Topic 5.1 Cellular Respiration

Question 1

Energy definition

Answer 1

The capacity of a system to do work

Question 2

Why do we need energy

Answer 2

-Metabolism
-Movement
-Active transport
-Maintenance/repair/division of cells
-Production of substances
-Maintenance of body temperature

Question 3

Mononucleotide substance

Answer 3

ATP

Question 4

Polynucleotide substance

Answer 4

DNA

Question 5

ATP consists of:

Answer 5

-Adenine (a nitrogenous base)
-Ribose (a pentane sugar)
-Three inorganic phosphate groups

Question 6

ATP reaction

Answer 6

ATP + water ⇌ ADP + Pi (energy)

Question 7

Phosphorylation

Answer 7

A phosphate molecule is added to some organic compound (eg. glucose and ADP)

Question 8

What is ATPase?

Answer 8

The enzyme that catalyses the breakdown of ATP
(ATP synthase catalyses the synthesis of ATP)

Question 9

Where does the energy to produce ATP usually come from?

Answer 9

Usually from the breakdown (catabolic) or redox reactions.

Question 10

Advantages of ATP

Answer 10

-Instant source of energy in the cell
-Releases energy in small amounts
-Resynthesised
-It is mobile and transports chemical energy to where it is needed in the cell
-Universal energy carrier and can be used in many chemical reactions

Question 11

ATP is used in:

Answer 11

-Active transport
-DNA synthesis
-Protein synthesis
-RNA synthesis
-Photosynthesis
-Muscle contraction
-Control of cytoskeleton

Question 12

Why is ATP suited to its function?

Answer 12

-Can be reformed (made again)
-Broken down in one step/immediate source of energy
-Release of energy is small manageable amounts
-Phosphorylation reduces activation energy

Question 13

Aerobic respiration definition

Answer 13

Aerobic respiration refers to the cellular respiration that depends on oxygen

Question 14

Aerobic respiration equation

Answer 14

Glucose + oxygen –> carbon dioxide + water
C6H12O6 + 6O2 –> 6CO2 + 6H2O

Question 15

How do cells oxidise glucose?

Answer 15

Cells have to oxidise glucose in a much more controlled way so that the heat generated does not destroy them.
The heat is spread over many biochemical reactions which occur in a series of steps.

Question 16

Labeled mitochondrion

Answer 16

Question 17

Glycolysis

Answer 17

Glycolysis occurs in the cytosol of the cell
(Pyruvate enters the mitochondria via active transport).

Question 18

Purpose of glycolysis

Answer 18

-To produce reduced coenzyme
-To produce a molecule which can enter the mitochondria as glucose is too large to enter

Question 19

The Kreb’s cycle

Answer 19

-Consists of a series of enzyme- controlled reaction
-2C Acetyl CoA enters the circular pathway from the link reaction
-4C oxaloacetate accepts the 2C acetyl fragment from acetyl CoA to form the 6C citrate
-Citrate is then converted back to oxaloacetate through a series of redox reactions

Question 20

Products of Kreb’s cycle

Answer 20

-2C
-3NADH
-FADH2
-ATP

Question 21

The role of the Kreb’s cycle

Answer 21

• Completely oxidises pyruvate/acetyl CoA.
• To release as much energy as possible.
• To generate ATP.
• To produce reduced coenzyme/NADH
• So that ATP can be produced by oxidative phosphorylation.

Question 22

The link reaction

Answer 22

Involves the conversion of pyruvate to form a compound acetyl coenzyme A
1) Pyruvate is oxidised in enzymes to produce acetate and CO2, requiring the reduction of NAD to NADH
2) Combination of acetate with conenzyme A (2C) to form acetyl coenzyme A
—>Acetyl coenzyme A can now enter the Kreb’s cycle.
(pyruvate + NAD + CoA –> acetyl CoA + NADH + CO2)

Question 23

Products of link reaction

Answer 23

-Acetyl Coenzyme A
-CO2
-NADH

Question 24

Oxidative phosphorylation requires:

Answer 24

The final stage of aerobic respiration
Requires:
-oxygen
-reduced NAD and FAD which are carrying hydrogen
-electron carriers (cytochromes)

Question 25

What is a cytochrome?

Answer 25

Electron carrier H --> H+ + e- Hydrogen atoms are split into the protons and electrons

Question 26

Electron Transport Chain

Answer 26

(A series of carrier proteins embedded in membrane off the cristae of mitochondria) The four steps: -glycolysis -pyruvate oxidation -the Krebs cycle -oxidative phosphorylation ---> Oxygen acts as final electron acceptor.

Question 27

Products of electron transport chain

Answer 27

-ATP -Water -NAD -FAD

Question 28

Oxidative phosphorylation

Answer 28

1) Hydrogen atoms are split into H+ ions and electrons by reduced NAD/FAD 2) The electrons enter the first coenzyme and give the energy needed for the H+ ions to move from the matrix to the inter membrane space by a series of redox reactions driven by oxygen as the terminal acceptor of electrons 3) a 1/2O2 molecule joins two H+ ions to form a H2O molecule 4) H+ flow back through stalked particles 5) This energy is used to synthesise ATP from ADP and inorganic phosphate by a condensation reaction.

Question 29

Chemiosmosis

Answer 29

The process that moves hydrogen ions through the membrane along a concentration gradient. It links the electron transport chain with production of ATP. (ATP synthase catalyses ADP + Pi --> ATP)

Question 30

Anaerobic respiration

Answer 30

(Partial breakdown of glucose in oxygen-deprived conditions to produce a limited ATP yield) -Lack of oxygen -Happens in the cytoplasm -Produces lactic acid -Includes glycolysis -Generates ATP + NADH -NADH is oxidised by a fermentation

Question 31

Anaerobic fermentation: ethanol fermentation

Answer 31

1)Pyruvate is decarboxylated to ethanal (CO2 is produced) 2) Reduced NAD transfers its hydrogen to ethanal to form ethanol by enzyme alcohol dehydrogenase) --Ethanal is a hydrogen acceptor --Ethanol can't be further metabolised so it is a waste product

Question 32

Anaerobic fermentation: lactate fermentation

Answer 32

1) Reduced NAD transfers its hydrogen to pyruvate to form lactate 2) Pyruvate is reduced to lactate by enzyme lactate dehydrogenase --Pyruvate is the hydrogen acceptor --Lactate can be further metabolised (Lactate is transported to liver in bloodstream; enters link reaction in liver cells or is converted to glycogen).

Question 33

Anaerobic and aerobic similarities

Answer 33

-Both happen in the cytoplasm -Both include glycolysis -Both generate 2ATP, 2NADH and 2 pyruvate -Both need glucose

Question 34

Anaerobic and aerobic differences

Answer 34

-Aerobic is in the presence of oxygen, anaerobic isn't -Anaerobic produces lactic acid -NADH in anaerobic respiration is oxidised by fermentation

Question 35

The 4 main stages aerobic respiration and where do they occur?

Answer 35

-Glycolysis : cytoplasm -Link reaction: mitochondrial matrix -Krebs cycle: mitochondrial matrix -Oxidative phosphorylation (via ETC): membrane of cristae

Question 36

Advantage of producing ethanol/lactate during anaerobic respiration

Answer 36

Converts reduced NAD back into NAD so glycolysis can continue.

Question 37

Disadvantage of producing ethanol during respiration

Answer 37

Dissolves cell membranes so cells die when concentration is above 12%.

Question 38

Principle behind the respirometer

Answer 38

Pressure changes in the boiling tube due to CO2 production (anaerobic experiments) or O2 consumption (aerobic experiments) cause a drop of coloured liquid to move.