Chapter 6 - Energy and Life

Question 1

Thermodynamics

Answer 1

Study of energy transfer and transformation

Question 2

Anabolic pathway

Answer 2

Build up of simple –> complex molecules

• dehydration (condensation)
• endothermic reaction (requires energy input)
  e. g. photosynthesis

Question 3

Catabolic pathway

Answer 3

Breakdown of complex –> simple molecules

• hydrolysis
• exothermic reaction (gives out energy)
  e. g. respiration

Question 4

Energy

Answer 4

capacity to cause change

Question 5

Thermal energy

Answer 5

type of kinetic energy

-generated by friction, collision, random movement of particles

Question 6

Potential energy

Answer 6

energy that matter possess as a result of its location, position (gravity, electron shell), structure (chemical energy) and concentration gradient (proton motive force, electrochemical gradient)

Question 7

Laws of Thermodynamics

Answer 7

1) Law of energy conservation
- energy cannot be created/destroyed, only transferred and transformed
2) total entropy of universe must increase
- when energy transfers/transforms, entropy of the universe always increases

Question 8

Spontaneous reaction

Answer 8

occurs without input of energy 
exothermic reactions (ΔG < 0)

Question 9

enthalpy

Answer 9

total energy

Question 10

Gibbs free energy (G)

Answer 10

portion of system’s energy that can do the work
=work capacity
ΔG = ΔH - TΔS

Question 11

exergonic reaction

Answer 11

releases energy (energy of reactants > energy of products)
spontaneous reaction

Question 12

endergonic reaction

Answer 12

requires energy (energy of reactants < energy of products) 
non-spontaneous reaction

Question 13

Characteristics of unstable systems

Answer 13

• rich in energy (G), highly organized
• greater work capacity
• have tendency to change spontaneously to more stable state

will change to decrease the free energy of the system (ΔG < 0), released free energy can be used to do work

Question 14

Characteristics of stable systems

Answer 14

• lower in energy (G), unorganized

- low working capacity

Question 15

Energy state in living organisms

Answer 15

• living organisms are open systems that try to move away from equilibrium
• maintain higher G value - highly organized state and low entropy

Question 16

ATP

Answer 16

Adenosine Triphosphate

-phosphates connected by phosphoanhydride bridge]

Question 17

Spontaneous reaction

Answer 17

requires input of energy 
endothermic reactions (ΔG > 0)

Question 18

Non-protein helpers of enzyme activity

Answer 18

1) Cofactor
- inorganic transition metals
- prosthetic groups
e. g. Fe, Mg, Cu
2) Coenzyme
- organic
e. g. Vitamin B2 (Riboflavin, FAD+), B3 (Niacin, NAD+) working as electron carriers in cell respiration

Question 19

Prosthetic groups

Answer 19

• type of cofactors
• emphasizes structural aspect
• bind tightly to proteins or enzymes —> difficult to remove

Question 20

Lock and Key Model

Answer 20

not used

• unchangeable fitting of complementary shapes (correct size and shape) of the enzyme and its substrate
• limitation: cannot explain the flexible structure of enzymes

Question 21

Induced Fit Model

Answer 21

• upon substrate binding to enzyme, structural changes occur in active site
• active site continues to change until the substrate is completely bound to the enzyme’s active site

Question 22

Inhibitor

Answer 22

chemicals that inhibit enzyme activity

1) competitive inhibitor
- molecular mimic of substrate
- competes with substrate to bind to active site
- reversible
e. g. molecular mimics like endorphin and morhipne
2) non-competitive inhibitor
- no competition with other substrates
- bind to cell to shape change shape and size
- irreversible

Question 23

Allosteric regulation

Answer 23

binding of regulatory molecule to an enzyme’s allosteric site to affect the activity and structure of the enzyme

Question 24

Regulatory molecules

Answer 24

1) activator
- promote enzyme activity
e. g. ADP, AMP for cellular respiration
2) inhibitor
- inhibit enzyme activity

Question 25

Cooperativity

Answer 25

type of allosteric activation

• binding of one substrate molecule to active site of one subunit locks all other subunits in active conformation
• e.g. hemoglobin - active state with allosteric molecule (O2), inactive state without allosteric molecule