C1: Aerobic respiration Flashcards
What are the four stages of aerobic respiration
Glycolysis
Link reaction
Krebs cycle
Electron transport chain
What type of organisms carry out respiration
All living organisms
Why do all living organisms carry out respiration
To provide energy for the cells
Define aerobic respiration
The release of large amounts of energy, made available as ATP, from the breakdown of molecules, with oxygen as the final electron acceptor
Describe respiration
It is a catabolic process involving a series of enzyme-controlled reactions
Energy rich respiratory substrates (glucose or fatty acids) are broken down their high energy bonds (C-C, C-H and C-OH) are broken, and lower energy bonds are formed. The excess energy released is used to phosphorylate ADP to ATP or is lost as heat energy.
Where does glycolysis take place
Cytoplasm
Describe Glycolysis
Glucose is phosphorylated using 2ATP into hexose phosphate.
The hexose phosphate splits into two triose phosphates.
The oxidation of these triose phosphates yields 2ATP by substrate level phosphorylation. Dehydrogenation releases 2 Hydrogens, these hydrogens reduce NAD. The resulting 2x 3C pyruvates diffuse into the mitochondria.
What are the products of glycolysis
Include an equation
overall per glucose molecule
2 ATP
2 reduced NAD
2 Pyruvate
Glucose + 2 ATP + 2 NAD —-> 2 Pyruvate + 4 ATP + 2 reduced NAD
Define substrate level phosphorylation
When a phosphate group is transferred from a donor molecule to ADP which produces ATP.(glycolyis)
OR
When enough energy is released from a reaction to bind ADP to Pi (Krebs)
Define dehydrogenation
the removal of one or more hydrogen atoms from a molecule
Where does the link reaction take place
The mitochondrial matrix
Describe the link reaction
Decarboxylation of pyruvate catalysed by decarboxylase releases carbon dioxide.
Dehydrogenation catalysed by dehydrogenase releases 2 hydrogen atoms converting NAD to reduced NAD.
This forms acetate.
The addition of coenzyme A to acetate forms acetyl CoA (2C) which enters the Krebs cycle
What are the products of the link reaction
Include an equation
Actetyl Coenzyme A
CO2
reduced NAD
Pyruvate + CoA —> AcCoA + CO2 + reduced NAD
Define decarboxylation
The removal of a carboxyl group from a molecule releasing CO2
Where does the Krebs cycle take place
The mitochondrial matrix
Describe the Krebs cycle
AcCoA is added into the cycle at a 4C acid to form a 6C acid (Citric) which is decarboxylated and dehydrogenated to a 5C acid which undergoes dehydrogenation and decarboxylation again to form a 4C acid which with the addition of 2 waters is ddehydrogenated again which forms a 4C acid which is dehydrigenate again to form anothther 4C acid which has water added onto it and the cycle repeats
AcCoA combines with a 4C compound to form a 6C compound.
Decarboxylation forms a 5C compound and dehydrogenation occurs reducing NAD.
Decarboxylation forms a 4C compound and dehydrogenation to reduce NAD. There is also substrate level phosphorylation forming 1 ATP.
Dehydrogenation of this 4C compound forms reduced FAD.
Dehydrogenation again of a 4C coompound forms reduced NAD.
What are the products from one Krebs cycle
how many waters are added
2 CO2
3 Reduced NAD
reduced FAD
ATP by substrate level phosphorylation
+ 4 H2O
Where does the Electron transport chain take place
The Inner mitochondrial membrane
Define oxidative phosphorylation
The energy for making ATP comes from redox reactons and is released in the transfer of electrons along a chain of electron carrier molecules.
Describe the passage of electrons in the electron transport chain
High energy electrons from H atoms are provided by NAD and FAD to a series of electron carriers in the ETC.
The energy from the electrons are used by proton pumps.
The electrons pass along the chain of carrier molecules providing energy for each of these proton pumps.
At the end of the chain these electrons combine with H+ and oxygen to form water.
Describe the passage of protons in the electron transport chain
Protons accumulate in the inter mitochondrial space so the concentration of protons is higher than in the matrix. so this forms an electrochemical gradient which is maintained by the proton pumps. Protons diffuse back into the mitochondrial matrix via the enzyme ATP synthetase and their electrical potential energy provides suffiecient energy to phosphorylate ADP to ATP
At the end of the chain protons combine with H+ and oxygen to form water.
Describe the difference between reduced NAD and reduced FAD
reduced NAD utilises 3 proton pumps
whereas reduced FAD utilises 2 proton pumps
so eventually 3 ATP are formed per reduced NAD
and 2 ATP are produced per reduced FAD
Name alternative respiratory substrates other than glucose
Lipids:
Glycerol can be converted into triose phosphate for use in glycolysis
Fatty acids are split into 2C acetate fragments which feed into the krebs cycle as AcCoA
Proteins:
Amino acids are deaminated in the liver into urea and different acids, one of which is pyruvate that is used in the link reaction the others are fed into the krebs cycle as different stages.
Use equations to describe the phosphorylation of glycerol
Glycerol + ATP –> glycerol-3-phosphate + ADP + Pi
Glycerol-3-phosphate + NAD —–> reduced NAD + triose phosphate
Why do Organisms respire Fat
More C atoms so more CO2 produced. Muscles have a limited blood supply therefore eventually more CO2 will be produved than can be removed. So they respire glucose
Longer chain lipids have more H atoms, so more NAD and FAD are reduced resulting in moe ATP being produced by oxidative phosphorylation.
More H produced so more metabollic water formed = good for desert animals so they respire fat
What tissues respire fat
Tissues with a rich blood supply Eg: The liver respires fat
When are lipids and proteins used as repsiratory substrates ?
Lipids: when carbohydrate levels within the body are low ( glycogen and blood glucose)
proteins: when carbohydrate and fat are lacking in the diet tissue protein is broken down
In aerobic respiration what is the theoretical maximium yield for ATP
per glucose
Total: 38 ATP per glucose
Net 2 ATPs in glycolysis (substrate-level phosphorylation)
2 ATPs in the Krebs cycle (substrate-level phosphorylation)
34 ATPs from oxidative phosphorylation as 10 reduced NAD (2 from glycolysis, two from the link reaction, six from the Krebs cycle) forms 30 ATP and 2 reduced FAD (Krebs cycle) forms 4 ATP
Why is the maximum yield never quite reached
proton leakage across the inner ‘impermeable’ membrane ( It doesnt pass through ATP synthestase)
ATP is used to move pyruvate, reduced NAD, reduced FAD and ADP into the matrix
Molecules may leak through membranes
