Cell Biol Chapter 2 outline
Energy and Enzymes
I. Energy
A) Forms of energy
1)kinetic
2) potential
B) units of energy = kilocalories (kcal) e.g. kcal/mol
C) energy uses by cells
1) synthesis (biosynthesis)
2) mechanical work
3) active transport
4) bioluminescence
D) Sources of energy for cells (life)
1) forms available
a) chemical
b) light
2) classification according to energy sources
a) phototrophs “light feeders”
b) chemotrophs “chemical feeders”
3) classification according to carbon source
a) autotrophs = inorganic
b) heterotrophs = organic
4) combined classification scheme e.g. chemoheterotrophs
II. Thermodynamics
A) Free energy (G) [change in free energy = D G]
1) for a reaction of : A Æ B; D G = GB-GA
2) exergonic versus endergonic
3) D G = D E - T D S (E = enthalpy; T = temp in Kelvins; S = entropy)
4) D G' and D Gº'
see conversion of DHAP to G3P
5) “spontaneous” reactions
B) coupled reactions
- “high” energy molecules and their D Gº'
- creatine and creatine phosphate
- NAD, FAD, NADP, FMN
C) ATP as energy currency of the cell
1) structure
2) uses of ATP and “ATP cycle”
III. Activation energy and reaction rates
A) activation energy required for reactions
B) factors influencing the rate of a reaction
1) temperature
2) concentration of reactants
3) pH
4) enzymes (catalyst)
IV. Enzymes
A) characteristics of enzymes
1) catalytic power
2) specificity - “lock and key”
3) active site
B) general mechanism of enzyme action
1) chymotrypsin
C) factors influencing enzyme activity
1) pH
2) temperature
3) cofactors
D) enzyme kinetics
1) Km and Vmax
2) Michaelis Menten kinetics
v = Vmax [S] /Km + [S]
3) double reciprocal plots (Lineweaver - Burk plots)
4) inhibitors
a) competitive
b) noncompetitive
E) control of metabolism (at level of enzymes)
1) isoenzymes or isozymes
2) covalent modification
3) allosteric enzymes
a) feedback inhibition
b) positive and negative effectors
4) proteolytic cleavage