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AP Bio: Chemistry of Life

Terms in this set (126)

The structure of water is the key to its special propeties. Water is made up one atom of oxygen and two atoms of hydrogen, bonded to a form a molecule
- - Ice: The openings in the lattice make ice less dense than liquid water, so it floats. That causes water to freeze from the top down, so there's always liquid in which organisms can live. Ice floats because of the weakness of hydrogen bonds. This weakness allows hydrogen bonds to constantly break and reform, allowing molecules to periodically approach one another in the liquid state. In the solid state the hydrogen bonds become rigid and form of a crystal that keeps the molecules separated and less dense. This keeps larger bodies of water from freezing solid, allowing life to exist in ponds, lakes, and even oceans
- Cohesion is allowed to happen because of hydrogen bonding, and it contributes to a high surface tension, creating a water surface that is firm enough to allow many insects to walk upon it without sinking, also enables plants to transport water from the roots to the leaves against the force of gravity. It is the linking of like molecules
- Adhesion: Water is transported in plants through both cohesive and adhesive forces; these forces pull water and the dissolved minerals from the roots to the leaves and other parts of the plant.
- Capillary Action: Adhesion is observed when water "climbs" up the tube placed in a glass of water: notice that the water appears to be higher on the sides of the tube than in the middle. This is because the water molecules are attracted to the charged glass walls of the capillary more than they are to each other and therefore adhere to it. This type of adhesion is called capillary action. It also allows water to move through plant roots and stems and the smallest blood vessels in your body - as one molecule moves up the tree root or through the capillary, it 'pulls' the others with it.
- Heat capacity: moderation of temperature is possible because of water's high specific heat. The amount of heat required to raise or lower the temperature of a substance by 1 degrees celsius. Water has a high specific heat because the hdyrogen bonds between the water molecules must be ddisrupted to raise the temperature. water must lose a large amount of heat and form many additional hydrogen bonds for its temperature to decreatse. This allows our bodies to maintain homeostasis, and Eath's oceans to be relatively stable.
- Universal Solvent: Water is considered the universal solvent because it can dissolve a lot of things. Ionic substances are soluble in water because the poles of the polar water molecules interact with the ionic substances and separate them into ions. Substances with polar covalent bonds are similarly soluble because of the interaction of their poles with those of water
- surface tension: Because of the hydrogen bonding, water molecules are strongly attracted to one another, which gives water a high surface tension. The molecules at the surface of the water "stick together" to form a type of 'skin' on the water, strong enough to support very light objects. Insects that walk on water are taking advantage of this surface tension. Surface tension causes water to clump in drops rather than spreading out in a thin layer.
- Enzymes are proteins, meaning that they are strings of amino acids connected together by peptide bonds that form a certain structure. Proteins have several different structures in how they may exist - primary, secondary, tertiary, and quaternary. The primary structure of a protein is just the linear sequence of amino acids. The secondary structure involves hydrogen bonding between amino acids. The tertiary structure involves bonding between R-groups and the quaternary structure usually involves multiple protein interactions. Denaturing at high temperatures occurs because high temperatures rupture some of the bonding that occurs in these quaternary/tertiary/and secondary protein structures. Once these bonds are broken, the enzyme (protein) is reduced to its primary structure with just peptide bonds occurring - the functional structure of the enzyme is lost and it is no longer functional. This works for most proteins. In the case of the enzyme, however, when the structure is lost, the active site and allosteric site also lose their functionality and therefore no substrate may bind to the enzyme
- H ions have a positive charge which means that they are attracted to the negative parts of certain molecules (or negative ions).An enzymes tertiary structure is held in place by a number of ionic and hydrogen bonds. These bonds help to ensure that the active site of the enzyme is held in the right shape. These bonds occur because of the attraction between oppositly charged groups on the amino acids that make up the enzyme protein.Because of the charge of the H+ ions, they are able to interfere with the hydrogen bonds and the ionic bonds that are holding the enzymes tertiary structurre in place. This means that increasing or decreasing the concentration of hydrogen ions in a soluition around an enzyme ( changing the pH of the solution) can alter the tertiary structure of the enzyme molecule. So changes in pH can also cause changes to the shape of the active site, therefore denaturing it.
a.) A phospholipid molecule contains a hydrophilic "head" and two hydrophobic fatty acid tails. In cell membranes, surfaces, phospholipids are arranged in a bilayer in which the hydrophilic heads are in contact with the cell's watery interior and exterior whereas the tails are pointed away from water and toward each other in the interior of the membrane. The fatty acid chains of phospholipids can contain double bonds which make them unsaturated. Because of the kinks in the tails, phospholipids aren't packed together tightly, which contributes tot he fluidity of the membrane. The fluidity of the cell membrane is very important in its function; the less fluid the membrane is, the more impermeable it is. There is an optimum permeability for the cell membrane at which all the substances necessary for metabolism can pass into and out of the cell. The fluidity of cell membranes enables hydrophobic molecules such as hydrocarbons, carbon dioxide, and oxygen to dissolve in the bilayer and easily cross teh membrane. However, ions and polar molecules (including water, glucose, and other sugars) cannot readily pass through because of the hydrophobic interior. Protein channels and transport proteins allow these required substances to cross membranes
2.) There are numerous functions of proteins in the membrane. One important function is tahat some proteins protrude on the extracellular side of the membrane and serve as receptors for signaling molecules. A second function is seen with proteins that extend through the interior of the bilayer and serve as channels for the passage of molecules or ions that cannot pass through the phospholipids.