Pack 5 – Respiration and Enzymes

Question 1

Aerobic respiration equation:

Answer 1

C6H1206 + O2 = CO2 + H20

Question 2

ATP

Answer 2

The energy transfer molecule

Question 3

How is ATP synthesised?

Answer 3

By adding inorganic phosphate to ADP

Question 4

ATP synthesized equation:

Answer 4

ADP + Pi -> ATP

Question 5

Redox reactions:

Answer 5

• During chemical reactions, existing bonds are broken and new bonds are formed
• This involves the transfer of electrons when atoms turn into ions

Question 6

2 hydrogen carriers:

Answer 6

1. NAD
2. FAD

Question 7

What are hydrogen carriers also known as?

Answer 7

Co-enzymes

Question 8

Co-enzymes

Answer 8

Molecules that work closely with enzymes

Question 9

Co-enzymes role:

Answer 9

• Help transfer hydrogen
• Easily accept hydrogen and become reduced, then give them up and become oxidised

Question 10

What are the 4 stages of aerobic respiration?

Answer 10

1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Electron transport chain

Question 11

Where does glycolysis take place?

Answer 11

In the cell cytoplasm

Question 12

Glycolysis

Answer 12

• Glycogen is hydrolysed into glucose (6C)
• Glucose is converted into intermediate 3 carbon compounds (x2)
• These intermediate compounds are converted into 3 carbon pyruvate (x2)
• ATP (net x2) is produced

Question 13

Where does the link reaction take place?

Answer 13

The mitochondrial matrix

Question 14

Link reaction

Answer 14

• Pyruvate (3C) enters the mitochondrial matrix
• Pyruvate is converted into acetyl CoA (2C)

Question 15

Where does the Krebs cycle take place?

Answer 15

In the mitochondrial matrix

Question 16

Krebs cycle

Answer 16

• Acetyl CoA (2C) enters the Krebs cycle and combines with a 4 carbon compound
• In a circular pathway of reactions, the original 4 carbon compound is recreated
• ATP (x1) is produced as a result

Question 17

Electron transport chain

Answer 17

• The reduced NAD (and reduced FAD) molecules that were produced in the last 3 stages release hydrogen ions and electrons
• Reduced NAD then becomes NAD again (and reduced FAD becomes FAD)
• The hydrogen ions move into the intermembrane space and then diffuse back into the mitochondrial matrix through an enzyme called ATPsynthase – this is known as chemiosmosis
• As a result, ATP (x38) is produced

Question 18

Where does the electron transport chain take place?

Answer 18

On the mitochondrial inner membrane

Question 19

How many carbons does glucose have?

Answer 19

6

Question 20

How many carbons does pyruvate have?

Answer 20

3

Question 21

How many carbons does acetyl CoA have?

Answer 21

2

Question 22

Where does anaerobic respiration take place?

Answer 22

In the cytoplasm

Question 23

Anaerobic respiration process:

Answer 23

• Pyruvate is converted into lactate (lactic acid)
• The pyruvate accepts the hydrogen from the reduced NAD and NAD is recreated
• NAD can then be reused in glycolysis
• ATP (x2) can still be produced

Question 24

Enzymes

Answer 24

Are globular proteins that act as biological catalysts

Question 25

What do enzymes do?

Answer 25

Speed up chemical reactions that would otherwise occur very slowly at the temperature within cells

Question 26

Active site in an enzyme:

Answer 26

The precise three-dimensional shape adopted by an enzyme includes a depression on the surface of the molecule

Question 27

What does the active site within an enzyme do?

Answer 27

The part of the enzyme molecule with the catalytic function

Question 28

How do enzymes work?

Answer 28

- Molecules with a complementary shape, known as the substrate, can fit into the active site - The enzyme holds the substrate molecule(s) in such a way that they react more easily - When the reaction has taken place the products are released, leaving the enzyme unchanged

Question 29

Lock-and-key theory of enzyme action:

Answer 29

The substrate is often likened to a ‘key’ which fits into the enzyme’s ‘lock’

Question 30

Induced fit theory of enzyme action:

Answer 30

When the substrate/s enters the active site, the enzyme molecule changes shape slightly, fitting more closely around the substrate

Question 31

How are substrates converted into products?

Answer 31

- Breaking chemical bonds requires energy, while energy is released when bonds form - The energy needed to break bonds and start the reaction is known as the activation energy

Question 32

Intercellular enzyme reactions:

Answer 32

Reactions occurring inside cells

Question 33

Extracellular enzyme reactions

Answer 33

Reactions that occur in issue fluid, blood or other aqueous solutions in the organism

Question 34

4 factors that affect the rate of enzyme-controlled reactions?

Answer 34

- Substrate concentration - Enzyme concentration - Temperature - pH