Unit 2 was titled miniature biology. It was about atoms, water, and the four macro-molecules, lipids, nucleic acid, proteins, and carbohydrates, with extra focus on a type of protein called an enzyme.
Atoms are the smallest unit of matter that can't be divided into smaller pieces. Atoms are made of protons, which have a positive charge, and neutrons, which have a neutral charge, in the nucleus, and electrons, which have a negative charge, circling around the nucleus. The number of protons and electrons are always the same in an atom. The number of neutrons can change, but the element will still have the same chemical properties and be called an isotope. Elements are pure substances made of only one type of atom. Atoms can bond together in several ways. 3 of the bonds are ionic, covalent, and hydrogen. Ionic bonds are when one atom gives an electron to another atom, creating a positive ion (the atom that gave the electron) and a negative ion (the atom that received the electron) which are attracted together. Covalent bonds are when 2 atoms share electrons. The electrons circle around both atoms, but tend to stay more towards the atom with more protons because it has a more positive charge, which attracts the negative electrons. This causes an molecule to be polar, where one part is more negatively charged, and another part of the molecule is more positively charged. An example of this is water, where the oxygen is more negatively charged, and the hydrogen atoms are more positively charged. In water, hydrogen bonds can form where two oppositely charged part of polar molecules have a weak attraction towards each other. When atoms react, they bond to form a new substance which has completely different chemical properties than the original atoms that it came from.
Water, as previously mentioned, is a polar molecule, with a negative oxygen atom, and two positive hydrogen atoms. This makes water cohesive, which causes it to hydrogen bond to itself and stick together, which causes water to bead up in dew. It is also adhesive, which makes it hydrogen bond to other surfaces, like a meniscus on a graduated cylinder. When both adhesion and cohesion are combined in a small enough area, it causes capillary action, which can make water flow up against the pull of gravity. Water is known as the universal solvent, because it can dissolve many things. Substances that dissolve things are called solvents, and the things that are dissolved are called solutes. Everything has a pH, which is its level of acidity. If something has a pH of 7, it is neutral. If it is above 7 to a maximum of 14, it is basic. If it is below seven to a minimum of 1, it is acidic. Acids are sour, corrosive to metal, and have more positive H+ (hydrogen) ions than negative OH- (hydroxide) ions. Bases are bitter, and have more OH- ions than H+ ions. When if either an acid or a base is combine with the opposite, it becomes less basic or less acidic.
The four macro molecules are lipids, proteins, nucleic acid, and carbohydrates. All macro-molecules are made of carbon, which has the ability to bond with itself. Carbohydrates are made up of one or more rings of carbon, hydrogen, and carbon. They are used to store energy in animals, and make up the structure of plants. When a carbohydrate is made of only one ring, it is a monosaccharide, like fructose. When it is made of 2 or more rings, it is a disaccharide, like lactose. When it is made of 3 or more rings, it is a polysaccharide, like starch. Monosaccharides and polysaccharides taste sweet, and polysaccharides don't. Proteins are made of a combination of 20 total amino acids. They have several levels of structure. First in the primary structure, which is the amino acids bonding together. Multiple amino acids bonded together are polypeptides. The next level is the Secondary structure. The bonded amino acids hydrogen bond together to form a helix. Next is the Tertiary structure, where the amino acid bonds cause folding. Then the last level is the Quaternary Structure, where multiple tertiary structures bond to make a large protein.
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