Introduction to Metabolism

Question 1

What is metabolism ?

Answer 1

Means by which organisms extract energy from their environment and use this to synthesize large molecules

Question 2

What are examples of disorders which involve changes in the balance of metabolic activities ?

Answer 2

Obesity, diabetes

Question 3

What is the resting human consumption of Oxygen per minute ? How much does it increase in exercise ?

Answer 3

250 ml O2/min

Can increase x5 during exercise

Question 4

What is Oxygen used for ?

Answer 4

To oxidize (add oxygen to/remove electrons from molecules) substrates and produce energy for the body’s needs

Question 5

What is catabolism ? Does it require or release energy ?

Answer 5

Breakdown of large molecules to smaller ones

Releases energy

Question 6

What is anabolism ? Does it require or release energy ?

Answer 6

Process by which large molecules are built from smaller ones

Requires an energy input

Question 7

What is the equation for change in free energy ?

Answer 7

ΔG=ΔGo +RTloge [C][D] / [A][B] for reaction A + B ↔ C + D
where,
ΔG = Free energy change for the reaction with reactants at the concentrations given
ΔGo = Standard free energy change (when all reactants are present at a concentration of 1.0 M)
R = Gas constant
T = Absolute temperature

Question 8

What is the sign of the free energy change for a spontaneous reaction ?

Answer 8

Free energy change (ΔG) is negative

Question 9

Does the magnitude of the free energy change say anything about rate of reaction ? If not, which value does tell us about rate of reaction ?

Answer 9

Free energy of activation (ΔG*)

Question 10

True or False: a sequence of coupled reactions can take place without energy input as long as there is a overall negative change in free energy (ΔG) between the starting materials and the final product(s) of the reaction sequence.

Answer 10

True

Question 11

What is the form in which the energy released during catabolism is captured and stored ?

Answer 11

ATP

Question 12

What is the molecular formula of inorganic phosphate ?

Answer 12

(PO4)3-

Question 13

Does the conversion of ATP into ADP release or require energy ? How much ?

Answer 13

Releases energy

-7 to -12 kcal/mol

Question 14

What kind of reaction is the conversion of ATP into ADP ?

Answer 14

Hydrolysis

Question 15

What are some molecules which may serve a role similar to that of ATP and ADP ?

Answer 15

GTP and GDP

Question 16

How is ATP formed ?

Answer 16

Product of oxidation of fuel molecules

Question 17

How much ATP does a resting human consume in 24 hours ?

Answer 17

40 kg

Question 18

How much ATP may a human consume in a minute of exercise ?

Answer 18

0.5 kg

Question 19

What is ATP used for ?

Answer 19

• Body movement (via muscular contraction)
• Cellular movements (via cytoskeleton)
• Active transport
• Synthesis of large molecules

Question 20

What is meant by free energy ?

Answer 20

“amount of work that a thermodynamic system can perform”

Question 21

What are the main ways in which metabolism can be regulated ?

Answer 21

1. Changes in amounts of substrates and products of pathways (e.g. ratio of ATP to ADP + Pi affects energy producing and energy-requiring pathways in opposite ways)
2. Changes in amounts of key enzymes
3. Changes in activity of key enzymes:
   • Allosteric changes
   • Effects of substrate and downstream products on enzyme activity
   • Covalent modification of enzymes (e.g. phosphorylation)
   • Hormones (e.g. insulin, glucagon and adrenaline) can have a major regulatory effect on some enzyme