Mod. 5 Respiration and the mitochondria

Question 1

What are the different parts of a mitochondrion?

Answer 1

outer membrane
inner membrane
inter membrane space
stalked particles
crista (folds of inner membrane)
inter-membrane space (high pH)
matrix (inside inner membrane, low pH, contains plasmids)

Question 2

what is the energy stored in food used for?

Answer 2

makes ATP which is used for DNA replication, protein synthesis, active transport etc.

Question 3

How is ATP used?

Answer 3

Fires off a phosphate group which releases 30.6 kJ mol-1 of energy which is used to power processes in the cell e.g. synthesis, active transport, muscle contraction.

Question 4

What is the purpose of the pH gradient maintained in the mitochondrion?

Answer 4

Chemiosmosis. H+ ions diffuse into cell down the concentration gradient through stalked particles which is a channel protein with ATP synthase on the end. 3 H+ ions create enough energy for 1 ATP.

Question 5

How are H+ ions removed from the matrix to maintain a concentration gradient?

Answer 5

• H+ ions are removed by active transport in the protein transport chain. NAD2H transfers 2H onto the first protein, reducing it. This changes the shape of the protein allowing 3H+ through. this repeats for the other 2 large proteins in the transport chain.
• The concentration gradient is therefore maintained so ATP can be produced.

Question 6

How does the electron transport chain work?

Answer 6

• The first protein in ETC is reduced by 2H from NADH. The protein changes shape, allowing 3H+ ions out.
• Electron flow along ETC reduces proteins, providing energy to pump H+ from proteins to IMS.
• At the end of the ETC, low energy electrons are removed by O2 (inhaled) to find electron acceptor to form water.

Question 7

What is glycolysis?

Answer 7

• The breakdown of glucose to create ATP.
• glucose receives phosphate group from 2ATPs to activate it. It splits into 1,6 fructose bisphosphate.
• 1,6 fructose bisphosphate is split into 2 molecules of sugar phosphate which are oxidised by NAD and have 2 phosphate groups removed by 2ADP (becomes 2ATP) to make pyruvate.

Question 8

What is link reaction?

Answer 8

• the process that links glycolysis and the krebs cycle.
• pyruvate is transported into the IMS then the matrix by active transport through transport proteins.
• once in the matrix, dehydrogenase enzyme dehydrogenates the enzyme by reducing NAD to NADH which carries hydrogen to the ETC.
• carboxylase enzyme acts to make CO2 which diffuses out of the cell and is transported in the blood stream to be exhaled from lungs.
• the final product is acetyl, which combines with co-enzyme A to create acetyle con-enzyme A.

Question 9

What is the Krebs cycle?

Answer 9

• Acetyl co-enzyme A feeds in combining with oxaloacetate to make citrate.
• citrate is oxidised by NADH and decarboxylase removes CO2 to make a-keto-glutarate.
• a-keto-glutarate is reduced by NAD and decarboxylase removes CO2 to make succinate.
• succinate creates an ATP by substrate level phosphorylation and FAD oxidises it to make fumarate
• fumarate becomes malate.
• malate is oxidised by NAD to become oxaloacetate and the cycle repeats once it combines with acetyl.

Question 10

How many ATPs are produced from glycolysis, link reaction and Krebs cycle?

Answer 10

glygolysis - 8
link reaction - 6
krebs cycle - 24
total: 38 ATP

Question 11

How are lipids used to make ATP?

Answer 11

• break down into fatty acids and glycerol.
• glycerol goes through a series of reactions to become pyruvate and feeds into the process from there.
• fatty acids have large carbon chains and small 2C chains are snipped off the end and become acetyl to feed into the Krebs cycle.

Question 12

How are proteins used to make ATP?

Answer 12

• proteins are broken down into amino acids
• amino acids undergo reactions to become pyruvate, acetyl or become any of the molecules in the Krebs cycle.
• as a result of these changes, the amino group is stored.
• urea is made.

Question 13

Under what circumstances does anaerobic respiration occur?

Answer 13

• in the absence of O2.
• the electron transport chain shuts down because there is not oxygen to oxidise the final protein in the chain.
• therefore the Krebs cycle and link reaction shut down.
• only source of ATP is by substrate level phosphorylation in glycolysis.

Question 14

What are the processes of anaerobic respiration?

Answer 14

Glucose—-(2ADP to 2ATP)–(2NAD to 2NADH)–>pyruvate
pyruvate —(decarboxylase make CO2)—> ethanal
ethanal—–(2NADH to 2NAD)—> ethanol

Question 15

What is oxygen debt?

Answer 15

Oxygen needed to make CO2 and H2O from lactate in the liver after anaerobic respiration.