 2 pyruvate and 2 NADH
But for the process to repeat, the NADH must be oxidised
So the Hydrogens from NADH are transferred to the pyruvate, forming lactic acid and NAD
Catalysed by the enzyme lactate dehydrogenase
What happens to lactic acid? Why is lactic acid toxic?
Travels in the blood to the liver
Lactate dehydrogenase also catalyses lactate to pyruvate, when can enter the Krebs Cycle
Or recycled into glucose and glycogen
Weak acid- alter the pH and cause enzymes to function incorrectly if it builds up
What is the process of anaerobic respiration in yeast and plants?
Glycolysis
Enzyme pyruvate decarboxylase catalyses the formation of ethanal from pyruvate (oxidative decarboxylation)
Ethanal accepts H from NADH, forming ethanol and NAD
Ethanal is toxic so can kill yeast if it builds up
What are the benefits and cons of anaerobic respiration?
Anaerobic- as glucose only partially broken down, more glycolysis per minute, and yield of ATP large
But it does not fully break down glucose, so per glucose molecule, yield 1/15th of aerobic
What is a respiratory substance?
An organic substance that can be oxidised by respiration to release energy to make ATP
Rank biomolecules in order the most ATP production? Why is this?
Lipids>proteins>carbohydrates
Based on number of C-Hs present, more protons for chemiosmosis
What is RQ?
moles CO2 / moles O2
If =1 carbohydrates
Smaller the better
If greater than one, anaerobic respiration
Often a mix, respiring more than one
What do plants produce when they respire anaerobically?
Ethanol and Carbon dioxide