Biology 172 Lecture 6
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Less enzyme results in a ....
lower Vmax (fewer products in a given time) (fewer active sites)
Rate of reaction increases as ...
increase [S] to a maximum rate (velocity, Vmax)
- Environmental Factors
- Irreversible Inhibition
- Reversible Inhibition
- Allosteric Enzymes
Temperature will affect the ____ _____ of the substrates
- inhibitor binds to enzyme by covalent bonds, conformation is altered
- e.g nerve gas
- Competive inhibitor
- Noncompetive inhibitor
Competitive inhibition directly ...
blocks the active site
- Compete with S for active site of enzyme Often resemble S
- Bind to enzyme with weaker bonds
Some antibiotics, anticancer drugs, herbicides, pesticides To design the inhibitor must
have knowledge of active site / "S" structure
- Molecule binds away from active site and alters active site function
- NOT overcome by changes in substrate concentration (i.e Vmax will be LOWER)
- Reversible and non-reversible (covalent modification enzyme)
Allosteric regulation occurs when ...
a regulatory molecule binds away from the active site.
Allo = dteric =
An Enzyme's Activity is ..
Enzymes are limited in their catalytic flexibility by the chemistry provided by ....
the R-group of amino acids. For example, none of the R-groups can absorb visible light, or bind oxygen (O2) as a carrier.
Cofactors and Coenzymes are additional ...
non-protein factors that can work with protein to provide a broader range of chemistries at active sites, allowing enzymes to catalyze a wider range of reactions
Cofactors are ...
- small non-protein molecules required for an enzyme to function normally.
- Usually inorganic (metal) ions
Coenzymes are ...
- Organic cofactors: NAD, CoA, vitamins
- Derived form vitamins - hence the dietary requirement
- Provide enzymes with a broader range of catalytic reactions
Most drugs are ...
- Competitive inhibitors
- Most of the rest are non-competitive inhibitors
The mevalonate pathway ...
synthesizes cholesterol and many other metabolites
reductase is an enzyme that catalyzes the first step in the pathway
- HMG-CoA reductase uses HMG-CoA as a substrate
- Decreases blood cholesterol.
- Its mechanism of action is to inhibit cellular synthesis of cholesterol.
- When cellular synthesis of cholesterol is decreased with Lipitor, cells respond by taking up cholestrol from the blood
Lipitor, Zocor, Crestor, Pravachol are all competitive inhibitors of HMG-CoA reductase
- Reverse transcriptase is a key enzyme for HIV replication
- Multiple AIDS drug target this enzyme for inhibition
competitive inhibitor, binds at active site
non-competitive inhibitor, binds adjacent to active site
4 groups of Lipids
- Fatty Acids
- Other Lipids
- Not polymers
- Mostly composed of hydrocarbon
- Mostly hydrophobic
- Fuel storage, membranes, hormones Very diverse class of biological molecules. Waves, some pigments, vit A, vit D, cholesterol
- Store a LOT of energy - so release a lot of energy when broken down
- Hydrocarbon chains with terminal carboxyl group
- May be saturated (no double bonds) or unsaturated (with double bonds)
- Not water soluble
Double-bonds in fatty acids determines ______
- no double-bonds in hydrocarbon chain
- solid at room temperature
- double-bonds in hydrocarbon chain
- liquid or oil = more fluid
glycerol linked by ester linkages to 3 acids
condensation (dehydration) reaction
linkage between glycerol and a fatty acid
Triacylglycerol = fats
- like triacylglycerides, but phosphate-containing compound replaces one fatty acid
- Have polar part (hydrophilic hear) and a non-polar part (hydrophobic tail)
- major component of membranes / make membranes
both hydrophilic and hydrophobic regions
2 ways to transport across membranes
- Passive Transport
- Active Transport
- provide permeability barriers for the cell
- composed of lipid bilayer (mostly phospholipids)
What affect membrane permeability
- Length and degree of saturation of the phospholipid tails
Membranes possess a fluid quality
- Phospholipids "drift" within one side of the bilayer
- Fluidity and permeability is enhanced by unsaturated fatty acid tails
- cholesterol (a steroid) stabilizes the membrane
- Stabilizes membranes by interacting with fatty acid tails of phospholipids
Membranes vary in composition
- From one species to another
- From one organelle type to another
- Phospholipids are different on each side of the bilayer
- Proteins are different on each side of the bilayer
- Different inside and outside faces
- Different lipids in the bilayer and different proteins on the cytoplasmic and extracellular sides of the membrane
Outside layer of the vesicle becomes ...
cytoplasmic side when it fuses
Inside face of ER/ Golgi becomes ...
outside (extracellular) face of plasma membrane
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