Topic 5

Question 1

Thermos

Answer 1

Heat

Question 2

Dynamis

Answer 2

Power

Question 3

thermodynamics

Answer 3

• study of energy of systems (ie cells, reactions, organisms)
• dictates whether reactions are favourable or not
• all of the chemical and physical reactions that take place in living organisms can be interpreted based on the laws of thermodynamics

Question 4

What is a living organism?

Answer 4

• an open system
• exchanges both matter and energy with its surroundings

Question 5

In any physical or chemical change

Answer 5

• the total amount of energy in the universe remains constant
• although the form of the energy may change

Question 6

System

Answer 6

• a biochemical reaction
• a metabolic pathway
• an individual cell
• an organism
• might convert one form of energy to another
• might lose energy
• when system loses energy, its surroundings gain that energy, so the total energy in the universe in conserved

Question 7

Surroundings

Answer 7

• everything else in the universe

Question 8

Universe

Answer 8

System + surroundings = universe

Question 9

First law of thermodynamics

Answer 9

• conservation of energy
• energy is neither created nor destroyed; only converted from one form to another

Question 10

Heat

Answer 10

A manifestation of the kinetic energy associated with the random motion of molecules

Question 11

Potential energy in cells

Answer 11

• concentration gradients
• electric potential (charge separation)
• chemical potential energy (bond energy)
• energy from chemical bonds breaking and forming is transformed into energy for work in the cells/body

Question 12

In biological systems, deltaH = deltaE

Answer 12

• deltaH is a direct measure of the change of energy, deltaE of a process
• a process that results in an overall decrease in energy of a system (negative deltaH) tends to be favoured
• depends only on the initial and I’d la states of the process - intermediate stages are irrelevant
• the value of deltaH depends on the number and kinds of chemical bonds in the reactants and products

Question 13

Exothermic

Answer 13

A chemical reaction gives off heat
- deltaH is negative

Question 14

Endothermic

Answer 14

Chemical reaction that absorbs hear
- deltaH is positive

Question 15

Enthalpy (H)

Answer 15

• can be measured by a bomb calorimeter

Question 16

Bomb calorimeter

Answer 16

Measures the change in temperature of a water jacket surrounding a reaction chamber during a chemical reaction

Question 17

The second law of thermodynamics

Answer 17

• systems have a tendency towards randomization (disorder)
• describes energy changes but does not tell us if a reaction is favorable/spontaneous

Question 18

How to predict whether a reaction is favourable?

Answer 18

• we must consider both enthalpy plus a second term, entropy, S

Question 19

Entropy

Answer 19

• a measure of disorder or randomness, which tens to increase in a spontaneous reaction:
• high disorder = high randomness = high entropy
• the tendency in nature is toward ever greater disorder in the universe - the total entropy is continually increasing

Question 20

Ice melting entropy

Answer 20

• process requires an input of energy (heat so deltaH is positive) but it happens spontaneously at room temperature
• molecules go from a more ordered state in ice to a less ordered state in water
• makes the overall reaction thermodynamically favourable

Question 21

Hydrophobic effect is a consequence of entropy

Answer 21

• nonpolar molecules spontaneously aggregate in an aqueous solution, increasing their order, (deltaS < 0, is negative)
• however the water molecules that were ordered around the non-polar molecules are no released, increasing their disorder (deltaS&raquo_space; 0, is positive)
• net deltaS for the system is positive, drives the aggregation of the non-polar (hydrophobic) molecules
• process is energetically favourable

Question 22

Protein folding is an entropy-driven process due to the hydrophobic effect

Answer 22

• an unfolded protein is disordered and therefore high in entropy whereas a folded protein is more ordered and lower in entropy
• however, in the unfolded protein hydrophobic regions are exposed to polar water molecules
• the water molecules must order themselves around the hydrophobic regions of the protein to maximize their hydrogen bonding - the organized water is low in entropy
• protein folding increase the order of the protein which is entropically unfavourable but it releases the ordered water molecules, which is entropically favourable - the net deltaS is positive
• protein folding also optimizes weak interactions which is enthalpically favourable

Question 23

What results in a net entropy increase in the universe?

Answer 23

• a chemical reaction may result in a decrease in entropy of the system
• the entropy of the surroundings may increase due to the release of heat