respiration Flashcards
respiration definition
the process by which the energy in food molecules is made available to organisms to do biological work
what type of reaction is respiration
catabolic (breaking things up)
how does respiration make energy available
the energy released in respiration is used to make ATP, which releases energy when broken down, allowing small manageable amounts of energy to be released which don’t cause damage
give the equation for respiration
C6C12O6 + 6O2 <> 6CO2 + 6H2O
give the equation for the break down of ATP
ATP»_space; ADP + Pi
removing the third phosphate releases the most energy, the other phosphates are rarely removed
what does the body need ATP for
- active transport
- cell division
- DNA synthesis
- DNA replication
- vesicle movement
- metabolic reactions
- synthesis of other large molecules
where does respiration take place
cytoplasm + mitochondria
outline the structure of the mitochondria
- 2 membranes - an outer membrane and a highly folded inner membrane called the cristae
- between the outer membrane and the cristae is the inter membrane space
- within the cristae is a fluid called the matrix
- floating in the matrix is ribosomes, granules, mitochondrial DNA
1 adaptation of mitochondria
highly folded cristae has a high SA:V so lots of space for reactions to occur and energy can be produced at a faster rate
1 adaptation of cells with mitochondria
very active cells have lots of mitochondria, which is also often larger/longer
how many stages are there in respiration + what are they
4
glycolysis
link reaction
kerbs cycle
oxidative phosphorylation
why are there 4 stages to respiration
if oxidation of glucose happened in 1 step the body cells would burn as so much heat is generated
where does glycolysis occur
cytoplasm
outline the process of glycolysis
- glucose - not very reactive, so it is phosphorylated - ATP > ADP
- this forms glucose-6-phosphate, which undergoes phosphorylation again - ATP > ADP
- this forms hexose bisphosphate - can no longer be transported out of the cell
- it is very unstable so it splits into 2 3C sugars - GALP and DHAP
- these sugars are then both dephosphorylated twice - ADP > ATP - and oxidised once by the removal of H+
- this H+ goes to reduce NAD+ > NADH
- the end product is pyruvate
what is NAD
an electron carrier in mammals
what are the final products of glycolysis
2NADH + net 2 ATP + 2 pyruvate
where does the link reaction occur
mitochondrial matrix
outline the process of the link reaction
- pyruvate is decarboxylated to produce CO2 and oxidised by the removal of H+
- this H+ goes to reduce NAD+ > NADH
- this forms a 2C molecule, which is added to coenzyme A
- this forms acetyl coenzym A
remember this occurs twice per glucose molecule, as 2 pyruvate are produced in glycolysis
what is the structure of pyruvate
CH3 - [C=O] - [C=O] -[O-]
what are the final products of both runs of the link reaction
2 acetyl coA + 2 NADH + 2CO2
where does the krebs cycle occur
mitochondrial matrix
what is the main purpose of the krebs cycle
to feed electrons into stage 4 of respiration
outline the process of the krebs cycle
- acetyl coA - a 2C molecule is converted to citrate 6C by the removal of CoA
- citrate is decarboxylated to produce CO2 and oxidised by the removal of H+
- this H+ goes to reduce NAD+ > NADH
- this forms a 5C intermediate, which is decarboxylated to produce CO2, oxidised by the removal of H+, dephosphorylated - ADP > ATP - oxidised twice by the removal of H+ and then oxidised again by the removal of H+
- the H+ removed go to reduce NAD+ > NADH, reduce FAD2+ > FADH2, and reduce NAD+ > NADH
- this forms oxaloacetate 4C
- this then combines with acetate 2C to reforms citrate 6C, cycle repeats
remember for each glucose molecule the cycle runs twice
what are the final products of both runs of the krebs cycle
4CO2 + 6 NADH + 2 FADH2 + 2 ATP
tune to remember krebs cycle
DeNa DeNa A Fa Na
where does oxidative phosphorylation occur
on the inner membrane of the mitochondria
outline the process of oxidative phosphorylation
- NADH and FADH2 release electrons + H+ ions
- electrons are passed along a chain of carriers within the inner membrane of mitochondria (electron transport chain)
- H+ is pumped out of matrix into the intermembrane space, using energy from electron transport chain
- protons accumulate and build an electrochemical gradient across membrane
- the movement of H+ down proton gradient as it moves through a transmembrane protein channel provides energy for ATP synthesis - chemiosmosis
- oxygen acts as the final electron acceptor, it combines with e- from the electron transport chain to make water
how many electrons does NADH carry
2 e-
how many electrons does FADH2 carry
2 e-
why is it important that NADH and FADH2 release their electrons in oxidative phosphorylation
this regenerates NAD+ and FAD2+, allowing glycolysis to take place so the cycle to continue
chemiosmosis definition
the process by which the movement of protons/H+ down their concentration gradient releases energy which is then used for ATP synthesis
give the equation for oxygen acting as the final electron acceptor
2e- + 2H+ + 1/2O2»_space; H2O
what are the 2 types of respiration
aerobic and anaerobic respiration
anaerobic respiration definition
when respiration occurs in conditions with little to no O2
what does a lack of oxygen during respiration mean
- there is no final electron acceptor
- this means the electron transport chain stops functioning
- no more ATP is produced via oxidative phosphorylation
- NADH and FADH2 aren’t oxidised so no NAD + FAD available for glycolysis so glycolysis stops
give the equation for anaerobic respiration in mammals
C6H12O6»_space; lactic acid
outline the process of anaerobic respiration in mammals
- glucose goes through the process of glycolysis to produce 2 pyruvate
- the H+ removed during this process goes to reduce NAD+»_space; NADH
- pyruvate is then reduced by the addition of H+ by NADH and the enzyme lactate dehydrogenase to produce lactate / lactic acid
- this allows NAD+ to be regenerated for glycolysis
what is the role of pyruvate in anaerobic respiration
it acts as a hydrogen acceptor
what does the body use lactate / lactic acid for
it can be further metabolised - either sent to the liver to be converted back into pyruvate, or converted into glucose / glycogen for storage
what harmful effect does the production of lactate / lactic acid have
if it builds up, it causes pH of cytoplasm to decrease, which can impact enzyme action, causing it to decrease
it can also cause feelings of soreness or cramps during intense physical exercise
what is the ATP yield of anaerobic respiration
2 ATP
what is the ATP yield of aerobic respiration
36 ATP
which type of respiration in mammals is more efficient + why
aerobic is more efficient
- anaerobic produces just 2 ATP although it is much faster
- aerobic produces 36 ATP, and despite taking much longer it is more efficient
what is anaerobic respiration in yeast / plants referred to as
fermentation
give the equation for fermentation
C6H12O6»_space; ethanol + CO2
outline the process of fermentation
- glucose goes through the process of glycolysis to produce pyruvate
- the H+ removed during this process goes to reduce NAD+»_space; NADH
- pyruvate is then decarboxylated by enzyme pyruvate decarboxylase to produce CO2 and ethanal
- ethanal is then reduced by the addition of H+ by NADH and enzyme alcohol dehydrogenase to produce ethanol
- this allows NAD+ to be regenerated for glycolysis
what is the role of ethanal in fermentation
it acts as a hydrogen acceptor
what is ethanol used for
it cannot be further metabolised - a waste product
summary - aerobic respiration
- is O2 required
- does glycolysis occur
- ATP yield
- is glucose completely broken down
- end products
- yes O2 is required
- yes glycolysis occurs
- 36 ATP is produced
- yes glucose is completely broken down
- end products are ATP, H2O, CO2
summary - anaerobic respiration in mammals
- is O2 required
- does glycolysis occur
- ATP yield
- is glucose completely broken down
- end products
- no O2 is not required
- yes glycolysis occurs
- 2 ATP is produced
- no glucose is not completely broken down
- end products are ATP, lactate
summary - fermentation
- is O2 required
- does glycolysis occur
- ATP yield
- is glucose completely broken down
- end products
- no O2 is not required
- yes glycolysis occurs
- 2 ATP is produced
- no glucose is not completely broken down
- end products are ATP, ethanol, CO2
respiratory substrate definition
an organic substance that can be oxidised by respiration releasing energy to make ATP
give 3 examples of molecules that can be used as respiratory substrates
carbohydrates
proteins
lipids
what is the main respiratory substrate
glucose
when might other respiratory substrates be used
when glucose runs out
how can lipids act as respiratory substrates
triglycerides can be hydrolysed by lipase to give glycerol + 3 fatty acids
- glycerol can be phosphorylated to form GALP, which can then be turned into pyruvate
- fatty acids are a proton source for oxidative phosphorylation, and they can be combined with coA then broken down into acetyl coA and used in the krebs cycle
how can proteins act as respiratory substrates
proteins can be broken down into amino acids, which can then be deaminated to produce a keto acid
- keto acids can enter the krebs cycle if they have glucogenic R groups
- alternatively they can be used as pyruvate / acetyl coA if they have ketogenic R groups
why are proteins only used for respiration as a last resort, when everything else is used up
proteins / amino acids often have other essential functions elsewhere in the cell e.g. making structural or enzymatic proteins
how much energy is given by a carbohydrate molecule
15.8 kJ g-1
how much energy is given by a protein molecule
17.0 kJ g-1
how much energy is given by a lipid molecule
39.4 kJ g-1
why do respiratory substrates all have different energy values
the energy values are dependent on how many protons are made available when broken down - more available protons = more ATP produced per molecule of substance
- the protons can be used for chemiosmosis, reducing NAD/FAD, or forming H2O
why do lipids produce so much more energy in kJ g-1 than other types of respiratory substrates
fatty acids are made of long hydrocarbon chains with lots of protons, so lots of ATP can be produced per molecule
why is glucose used as the main substrate if carbohydrates gives the least amount of energy in kJ g-1
it is easily broken down
give the formula for the respiratory quotient RQ
CO2 produced / O2 used
- in moles
- RQ values are specific to different substrates
what is the RQ of glucose
approximately 1
what does it mean if RQ<1
this suggests some anaerobic respiration is taking place as CO2 produced > O2 used up
how can moles be found for working out the RQ
an equation with the substrate in question should be constructed + balanced, then the balancing numbers can be used to calculate RQ
e.g. for glucose
C6H12O6 + 6O2»_space; 6CO2 + 6H2O
ratio is 6:6 = 1:1 so RQ = 1/1 = 1
what is the RQ for proteins
0.9
what is the RQ for lipids
0.7
why is the RQ in proteins and lipids so low
it is because of the H:C ratio - more H atoms = more O2 needed to accept it
what is RQ for anaerobic respiration in mammals
it cannot be calculated as no O2 is used and no CO2 is produced
what is the RQ for fermentation
it tends towards infinity as no O2 is used but CO2 is produced
x/0 = infinity
what is a respirometer
a piece of equipment used to measure the rate of O2 consumption during respiration
outline a method to find RQ with a respirometer
- set up respirometer and run the experiment with seeds or invertebrates and soda lime in both tubes
- in the control tube should be glass beads = to the volume of the organism used
- use the manometer reading to calculate the change in gas vol in a given time - x cm3 min-1 - this is the O2 consumption
- formula for gas vol = πr^2h (cylinder vol)
- allow air to re-enter the tubes via screw caps, and reset the apparatus
- run the experiment again removing soda lime from both test tubes, the manometer reading this time will give you both O2 consumed and CO2 produced - y cm3 min-1
- the CO2 produced can be calculated with the 2 readings, x-y cm3 min-1
- if the CO2 produced = O2 consumed, the level of manometer fluid will not change and y will = 0,
what is the purpose of soda lime in a respirometer
it removes CO2 so only O2 affects movement of the fluid
what is different if seeds are being used in a respirometer instead of invertebrates
the seeds will be respiring and photosynthesising
if seeds are being used, why should soda lime not be used
this would remove CO2 and so prevent photosynthesis from occuring
if seeds are being used, what can the respirometer be used to measure
since seeds will be respiring and photosynthesising, both of these processes will affect movement of the fluid, so the rates can be compared - if the fluid doesn’t move, it suggests the rates of both are equal - compensation point
what can this method be used to investigate
the effects of different changing factors on the RQ
e.g. temp with water baths, substrate type or conc,etc
outline a method to determine the effect of temp on fermentation
- add yeast suspension to test tubes containing certain conc of glucose
- put test tubes in a temp controlled water bath for 5 mins
- add a small amount of DCPIP to test tube and immediately start stopwatch
- record time taken for solution to lose all blue colour
- repeat across a range of temperatures
how does the DCPIP experiment work
DCPIP is an electron acceptor, so can accept electrons during oxidative phosphorylation causing it to be reduced and turn colourless
faster rate of respiration = faster decolourisation of DCPIP
