Topic 4 - Enzymes - Biology 241 - University of Calgary

• Proteins that speed up metabolism or chemical reactions.

Enzymes

• Polypeptide folded into functional 3-D shape.

Proteins

• An organic compound containing a carboxyl group, amino group, and an R group.
• Building blocks of proteins.

Amino Acids (2)

• Portion of an amino acid that makes each amino acid different from each other.
• Decides polarity, size, structure, etc.

R Group (2)

• Short chains of amino acids that can function as neurotransmitters or hormones.

Peptides

• A peptide with 10+ amino acids linked together by peptide bonds.

Polypeptide

• Literal sequence of amino acids.

Primary Structure

• Formed by folding and twisting of the amino acid chain due to hydrogen bonding.
• Forms helices or sheets.

Secondary Structure

• Formed when the secondary structure folds again into a 3-D shape.

Tertiary Structure

• Group of tertiary structures consisting of more than one polypeptide chain bonded together.

Quaternary Structure

• End of a polypeptide or protein that has a free amino group.

N-terminus

• The end of a polypeptide or protein that has a free carboxyl group.

C-terminus

• A protein with all identical subunits.

Homomeric

• A protein with some subunits that are non-identical.

Heteromeric

• Minimum amount of energy required to start a chemical reaction.

Activation Energy

• High-energy intermediate state of the reactants during a chemical reaction that must be achieved for the reaction to continue.

Transitional State (Summit)

• The difference between the reactants and transition states free energy.

Activation Barrier

• Increase the temperature.
• Increase the concentrations of the reactants so the reactants collide more often.
• Increase the surface area so that the reactants collide more often.
• Add a catalyst.

What are some ways to speed up a chemical reaction? (4)

• A region that interacts with a substrate, causing the enzyme's shape to change.

Active Site

• A temporary complex formed when an enzyme binds to its substrate molecule(s).

Enzyme-Substrate Complex

• The change in the shape of an active site so it binds better with the substrate, forcing it into a transition state. Once the reaction is complete, the enzyme releases the product and returns to its original shape.

Induced Fit

• Bringing reactants closer together.
• Exposing reactants to altered charge environment that promotes catalysis.
• Changing the shape of a substrate molecule.

What are some ways enzymes lower activation energy? (3)

• Use of energy released from exergonic reactions to drive endergonic reactions.
• Enzymes do this by becoming phosphorylated or reduced.

Energy Coupling Reactions (2)

• The concentration of the enzyme and the concentration of the substrate.

What factors effect the rate of an enzyme reaction? (2)

• Loss of protein structure due to heat, pH changes, or a non-competitive inhibitor.

Denaturation (3)

• Loss of protein activity from denaturation.

Inactivation of Proteins

• Is chemically like the substrate and binds noncovalently to the enzyme at the active site. However, it undergoes no reaction and prevents the substrate from entering the active site.

Reversible Competitive Inhibitor

• Not chemically like the substrate and binds noncovalently to the enzyme at the allosteric site. This changes the shape of the active site and reduces the enzyme's substrate affinity.

Reversible Noncompetitive Inhibitors

have both an active site for substrate binding and an allosteric site for binding of an allosteric effector (activator, inhibitor)

allosteric enzymes

• Binds to the enzyme which changes shape to a more active form.

Allosteric Activator

• Binds to the enzyme which changes shape to a less active form.

Allosteric Inhibitior

• A method of metabolic control in which the final product of a pathway that binds to the enzyme and inhibits it (turns it off).

Feedback Inhibition

• The acceleration of a chemical reaction by a catalyst.

Catalysis

• H-bonds.
• Ionic bonds.
• Van der Waals forces.
• Covalent bonds.

Tertiary structures can form what types of bonds and forces? (4)

• Activation energy.

During glycolysis, the bonds in the reactants are stable, therefore, to destabilize the bonds what energy must be added to the reaction to get it going?

• Changing the concentration of inhibitors and activators.

How do cells control enzyme kinetics?

• When all the active sites of the enzyme are filled with substrate.

Plateau Region

• Highest.

The molecule with the ____________ concentration will outcompete the other.

• Vmax = the same.
• Km = increases.

When you have a competitive inhibitor, what happens to the Vmax and Km?

• Vmax = decreases.
• Km = very similar.

When you have a non-competitive inhibitor, what happens to the Vmax and Km?

• High.

_____ concentrations of the substrate do not outcompete the inhibitor.