Biology Homework due 7/20/10

1. To put it simply, kinetic energy is the energy of motion. Potential energy is stored energy.

To put it less simply, kinetic energy, the energy of motion, is energy in action, energy doing its thing, in the prime of its life. Potential energy, however, isn’t quite ready yet; it’s still in middle school, unsure of itself, timid, perhaps because it’s a bit pimply or probably because it hasn’t grown as tall as the other boys, but either way, it’s just biding its time. It’s waiting, about to take action for once in its so far unremarkable but promising life.

Let’s move beyond middle school. Imagine, for a moment, that we’re at the NASA launch station at Cape Canaveral. The space shuttle Discovery sits on the pad, ready to blast off. “T-10.” The countdown begins. “7." While all systems are online and ready, the rocket fuel sits in the tank. “5.” This fuel is potential energy—chemical energy—and as yet untapped. “3. 2. 1.” However, as soon as the countdown ends and the fuel ignites, its potential energy becomes kinetic energy, the propellant participating in a combustion reaction ferocious enough to hurdle thousands of tons of metal, along with a few hundred meager pounds of human, into the atmosphere.

The pimply teenager has shed his glasses and bowl cut, and can now be seen in Ocean’s Eleven as Danny Ocean and on the cover of People Magazine as The Sexiest Man Alive, but in our hearts, he’s George Clooney. He has done it. He has become kinetic energy.

2. An enzyme is a biological catalyst, nearly always a protein molecule save for ribozymes, which are made of RNA, and some others. An enzyme allows the component or components of the reaction—the substrate(s)—to separate into several products (degradation) or join into one product (synthesis). The substrates bind at the active site of the enzyme and are released as products when the reaction ends, leaving the enzyme in its original form to continue catalyzing reactions.

Factors that affect the function of these catalysts include temperature and pH, extremes in both of which change the shape of the enzyme so that its active site can no longer accept substrates.

But what makes enzymes so great? Are they really necessary? Couldn’t our bodies function without them? Well, I don’t think so. Yes, some of these reactions could certainly occur, mostly by chance, without enzymes. You’re right about that. However, enzymes greatly decrease the energy of activation, increasing the rate and efficiency of the reaction.

Enzyme inhibition is a serious issue facing enzymes these days. When a molecule binds to the enzyme, changing its shape so that it can’t accept substrates, we call it enzyme inhibition. There are two types of enzyme inhibition: noncompetitive and competitive.

Noncompetitive inhibition is when a molecule binds to an enzyme at an allosteric site—not its active site—to change its shape, forcing it to refuse substrates. Competitive inhibition is when a molecule binds at the active site, mimicking the substrates and preventing them from reacting.

Imagine you’ve applied to study at a university, specifically to major in communications. Unfortunately, your admission was denied because the school met its quota of total students—someone in the math department got your spot. This is noncompetitive inhibition. Now imagine another, slightly more unfortunate scenario: you’ve applied to study at a university, specifically in the college of communications. Unfortunately, your admission was denied because the college of communications met its quota of total students—someone in the department to which you applied got your spot. This is competitive inhibition, and it is usually slightly more frustrating than noncompetitive inhibition.