Nonpolar Amino Acids
Glycine, Alanine, Valine, Leucine, Isoleucine, Proline, Cysteine, Methionine, Phenylalanine, Tryptophan
Polar Amino Acids
Serine, Threonine, Tyrosine, Asparagine, Glutamine
Basic Amino Acids
Lysine, Arginine, Histidine
Acidic Amino Acids
Aspartic Acid, Glutamic Acid
The only amino acid that forms disulfide bonds in protein structure
Cysteine
X-Ray Crystallography
A common method of analyzing the 3-dimensional structure of protein; a beam of x-rays is directed at crystals of the protein to be analyzed, and the pattern of x-rays that pass through the protein crystal is detected on x-ray film; as the x-rays strike th
Protein Primary Structure
The sequence of amino acids in the protein's polypeptide chain
Protein Secondary Structure
The regular arrangement of amino acids within localized regions of the polypeptide; most common examples are the alpha helices and beta sheets in proteins
Alpha Helix
A characteristic structural component of most all proteins in which a region of a polypeptide coils around itself like a spiral, with the C=O group of one peptide bond forming a hydrogen bond with the N-H group of a peptide bond located four residues down
Beta Sheet
A characteristic structural component of most all proteins in which two parts of a polypeptide chain lie side by side with hydrogen bonds between them; can be formed between several polypeptide strands, which can be oriented in either the same or opposite
Protein Tertiary Structure
The overall folding of a single polypeptide chain as a result of interactions between the side chains of amino acids that lie in different regions of the primary sequence; a critical determinant of this is the localization of hydrophobic amino acids in th
Protein Domains
The basic units of tertiary structure; folded 3-dimensional structures usually containing between 50 and 200 amino acids
Protein Quaternary Structure
The interactions between different polypeptide chains in proteins composed of more than one polypeptide; the protein hemoglobin demonstrates this aspect of protein structure
How does cholesterol affect plasma membrane fluidity?
At high temperatures, cholesterol reduces membrane fluidity because it hinders movement of the surrounding phospholipids; at low temperatures, cholesterol helps to maintain membrane fluidity because in hinders the surrounding phospholipids from packing to
Integral Membrane Proteins
Membrane proteins that are embedded directly within the lipid bilayer; most span the entire bilayer, with portions exposed on both sides of the membrane
Peripheral Membrane Proteins
Membrane proteins that are not embedded into the lipid bilayer, but are associated with the membrane indirectly, generally by interactions with integral membrane proteins
Channel Proteins
Class of membrane transport proteins that form open pores through the membrane, allowing the free passage of any molecule of the appropriate size, such as inorganic ions
Carrier Proteins
Class of membrane transport proteins that selectively bind and transport specific small molecules, such as glucose; they bind specific molecules and then undergo allosteric transitions (conformational changes) that open channels through which the molecule
What molecules can freely diffuse through the plasma membrane without the aid of a protein?
Only small, uncharged molecules; this includes both small uncharged nonpolar molecules, such as carbon dioxide and oxygen, and small uncharged polar molecules, such as water and ethanol
What molecules cannot freely diffuse through the plasma membrane and require the aid of a protein?
Large uncharged polar molecules, such as glucose and galactose, and all charged molecules, including H+ ions
Passive Transport
Proteins transporting molecules across the plasma membrane (or other membranes) in the energetically favorable direction, as determined by concentration and electrochemical gradients; requires no use of ATP
Active Transport
Proteins transporting molecules across the plasma membrane (or other membranes) in the energetically unfavorable direction, such as transporting a molecule against the concentration gradient; requires the use of energy from ATP
Two-Dimensional Gel Electrophoresis
Method of identifying proteins within cells in which the proteins are subjected to two electrophoresis processes; the first electrophoresis separates the proteins according to charge (in the horizontal axis), and the second electrophoresis separates the p