Respiration

Question 1

Why is ATP not good for long term store of energy?

Answer 1

Phosphate bonds are not stable

Question 2

What are the main roles of ATP?

Answer 2

Energy currency
Phosphates removed by hydrolysis
Release 30.6kJ per mole of ATP molecules
ATP releases energy in small packets that will not damage the cell

Question 3

Name uses of ATP in the cell

Answer 3

-Active transport
-Muscle contraction
-Glycolysis
-Protein synthesis
-DNA replication
-Secretion
-Endocytosis

Question 4

Why do animals need lots of ATP?

Answer 4

Its unstable
Cant be stored
Only releases in small packets of energy

Question 5

Properties of ATP

Answer 5

SMALL moves easily in and out of cells
WATER SOLUABLE energy requiring processes take place in aqueous solution

easily regenerated
releases energy in small quantities
energy within bonds is not too big to be lost as heat

Question 6

What is respiration?

Answer 6

A series of enzyme controlled reactions
The process by which organic molecules are broken down in a series of stages to synthesise ATP

Question 7

What does NAD stand for?

Answer 7

Nicotinamide Adenine Dinucleotide

Question 8

Where does glycolysis occur?

Answer 8

In the cytoplasm

Question 9

What occurs during glycolysis?

Answer 9

1. 2 ATP molecules needed
   2 phosphates released and attach to glucose
   forms hexose bisphosphate
2. This splits into 2 triose phosphates (TP)
3. Another phosphate is added to form 2 triose bisphosphates
4. Dehydrogenation of 2 triose bisphosphates forms
   2 pyruvates
   2 NADH
   2 ATP

Question 10

Where does the link reaction occur?

Answer 10

Matrix of the mitochondria

Question 11

What occurs during the link reaction?

Answer 11

1. Pyruvate looses 1 carbon
   CO2 is released
   decarboxylation by pyruvate decarboxylase
2. Pyruvate is oxidised by removing hydrogen
   hydrogen forms NADH
3. Leaves 2C molecule acetyl
   combines with CoA
   forms acetyl CoA
4. Products
   CO2 (2)
   NADH (2)
   acetyl CoA (2)
   NO ATP PRODUCED

Question 12

Where does the krebs cycle occur?

Answer 12

Matrix of the mitochondria

Question 13

What occurs during the krebs cycle?

Answer 13

1. Acetyl CoA joins with 4C Oxaloacetate
   Forms citrate
   CoA released to be used in the link reaction
2. Citrate decarboxylated and dehydrogenated
   Forms NADH
3. 5C compound created decarboxylated and dehydrogenated
   Forms NADH
4. 4C compound altered 3 times
   ATP made
   NAD an FAD causes further dehydrogenation

Question 14

Where does oxidative phosphorylation occur?

Answer 14

Cristae and intermembrane space

Question 15

What occurs during oxidative phosphorylation?

Answer 15

1. NADH combines with protein complex1
2. NAD reused in glycolysis link reaction and krebs cycle
   Hydrogen becomes 2H+ 2e-
3. 2e- passes along electron transport chain - provides energy
   H+ pumped into intermembrane space
4. Reduced FAD becomes oxidised at second complex
   H+ remains in matrix and combines with O2—>H2O
5. More H+ pumped into intermembrane space due to electron movement
6. Chemiosmosis (ADP+Pi=ATP)
   H+ goes through ATP synthase
7. 2H+ combines with 2H+ and 4e- and O2 to form water
   O2 is the final electron acceptor

Question 16

Which stages of respiration do substrate level phosphorylation?

Answer 16

Glycolysis
Krebs cycle

Question 17

How many turns does the krebs cycle do for 1 glucose?

Answer 17

2 because 2 acetyl CoA were made in the link reaction

Question 18

What are the products of the krebs cycle? (2 turns)

Answer 18

6 reduced NAD
2 reduced FAD
2 ATP
4 CO2

Question 19

How many ATP molecules are made from one glucose?

Answer 19

1 NADH = 3 ATP
1 FADH = 2 ATP
10 NADH x 3 = 30 ATP
2 FADH x 2 = 4 ATP
+ ATP from krebs and glycolysis (4)

38 ATP molecules from one glucose

Question 20

Explain the difference between photo phosphorylation substrate level phosphorylation and oxidative phosphorylation

Answer 20

• Photophosphorylation produces ATP in the presence of light
• Substrate level photophosphorylation produces ATP by removing a phosphate from a compound in a reaction pathway
• Oxidative phosphorylation produces ATP by using oxygen as a final electron acceptor and an electron transport chain

Question 21

State the key points of chemiosmosis and oxidative phosphorylation

Answer 21

-occurs in the mitochondria of the cell
-involves in a membrane and matrix
-hydrogen ions pumped out of matrix into intermembrane space by movement of H+
-proton gradient created
-creates proton motive force
-use of ATP synthase
-H+ ions move from high to low concentration through ATP synthase enzymes to make ATP

Question 22

Anaerobic respiration

Answer 22

NO OXYGEN
Only glycolysis occurs which produces 2 ATP molecules net by substrate level phosphorylation from 1 glucose
Less ATP as glucose is not fully broken down

Question 23

Organisms and their ability to survive in certain conditions

Answer 23

Obligate anaerobes (bacteria) CANT survive in the presence of oxygen

Facultative anaerobes (yeast) synthesise ATP by aerobic respiration if O2 is present but can switch to anaerobic respiration if O2 is not present

Obligate aerobes (humans) CAN only survive in the presence of O2 (muscle cells can respire without oxygen but only for short periods of time and oxygen needed to break down lactic acid)

Question 24

Alcoholic fermentation in yeast (and many plants)

Answer 24

NOT REVERSIBLE
pyruvate converted to ethanal (pyruvate decarboxylase) (CO2 released)
ethanal then accepts a hydrogen atom from NADH to form NAD
ethanol is also made (ethanol dehydrogenase)
NAD can continue to act as a coenzyme
glycolysis continues to make the ATP

Question 25

Why must ethanol be removed from the yeast?

Answer 25

Ethanol kills the yeast

Question 26

Lactate fermentation in animals

Answer 26

REVERSIBLE pyruvate acts as a hydrogen acceptor and takes the hydrogen from reduced NAD pyruvate is converted into lactate (lactate dehydrogenase) NAD is regenerated oxygen debt created as oxygen needed to convert the lactate back to glucose in the liver

Question 27

Why cant lactate fermentation occur indefinitely?

Answer 27

lactic acid causes muscle cramps

Question 28

What are the benefits of anaerobic respiration?

Answer 28

NAD gets recycled allows glycolysis to happen some ATP produced

Question 29

Respiring proteins

Answer 29

proteins made of amino acids they generally have more hydrogens for NAD to accept to use in oxidative phosphorylation once proteins are hydrolysed into amino acids they are deaminated amino acids broken down into keto acids this form pyruvate which is then used in the link reaction

Question 30

Respiring triglycerides

Answer 30

lipids are made up of glycerol and fatty acids which have many hydrogen on them lipase enzyme hydrolyses triglyceride into fatty acids and glycerol glycerol converted to pyruvate then undergoes oxidative decarboxylation produces an acetyl group picked up by co enzyme A makes acetyl CoA fatty acids undergo beta oxidation CoA is added to each fatty acid to form many C acetyl CoA these go to krebs cycle

Question 31

Respiratory substrates and their mean values

Answer 31

Carbohydrates 16/kJ g-1 Lipid 39/kJ g-1 Protein 17/kJ g-1 lipids have double this is why seeds have lipids present to provide energy in the form of ATP for germination

Question 32

Why is the ratio of carbon to hydrogen atoms important in respiratory substrates?

Answer 32

Hydrogen atoms attach to NAD and FAD More hydrogen atoms, more NAD and FAD so more H+ ions travel through ATP synthase as a result of chemiosmosis More energy released to form ATP form ADP and Pi

Question 33

Respiratory quotient (RQ)

Answer 33

RQ= vol of CO2 produced/ vol of O2 consumed LIPID RQ = 0.7 ( ratio of H:C is much higher then carbs) PROTEIN RQ = 0.9 ( ratio of H:C is slightly higher than carbs)