Lecture 7 - Intro. to Metabolism and Energy

Question 1

What is metabolism?

Answer 1

the totality of an organisms chemical reactions, managing the materials and energy resources of the cell

Question 2

What is anabolism?

Answer 2

• reactions that require energy to organize the cell
• ADP is recycled for catabolic reactions
• DNA replication

Question 3

What is catabolism?

Answer 3

• reactions that release energy from the breakdown of nutrients
• ATP from these reactions drive the energy needs of anabolic reactions

Question 4

What are energy and work?

Answer 4

energy = capacity to cause or the capacity to do work, that is the capacity to change or move something 
work = a force acting on an object over a distance

Question 5

What are the two main energy types?

Answer 5

potential = stored energy due to position or composition 
kinetic = energy due to movement

Question 6

What are the laws of thermodynamics?

Answer 6

• study of energy transformations
• 1st law = energy cannot be created or destroyed, can only be converted/transformed from one form to another
• 2nd law = entropy of the universe is always increasing (reactions will be spontaneous if the disorder of the system is increased, the system will become more stable)

Question 7

What is free energy?

Answer 7

• portion of a system’s energy that is available to perform work

Question 8

What happens if the free energy is negative?

Answer 8

• spontaneous reactions
• exergonic
• energy released
• catabolic
• ex) cellular respiration

Question 9

What happens if the free energy is positive?

Answer 9

• non-spontaneous reactions
• endergonic
• requires energy
• anabolic
• ex) photosynthesis

Question 10

What is energy coupling?

Answer 10

• energy from exergonic reactions are used to power endergonic reactions
• sodium/potassium pump

Question 11

What is ATP?

Answer 11

• the cellular energy currency
• ATP = adenosine triphosphate
• major source of energy in cells
• contains potential energy due to position and composition
• hydrolysis of these bonds release energy (exergonic)
• ATP -> ADP + Pi,
• free energy = -13 kcal/mol under cellular conditions and therefore hydrolysis of ATP to ADP can do 13kcal of work

Question 12

What are enzymes?

Answer 12

• biological catalysts that provide an alternative energy path for a reaction to proceed with a low activation energy
• function in both exergonic and endergonic reactions
• highly regulated in the cell
• lower activation energy barrier necessary for reactions to occur without changing the free energy
• catalytic protein that speeds up a reaction without being consumed
• end in “-ase”

Question 13

Do enzymes change the free energy?

Answer 13

NO

Question 14

How do enzymes work?

Answer 14

• bind and act on substrates
• very specific to their substrate
• have an active site
• catalytic site (active site) has geometric and chemical compatibility with the substrate

Question 15

What is Catalysis?

Answer 15

• often proceeds by induced fit
• slight change in enzyme shape to accommodate substrate
• reactants converted to products
• enzyme is unchanged by reaction and can be reused

Question 16

How can enzymes lower the activation energy?

Answer 16

1) bring reactants closer together
2) active site contains a unique chemical environment favorable for a reaction
3) physically stress bonds to be broken
4) covalently stabilize reaction intermediate
5) place substrates in the correct orientation

Question 17

What is enzyme inhibition?

Answer 17

• certain chemical selectively inhibit the action of specific enzymes

Question 18

What are the types of enzyme inhibitors?

Answer 18

• competitive = binds the active site but does not participate in a reaction, can be outcompete by an increase in the substrate
• non-competitive = binds the site on the enzyme that is no the active site and block enzyme activity