Cell and Molecular Biology Ch. 1 pt 2 Flashcards
Microscopy cont. What does centrifugation do?
Prepares sample for observ. or further experim. by spinning and separating liquified cell homogenates into layers based on density
Order in which cell parts separate via centrifugation:
- Most dense pelleting first
- Least dense pelleting last
Order in which cells separate via centrifugation starting from first component to pellet at the bottom and progressively spinning faster:
Nuclei layer –> mitochondria/chloroplasts/lysosomes –> microsomes/small vesicles –> ribosomes/viruses/larger macromolecules
Centrifugation can be ________ centrifugation or density centrifugation.
Differential - relies on density, shape, and speed at which macromolecule travels
- Spin pattern is differential: spin, separate dense pellet, and repeat.
What does differential centrifugation form?
Continuous layers of sediment, where insoluble proteins are found in the pellet while soluble proteins remain in the supernatant, liquid above the pellet.
Characteristics of chemical rxns
The concentration of reactants and products determines which way the rxn will go.
When a rxn is in equilibrium, the _____ of formation of reactants and products is equal and there is ___ net production.
Rate; 0
Chemical rxns in which small molecules are assembled into larger molecules are ________ rxns.
Anabolic - Energy is required
When large molecules are broken down into small molecules, it is a ________ process.
Catabolic - Energy is released
What are globular proteins that act as ________.
Catalysts
What lowers the activation energy of a rxn, thereby accelerating the rate of the overall rxn.
Catalysts
Are enzymes substrate-specific?
Yes, they remain unchanged during the rxn, catalyze both forward and reverse directions of the rxn, have varying fxn based on pH and temp., and have an active site that binds substrates via induced fit.
What are non-protein molecules that assist enzymes usually by donating or accepting some component of a rxn, such as electrons or functional groups.
Cofactors
What are organic cofactors called?
Coenzymes, and they are commonly derived from vitamins
True or False. Coenzymes usually donate or accept electrons.
True
________ cofactors are usually metal ions like Fe2+ and Mg2+.
Inorganic
If the cofactor binds tightly or covalent to the enzyme, it is referred to as a __________ group.
Prosthetic
______ is a common source of activation energy, and the compound stores its potential energy in the form of _______ chemical energy.
ATP; chemical
New ATP is formed via ____________, _______ and ___________ come together using energy from an energy rich molecule like glucose.
Phosphorylation; ADP and phosphate
Why must enzymes be strictly regulated?
To ensure that they are only functional for specific use.
Enzymes can be regulated using the following methods (6)
- Km
- Allosteric enzymes
- Competitive inhibition
- Noncompetitive inhibition
- Uncompetitive/ anti-competitive inhibition
- Cooperativity
Regulation of Enzymes: What is Km
Michaelis constant which represents the substrate concentration at which the rate of rxn is half of the max velocity of the enzyme, or Vmax
Regulation of Enzymes: Allosteric enzymes have both an ________ _______ for substrate binding and an __________ site for the binding of an allosteric effector (can be an activator or inhibitor)
Active site; allosteric
Regulation of Enzymes: _________ inhibition: a substance that mimics the substrate and inhibits the enzyme by binding at the active site.
Competitive
The effect of competitive inhibition can be overcome by increasing ________ concentration.
Substrate. Remember, Km is raised but Vmax is not.
Regulation of Enzymes: Noncompetitive inhibition - substance inhibits enzyme by binding elsewhere than the active site, allowing the ______ to still bind, but the rxn is prevented from _______________.
Substrate; completing. Remember, Km is unchanged but Vmax is lowered.
Regulation of Enzymes: Describe uncompetitive/ anti-competitive inhibition.
Occurs when an enzyme inhibitor binds only to the formed enzyme-substrate (ES) complex, preventing formation of product.
In a way, Km inversely represents binding affinity: a small Km indicates that an enzyme requires a ______ amount of substrate to become saturated.
Small; hence, the max velocity is reached at relatively low substrate concentrations.
A large Km indicates the need for _______ substrate concentrations to achieve max rxn velocity.
High; A higher Km equates to worse substrate binding, while a lowered Km equals better substrate binding.
Review: __________ inhibitor
- same Vmax, different Km
Competitive
Review: _________ inhibitor
- same Km, different Vmax
Non-competitive
Regulation of Enzymes: Cooperativity
Phenomenon that occurs where an enzyme becomes more receptive to additional substrate molecules after one substrate molecule binds to the active site
Example of cooperativity
Hemoglobin is a quaternary protein with 4 subunits that each has an active site for binding oxygen. As the first oxygen binds, the other active sites become increasingly likely to bind oxygen. Note: hemoglobin is NOT an enzyme.
