POB Ch. 8

Enzymes

A more effective way to speed up a reactions in a living system is to lower the energy barrier by bringing the reactants close together. In living cells, ______________ accomplish this task.

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Another metabolic pathway involves the conversion of molecules X to Y to Z to Q. Enzyme 1 catalyzes the first reaction, enzyme 2 catalyzes the second, and enzyme 3 catalyzes the third. If enzyme 1 is activated by molecule Q and the gene for enzyme 1 is inhibited from being expressed, which set of simulation conditions will best model this system?

1. Chemical Reactions 2. Not 3. Highly

Catalysts increase the rates of chemical reactions. Most nonbiological catalysts are __________ specific. Most biological catalysts are ___________ specific.

By binding to a site other than the active site and causing a conformational change in the enzyme.

How do allosteric regulators affect their target enzymes?

Substrates; Active Site

In an enzyme-catalyzed reaction, the reactants are called _________________. These molecules bind to a particular place on the enzyme protein called the ___________________, where catalysis takes place. *The specificity of an enzyme in speeding up a particular reaction results from the exact three-dimensional shape and structure of its active site, into which only a narrow range of substrates can fit.

enthalpy (H)

In biological systems, the total energy is called _____________________.

Lysosomal enzymes have an amino acid sequence and therefore tertiary structure that exposes their active site at pH 4.8. At pH 7.2, the tertiary structure does not expose the active site, so the enzyme is inactive.

Inside the cell, the pH of the cytoplasm is typically 7.2, but inside the lysosome the pH is 4.8. A protease, which catalyzes the hydrolysis of proteins, is active within the lysosome but is inactive in the cytoplasm. How can this occur?

Law Of Thermodynamics

Laws derived from studies of the physical properties of energy and the ways energy interacts with matter.

Yes. In this case, activation energy is needed to make the substrate(s) able to take up energy and then the reaction proceeds.

Q: Would activation energy be required for an endergonic reaction?

Activation Energy (Ea)

The energy barrier that blocks the tendency for a chemical reaction to occur.

Noncompetitive Inhibitor

The binding of an effector molecule at a regulatory site of an enzyme causes an alteration of the geometry of the active site and loss of enzymatic activity. This effector binding is freely reversible. This is an example of?

equal to the energy needed by the reverse reaction of ADP + Pi → ATP.

The energy released by the hydrolysis of ATP to ADP and Pi is

Transition-State intermediates

What are unstable molecules in a reaction which is formed during the reaction when reactants change into products? *These have higher free energies than either the reactants or the products. Their bonds may be stretched and therefore unstable

Endergonic reactions are coupled in time and space with exergonic reactions, which increase the disorder and release the energy needed for the endergonic reactions to proceed. Overall, organisms need to take in energy from their environment continually to maintain these reactions.

What makes it possible for endergonic reactions to proceed in organisms?

A set of interdependent pieces

Which is present in any biological system?

Transition state > products > reactants

Which series best summarizes the relative energies of the different stages of an endergonic chemical reaction?