Module 5 Flashcards
Why phosphorylate?
- Changes the glucose molecule so it is unable to leave the cell through glucose transporters in the cell membrane.
- Maintains the glucose concentration gradient for diffusion of glucose out of the blood and into the cell, as it doesnt affect the glucose concentration
- Takes the glucose to a higher energy level. This makes it unstable and therefore more reactive, so it is easier to split.
Why is the mitochondria the location of respiration?
cristae have large SA for oxidative phosphorylation
matrix as has enzymes needed for krebs cycle and link reaction
outer mitochondrial membrane seperates contents from rest of cell and creates cellular compartment for conditions ideal for aerobic respiration
inner mitochondrial membrane contains electron transport chains and ATP synthase
intermembrane space has protons pumped into it. small space so concentration builds up quickly
Anabolic
Catabolic
- Building larger molecules from smaller molecules (using energy – endergonic).
- Breakdown of larger molecules to smaller molecules (releasing energy – exergonic).
Metabolic pathway
Metabolites/ intermediates
Metabolism
- A sequence of metabolic reactions.
- The individual molecules in the pathway.
- The net result of anabolism and catabolism.
Glycolosis
Occurs in cytoplasm of all cells where glucose is broken down into pyruvate. Does NOT need oxygen.
Link reaction
Occurs in matrix of mitochondria. Pyruvate is dehydrogenated (hydrogen removed) and decarboxylated (carboxyl removed) and converted to acetate.
Krebs cycle
Occurs in the matrix of mitochondria. Acetate is decarboxylated and dehydrogenated.
Oxidative phosphorylation
Occurs on the folded inner membrane (cristae) of mitochondria. This is where ADP is phosphorylated to ATP.
What is CoA made of and what is its function?
- Made from pantothenic acid (B-group vitamin), adenosine (ribose + adenine), 3 phosphate groups and cysteine.
- CoA carries the acetate (ethanoate) groups made in the link reaction into the Krebs Cycle.
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What is NAD?
What is is made of?
What does it do?
- Organic, non-protein coenzyme called nicotinamide adenine dinucleotide (NAD)
- Made of 2 linked nucleotides.
- Made in the body from nicotinamide (Vitamin B3), 2 ribose, adenine and 2 phosphate groups.
- It is the nicotinamide ring that can accept hydrogen atoms.
- When NAD accepts two hydrogen atoms it is known as reduced NAD.
- The reduced NAD transports the hydrogen to the inner mitochondrial membrane, where it will be used to generate more ATP in the electron transport chain.
- Once it has dropped off the hydrogen in the mitochondrion the NAD is in its oxidised form again and free to accept more hydrogen
Why does reduced NAD and FAD actually contribute less ATP?
- Some of the ATP produced is used to actively transport pyruvate from the cytoplasm of the cell into the matrix of the mitochondrion.
- Some ATP is used to bring reduced NAD from glycolysis in the cytoplasm into the mitochondrion.
- Some energy is used to transport ADP from the cytoplasm into the mitochondrion.
- Some H+ ions leak back across the mitochondrial membrane reducing the proton motive force that generates ATP.
Electron transport chain stages
- Reduced NAD delivers 2 hydrogen atoms to Complex I. These atoms split into 2H+ ions and 2e-. The electrons are passed on to Complex II and this process releases enough energy to pump the H+ ions against their concentration gradient from the matrix into the intermembrane space of the mitochondrion.
- The electrons from NAD continue from Complex II to Complex III. The energy released at this stage is NOT enough to pump H+ ions from the matrix into the intermembrane space.
- Reduced FAD from the Krebs Cycle drops off 2H atoms directly to Complex II (bypassing Complex I). Again, these hydrogen atoms split into 2H+ and 2e-. The electrons are passed onto Complex III but the H+ ions remain in the matrix due to lack of energy for pumping at this stage.
- The four electrons (the 2 from the NAD and the 2 from the FAD) pass from Complex III to Complex IV. The energy released is enough to pump H+ions from the matrix into the intermembrane space.
- The 4 electrons move from Complex IV into the matrix where they combine with 4H+ ions and O2 to form H20. The energy released at this stage IS enough to pump H+ ions into the intermembrane space.
Chemiosmosis
- The pumping of H+ ions into the intermembrane space generates a electrochemical gradient and a proton (pH) gradient. This generates a proton motive force that should lead to the diffusion of H+ ions back into the matrix.
- However, the membrane is relatively impermeable to H+ ions, and the only way they can return to the matrix is through the ATPsynthase enzyme complex.
- As the H+ moves through this complex it catalyses the formation of ATP from ADP and Pi.
- It is this stage that is known as oxidative phosphorylation. You are phosphorylating the ADP to form ATP by using oxygen as the final electron acceptor (gets reduced) of the electron transport chain to form water
Respiratory substrates definition
- A respiratory substrate is an organic molecule that may be used in respiration to release energy.
- Different substrates release different amounts of energy when respired.
Glucose as a repsiratory substrate
- Glucose is the main respiratory substrate (the brain can only use glucose).
- starch and glycogen can be broken down into glucose and other carbs can be changed to glucose by isomerisation
- carbs release 16 energy KJ g-1
Protein as a respiratory substrate
- When starving, protein can also be used.
- Protein is hydrolysed to amino acids.
- It can be converted to pyruvate, acetate or enter the Krebs cycle directly.
- 17 KJg-1 energy
- There is a little more energy released as the number of hydrogen atoms accepted by NAD per aa is slightly more than for a molecule of glucose
Lipids as respiratory substrates
- Lipids are an important respiratory substrate (especially for muscles).
- They are first hydrolysed to glycerol and fatty acids.
- Glycerol can be converted to glucose and join the glycolysis pathway.
- Fatty acids combine with Acetyl Co-A used in krebs cycle. This is called the beta oxidation pathway which produces reduced NAD and reduced FAD
- 39 KJg-1 energy
- lots of ATP as lots of H atoms, so lots of reduced NAD and greater proton motive force/gradient. most ATP comes from oxidative phosphorylation in repsiration
- Also use more oxygen to respire as produce more water
How much energy is needed to produce 1 molecule of ATP?
30.6KJ
lots of energy is lost as heat instead of producing ATP
What is the equation for respiratory quotients?
How do you get the values?
what are the values for carbohydrates, lipids and proteins?
Co2 released/ 02 uptake
using a respirometer
carbs: 1 (6CO2 molecules required to completely repire 1 molecule of glucose producing 6CO2)
proteins: 0.9
lipids: 0.7
What values do aerobic, anaerobic and combination respiration produce?
normally 0.8-9 showing a mixture of respiratory substrates used
a combination of anaerobic and aerobic produces a RQ greater than 1 but its hard to tell when anaerobic starts
purely anaerobic has a infinity
only aerobic is less than 1
Explain the method for the respirometer (measures volume of oxygen used in living organisms)
1. carefully weigh out 5g of soda lime pellets (absorb co2 so o2 taken up can decrease the volume and cause dye to be drawn up equivalent to volume of O2 used) and add to tube A and B
- fill the wire basket for tube A with 5g of maggots and place into tube A, being careful the maggots dont touch the soda lime pellets as they are very corrosive
- fill the wire basket for tube B with 5g glass beads and place into tube B. This is as a control with the same mass/vol as the maggots so that any external factors affecting 1 side will affect the other the same without respiring. dead maggots would be better. increase in temperature would would increase gas volume but will happen in both tubes no overall effect- valid measurements
- the repirometer U-tube has already been filled with manometer fluid. connect the respirometer to the two tubes making sure the 3 way taps are both turned to the upward position so the equiptment is open to the atmosphere while setting up the experiment
- turn both taps to the downward position and note the position of the manometer fluid and start the timer
- after 10 minutes record the distance the manometer fluid has moved. use formula to see how many cm3 1 division is
- calculate volume of oxygen comsumed in min-1g-1 for the maggots- pier2
beaker of water can control temperature but not all equiptment in water
syringe for repeats
What happens to the lactate formed in anaerobic respiration?
- carried away in the blood to the liver
- when more oxygen is avaliable the lactate is converted back to pyruvate to enter the kerbs cycle or its recycled back into glucose and glycogen
- muscle fatigue is not caused by a build up of lactic acid but actually the reduction in pH from lactate dissociating into lactic acid that reduces enzyme activity in the muscle cells
- reduces amount of ATP cannot mainatin vital processes for a long period of time, as only 2 ATP from glycolysis
Facultative anaerobe
Obligate anaerobes
Obligate aerobes
- can live without oxygen, but uses it when is present eg. yeast
- cant survive in the presence of oxygen
- need oxygen eg mammals as O2 is eventually required and products of anaerobic need to be broken down by O2
Why can anaerobic respiration occur in yeast?
How is yeast grown for alcohol?
The enzyme pyruvate decarboxylase is only in yeast
Yeast grows faster in aerobic conditions so in the brewing industry the yeast is first grown with oxygen then grown under anaerobic conditions for alcoholic fermentation to take place
















