Ch. 2 Flashcards
What is bioenergetics?
Energy conversion in biological systems
- Observed in photosynthesis
What is the importance of chemical energy?
- Used by organisms to perform work
- Essential for cell survival
- Usually obtained from the environment
What are the different types of work?
- Osmotic
- Chemical
- Mechanical
What is osmotic work?
Maintains varying [solute] across biological membranes
- Na+/K+ pump
What is chemical work?
Biosynthesis (anabolic) and degradation (catabolic) of organic molecules
What is mechanical work?
Muscle contraction in animals
What are redox reactions?
- Series of linked oxidation-reduction reactions
- Transfer electrons from one compound to another in sequential fashion
- Used in processes where chemical work is performed and energy is made
What is reduction vs oxidation?
Reduction: gain of electrons (GER)
- Increase in number of hydrogens
- Decrease in number of bonds to oxygen
- Becomes more negative
Oxidation: loss of elections (LEO)
- Decrease in number of hydrogens
- Increase in number of oxygens
- Becomes more positive
What is a system (thermodynamics)?
Collection of matter in a defined space
What are the surroundings (thermodynamics)?
All the space not included in the system
What are the types of systems?
- Open = matter and energy are freely exchanged with the surroundings
- Closed = only energy is exchanged with the surroundings
- Isolated = neither matter nor energy is exchanged with the surroundings
What is the first law of thermodynamics?
- Energy can be neither created nor destroyed
- Can only be converted from one form to another
- Energy has an effect on enthalpy (H)
What is the second law of thermodynamics?
All spontaneous processes in the universe tend toward disorder (entropy, S) in the absence of energy input
What is exothermic vs endothermic?
- Exothermic: reaction releases heat (feels hot), -ΔH
- Endothermic: reaction absorbs heat (feels cold), +ΔH
What is entropy?
Measure of disorder
- Increases when there is more dispersal of energy in a system
- Ex. protein to amino acids
What is Gibbs free energy?
- The difference between enthlapy (H) and the entropy (S) at a given temp
- ΔG = ΔH - TΔS
- (Standard conditions are 298K and 1atm)
- ΔG = ΔH - TΔS
- For biochemocal standar conditions: (pH = 7, H2O constant [55M])
- ΔG’ = ΔH - TΔS
What is the Gibbs free energy equation for cellular conditions?
ΔG = ΔGº’ + RT(lnQ)
- If reaction is at equilibrium: ΔG’ = RT(lnQ)
What are exergonic vs endergonic reactions?
Exergonic: ΔG < 0 (negative)
- Forward reactions
- Reaction is favorable and spontaneous
Endergonic (have to put energy into system): ΔG > 0 (positive)
- Reverse reactions
- Reaction is unfavorable and nonspontaneous
What is the relationship between ΔGº and Keq?
ΔGº = -RT(lnKeq) (at equilibrium)
- Keq
- Keq > 1: favors formation of products
- Keq < 1: favors formation of reactants
- Keq = 1: neither reactants nor products are favored
What are biochemical standard conditions?
- pH = 7
- [H2O] = 55.5 M
- Mg2+ = 1 mM (when involved in reactions)
- Usually stabilizes negative charges on ATP
Explain coupled reactions.
- Endergonic reaction can be coupled to exergonic reaction to become overall favorable as long as the exergonic reaction has an absolute value greater than the endergonic reaction
- Ex. ATP hydrolysis
- Must add the free energies of the separate reactions to find the overall free energy
What is energy charge?
Relationship between [ATP], [ADP], and [AMP] at any given time in a cell
What does a high vs low energy charge mean?
- High EC: More ATP vs. ADP and AMP
- Anabolic
- Low EC: More ADP and AMP vs. ATP
- Catabolic
What are catabolic pathways?
Convert energy-rich compounds into energy-depleted compounds
- Low EC
- Generate ATP and reduced coenzymes (NADH, FADH2, NADPH) using stored fuels
What are anabolic pathways?
Reactions that produce biomolecules from smaller molecules
- High EC
- Use ATP to replenish stored fuels
Explain the polarity of water.
Hydrogen bonding occurs when a hydrogen atom is covalently bonded to an electronegative atom and in close proximity to another electronegative atom
- “Shared” between the 2 electronegative atoms
What kind of stuff is water good at dissolving?
- Polar
- Partially charged
- Fully charged
What are the kinds of weak noncovalent interactions in biomolecules?
- Hydrogen bonds
- Ionic interactions
- Van der Waals interactions
What are hydrogen bonds?
Bonds between hydrogen atoms on an electronegative donor group and another electronegative atom
What are ionic interactions?
Bonds between oppositely charged atoms
- Electrostatic interactions
- Strength of bond depends on distance between the ions and the environment between them
- Salt bridges in proteins
What are van der Waals interactions?
Temporarily occur between the dipoles of nearby electrically neutral molecules
- Depend strongly on the distance between the two atoms
What are hydrophobic effects?
- Occur between nonpolar molecules
- Don’t form hydrogen bonds with water
- Important role in protein folding reactions
- Hydrophobic regions cluster together away from water
What is osmosis?
Diffusion of solvent molecules from a region of lower solute concentration to higher solute concentration through semipermeable membrane
- Can be affected by osmotic pressure
What is the pH equation?
What is the Henderson-Hasselbach equation?
What are buffers?
Aqueous solutions that resist small changes in pH
Draw and label a titration curve.
Explain biological membranes.
- Physical barriers in living systems
- Contain amphipathic lipid molecules that self-assemble into a bilayer
- Majority of amphipathic lipids are phospholipids
- Membrane fluidity depends on phospholipid composition
- Cholesterol helps it be more semisolid (vs. fluid)
Explain phospholipid bilayers.
- Hydrophilic polar head orient toward aqueous environment
- Hydrophobic nonpolar tails located near interior of membrane
What is phospholipid flipping?
- Proteins and lipids can move in membranes
- Lateral mobility depends on
- Temperature
- Distribution of saturated and unsaturated lipids and cholesterol
- Density and types of proteins embedded in the membrane
- Transverse flipping is normally very slow
- Flippases use energy from ATP hydrolysis to catalyze phospholipid flipping
