Biochemistry Flashcards
Orbitals
a region around the nucleus of an atom with a high probability of containing an electron. The position of electrons can only be described by these probability distributions.
Cation
A positively charged ion
Anion
A negatively charged ion
Isotopes
Different forms of the same element with the same number of protons but different numbers of neutrons
Radioactive Isotopes
An isotope that is unstable and undergoes radioactive decay, releasing energy
Energy levels
A discrete level, or quantum, of energy that an electron in an atom possesses. To change energy levels, an electron must ABSORB or RELEASE energy
Oxidation
Loss of an electron by an atom or molecule; in metabolism often associated with a gain of oxygen or a loss of hydrogen.
Valence Electrons
An electron in the outermost energy level of an atom
Octet Rule
Rule to describe patterns of chemical bonding in main group elements that require a total of eight electrons to complete their outer electron shell.
Why is the molecule formed by two hydrogen atoms stable?
- It has no net charge (meaning the molecule formed with the covalent bonding isn’t charged because it still contains two protons and two electrons)
- The octet rule is satisfied (two orbiting electrons in its outer shell)
- It has no unpaired electrons
Electronegativity
A property of atomic nuclei that refers to the affinity of the nuclei for valence electrons; a nucleus that is more electronegative has a greater pull on electrons than one that is less electronegative.
Nonpolar
Said of a covalent bond that involves equal sharing of electrons. Can also refer to a compound held together by non polar covalent bonds.
Polar covalent bonds
A covalent bond in which electrons are shared unequally due to differences in electronegativity of the atoms involved. One atoms has a partial negative and the other partial positive charge, even though the molecule is electrically neutral overall.
What are the three factors which influence chemical reactions? and why?
- Temperature (heat increases rate of reaction)
- Concentration of reactants and products (reactions act quicker when more reactants are available)
- Catalysts (they naturally speed up chemical reactions)
Hydrogen bonds
A weak association formed with hydrogen in polar covalent bonds. The partially positive hydrogen is attracted to partially negative atoms in polar covalent bonds. In water, oxygen and hydrogen in different water molecules from hydrogen bonds.
Surface Tension
A tautness f the surface of a liquid, caused by the cohesion of the molecules of liquid. Water has an extremely high surface tension.
Hydrophobic
Literally translates as “water-fearing”and describes non polar substances that are not soluble in water. Non polar molecules in water associate with each other and form droplets
Hydrophilic
Literally translates to “water-loving” and describes substances that are soluble in water. These must be either polar or charged (ions).
Hydrophobic exclusion
The tendency of non polar molecules to aggregate together when placed in water, Exclusion refers to the action of water in forcing these molecules together.
mole
the weight of substance in grams that corresponds to the atomic masses of all the component atoms in a molecule of that substance. One mole of a compound always contains 6.02 x 10^23 molecules.
mole concentration
concentration expressed as moles of a substance in 1 L of pure water.
acid
any substance that dissociates in water to increase the hydrogen ion (H+) concentration and thus lower the pH.
base
any substance that dissociates in water to absorb and therefore decrease the hydrogen ion (H+) concentration and thus raise the pH
buffer
A substance that resists changes in pH. It releases hydrogen ions (H+) when a base is added and absorbs H+ when an acid is added.
functional group
A molecular attached to a hydrocarbon that confers chemical properties or reactivities. Examples include hydroxyl (OH), carboxylic acid (COOH) and amino groups (NH2)
Isomers
One of a group of molecules identical in atomic composition but differing in structural arrangement; for example glucose and fructose
polymer
A molecule composed of many similar or identical molecular subunits; starch is a polymer of glucose
monomer
The smallest chemical subunit of a polymer. The monosaccharide of alpha glucose is the monomer found in plant starch, a polysaccharide.
dehydration reaction
A type of chemical reaction in which two molecules join to form one larger molecule, simultaneously splitting out a molecule of water; one molecule is stripped of a hydrogen atom, and another is stripped of a hydroxyl group, resulting in t he joining of the two molecules, while the H and the OH real eased may combine to form a water molecule.
hydrolysis
A reaction that breaks a bond by the addition of water. This is the reverse of dehydration, a reaction that joins molecules with the loss of water.
monosaccharides
A simple sugar that cannot be decomposed into smaller sugar molecules
disaccharide
A carbohydrate formed of two simple sugar molecules bonded covalently.
cellulose
The chief constituent of the cell wall in all green plants, somoe algae, and a few other organisms; an insoluble complex carbohydrate formed of microfibrils of glucose molecules.
polysaccharides
a carbohydrate composed of many monosaccharide sugar subunits linked together in a long chain; examples are glycogen, starch and cellulose
starch
An insoluble polymer of glucose; the chief food storage substance of plants
glycogen
animal starch; a complex branched polysaccharide that serves as a food reserve in animals bacteria and fungi
chitin
A tough, resistant, nitrogen-containing polysaccharide that forms the cell walls of certain funny, the exoskeleton of arthropods, and the epidermal cuticle of other surface structures of certain other invertebrates.
DNA
The genetic material of all organisms; composed of two complementary chains of nucleotides wound in a double helix.