Biology homework due 7/12/2010

1. There are several differences between animal and plant cells. While animal cells have many small vacuoles, plant cells have one large central vacuole. Also, while the two types of cells both have a semi-impermeable cellular membrane made of a phospholipid bilayer, only plant cells have cell walls, made of cellulose, which animals enjoy as fiber and humans appreciate as “nature’s broom.” One will also find that although both animal and plant cells have mitochondria, only plant cells have chloroplasts and thus the ability to photosynthesize, and aren’t we all jealous.

The cells differ in their energy storage devices, too. Animal cells store energy in the form of glycogen, long interconnected structures of glucose, whereas plant cells store glucose in the form of starch, which is similar to glycogen in that both are chained polymers of glucose. Glycogen just has slightly more branching.

Also, animals tend to store lipids as solid fat, while plants store lipids as liquid oils. Either way, we’ve got options.

2. DNA is simply a polymer formed of nucleotides—molecules composed of the sugar deoxyribose, a phosphate group (AMP, ADP, or ATP), and a ring shaped nitrogenous base either purine or pyramidine in nature. Because DNA is double-stranded, it forms a shape called a double-helix, delighting in a spiral of near genetic infinity. In the nucleus it is tightly coiled into chromatin, but during cellular mitosis and meiosis it obligingly unfurls its squiggly length to coil and form chromosomes, allowing the division and redistribution of cellular instructions.

3. The differences between DNA and RNA may appear minor on paper, but in physical reality, boy are they extensive! Firstly, DNA contains the saccharide Deoxyribose while RNA contains Ribose. Deoxyribose has one oxygen fewer than RNA, allowing for ease of recognition to cellular enzymes. Just imagine you're an identical twin (but we know, inside you’re different—one of you plays basketball, the other one swims, we get it); in order for your grandmother to recognize and thus monetarily reward both of you, you and your brother decide to wear different colored clothes. This way, all enjoy a calm Chanukah dinner.

Another difference is in the nucleotides that comprise the polymers; the nitrogenous bases in DNA are adenine, cytosine, guanine, and thymine. In RNA, the bases are adenine, cytosine, guanine, and uracil.

But yet another difference beckons our attention: as mentioned before, DNA is double stranded, dictating that it shape itself into a double-helix; however, RNA is single stranded (usually), and thus feels no compulsion (nor does it have the ability, usually) to do the same as its close and better appreciated relative.

4. ATP is known in academic circles as Adenosine Triphosphate and on the street as “cellular currency.” The molecule consists of adenosine connected to three phosphate groups. In “spending” one phosphate molecule, ATP creates both ADP, Adenosine Diphosphate, and free electrons, whose innocent enthusiasm can be manipulated for cellular purposes, providing energy. ADP, however, is not nearly as useful as ATP. Confides Shylock from Shakespeare’s Merchant of Venice,

“I hate him for he is ATP;
But more for that in low simplicity
He lends out electrons gratis, and brings down
The rate of usance here with us in Venice.”

(The Merchant of Venice, Act I: Scene 3, line 42-45)

5. Organic molecules abound in nature, as nature is made of them. Carbohydrates enjoy prominence in the organic community, the element carbon being central to their success in all life as we know it, although that can be said about every organic molecule, I suppose. But what really makes carbohydrates special is their propensity for storing energy you don’t need now but will probably want soon, which is why they’ve been said to be the passenger-side seat of organic compounds.

Although lipids are no doubt both organic and quite useful, they suffer from a bad reputation, as Americans like to hoard them in their bodies, generally trying to impress the world with how many they can manage to fit inside one human shell. Doubtless, they are organic.

Proteins have managed to hold a fond place in the public heart for as long as the public has had the pleasure of their acquaintance. Ferraris in the world of organic compounds, proteins always impress with their flashy power and streamlined curves and lines. Yes, they can get you to work on time, but they can also tear up the autobahn like James Dean.

If organic molecules are The Beatles, nucleic acids must be Ringo; without them, everything falls apart, but even when you watch them do their thing in the context of the bigger operation, you just aren’t as impressed as you know you should be, and probably tend to give more credit to the proteins and the carbohydrates, maybe even the lipids. However without them, there would be no cells, at least not as we know them, and once in a while they’re responsible for mutations that either look really cool and work great or fail miserably, only to disappear and be remembered later as a silly idea that yes, seemed to have the potential for success upon conception, but should probably have never made it into distribution.