16.4 & 16.5 Chemistry review exam #4

What are some biological functions performed by proteins/enzymes?

- Catalyzing chemical reactions - Transporting molecules - Providing structure and support - Regulating gene expression - Transmitting signals - Defending against infection - Controlling metabolism

What is the ending of the name for a protein that is an enzyme?

-ase

List some specific ways intermolecular forces are important for the functioning of nature. Which specific IMF are involved?

1. Base recognition for RNA/DNA <- h-bonding 2. degree structure <- backbone atoms (h-bonds) 3. degree structure <- side chains (IMF)

Why does heat (high temperatures) slow down enzyme activity?

At higher temperatures, enzyme activity increases as reacting molecules move faster to cause more collisions with enzymes

Why does cold (low temperatures) slow down enzyme activity?

At low temperatures, most enzymes show little activity because there is not a sufficient amount of energy for the catalyzed reaction to take place

What are the three types of intermolecular forces?

Londen dispersion, h-bonds, dipole-dipole

What is the active site of an enzyme?

This active site is often a small pocket within the larger tertiary structure that closely fits the shape of the substrate

Nearly all enzymes are ______________________ .

proteins

What is the role of the protein "DNA polymerase"?

synthesize a new strand of DNA by adding nucleotides to the 3' end of a pre-existing strand

What are three factors that effect enzyme activity?

temperature, pH, and the presence of inhibitors

Why do you think the linkage between two nucleotides is called a "phosphodiester" bond?

The term "phosphodiester" indicates the presence of two ester bonds (-O-C=O) between the phosphate group and two sugar molecules. The name is derived from the combination of "phosphate", which refers to the phosphate group, and "diester", which refers to the two ester bonds

What is the function of a catalyst?

A catalyst increases the reaction rate by changing the way a reaction takes place but is itself not changed at the end of the reaction

What is "competitive inhibition"?

A competitive inhibitor competes with substrate for binding to an active site.

What is the "induced fit" model for enzyme action?

A model of enzyme action in which the shapes of the substrate and its active site adjust to give an optimal fit

What are enzymes?

A protein that catalyzes biological reactions

What is the activation energy of a reaction and how do catalysts/enzymes affect the activation energy of a reaction?

Activation energy is the minimum amount of energy required for a reaction to occur Catalysts & enzymes lower the activation energy The active site of the enzyme, a region on its surface that binds to the substrate, facilitates the reaction by lowering the activation energy. In addition, enzymes can also increase the reaction rate by properly orienting the substrate molecules and applying a specific amount of force to break and form chemical bonds.

What is the "lock and key" model for enzyme action?

An early theory of enzyme action, called the lock-and-key model, described the active site as having a rigid, nonflexible shape.

What are biological catalysts called?

Bilogical catalysts are called enzymes

How do changes in pH affect enzyme activity? Why?

Enzymes are most active at their optimum pH, the pH that maintains the proper tertiary structure of the protein If a pH value is above or below the optimum pH, the R group interactions are disrupted, which destroys the tertiary structure and the active site

What type of reaction forms the phosphodiester bonds?

The phosphodiester bonds are responsible for linking nucleotides together to form the sugar-phosphate backbone of DNA and RNA molecules

Why are enzymes very specific in the reactions they catalyze?

The active site of a particular enzyme fits the shape of only a few types of substrates, which makes an enzyme very specific about the type of substrate it binds. Within the active site, the R groups of specific amino acids interact with the functional groups of the substrate to form hydrogen bonds, salt bridges, or hydrophobic interactions.

What is a substrate?

The molecule that reacts in the active site in an enzyme-catalyzed reaction

How do enzymes, in general, perform their function?

perform their function by lowering the activation energy required for a chemical reaction to occur -> thereby accelerating the reaction rate

What is the role of the protein "helicase"?

unwind the double-stranded DNA molecule by breaking the hydrogen bonds between complementary base pairs, thereby separating the two strands and allowing access to the genetic information stored in the DNA