Bio Lecture 8

Many drugs used for HIV are competitive inhibitors of the viral enzyme HIV protease. Therefore, these drugs must have structures that..

are similar to the substrates of HIV protease

How does an enzyme increase the rate of a reaction?

by lowering the activation energy

Rates of enzyme catalyzed reactions can be controlled by?

changing the amount of enzyme present in the cell and changing the ability of the enzyme to function

What does it mean that enzymes are specific? Describe the property/feature of enzymes makes them specific. What other features of enzymes?

Enzymes are specific because they catalyze ONE reaction; enzymes are composed of amino acids which are covalently bonded to each other forming chains; the charges of amino acids are then noncovalently bonded forming the complex 3D folded structure of enzyme; this influences the shape of the active site which only permits certain substrates to fit Other features: highly effective, able to make chemical reactions occur more rapidly;

Can an enzyme alter the amount of energy released or required for a reaction?

No. Enzymes influence activation energy and rates or reactions but do not alter energy required or released.

Explain why altering enzyme activity is the main way reaction rates are controlled in cells.

Regulating cellular reactions is essential to make sure the right molecules are formed or destroyed for proper functioning and to prevent wasting energy and resources and all cellular reaction require an enzyme to occur fast enough to be useful

Generally, increasing the amount of substrate does what to rate of a reaction when an enzyme is present? what does that graph look like? Include enzyme saturation in response.

Adding more substrate can increase the rate at which products are formed through enzyme activity. @ a certain point enough substrate will be present that all the enzyme's activity sits are full and adding even more will not increase activity. this is called enzyme saturation.. graph: the graph has a logarithmic curve and levels off once enzyme saturation is reached

In what conditions is the activity of an enzyme affected?

Changes in pH can change the shape of an enzyme and its ability to interact with substrates; as temperature increases enzyme ability increases but at a certain point denaturing occurs which will decrease enzyme activity and break the noncovalent bonds.

Draw a graph of free energy versus reaction progress for an energy-releasing reaction. Now add a line (curve) that shows the reaction in the presence of an enzyme able to catalyze the reaction.

Graph: Draw traditional activation energy curve, but then draw a curve that cuts below initial transition state showing the new activation energy required for reaction to jumpstart

What do you predict would happen to an enzyme's ability to function if the shape of an enzyme's active site was altered? Explain your answer.

If the enzyme's active site was altered the enzyme would no longer be receptive to the substrates it once catalyzed making it ineffective....goes along with specificity of enzyme...reaction rate will decrease.

You mix an enzyme with a certain amount of substrate and a competitive inhibitor. If you added a ton more substrate to the reaction, would the inhibitor be more, less, or equally effective? What about if you used a noncompetitive inhibitor? Explain your answers.

Increasing the amount of substrate will decrease the competitive inhibitors effectiveness; increasing the amount of substrate will not affect the noncompetitive inhibitors effectiveness Mastering Bio Input: Competitive inhibitors interact in the active site of an enzyme, therefore addition of more substrate decreases the ability of a competitive inhibitor to inhibit an enzyme. With lots of substrate around, the enzyme is much more likely to interact with the substrate than the inhibitor. Noncompetitive inhibitors interact with an enzyme in a place that's different from the active site. Therefore, no matter how much substrate is around, the inhibitor can still bind to the enzyme. This means that increasing the amount of substrate will not alter the effectiveness of a noncompetitive inhibitor.

Lactase is an enzyme that catalyzes the conversion of lactose (a disaccharide) to glucose and galactose (two monosaccharides). Explain what the term catalyzes means in this context.

Lactase is an enzyme that can break down lactose into monomers/monosaccharides. Lactose binds/interacts with lactase's active site; the enzyme begins to change shape straining the bonds that need to be broken; this change of shape lowers activation energy/ makes forming transition state energetically easier; the products are then released from enzyme.

List the features of a reaction that are changed by addition of an enzyme that can catalyze the reaction. Now list the features of a reaction that are NOT changed.

The features that change in addition of an enzyme are activation energy and rate or reaction. The free energy of substrates(reactions) and products along with the total energy released or required is not changed. Mastering Bio Input: Enzymes decrease the activation energy for a reaction by lowering the free energy of the transition state, and therefore increase the rate (speed) at which the reaction occurs. Enzymes do NOT alter the free energy of the substrates or products of the reaction, and therefore cannot change the total amount of energy released or required by the reaction.

Describe the general process by which enzymes catalyze a reaction. In your description, include an explanation of how enzymes increase the rate of a reaction.

The substrates/reactant binds with the enzyme active site. The active site has a specific shape and forms many noncovalent bonds with reactants. This interaction of substrates causes the enzyme to change shape. Strains are put on the bonds that need to be broken and atoms that need to form bonds are put near each other. This change of shape is primarily responsible for the decrease in activation energy, makes forming in transition state energetically easier. Lastly the products form and are released from enzyme note: the enzyme is unchanged and can catalyze more reactions

What can be introduced to an enzyme that would increase its activity? decrease its activity?

introduce an activator; a molecule that increases the enzyme activity...interaction of an activator allows enzyme to interact better with its substrates introduce an inhibitor; a molecule that decreases an enzymes activity... interaction of an inhibitor makes this enzyme less able to interact with its substrates

What are the different categories of inhibitors?

irreversible inhibitors: gets attached to an enzyme by covalent bonds (strong interaction) and permanently changes the shape of active site of enzyme and prevents substrates from entering; shuts down enzyme reversible inhibitors: can interact and dissociate with enzyme; there are competitive inhibitors (interact in active sites and block interaction of substrate) and noncompetitive reversible inhibitors (interaction changes enzyme shape and decreases ability of enzyme to interact with substrate... Note: competitive inhibitors interact in the free active site therefore they must have structures similar to the substrates of the enzyme

In the context of cellular energy transformation processes ______ electron carriers have electrons, and transfer of electrons from molecules with lower affinity for electrons to molecules with higher affinity for electrons ______ energy.

reduced; releases Mastering Bio Info: Electron carriers are molecules that accept and give up electrons to pass electrons around in cells. The reduced form of an electron carrier has electrons, while the oxidized form can accept electrons. Passing electrons from a molecule that has a lower affinity for electrons to another molecule that has a higher affinity for electrons releases energy.