C1 - Respiration Flashcards
What bonds are broken in respiration?
C-C
C-H
C-OH
And then lower energy bonds are formed.
Does ATP produce energy?
NO
It releases it when hydrolysed.
What are the 4 main stages of aerobic respiration?
Glycolysis
Link reaction
Kreb’s cycle
Electron Transport Chain
Why does glycolysis happen in the cytoplasm?
Glucose can’t pass through the mitochondrial membranes.
+
Even if it could, enzymes for its breakdown aren’t present in the mitochondria anyway.
What is the result of the phosphorylated glucose - Glucose diphosphate?
Polar = less likely to diff. out of cell.
More reactive = less activation energy is required for the enzyme-controlled reactions.
Define dehydrogenation
Removal of 1 or more H atoms from a mol.
Define carboxylation
Removal of a carboxyl group from a mol. in which CO2 is released.
What is the link reaction?
Linking glycolysis to the Kreb’s cycle:
Pyruvate diff. from cytoplasm into mitochondrial matrix.
Pyruvate is dehydrogenated + decarboxylated to form an (2C) acetyl group each.
Both are picked up by CoA to then become AcCoA (2C)
What can happen to pyruvate if O2 is present during the Kreb’s cycle?
Some of the chemical potential energy in the pyruvate can be released.
What equation can be used to summarise the link reaction?
Pyruvate + NAD + CoA —- AcCoA + red. NAD + CO2.
Where does the link reaction and Krebs cycle take place?
Mitochondrial matrix
What is the function of red. NAD + red. FAD from the Krebs cycle?
Deliver H atoms to ETC on inner mitochondrial membrane.
What are the 2 significant types of reactions in the Kreb’s cycle?
DECARBOXYLATION (happens twice). 6C acid – 5C acid – 4C acid
DEHYDROGENATION (4 times). to give 3 mol. of red. NAD + 1 mol. of red. FAD.
What happens to the acetate group from the original glucose molecule by the end of the Krebs cycle?
Entirely broken down to CO2 + H20.
What is the energy in the bonds of the glucose mol. carried by?
By e- in the H atoms in red. NAD + red. FAD.
How many times does the Krebs cycle have to turn for each glucose molecule and why??
Twice for each glucose mol.
Because each glucose mol. makes 2 mol. of pyruvate so 2 mol. of AcCoA.
How many of each products is made per glucose put through glycolysis, the link reaction + the Krebs cycle?
CO2 = 6
Red. NAD = 10
Red. FAD = 2
ATP = 4
38 ATP is produced during aerobic respiration but only 4 in glycolysis, the link reaction + the Krebs cycle from one glucose molecule. Where does the rest come from?
For every red. NAD you get 3 ATP in the E.T.C = 30 ATP
For every red. FAD you get 2 ATP in the E.T.C = 4 ATP
Where is the electron transport chain located?
Cristae in the inner mitochondrial membranes.
What are cytochromes?
Proteins conjugated to iron or copper.
These metal ions are oxidised + reduced by e- transport.
The reactions they catalyse release energy which is carried by ATP.
How are H atoms carried into the E.T.C?
By coenzymes NAD + FAD.
NAD earlier than FAD.
What happens to the pyruvate produced during glycolysis if O2 is absent?
Converted to lactate.
- Necessary to reoxidise reduced NAD so that glycolysis can continue.
When does fermentation happen?
2nd stage of anaerobic respiration after glycolysis
What does the shortage of O2 in the cells mean for anaerobic respiration?
Must find another way to convert reduced NAD back into NAD.
== Fermentation
Lactate fermentation
Each pyruvate mol. produced takes up 2 H mol. (from red. NAD in glycolysis) to form lactate.
NAD can then be recycled.
Where can the lactate be taken away from cells to?
Liver to be converted into glycogen through the Cori cycle.
What is the gross production of ATP by substrate level phosphorylation in glycolysis
4 ATP
What is the purpose of the ETC?
To produce ATP through chemiosmosis by carrying out oxidative phosphorylation
How many proton pumps are involved in the ETC?
3
1 Red. NAD is able to produce 3 ATP due to it passing through all 3 pumps.
1 Red. FAD is able to produce 2 ATP due to only passing through 2nd + 3rd pump.
Describe the ETC
Red. NAD is oxidised at 1st P pump by losing 2H. Then split – 2e- + 2H+.
High energy e- fuel the 1st P pump to pump 2H+ from MATRIX — inter membranous space.
2 e- then passed to mobile e- carrier in membrane which takes e-‘s to 2nd P pump. Energy is used to pump 2 P across membrane into IM Space.
Repeat stage 3 at 3rd P pump.
2e-‘s then passed to O2 (final e- acceptor) to combine w. 2H+ —- H20.
==== P Pumps create a P gradient between IM space + matrix. == P diff ⬇️ conc. grad. through ATPsynthase. Energy released is used to ADP+Pi– ATP
Where would cyanide bond in the ETC?
On the 3rd proton pump and would have the same effect as if there was no O2 present.
What is the theoretical max. no. of ATP mol. that can be produced from 1 glucose?
Why doesn’t this actually happen?
38 ATP
Doesn’t happen because:
- ATP is used to move PYRUVATE, ADP + RED. NAD across inner mit. memb.
- Proton leakage across inner memb. rather than passing through ATP synthase.
How many ATP are produced by substrate-level phosphorylation and oxidative phosphorylation?
Substrate-level = 4
Oxidative = 34
If 1 mole of glucose is combusted in O2, it produces 2880kJ.
The energy required to make a molecule of aTP is 30.6kJ/mol.
Calculate the efficiency of aerobic respiration
(38 ATP x 30.6 ) / 2800 x 100 = 40.4%
Mechanism B = If cytoplasmic levels of red. NAD are low, then an alternative pathway is used whereby reduced NAD passes its electrons to FAD in the inner mitochondrial membrane.
Explain why the ATP yield per glucose mol. will be decreased if mechanism B is used.
Red. FAD only uses the 2nd + 3rd proton pump.
Only 2 ATP mol. are produced per Red. FAD.
Describe the production of nitrogenous waste and state where this take place when proteins are broken down to use as a respiratory substrate
Deamination results in a keto acid/ammonia being left.
Amino group + CO2 — urea
In the liver
Suggest what might happen to the energy from the break down of glucose which isn’t transferred to ATP
Lost as heat
Why is ATP better than glucose as an immediate energy source for cell metabolism
Releases in smaller amounts
In 1 reaction by single enzyme - ATPase
Energy is available quicker
List uses of ATP in a liver cell
Active Transport
Phagocytosis
Synthesis of glycogen
Bile production
Cell division
If a pond freezes over during winter, goldfish can remain alive in the water under the ice. Explain why they use CHO stores in their bodies much faster in these conditions.
CHO as they’re respiring anaerobically.
Less efficient as it requires more glucose for the same amount of ATP so more is needed to be carried out.
Why do lipids produce more ATP than CHO.
1 x 2C fragment produces 12 ATP.
Does glycolysis occur for alternative respiratory substrates (not glucose)?
NO
Describe briefly what happens to a mol. of CO2 removed by decarboxylation
Diff. out of mit. into blood.
Carried as H carbonate ions
Breathed out
Suggest why the substrate level phosphorylation is referred to as the ‘simplest and oldest way to make ATP’.
Doesn’t involve a complex series of carriers + pumps.
Doesn’t require ATP synthase.
Doesn’t need an electrochemical gradients
Doesn’t require O2.
Where does fermentation occur
Cytoplasm
Cyanide inhibits the enzyme cytochrome oxidase and prevents the reg. of NAD. Explain why cyanide could be used to confirm which sample contained resuspended mitochondria.
Cyanide would only affect mit. as cytochrome oxidase is part of the ETC.
No NAD would be available to act as H acceptor = Krebs cycle would stop = no CO2 would be produced.
Explain why the rate calculated from a graph for the 1st 30 secs would be lower than the initial rate
Less glucose available as reaction progresses.
All active sites are occupied at the start.
Name 2 body fluids that could be analysed using a glucose biosensor
Blood + urine
Name substances for which there would be a net movement into the mitochondria
ADP
Red. NAD
Pi
O2
Pyruvate
Name substances for which there would be a net movement out of the mitochondria
CO2
H20
ATP
NAD
Glucose is oxidised to pyruvate during the process of glycolysis. Explain why glycolysis is said to involve oxidation
Because oxidation involves the removal of H+
