respiration Flashcards
What is the equation for aerobic respiration
C6H12O6 +6O2 -> 6Co2+ 6H2O
How many ATP doe aerobic respiration theoretically produce
- 38
- range of 32-38 is accepted
Who performs aerobic respiration
obligate aerobes
Give examples of faculatative anaerobes
bacteria and yeast
aerobic respiration
- release large amounts of energy as ATP from the breakdown of molecules where oxygen acts as the terminal electron acceptor
Anaerobic respiration
release of relativley little energy as ATP from the breakdown of molecules in the absence of oxygen by substrate level phosphorylation
Dehydrogenation
removal of hydrogen atoms performed by dehydrogenase enzymes
Where does glycolysis occur
cytoplasm
Does glycolysis require oxygen
no
Describe the steps of glycolysis
- glucose is phosphorylated to produce glucose diphosphate
- this makes glucose more reaction (by lowering the activation energy of the reaction involved) making it easer to split into triose phosphate
- 2NADs are reduced to NADH when triose phosphate is dehydrogenated
- 4 ATP are produced by substrate level phophorylation and pyruvate is produced
- 2ATP are used to phophorylate glucose the net gain is 2 ATP
What happens after glycolysis if oxygen is available
- pyruvate moves to the link reaction and its products move onto the krebs cycle where more NAD is reduced and some ATP is produced directly
Descarboxylation
the removal of carbon dioxide performed by decarboxylase enzymes
Where does the link reaction occur and what does pyruvate have to do
mitcochondiral matrix
so pyruvate has to diffuse into the mitochondria
Does the link reaction require oxygen
yes
How many times does the link reaction occur per glucose molecule
- twice as there are two molecules of pyruvate
Describe the steps for the link reaction
- pyruvate diffuses into the mitochondrial matrix where it is dehydrogenated and the hydrogen released reduces NAD]pyruvate is decarboxylted producing acetyl
- coenzyme A (CoA) is added to form acetyl CoA which enters the Krebs cycle
Where does the krebs cycle occur
- mitochondirl matric
Does the krebs cycle require oxygen
yes
How many times does the krebs cycle occur
- happens twice per glucose molecule (as there are two molecules of acetyl CoA )
Describe the steps of the krebs cycle
- acetyl CoA joins a [4C] acid to produce a [6C] acid
- [6C] acid is decarboxylated releasing 1 molecules of CO2 and dehydrogeated reducing 1 NAD molecule
- the resulting [5C] acid is decarboxylated releasing 1 molecules of CO2 and dehydrogenated reducing 2 NAD and 1 FAD molecules
- ATP is produced directly by substrate level phosphorylation
- the resulting [4C] acid combines with acetyl CoA and the cycle repeats
Does the electron transport chain require oxygen
yes - terminal electron acceptor
Where does the electron transport chain occur
inner membrane of the mitochondira (cristae)
Describe the steps of the electron transport chain
- NADH joins the first proton pump and is dehydrogenated releasing the hydrogen atoms which split into protons and electrons
- the protons are pumped across the membrane using energy from high energy electrons as the electrons pass to the next proton pump
- as electrons pass the second proton pump they provide energy to pump a further pair of protons from the matrix to the inter membrane space
- the electrons pass the third proton pump a further two protons are pumped across creating a proton gradient
- as the electrons pass to the terminal electron acceptor (oxygen) two protons pass back into the matrix through the stalked particles (ATP synthetase) doesn the proton gradient phosphorylating ADP into ATP
- proton movement here is referred to as chemiosmosi
- water is formed from 2H+, 2e- and 1/2O2
- NADH uses three proton pumps so generates 3 ATP
- FADH joines the second proton pump so only generates 2 ATP
What are the products of glycolysis
2ATP
2NADH
What are the products of the link reaction
2NADH
2CO2
What are the products of the krebs cycle
- 2ATP
- 6NADH
- 2FADH
- 4CO2
What are the products of the electron transport chain
34 ATP
6 H2O
When does anaerobic respiration occur
- occurs in organisms where oxygen is absent
What steps occurs in anaerobic respiration
- glycolysis
- lack of oxygen prevents the link reaction, krebs cycle and the electron transport chain from occurring
What is the consequence of oxygen not being present form repsiration
- NADH is not oxidised in the electron transport chain so NAD is not generates
- as dehydrogenation occurs before production of the final 4 ATPs in glycolysis the lack of NAD would stop ATP production
Describe how animals overcome the lack of oxygen
- for a short time they can reuce pyruvate to lactate using hydrogen from NADH regenerating NAD allowing glycolysis to continue
describe how plant and yeast overcome the lack of oxygen
- pyruvate is first decarboxylates to ethanal and then reduced to ethanol using hydrogen from NADH
Why should anaerobic conditions occur for a short time
- lactate and ethanol build up quickly so can build up and cannot be sustained indefinitley
Can lactate be broken down further
in animals anaerobic respiration creates an oxygen debt which requires lactate to be oxidised later releasing further energy
Can ethanol be broken down further why is this a problem
no so it can accumulate to reach toxic concentrations
How many ATP can be produced from anaerobic respiration
2 ATP
Describe the effieciency of respiration
- one mole of glucose contains 2880KJ of energy
- the energy liverated from the hydrolysis of ATP = 30.6KJ per mol
- assume theoretical yield of 38 moles of ATP form a mole fo glucose
- (30.6x38)/28880 x 100 = 40.4%
Describe how lipids can be used as an alternative respiratory pathway
- can be respired when carbohydrate supplies are low
- lipids are hydolysed into glycerol which is phosphorylates and dehydrogenated to form triose phosphate which can enter glycolusis
- fatty acids are split into two carbon molecules that enter the krebs as acetly CoA
why are more CO2 and water made when fatty acids are respired
- lager numbers of carbon and hydrogen atoms
Describe how proteins can be used as a respiratory patheways and when
- metabolised when fats and carbohydrates are unavailable or when diet contains a high proportion of protein
- the excess amino acids are deaminated in the lived
- the amine group NH2 is converted to urea in the liver
- and the urea is excreted bia the kidneys as urine
- the carboxyl group that remains can be converted into a number of different krebs cycles intermediates
Why do experiments with artifical hydrogen acceptors create problems
- it is difficult to determine the end point as the time taken for colour to change is subjective
- produces a reprical graph - short time represent a high rate of repiration
What do we use to record results to improve reliability with experiments with artificial hydrogen acceptors
- using a colorimeter to measure how dark the solution is (% transmission) is a good improvement to determine the end point of a reaction
Describe the experiment with artificial hydrogen acceptors
- a number of artificial hydrogen acceptors eg methylene blue (turns colourless when reduced) or TTC (which turns red when reduced) can be used with yeast to measure the rate of respiration
- the time taken for the colour change to occur can be measured under a number of different intependent variables eg temperature or glucose concentration
