Studied by 9 peopleCovalent Bond
A bond between atoms in which the electrons between the atoms are shared.
Ionic Bond
A bond between atoms that involves a transfer of valence electrons from the less electronegative atom to the more electronegative atom.
Nonpolar Covalent Bond
A covalent bond in which the two atoms equally share the electrons. Nonpolar covalent bonds occur when the electronegativity difference between the two atoms involved is minimal.
Polar Covalent Bond
A covalent bond in which the electrons in the bond are not equally shared between the atoms in the bond because of a large difference in electronegativities between the atoms.
Electronegativity
The ability of an atom to attract electrons.
Hydrogen Bond
The intermolecular electrostatic attraction that occurs between a hydrogen atom that is bonded to a more electronegative atom on one molecule and a more electronegative atom on a different molecule.
Adhesion
The attraction of a molecule to a different type of molecule. For example, the attraction of water to other polar molecules such as ammonia.
Cohesion
The attraction of a molecule to the same type of molecule. For example, the high surface tension of water is because of its cohesion.
Capillary Action
The movement of water up a narrow tube because of it adhesive and cohesive properties. Capillary action is important in the movement of water up the xylems of plants.
Specific Heat
The quantity of heat required to raise the temperature of one gram of a substance one degree Celsius. Water has a very high specific, which leads to the ability of swear to provide a colling function and the ability of large bodies of water to stabilize climate.
Density of Ice
The density of ice is its mass per unit volume. Because of water’s ability to form hydrogen bonds, the crystalline structure of ice takes up more volume than an equivalent mass of liquid water; therefore, the density of ice is less than the density of liquid water, and ice floats.
Solvent
The liquid in which a solute is dissolved to form a solution. The solvent is the most prevalent material in a solution. Water’s ability to form hydrogen bonds makes it a good solvent for both ions and p
Solute
The solid, liquid, or gas dissolved in a solute to make a solution. One solution may have multiple solutes.
pH
pH = -log[H+]. As the concentration of hydrogen ions increase, the pH decreases. pH is a logarithmic scale, so a difference on one pH unit means there is a tenfold difference in hydrogen ion concentrations.
Buffer
A solution that resists change in pH. Buffers are important in maintaining homeostasis in living organisms.
Surface Tension
The tension in the surface of a liquid caused by its cohesive properties. Water’s hydrogen bonds lead to water’s high cohesive properties and high surface tension.
NCHOPS
A mnemonic for remembering the elements most frequently found in biological molecules: Nitrogen, Carbon, Hydrogen, Oxygen, Phosphorus, and Sulfur.
Organic Molecules
Chemical compounds in which one or more atoms of carbon are covalently bonded to atoms of other elements. Organic molecules particularly important in biology include carbohydrates, lipids, nucleic acids, and proteins.
Carbohydrates
A sugar molecule or polymer of sugar molecules used primarily for energy or to give structure to living organisms.
Monosaccharides
A single sugar unit or monomer. Examples include glucose, fructose, and galactose.
Disaccharides
Two sugar monomers that are connected by glycosidic linkage. Examples include sucrose (made of glucose and fructose) and lactose (made of glucose and galactose).
Polysaccharides
Multiple sugar monomers connected by glycosidic linkages. Functions include energy storage (such as in glycogen) and structural support (such as in cellulose).
Glycogen
A polysaccharide formed from multiple glucose monomers that is used for energy storage in animals.
Starch
A polysaccharide formed from multiple glucose monomers that is used for energy storage in plants.
Cellulose
A polysaccharide formed from multiple glucose monomers connected with a very sturdy β-glycosidic linkage that is used for structural support in plant cells.
Lipids
Biological molecules that are largely nonpolar and include fatty acids, steroids, and phospholipids. Lipids function in energy storage, insulation, cell signaling, and membrane structure.
Fatty Acid
A lipid with a long carbon chain attached to a carboxylic acid group. Fatty acids are nonpolar and are important in plasma membrane structure.
Unsaturated Fatty Acid
A fatty acid in which some of the carbons in the carbon chain are connected by double bonds. Unsaturated fatty acids typically are liquid at room temperature and give flexibility to membranes.
Saturated Fatty Acids
A fatty acid in which all of the carbons in the carbon chain are connected with single bonds. Saturated fatty acids typically are solid at room temperature and give rigidity to membranes.
Amino Acid
A building block or monomer from which proteins are made. Amino acids consist of a central carbon that has a carboxyl group, and amino group, and a variable R-group attached. The identity of the R-group determines the identity and properties of the amino acid.
Primary Structure
The sequence of amino acids in a polypeptide chain. Primary structure is formed by peptide bonds between the amino acids.
Secondary Structure
The arrangement of amino acids in a polypeptide chain driven by hydrogen bonding between the amino acids in the polypeptide chain. Two forms of secondary structure are alpha helices and beta sheets.
Tertiary Structure
Driven by interactions between the R-groups in a polypeptide chain and can include hydrophobic interactions, hydrogen bonding, and disulfide bridges.
Quaternary Structure
This is found only in proteins that are composed of more that one subunit (examples are hemoglobin and collagen).
Denatured
Describes a protein that has changed its shape and does not function as usual. This may be caused by changed in temperature, pH, or salt concentration.
Nucleic Acids
Molecules that can store or transmit genetic information and contain a sugar-phosphate backbone and nitrogenous bases (purines and pyrimidines).
DNA vs RNA
DNA | RNA | |
|---|---|---|
Sugar | Deoxyribose | Ribose |
Bases | A, C, G, and T | A, C, G, and U |
Location | Nucleus | Nucleus and cytoplasm |
3D Structure | Double helix | Single-stranded (mRNA) and can fold into 3D structures (rRNA and tRNA) |
Antiparallel
Describes the orientation of the two strands of the DNA double helix. One strand of the DNA double helix starts with a 5’ phosphate group. The complementary strand would start with a 3’ hydroxyl group.
Amphipathic
Describes molecules, such as phospholipids, that have both polar and nonpolar components.
Glycolipids
Lipids with added carbohydrate groups. In cell membranes, these function in cell recognition.
Glycoproteins
Proteins with added carbohydrate groups. In cell membranes, these function in cell recognition.
Steroids
Lipids that have a flat structure made of four fused carbon rings with additional functional groups attached. Steroids can function as ligands in cell signaling. Cholesterol is a steroid that can help regulate the flexibility of cell membranes.
Proteins
Biological molecules that are made of chains of amino acids joined by peptide bonds. Proteins have many functions, including molecule transport, reception of signals, enzyme catalysis, and intercellular joining.
Alpha Helices
The coiled structure of a polypeptide chain that is held together by hydrogen bonds between the carboxyl and amino groups within a polypeptide chain. Alpha helices are a type of secondary protein structure.
Beta Sheets
A type of secondary structure found in proteins in which two or more parallel and adjacent polypeptide chains are arranged so that hydrogen bonds can form between the carboxyl and amino groups on different chains.
R-groups
The R-group, also known as the side chain, gives amino acids their specific properties. R-groups can be polar or nonpolar and can be uncharged or carry positive or negative charges. The R-group on an amino acid determines the identity of the amino acid.
Deoxyribose
A five-carbon sugar found in DNA. Deoxyribose does not contain a hydroxyl group on its 2’ carbon, and this gives deoxyribose a greater stability than ribose.
Ribose
A five-carbon sugar found in RNA. Ribose contains a hydroxyl group on its 2’ carbon, and this gives ribose a lower stability than deoxyribose.
Purines
A type of nitrogenous base found in DNA and RNA. Purine contain two fused hydrocarbon rings. Examples of purines are adenine and guanine.
Pyrimidines
A type of nitrogenous base found in DNA and RNA. Pyrimidines contain one hydrocarbon ring. Examples of pyrimidines are cytosine, thymine, and uracil.
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