FINAL - CH2 Flashcards
Bioenergetics is defined as
energy conversion in biological
system
Bioenergetics is the study of
the various types of energy transformations that occur in living organisms
3 types of work:
Osmotic: Maintains varying [solute] across biological
membranes
Chemical: Biosynthesis and degradation of organic
molecules
Mechanical: Muscle contraction in animals
Energy pathway:
Solar energy –> Photosynthesis –> Chemical energy –> Work (3 types)
Homeostasis
Highly ordered steady state
Requires energy and delays equilibrium
Example: Living organisms
Equilibrium
Homeostasis is no longer maintained.
Macromolecules tend to equilibrate to their surroundings.
Example: Non-living organisms
Reduction
Gain of electrons
Increase in the number of hydrogens
Decrease in the number of bonds to oxygen***
Oxidation
Loss of electrons
Decrease in the number of hydrogens
Increase in the number of oxygens***
System
Collection of matter in a defined space
Surroundings
All the space not included in the system
Thermodynamics is the study of
the changes in energy that accompany events in the universe
System + Surroundings =
Universe
Open system
Matter and energy are freely exchanged with the
surroundings
Closed system
Only energy is exchanged with the surroundings
Isolated system
Neither matter nor energy is exchanged with the
surroundings
First law of thermodynamics
Energy can be neither created nor destroyed only transformed from one form to another
ΔE = Efinal – Einitial
Descriptions of Enthalpy
Exothermic:
Reaction releases heat
Has a –ΔH
Endothermic:
Reaction absorbs heat
Has a +ΔH
2nd law of thermodynamics
spontaneous processes in the universe tend toward disorder in the absence of energy input
ΔSuniverse = ΔSsystem + ΔSsurroundings > 0
At equilibrium,
ΔG = 0, the rate of formation of products and reactants is equal
Gibbs Free Energy
ΔG
Amount of energy capable of doing work
Exergonic vs. Endergonic Reactions
Exergonic: ΔG < 0, Reaction is overall favorable and spontaneous
Endergonic: ΔG > 0, Reaction is overall unfavorable and non-spontaneous
Standard Free Energy Change
ΔG°
At standard conditions: 1 atm, 298 K, 1M
Keq
A + B –> C + D
Keq = [C]eq [D]eq / [A]eq [B]eq
If Keq < 1, favors formation of reactants
If Keq > 1, favors formation of products
If Keq = 1, reaction is at equilibrium
Biochemical Standard Conditions
ΔG°’
1 atm, 298 K, 1M
pH = 7
[H2O] = 55.5 M
Mg2+ = 1 mM
A common coupling reaction
ATP hydrolysis
____ is a carrier of chemical energy
ATP
EC
Energy charge
Cells regulate the EC between _____
0.7–0.9
In catabolic pathways Energy charge (EC) is _____
low
In anabolic pathways Energy charge (EC) is _____
high
Water is a ______ and a ______ in
biochemical reactions
solvent
reactant
Water is ___ of the weight of
most organism
70%
Angle in water molecules
104.5°
The typical lifetime of an H-bond is
1 x10^-12 s
it is shorter as temperature increases
each water molecule can form ____ hydrogen bonds.
four
__________ occurs between the oxygen atom of one water and the hydrogen of another
electrostatic attraction
H-bonding is especially strong in water because
- the O—H bond is very polar
- there are 2 lone pairs on the O atom
- Each H2O molecule can form four H bonds to other molecules
Important property of H2O
Ice has a lower density than water
Why is ice less dense than liquid water?
each water molecule interacts tetrahedrally with four other water molecules
This creates a regular lattice structure, which causes ice to be less dense (expands)
__________ gives water its unusual
properties
Hydrogen bonding
The attraction between the partial electrical charges is
greatest when the three atoms involved lie in _____________
a straight line
Hydrophobic Effect
The tendency of water molecules to minimize their contact with hydrophobic molecules
forming “cages”
Dialysis
Diffusion of solutes
Hemodialysis
Acts as an artificial kidney
reversible ionization
H2O –> H3O+ + OH-
Proton jumping:
the proton can rapidly
jump from one water molecule to the
next
pH + pOH
= 14
Conjugate Base:
base formed by the removal of a proton from an acid
Smaller Pka
Stronger acid
Larger Pka
Weaker acid
Smaller Ka
Weaker acid
Larger Ka
Stronger acid
[H+] [OH-] =
1 x 10^-14 = Kw
Water density
1000 g/L
MW of water
18 g/mol
Buffers
solutions that resist changes in pH upon addition of acid or base
maximum buffering “capacity”
near the pKa of the molecule ± 1 pH
Mass-action ratio
Q
Keq = [C]i [D]i / [A]i [B]i
Removing _____ from the blood helps increase the pH
CO2
Removing ______ from the blood helps lower the pH
HCO3-
3 types of membranes
Plasma membrane
Endomembranes
Mito/Chlor membranes - required for life
Pka =
-log Ka
