5.2.2 respiration

Question 1

why do organisms need to respire
5.2.2(a)

Answer 1

respiration uses glucose to make ATP from ADP and Pi

Question 2

how can we release energy from biological processes
5.2.2(a)

Answer 2

ATP can be hydrolysed to release energy needed for biological processes
-active transport
-endocytosis and exocytosis
-synthesis of polymers

Question 3

describe the mitochondria
5.2.2(b)

Answer 3

inn booklet

Question 4

how is the inner mitchondrial membrane adapted for respiration reactions
5.2.2(b)

Answer 4

-it has embedded proteins and enzymes forming a electrons transport chain which provides a site for oxidative phosphorylation
-ATP synthase is also embedded in the inner mitochondrial membrane
-There is a H+ gradient across the inner mitochondrial membrane, with the inter-membrane space having a very high H+ concentration

Question 5

which molecules in respiration are coenzymes
5.2.2(f)

Answer 5

NADH, FADH2 and CoA

Question 6

describe the process of oxidative phosphorylation
5.2.2(g)

Answer 6

1. NADH and FADH2 are oxidised. The hydrogen atoms that they lose are split into H+ and e-, and the e- enter the electron transport chain.
2. e- are passed along the electron transport chain, losing energy as they go
3. The energy lost by e- is used to pump H+ from the matrix into the intermembrane space
4. At the end of the electron transport chain, the electrons are accepted by O2 (final electron acceptor) in the following reaction: 2H + 2e- + ½ O2 -> H2O
5. Chemiosmosis takes place: H+ flow down their electrochemical gradient, through ATP synthase, which catalyses the following reaction: ADP + Pi -> ATP

Question 7

why is this called oxidative phosphorylation
5.2.2(h)

Answer 7

· This is called oxidative phosphorylation as it is the phosphorylation of ADP using energy from the oxidation of glucose (or other respiratory substrates)

Question 8

where is the the location of the electron transport chain and ATP synthase
5.2.2(g)

Answer 8

-the cristae of the mitochondrial inner membrane is where they are located

· they provide a site for the relevant proteins and enzymes

· they allow compartmentalisation of the inter-membrane space so an electrochemical gradient of H+ can be established

· they provide a large surface area so that oxidative phosphorylation can occur at a rapid rate

Question 9

what is chemiosmosis
5.2.2(h)

Answer 9

Chemiosmosis is the flow of H+ down its electrochemical gradient through ATP synthase. This flow provides the energy needed for ATP synthase to carry out phosphorylation

Question 10

in respiration what is the phosphorylation of ADP using chemiosmosis called and why
5.2.2(h)

Answer 10

In respiration, the phosphorylation of ADP using chemiosmosis is called oxidative phosphorylation. This is because the energy needed to create the H+ electrochemical gradient originally came from a series of reactions involving the oxidation of glucose molecules to reduce NAD and FAD.

Question 11

in photosynthesis what is the phosphorylation of ADP using chemiosmosis called and why
5.2.2(h)

Answer 11

In photosynthesis, the phosphorylation of ADP using chemiosmosis is called photophosphorylation. This is because the energy needed to create the H+ electrochemical gradient originally came from light energy liberating electrons from chlorophyll a.

Question 12

how does aerobic respiration take place
5.2.2(i)

Answer 12

If oxygen is absent:

· O2 cannot act as the final electron acceptor at the end of oxidative phosphorylation, so the electron transport chain stops

· H+ are no longer pumped into the inter-membrane space so the electrochemical gradient for H+ decreases

· Chemiosmosis stops

· ATP synthesis stops

· NADH and FADH2 build up as they can’t pass their electrons to electron carriers in the ETC

· NAD and FAD run out

· The Krebs cycle and link reaction stop because there is no NAD or FAD available to oxidise the intermediates

In the absence of oxygen, only glycolysis can take place. This can keep the organism / cell / tissue alive for a short period of time until aerobic respiration can resume.

NAD is needed for the final step of glycolysis, where the net 2 ATP are made. Because of this, organisms need a pathway where NAD can be regenerated from NADH

Question 13

which organisms use the ethanol fermentation pathway
5.2.2(i)

Answer 13

fungi and plants

Question 14

which organisms use the lactate fermentation pathway
5.2.2(i)

Answer 14

animals an bacteria

Question 15

what is a respiratory substrate
5.2.2(j)

Answer 15

a respiratory substrate is a molecule that can be oxidised to produce NADH and FADH2 for the electron transport chain.

Question 16

what are the 2 types of respiratory substrate
5.2.2(j)

Answer 16

lipids and proteins

Question 17

what do lipids do
5.2.2(i)

Answer 17

triglycerides are hydrolysed to glycerol and fatty acids
glycerol is converted to triose phosphate which enters glycolysis
the rest of respiration proceeds as normal

Question 18

what do proteins do
5.2.2(j)

Answer 18

excess amino acids and deaminated in the liver
the amino group is removed forming ammonia which is converted into urea then excreted
the remainder of the amino acid is excreted is called a keto acid.
keto acids can be converted to pyruvate, acteyl CoA or one of the intermediates in the krebs cycle.

Question 19

what are the differences in respiratory substrate values
5.2.2(j)

Answer 19

more hydrogen atoms
more NADH and FADH2 an be made
the more ATP will be produced by oxidative phosphorylation

Question 20

what is the RQ
5.2.2(k)

Answer 20

RQ=CO2 produced / O2 consumed

Question 21

what is a respiratory substrate
5.2.2(k)

Answer 21

respiratory substrates that contain a lot of hydrogen produce a lot NADH and FADH2 and therefore a lot of electrons enter the electron transport chain. A lot of O2 must be used to accept the electrons at the end of the ETC.

Question 22

what is the RQ value of glucose/ carbohydrates
5.2.2(k)

Answer 22

1

Question 23

what is the RQ value of fatty acids
5.2.2(k)

Answer 23

0.7

Question 24

what is the RQ value of amino acids
5.2.2(k)

Answer 24

0.8 to 0.9

Question 25

when might an organisms RQ value be greater than 1
5.2.2(k)

Answer 25

if some of its tissues are respiring anaerobically so not using O2

Question 26

what is the purpose of soda lime in the respirometer
5.2.2(l)

Answer 26

absorbs CO2 so only o2 uptake is measured

Question 27

how could you calculate the volume of O2 taken up by an organism in the respirometer
5.2.2(l)

Answer 27

pi x r^2 x h

Question 28

what is the experimental control in the respirometer experiment
5.2.2(l)

Answer 28

tube containing the same mass of glass beads to control for small changes in external temperature or pressure.

Question 29

what is the purpose of a tap at the top of a respirometer

Answer 29

allows the respirometer to reach the same pressure as the environment during acclimatision

Question 30

the total volume of gas taken up by an organism in a respirometer without soda lime is equal to what

Answer 30

volume of 02 used - volume of co2 produced