What is a nucleophile and electrophile?
The concept of electrophilicity and nucleophilicity is similar to acidity and basicity. In its simples form, an electrophile is any atom or molecule that is electron deficient. A nucleophile is any atom or molecule that is electron rich. Thus a nucleophile is willing to donate or share its electrons with an electrophile. Nucleophiles generally have pi bonds, negative, or partially negative charge, whereas electrophiles have a positive or partially positive charge.
Explain how enzymes work.
Enzymes are proteins that help catalyze metabolic reactions in the body by lowering the activation energy. Enzymes are unique in that they are not consumed in the reaction, thus the enzyme itself is not altered during the reaction. An important thing to note is that enzymes do not catalyze reactions that would not have occurred if the enzyme wasn't present, enzymes merely speed up the reaction. Enzymes are proteins, and thus they are susceptible to denaturation. Enzymes work best at certain pH levels, temperatures, and solute concentrations. The generally accepted mechanism for enzymes is the induced-fit model. This model explains how the enzyme and substrate fit together. Enzymes can be inhibited through competitive inhibition and non-competitive inhibitions.
Explain the difference between prokaryotes and eukaryotes. How did eukaryotes come to existence.
Prokaryotes typically small, single celled organisms. Bacteria and Archaea are both prokaryotes. Prokaryotes do not have any membrane bound organelles, and thus are very simple in structure. Eukaryotes are much more complicated because they have many specialized membrane bound organelles inside of their cell. These membrane bound organelles include organelles like the mitochondria, chloroplasts, endoplasmic reticulum, Golgi bodies, etc. The theory of endosymbiosis explains how eukaryotes developed over time from prokaryotes. The theory involves the phagocytosis of one prokaryote by another. This creates a new organism with a prokaryote inside of it. Instead of killing the prokaryote inside, the host allowed the internal prokaryote to specialize and resulted in membrane bound organelles.