The Chemistry of Life Flashcards
Covalent bonds
The sharing of a pair of valence electrons by two atoms.
Nonpolar covalent bond
In a covalent bond between two atoms of the same element, the electrons are shared equally because the two atoms have the same electronegativity - the tug-of-war is a standoff.
Polar covalent bond
When one atom is bonded to a more electronegative atom, the electrons are not shared equally. Such bonds vary in their polarity, depending on the relative electronegativity of the two atoms. For example, the bonds between the oxygen and hydrogen atoms of a water molecule are quite polar.
Ionic bonds
A chemical bond resulting from the attraction between oppositely charged ions.
Molecule
Two or more atoms held together by covalent bonds
Electron
A subatomic particle with a single negative electrical charge and a mass about 1/2000 that of a neutron or proton. One or more electrons move around the nucleus of an atom.
Atom
The smallest unit of matter that retains the properties of an element.
Element
A substance that cannot be broken down to other substances by chemical reactions
Weak interactions
4 types Ionic interactions Hydrogen bonds Van der Waals interactions Hydrophobic interactions
Important properties
- They have a cumulative effect - individually they are weak, but together they provide reinforcing stability
- They are reversible
- They are transient
Hydrogen bonds
The strongest of the weak interactions. The partial positive charge on a hydrogen atom that is covalently bonded to an electronegative atom allows the hydrogen to be attracted to a different electronegative atom nearby.
This noncovalent attraction between a hydrogen and an electronegative atom is called a hydrogen bond.
Van der Waals interactions
Weak attractions between molecules or parts of molecules that result from transient local partial charges. Individually weak and occur only when atoms and molecules are very close together. When many such interactions occur simultaneously, however, they can be very powerful.
Ionic interactions
When a salt (such as NaCl) is placed in solution, the strong ionic bonds that are present in the crystal NaCl are weakened as each of the ions become surrounded by a hydrogen shell.
Ionic interactions can exist between any two chemical groups that have opposite charges.
Hydrophobic interactions
A type of weak chemical interaction caused when molecules that do not mix with water coalesce to exclude water.
Hydrogen shell
The sphere of water molecules around each dissolved ion.
Conformation
3D shape
Macromolecule
A giant molecule formed by the joining of smaller molecules, usually by a dehydration reaction. Polysaccharides, proteins, and nucleic acids are macromolecles
Monomer
The subunit that serves as the building block of a polymer
Polymer
A long molecule consisting of many similar or identical monomers linked together by covalent bonds
The building block principal
The mechanism by which all polymers are synthesised and broken down.
Key points:
The two ends of a biological polymer are always different, and the polymer is synthesised by step-wise addition of monomers
to one end.
Dehydration (also called condensation) reactions join monomers to form polymers.
Hydrolysis reactions break polymers down into monomers.
The joining of monomers is a process that requires an input of energy. This is accomplished by activating the monomers with energy before joining them together.
Special proteins called enzymes are used to carry out the dehydration and hydrolysis reactions. Without the correct enzymes, the reactions will not occur in the cell.
Dehydration reaction
A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule
Hydrolysis
A chemical reaction that breaks bonds between two molecules by the addition of water; functions in disassembly of polymers to monomers
Nucleic acid
A polymer consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.
Nucleotide
The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups.
Protein
A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.
Amino acid
An organic molecule possessing both a carboxyl and an amino group. Amino acids serve as the monomers of polypeptides.
Lipids
Varied in form and function. Not polymers or macromolecules. Hydrophobic. Include fats, phospholipids and steroids.
Glycerol
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Fatty acid
A carboxylic acid with a long carbon chain. Fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form a fat molecule, also known as a triacylglycerol or triglyceride.
Carbohydrate
A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides)
Monosaccharide
The simplest carbohydrate, acting alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, monosaccharides have molecular formulas that are generally some form of CH2O
Polypeptide
A polymer of amino acids. Different from a protein which consists of one or more polypeptides folded into a specific conformation.
