WK 5 & 6 (Metabolism)

Question 1

Metabolism

Answer 1

The sum total of the chemical reactions that take place in a living cell or multicellular organism

Question 2

Autotrophic organisms

Answer 2

able to synthesise biomolecules using C from CO2 (plants, photosynthetic bacteria)

Question 3

Heterotrophic organisms

Answer 3

Must synthesise biomolecules from more complex organic molecules (must feed off others)

Question 4

Catabolic pathways

Answer 4

The system of enzyme-catalysed reactions in a cell by which complex molecules are degraded to simpler ones with the release of energy

Question 5

Anabolic pathways

Answer 5

The system of enzyme catalysed reactions in a cell by which large molecules are made form smaller ones (biosynthesis)

Question 6

True or false

Catabolic and anabolic pathways can occur simultaneously but are regulated independently

Answer 6

True

Question 7

Glycolysis

Answer 7

Omnipresent metabolic pathway in the cytosol in which sugars are degraded into common metabolic intermediates and energy is produced

Question 8

Gluconeogenesis

Answer 8

Metabolic pathway in the cytosol in which sugars are generated from metabolic intermediates

Question 9

Common Metabolic Intermediates

Answer 9

Common degradative products of catabolism of energy yielding nutrients (sugars, protein and lipids)

Question 10

Citric Acid Cycle

Answer 10

Central metabolic pathway in all aerobic mechanisms that oxidize acetyl groups derived from food molecules to CO2.
Located in the mitochondria and generates reducing power (electrons)

Question 11

Oxidative phosphorylation

Answer 11

Process in the mitochondria in which ATP formation is driven by the transfer of electrons to oxygen molecules

Question 12

Catabolism stage 1

Answer 12

breakdown of foods into simple subunits

Question 13

Catabolism stage 2

Answer 13

Breakdown of simple subunits to Acetyl CoA; limited amounts of ATO and NADH produced

Question 14

Catabolism stage 3

Answer 14

Complete oxidation of acetyl CoA to H2O and CO2; large amounts of ATP produced in mitochondria

Question 15

Protein catabolism stage 1

Answer 15

Extracellular (gastrointestinal tract)
Denaturation (unfolding)
peptidases (proteolytic) release AA

Question 16

Protein catabolism stage 2

Answer 16

Within cells (cytoplasm)  
Amino acids - protein synthesis - interconversion

Question 17

Protein catabolism stage 3

Answer 17

Energy liberated (ATP)
Biosynthesis
NH3 enters urea cycle
Oxidative waste product formation

Question 18

Carbohydrate catabolism stage 1

Answer 18

Extracellular (gastrointestinal tract)
Amylases (saliva, pancreas)
Acid hydrolysis (random)
Alternate strategies for ruminants

Question 19

Carbohydrate catabolism stage 2

Answer 19

Within cells (cytoplasm) 
Monosaccharides - energy liberation (glycolysis), pyruvate (aerobic), lactic acid (anaerobic) 
Storage of polysaccharides 
Secondary pathways

Question 20

Carbohydrate Catabolism stage 3

Answer 20

Energy liberated (ATP) 
Liberation of intermediates for biosynthesis 
Oxidative waste product formation

Question 21

Sequential oxidation of food molecules differs from combustion of food molecules because:
a) Oxidation of food can occur in cells but combustion of food molecules cannot

b) Combustion of food results in all of the free energy lost as heat
c) The activation energy of each step of oxidation of food is smaller than the activation energy for combustion
d) All of the above

Answer 21

d)

Question 22

Lipid catabolism

Answer 22

Stage 1: Occurs extracellularly (gastrointestinal tract) and involves the hydrolysis of ester bonds catalysed by lipases and esterases to liberate glycerol and fatty acids which are absorbed into circulation where they quickly recombine. These lipids are circulated in both blood and lymph.

Stage 2: Occurs in the cytoplasm of cells where other lipases catalyse hydrolysis into fatty acids and glycerol. Glycerol enters glycolysis as an intermediate. Fatty acids are transported into mitochondria for oxidation.

Stage 3: Occurs in mitochondria where hydrocarbon tails of fatty acids are sequentially degraded by Beta oxidation. Each sequential oxidation results in the removal of 2 carbon atoms (which form the acetyl group of acetyl CoA) as well as NADH and FADH2. Acetyl-CoA enters the citric acid cycle and the activated carrier molecules are utilised in oxidative phosphorylation for the production of ATP. Both ATP and intermediates of these catabolic pathways can be utilised in biosynthesis and the by-products of oxidative degradation (CO2 and H20) are eliminated from the cell

Question 23

Is the conversion of Pyruvate to Acetyl-CoA irreversible?

Answer 23

Yes

Question 24

What molecules can degrade to pyruvate?

Answer 24

Some amino acids, carbohydrates, glycerol

Question 25

What molecules degrade directly to acetyl CoA (not via pyruvate)

Answer 25

Some amino acids, fatty acids

Question 26

Regulation of metabolism at a molecular level

Answer 26

Co-ordinated gene expression

Question 27

Regulation of metabolism at a cellular level

Answer 27

regulation of enzyme/substrate concentration & enzyme kinetics

Question 28

Regulation of metabolism occurs at a physiological level

Answer 28

Regulation/ co-ordination achieved by an integrated | nuero-endocrine axis

Question 29

Feedback mechanisms which regulate metabolism at a cellular level: a) Include the activation or inactivation of regulatory enzymes by products of chemical reactions. b) Are only important in amino acid biosynthesis. c) Always result in inactivation of regulatory enzymes. d) Always result in activation of regulatory enzymes.

Answer 29

a)