Chapter 6 - Energy and Life Flashcards
Thermodynamics
Study of energy transfer and transformation
Anabolic pathway
Build up of simple –> complex molecules
- dehydration (condensation)
- endothermic reaction (requires energy input)
e. g. photosynthesis
Catabolic pathway
Breakdown of complex –> simple molecules
- hydrolysis
- exothermic reaction (gives out energy)
e. g. respiration
Energy
capacity to cause change
Thermal energy
type of kinetic energy
-generated by friction, collision, random movement of particles
Potential energy
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)
Laws of Thermodynamics
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
Spontaneous reaction
occurs without input of energy exothermic reactions (ΔG < 0)
enthalpy
total energy
Gibbs free energy (G)
portion of system’s energy that can do the work
=work capacity
ΔG = ΔH - TΔS
exergonic reaction
releases energy (energy of reactants > energy of products) spontaneous reaction
endergonic reaction
requires energy (energy of reactants < energy of products) non-spontaneous reaction
Characteristics of unstable systems
- 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
Characteristics of stable systems
- lower in energy (G), unorganized
- low working capacity
Energy state in living organisms
- living organisms are open systems that try to move away from equilibrium
- maintain higher G value - highly organized state and low entropy
ATP
Adenosine Triphosphate
-phosphates connected by phosphoanhydride bridge]
Spontaneous reaction
requires input of energy endothermic reactions (ΔG > 0)
Non-protein helpers of enzyme activity
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
Prosthetic groups
- type of cofactors
- emphasizes structural aspect
- bind tightly to proteins or enzymes —> difficult to remove
Lock and Key Model
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
Induced Fit Model
- 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
Inhibitor
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
Allosteric regulation
binding of regulatory molecule to an enzyme’s allosteric site to affect the activity and structure of the enzyme
Regulatory molecules
1) activator
- promote enzyme activity
e. g. ADP, AMP for cellular respiration
2) inhibitor
- inhibit enzyme activity
Cooperativity
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
