Reaspiration. Flashcards
Site of glycolysis
Cytosol
NAD
Nicotinamide adenine dinucleotide
Main steps in glycolysis
Phosphorylation lysis phosphorylation dehydrogenation formation of ATP
What happens in the first step of glycolysis (Phosphorylation)?
2 ATP molecules are hydrolysed to release two phosphates, both attached to a glucose molecule, forms hexose bisphosphate
What happens in the second step of glycolysis (Lysis)?
Phosphorylation destabilises the molecule, splits into two triose phosphate molecules
What happens in the third step of glycolysis (Phosphorylation)?
Inorganic phosphate group is added to a triose phosphate molecule to form two triose diphosphate molecules
What happens in the fourth step of glycolysis (Dehydrogenation and formation of ATP)?
Two triose bisphosphate molecules are oxidised by the removal of hydrogen atoms, forms two pyruvate molecules, NAD coenzymes accept the removed hydrogens and are reduced to form two reduced NAD molecules, 4 ATP molecules are produced using phosphates from the triose bisphosphate molecules
What is the kind of phosphorylation done in glycolysis?
Substrate level phosphorylation
What happens in the link reaction?
Pyruvate enters the mitochondrial matrix by active transport by carrier proteins, pyruvate is dehydrogenated and decarboxylated, hydrogen atoms given to NAD to form NADH, resulting two carbon acetyl group is bound to coenzyme A to form acetylcoenzyme A
Technical name for the removal of carbon dioxide and hydrogen from the pyruvate
Oxidative decarboxylation
Substrate level phosphorylation
When a phosphate group is transferred from one substrate to another
First step of the Krebs Cycle
Acetyl group combines with oxaloacetate to mak citrate
Second step of the Krebs Cycle
Citrate is decarboxylated and dehydrogenated, one molecule of reduced NAD and a 5 carbon compound is made
Equation for the formation of reduced NAD
NAD^+ + 2H^+ + 2e^- -> NADH + H^+
Third step of the Krebs Cycle
Alpha ketoglutarate is decarboxylated and dehydrogenated, one molecule of reduced NAD and a 4 carbon compound is made
Fourth step of the Krebs Cycle
4 carbon compound isomerised, one molecule of ATP made by substrate-level phosphorylation
Fifth step of the Krebs Cycle
4 carbon compound dehydrogenated, one molecule of FADH2 is made
Sixth step of the Krebs Cycle
4 carbon compound dehydrogenated, one molecule of NADH made, oxaloacetate regenerated
Products of the Krebs Cycle (Both cycles)
6 NADH, 2 FADH2, 2 ATP, 4CO2
Role of electron carriers in oxidative phosphorylation
To dissociate hydrogen into a proton and an electron, to pass electrons along the chain so energy is released
Role of oxygen in oxidative phosphorylation
Final electron acceptor, forms water
Equation for the formation of water in oxidative phosphorylation
O2 + 4H+ + 4e- -> 2H2O
Where does oxidative phosphorylation happen?
Inner mitochondrial membrane
Process of oxidative phosphorylation
NADH is oxidised and donates hydrogen to NADH dehydrogenase, hydrogen dissociates into a proton and an electron, electrons are passed along the electron carriers, releases energy, energy used to pump protons through the inner mitochondrial membrane, proton gradient forms, potential energy builds up, protons flow down gradient, allows ATP to form by ATP synthase
Oxidative phosphorylation
The production of ATP in the presence of oxygen
What is ATP made from in oxidative phosphorylation?
ADP and Pi
Chemiosmosis
The diffusion of protons down a concentration gradient through a partially permeable membrane
Role of the electron transport chain in chemiosmosis
The protons are actively pumped into the intermembrane space using energy released from the transport of electrons down the chain
Role of proton gradients in chemiosmosis
Protons diffuse down the proton gradients through ATP synthase in the inner mitochondrial membrane
Role of ATP synthase in chemiosmosis
Protons diffuse down the proton gradient through ATP synthase which releases the energy required to synthesise ATP
Similarity between oxidative phosphorylation and photophosphorylation
Both use ATP synthase and chemiosmosis
Fermentation
Breakdown of complex organic compounds into simpler inorganic compounds without the use of oxygen or the involvement of an electron transport chain
Type of fermentation that occurs in mammals
Lactate fermentation
Process of lactate fermentation
Pyruvate acts as an hydrogen acceptor which oxidises the NADH, catalysed by lactate dehydrogenase, pyruvate converted to lactate, NAD regenerated, used to keep glycolysis going so small amount of ATP made
What is the reason for the oxygen debt that follow exercise?
Conversion of lactic acid to glucose requires oxygen
Why can’t lactate fermentation continue indefinitely?
Reduced quantity of ATP wouldn’t be enough to maintain vital processes, accumulation of lactic acid would decrease pH which would denature proteins
Type of fermentation that yeast does
Alcoholic fermentation
Process of alcoholic fermentation
Pyruvate converted into ethanal, catalysed by pyruvate decarboxylase, ethanal can oxidise NADH, ethanal becomes ethanol, NAD can be used to continue glycolysis
Benefits of being able to respire anaerobically
Anaerobic respiration is fast, failsafe for emergency situations, allows some organisms to survive in low-oxygen environments
Why does anaerobic respiration produce a much lower yield of ATP than aerobic respiration?
Organic compounds aren’t completely broken down, small quantity of ATP is synthesised by substrate-level phosphorylation alone
How to investigate respiration rates in yeast
Yeast suspension and glucose solution sealed in a flask to ensure anaerobic conditions, carbon dioxide released, pushes coloured liquid along capillary tube, distance moved and diameter of tube can find volume of gas produced
How to use data logging to investigate respiration rates in yeast
Yeast suspension and glucose solution in a flask, covered with layer of liquid paraffin, carbon dioxide sensor in flask, links to software
Explanation for RQ value of proteins
Have to be hydrolysed and amino acids have to be deaminated which requires ATP
Explanation for RQ value of lipids
Lipids have a lot of carbon-hydrogen bonds, require a lot of oxygen to break all the bonds, relatively little carbon dioxide is released
Equation for respiratory quotient
RQ = CO2 produced/ O2 consumed
Explanation for RQ value of carbohydrates
6 molecules of O2 are used to produce 6 molecules of CO2
How to do investigations into the effect of factors on the rate of respiration
Use a respirometer
How a respirometer is set up and used
Equal masses of controls and respiring things used, potassium hydroxide used as a carbon dioxide scrubber, volume of oxygen absorbed can be measured using the distance that the coloured fluid moves down the graduated tube
Role of the outer mitochondrial membrane
To separate the contents of the mitochondrion from the rest of the cell in compartmentalisation
Role of the inner mitochondrial membrane
To be the site of oxidative phosphorylation with electron transport chains and ATP synthase
Role of the cristae
Projections of inner membrane which increase surface area available for oxidative phosphorylation
Where does the Krebs Cycle occur?
Mitochondrial matrix
Number of ATP molecules produced by aerobic respiration
38
Obligate anaerobes
Can’t survive in the presence of oxygen
Facultative anaerobes
Can switch between aerobic and anaerobic respiration
Obligate aerobes
Can only survive in the presence of oxygen
What happens to lactic acid?
Transported by the liver
How is glycerol used as a respiratory substrate?
Converted to pyruvate, produce acetyl group, enters link reaction
Coenzymes involved in cellular respiration
NAD, FAD, coenzyme A, ATP
Why may ATP be considered a coenzyme?
Links reactions, energy released as a result of actions of one enzyme is used by another enzyme
Differences between use of NADH and FADH2 in oxidative phosphorylation
FAD electrons released further along the chain, lead to the production of less ATP
Why is the net yield of ATP less than the theoretical maximum?
Some ATP used to transport pyruvate into the mitochondrial matrix, some energy released in ETC lost as heat
