3.5 Respiration Flashcards
ATP Summary
Nucleotide derivative
Composed of the base adenosine, pentose sugar ribose + 3 phosphate groups
Substrate-level phosphorylation
mitochondrial matrix
Oxidative phosphorylation
mitochondrial cristae
glycolysis
cytoplasm
summary of glycolysis
the splitting of the 6C glucose into two 3C pyruvates
summary of the link reaction
the 3C pyruvate enter into a series of reactions to form acetyl coenzyme A, a 2C molecule
summary of Krebs
the introduction of acetyl coenzyme A into a cycle of REDOX reactions that yield some ATP and a large quantity of reduced NAD and FAD
summary of oxidative phosphorylation
the use of the electrons associated with reduced NAD and FAD from Krebs to synthesise ATP with water produced as a by-product
detailed steps of glycolysis
Phosphorylation of glucose to glucose phosphate:
Two molecules of ATP are hydrolysed to release two phosphate groups which are added onto the glucose 6C molecule. This provides the energy to activate glucose and lowers activation energy for the following enzyme controlled reactions. Forms glucose phosphate 6C.
Splitting of glucose phosphate:
Each glucose molecule splits into two 3C Triose Phosphate molecules, each with one phosphate group
Oxidation of triose phosphate:
Hydrogen is removed from TP by dehydrogenase enzymes and is accepted by NAD, reducing the coenzyme which then carries the protons and electrons to the mitochondrial cristae for oxidative phosphorylation. This oxidises TP.
Production of ATP:
Enzyme controlled reactions convert each oxidised TP into 3C pyruvate which produces two molecules of ATP, after being regenerated from ADP.
energy yield of glycolysis
One glucose molecule produces two molecules of TP so produces four molecules of ATP and two molecules of reduced NAD + pyruvate
Overall, one glucose produces two ATP, one RNAD, and one Pyruvate
detailed steps of link reaction
Pyruvate (2 molecules) are actively transported into the mitochondrial matrix by being actively pumped across the outer and inner mitochondrial membrane.
One molecule of pyruvate is decarboxylated and dehydrogenated to become oxidised to acetate. The 2C acetate combines with coenzyme A to form acetyl coenzyme A.
The decarboxylation of 3C pyruvate releases a carbon dioxide molecule, dehydrogenation releases two hydrogens. NAD accepts released hydrogens to form reduced NAD, which is later used to form ATP.
decarboxylation
the removal of a carboxyl group from a substrate
dehydrogenation
removal of hydrogen atoms from a substrate
Pyruvate dehydrogenase complex
catalyses the decarboxylation and dehydrogenation of 3C pyruvate
why does link need to occur in the matrix
the matrix contains specific enzymes to catalyse steps of the reaction and contains molecules of NAD.
yield of link
2 reduced NAD, 0 reduced FAD, 2 carbon dioxide and 0 ATP (2 rounds.)
The reaction has to go twice because two molecules of pyruvate are produced from glycolysis
detailed steps of the Krebs cycle
The 2C acetyl group released from acetyl coenzyme A combines with a 4C molecule to produce a 6 carbon molecule (citrate)
The 6 carbon molecule loses carbon dioxide and hydrogen to form a 4 carbon molecule in a series of reactions and a single molecule of ATP produced by substrate level phosphorylation (overall loses 2 molecules of carbon dioxide and reduced NAD)
The 4C compound is dehydrogenated to produce a different 4C compound and reduced FAD
Catalysis of an isomerase enzyme causes a different arrangement of the atoms so the original 4C oxaloacetate is regenerated and one molecule of reduced NAD is produced
yield of krebs
3 reduced NAD, 1 reduced FAD, 2 ATP and 2 CO2 released from Krebs each round. 0 ATP is used in Krebs and 2 are made so net is 2.
significance of Krebs
Breaks down macromolecules into smaller ones, pyruvate is broken down into carbon dioxide molecules
Produces hydrogen atoms which are carried by NAD to the electron transfer chain and provide energy for oxidative phosphorylation which leads to the production of ATP to provide metabolic energy for the cell
Regenerates 4C molecule that combines with CoA which would otherwise accumulate
Source of immediate compounds that are used by cells in the manufacture of fatty acids, amino acids and chlorophyll
absence of oxygen on Krebs and link
All FAD and NAD will be reduced so none will be available to take up the protons produced during Krebs so enzymes will stop working
the need for hydrogen to be removed in glycolysis in anaerobic
Without hydrogen, the already limited supply of NAD in cells will be entirely converted into reduced NAD, leaving no NAD to take up hydrogen produced from glycolysis
how is NAD replenished in anaerobic respiration
reduced NAD donates hydrogen to to the pyruvate molecule formed from glycolysis
products of anaerobic in plants
ethanol and carbon dioxide
products of anaerobic in animals
lactate
production of ethanol in some microorganisms
The pyruvate formed at the end of glycolysis loses a molecule of carbon dioxide
It also accepts hydrogen from reduced NAD to form ethanol
Pyruvate + reduced NAD = CH3CH2OH + carbon dioxide + oxidised NAD
production of lactate in animals
When oxygen is in short supply, NAD from glycolysis can accumulate and needs to be removed
In order to remove NAD, each pyruvate molecule produced takes up the two hydrogen atoms donated by the reduced NAD to form lactate
Pyruvate + reduced NAD = lactate + oxidised NAD
summary of eukaryotic anaerobic respiration
The products of glycolysis are two molecules of pyruvate and 2 of reduced NAD as well as a net gain of 2 ATP.
The pyruvate molecules accept the hydrogen atoms from reduced NAD, which is catalysed by lactate dehydrogenase
Pyruvate is reduced and converted to two molecules of lactate
The reduced NAD are reoxidised so glycolysis can continue because the coenzymes can accept the hydrogen atoms released during the oxidation of triose phosphate
effect of lactate accumulating
can cause cramping and muscle fatigue. It also causes pH changes which affect enzymes due to its acidic nature. Lactate needs to be taken to the liver to be converted into glycogen after being removed by the blood.
why can krebs or electron transfer chain not occur in anaerobic respiration
Pyruvate is converted to lactate or ethanol so is not available for krebs, means neither krebs or the electron transfer chain can take place so the only source of ATP in anaerobic respiration is glycolysis
detailed steps of oxidative phosphorylation
Reduced NAD and FAD deliver their hydrogen atoms to the electron transfer chain, re oxidising the coenzymes
Hydrogen atoms split to produce protons and electrons
Protons go into solution in the mitochondrial matrix
Electrons are accepted by the first electron carrier in the electron transfer chain
Iron 3 ion accepts the electron and is reduced to iron 2
This accepted electron is donated to the next cytochrome in the chain
Energy is released when each electron is donated to the next cytochrome which is used to pump protons from the matrix across the inner mitochondrial membrane and into the intermembrane space
Protons accumulate in the intermembrane space due to reduced permeability of the inner membrane and this forms a proton gradient across the membrane
Protons diffuse through the channels by chemiosmosis and cause a conformational change to the rotator ATP synthase
ATP synthase now catalyses the synthesis of ATP
Oxygen combines with electrons off the final protein in the electron transfer chain and with protons diffusing down the channel to form water
Oxygen acts as the final electron acceptor
why do reoxidised NAD and FAD return to the matrix
The reoxidised NAD and FAD coenzymes return to the matrix where they work with dehydrogenase enzymes and accept any released protons in the link reaction or krebs cycle, this allows the reactions to continue.
why is oxygen important as the final electron acceptor
otherwise the protons and electrons would ‘back up’ along the chain and respiration would stop.
why are electrons transferred down an energy gradient
The greater the energy that is released in a single step, the more of it that is released as heat and there is less available for more useful purposes. This is why electrons are transferred down an energy gradient where each carrier is at a slightly lower energy level, because energy can be released gradually and more usefully.
define respiratory substrate
organic molecules that can be oxidised by respiration to release energy to make molecules of ATP
Respiration of lipids
Hydrolysed to glycerol + fatty acids
Glycerol phosphorylated and converted to triose phosphate for use in glycolysis and Krebs
Fatty acid broken into 2C components converted to acetyl coenzyme A which is used in Krebs
Protons produced from high ratio of hydrogen atoms form a chemiosmotic gradient across the inner mitochondrial membrane to help form ATP in oxidative phosphorylation
respiration of proteins
Deamination necessary because the amine group is toxic so the amino acid cannot be stored if in excess unless it is removed
Depending on the number of carbons they contain, they enter at different points
E.g 3C to pyruvate, 4 + 5C to intermediates in Krebs
