Section 5 - Chapter 12: Respiration - old

Question 1

What are the 4 stages of aerobic respiration

Answer 1

• Glycolysis
• Link reaction
• Krebs Cycle
• Oxidative phosphorylation

Question 2

What are coenzymes

Answer 2

• A co-enzyme is a molecule that aids the function of an enzyme by transferring a chemical group from 1 molecule to another

Question 3

What are examples of co-enzymes in respiration and what do they do

Answer 3

• NAD, Co-enzyme A and FAD
• NAD and FAD transfer hydrogen
• Co-enzyme A transfers acetate between molecules

Question 4

What are the 2 different forms of cellular respiration

Answer 4

• Aerobic Respiration
• Anaerobic Respiration

Question 5

What does Aerobic Respiration and Anaerobic Respiration produce

Answer 5

• Aerobic: CO2, Water and a lot of ATP
• Anaerobic: lactate (animals), ethanol and CO2 (plants/fungi) and a little bit of ATP

Question 6

What happens in Glycolysis and what is the overall product?

Answer 6

• Splitting of a 6-carbon glucose molecule into 2 3-carbon pyruvate molecules

Question 7

What happens in the Link Reaction and what are the overall products

Answer 7

• The 3-carbon pyruvate molecules enter into a series of reactions which lead to the formation of acetyl co-enzyme A (2-carbon molecule)

Question 8

What happens in the Krebs Cycle and what are the overall products

Answer 8

• Acetyl Co-enzyme A goes into a series of oxidation-reduction reactions that yield some ATP and lots of reduced NAD and FAD

Question 9

What happens in Oxidative Phosphorylation and what are the overall products

Answer 9

• The use of electrons, associated with reduced NAD and FAD synthesise ATP with water produced as a by-product

Question 10

What are the 2 main stages in Glycolysis

Answer 10

• Phosphorylation
• Oxidation

Question 11

What happens in Phosphorylation in Glycolysis

Answer 11

1. Glucose is phosphorylated using a phosphate from ATP to create Glucose Phosphate and 1 ADP
2. ATP is used to add a phosphate to Glucose Phosphate to make Hexose Biphosphate
3. Each phosphorylated glucose molecule is split into 2 3-carbon Triose Phosphate

Question 12

What happens in Oxidation in Glycolysis

Answer 12

1. Hydrogen is removed from both Triose Phosphate molecules.
2. Hydrogens are transferred to NAD to form 2 reduced NAD
3. Enzyme controlled reactions convert each TP molecule in Pyruvate. (2 ATP produced - 4 in total)

Question 13

What are the products if Glycolysis and what are their uses

Answer 13

• 2 NADH - goes to oxidative phosphorylation
• 2 Pyruvate - Actively transported into mitochondrial matrix for link reaction
• 2 ATP - used for energy

Question 14

Where are the enzymes for Glycolysis found and what does this mean

Answer 14

• Found in the cytoplasm (takes place in cytoplasm)
• Glycolysis doesn’t require any organelle or membrane to take place
• It doesn’t require oxygen

Question 15

What happens in the Link Reaction

Answer 15

1. Pyruvate molecules are actively transported into the matrix of the mitochondria
2. Pyruvate (3C) is oxidised to acetate (2 C). 1 CO2 and 2 hydrogens (forms NADH) released for 1 pyruvate
3. The 2C acetate combines with co-enzyme A to produce acetyl coenzyme A

Question 16

What are the products of the Link reaction and where do they go

Answer 16

• 2 Acetyl co-enzyme A - To the Krebs Cycle
• 2CO2 - Released as a waste product
• 2NADH - To oxidative phosphorylation

Question 17

What are the main stages of the Krebs Cycle of Respiration

Answer 17

1. Formation of a 6C compound
2. Formation of a 5C compound
3. Regeneration of Oxaloacetate

Question 18

What happens in the Formation of a 6C compound in the Krebs Cycle

Answer 18

• The 2C acetyl CoA (from link reaction) combines with a 4C molecule (Oxaloacetate) to form a 6C compound Citrate.
• Co-enzyme A goes back to the link reaction to be used again.

Question 19

What happens in the Formation of a 5C compound part of the Krebs Cycle

Answer 19

• In a series of reactions. Citrate is converted into a 5C compound
• Decarboxylation occurs 1 CO2 is removed
• Dehydrogenation occurs. Hydrogen is removed and forms NADH

Question 20

What happens in the Regeneration of Oxaloacetate part of the Krebs Cycle

Answer 20

• The 5C compound turns into a 4C compound
• Decarboxylation and Dehydrogenation occurs and produces 1 ATP - substrate-level phosphorylation
• Produces 1 FADH, 2 NADH

Question 21

What are the products of the Krebs Cycle and what are their uses

Answer 21

• 1 co-enzyme A - reused in the next link reaction
• Oxaloacetate - Regenerated for the use in the next Krebs Cycle
• 2CO2 - waste
• 1 ATP - energy
• 3 NADH and 1 FADH - oxidative phosphorylation

Question 22

What is the importance of the Krebs Cycle

Answer 22

• Breaks down macromolecules into smaller ones - pyruvate broken into CO2
• Produces hydrogen atoms that are carried by NAD to electron transfer chain and provide energy for OP. This produces ATP
• It regenerates Oxaloacetate that combines with acetylcoenzyme A which would accumulate
• Is a source of intermediate compounds used by cells to manufacture substances like fatty acids, amino acids and chlorophyll.

Question 23

Practical:

1. What happens when you add hydrogen atoms to methylene blue
   2) Why use a control tube

Answer 23

1. Becomes reduced methylene blue (colourless)
2. Show that the yeast was responsible for the colour change (glucose didn’t change methylene blue/ didn’t change by itself)

Question 24

Tube A has yeast, glucose and methylene blue - colourless

Tube C has yeast, water, methylene blue - pale blue

Suggest explanation for the colours

Answer 24

1. Yeast uses glucose as a respiratory substrate producing hydrogen - taken up by methylene
2. Yeast uses stored carbohydrate as a respiratory substrate that has to be converted to glucose so the production of hydrogen is slower

Question 25

How might the results in tube A after 15 minutes been different if carried out at different temperature 60°c

Answer 25

* Remained this because enzymes involved in respiration are denatured at 60°c

Question 26

After 20 minutes tube A was mixed vigorously turning methylene blue again. How

Answer 26

* Air contains oxygen which would reoxidise methylene blue so it is blue

Question 27

What is the process of the electron chain in OP

Answer 27

1. Hydrogen atoms are released from NADH and FADH . They split into protons and electrons 2. Electrons move down ETC in a series of oxidation-reduction reactions. As they flow the energy they release causes active transport of protons across mitochondrial membrane into the inner membranal space 3. Protons accumulate in the inter membranal space they move into mitochondrial matrix via ATP synthase. The movement drives the synthesis of ATP 4. In the mitochondrial matrix at the end of ETC. Protons, electrons and oxygen from blood combine to form water. Oxygen is the final acceptor

Question 28

How are lipids used as a respiratory substrate

Answer 28

* Before being respired, lipids are first hydrolysed to glycerol and fatty acids * Glycerol is phosphorylated and converted to triose phosphate which enters glycolysis * Fatty acid is broken down 2-carbon fragment which are converted into acetyl coenzyme A * Hydrogen atoms are released

Question 29

How are proteins used as a respiratory substrate

Answer 29

* It is first hydrolysed to amino acids. * They have their amino group removed before entering the respiratory pathway at different points depending on the number of carbon atoms. * 3 carbon compounds - pyruvate * 4/5 converted to intermediates in the Krebs Cycle.

Question 30

What happens when there is an absence of oxygen

Answer 30

* Neither the Krebs cycle nor ETC can continue as all FAD and NAD will reduce * NO FAD or NAD will take up H+ from Krebs so enzymes will stop working * Leaves only glycolysis

Question 31

What do the 2 ways in Eukaryotic cells during anaerobic respiration produce

Answer 31

1. In plants and yeast the pyruvate is converted into ethanol and CO2 2. In animals the pyruvate is converted to lactate

Question 32

What happens in anaerobic respiration with plants/yeast

Answer 32

* The pyruvate molecule formed at the end of glycolysis loses a molecule of carbon dioxide to produce ethanal * This accepts hydrogen from reduced NAD to produce ethanol.

Question 33

What happens in anaerobic respiration in animals

Answer 33

* Produces lactate in means of overcoming a temporary shortage of oxygen * Lactate production occurs in muscles exercise may cause oxygen debt. * NAD can accumulate and must be removed therefore each pyruvate takes up 2 hydrogen atoms from NADH to form lactate.

Question 34

What happens to the lactate when there is oxygen again

Answer 34

* Lactate is oxidised to pyruvate * This can be further oxidised to release energy or converted to glycogen * Lactate can cause muscle cramp. Lactate is an acid - cause pH changes (enzymes)

Question 35

Energy from cellular respiration is derived from 2 ways

Answer 35

* Substrate-Level Phosphorylation: in Glycolysis and the Krebs Cycle. This is the direct transfer of a phosphate from a respiratory intermediate to ADP * Oxidative Phosphorylation: In the ETC. Involving energy of the hydrogen atoms from NAD/FAD.

Question 36

In anaerobic respiration how is ATP formed

Answer 36

* Pyruvate is converted to either ethanol or lactate. Not available for the Krebs Cycle or ETC. * Only ATP produced is from the Glycolysis stage