Cell and Molecular Part 1

• Actin: An abundant protein found in eukaryotic cells, its monomer is globular actin (G-actin) and its polymer is filamentous actin (F-actin), the monomers bind ATP, which is hydrolyzed to ADP after assembly onto a microfilament, there are nucleotide-dependent actin-binding proteins, which generate a wide variety of structures
• Action potential: Transient increase in membrane potential that propagates along the cell, rapid sequence changes of voltage across the cell determined by the relative ratio of ions and the permeability of these ions.
• Active transport: Movement up the concentration gradient, it requires energy and is usually powered by ATP hydrolysis. There are two types of Active transport: Direct & Indirect
• Amphipathic: A molecule having both hydrophilic and hydrophobic regions.
• Anterograde: Relating the endomembrane system, forward movement (moving from ER to the outside of the cell.
• Antiparallel: Relating to DNA, the two strands of DNA that form the double-stranded helix are in opposite orientations (3’-5’ and 5’ to 3’)
• ATP: A triphosphate nucleotide that is the fundamental unit of energy storage and use in a cell
• Aquaporins: It is a transmembrane water channel that allows rapid passage of water through membranes of specialized cells.  
• Aqueous: Of or containing water, typically as a solvent or medium.
• Basal bodies: The MTOC for flagella and cilia
• Base pairing: Relating to DNA/RNA, two complementary nucleotide bases that pair together to form a “rung of the DNA ladder”. Adenine pairs with Thymine (or Uracil in RNA), Cytosine pairs with Guanine.
• Carrier Protein: Proteins in the plasma membrane that help transport solutes that require facilitated diffusion by binding extracellular solutes; change shape to bring solute into the cell. They are highly specific and relatively slow.
• Centrioles: Associated with the structure of a centrosome, paired barrel-shaped organelles which aid in the organization of microtubules.
• Centrosome: Two centrioles surrounded by a pericentriolar material (made of proteins). The minus end of a microfilament is anchored at its base to centrosomal g-tubulin (a ring-shaped complex only found in centrosomes.
• Channel Proteins: Proteins on the plasma membrane that participated in facilitated diffusion by creating hydrophilic channels in the membrane to transport large, polar or charged solutes. They are variable specific, usually very rapid transport.
• Cholesterol: The most common animal steroid.
• Complementary: Relating to base pairing, combining in such a way as to enhance or emphasize the qualities of each other or another.
• C-Terminus: The end of a protein, the end of the chain with an exposed carboxyl group.
• Cytoskeleton: An organized, 3D arrays of interconnected protein structures located in the cytoplasm of a cell that gives a cell its distinct shape and internal organization.
• Depolymerization: How microtubules retract, the breaking of polymeric bonds, creating smaller components such as monomers and dimers.
• Direct active transport: Is when some transporters bind ATP directly and use the energy of its hydrolysis to drive active transport
• Directionality: The property of being directional or maintaining direction.
• Diffusion: Spontaneous movement of solutes and ions to achieve equilibrium. The movement occurs when there is a concentration gradient, and it is down the gradient.
• DNA: Deoxyribonucleic acid, the molecule that carries genetic information for the development and functioning of an organism.
• Dynamic instability: Relating to microtubules, the dynamic instability is reliant on the concentration of GTP-tubulin, forming a cap on the GDP tubulin, an unstable monomer. The lower the concentration of GTP tubulin, the more prone the microtubule is to depolymerization
• Dynein: A motor protein that uses chemical energy (ATP – one molecule per step) to power mechanical work. Dynein travels from the plus end to the minus end (towards the MTOC) of the microtubules.
• Endocytic vesicle: Formed by the invagination of the plasma membrane around an extracellular substance. They turn into early endosomes, which are used for sorting cellular materials.
• Endocytosis: The ingestion or taking in of extracellular matter by a living cell by the invagination of its membrane to form a vesicle for the transport of these materials into the cell. Will also remove lipids and proteins from the membrane.
• Endomembrane system: A network of organelles, including the endoplasmic reticulum (smooth and rough), Golgi complex and vesicles (endosomes and lysosomes) used for the trafficking of macromolecules in and out of the cell.
• Endosomes: A type of vesicle which carries and sorts material brought into the cell. Early endosomes formed from endocytic vesicles which can acquire digestive enzymes from the TGN to form lysosomes.
• ER-associated degradation: A form of quality control within the cell which ensures misfolded proteins are retained or degraded within the ER.
• Exocytosis: The fusion of secretory vesicles with the plasma membrane which results in the discharge of vesicle content into the extracellular space and the incorporation of new proteins and lipids into the plasma membrane.
• Extracellular matrix (ECM): Made of collagen (protein) and proteoglycans (glycoproteins) that were secreted from cells, specialized structures include cartilage. The ECM provides structural support and regulate cell migration, cell recognition, and cell adhesion.
• Facilitated Diffusion: Movement of solute down the concentration gradient with the help of carrier proteins and channels, energy is not required for this process, and it is used to transport large, polar and charged molecules that do not diffuse across the membrane.
• Fluidity buffer: Maintains the membrane fluidity in response to changes in temperature. Cholesterol is a fluidity buffer molecule (along with other sterols).
• Fluid mosaic: Refers to the structure of membranes, where there is a “fluid” bilayer of lipids (in constant motion) with a “mosaic” of associated proteins embedded within the lipids.
• Genes:  The basic physical and functional unit of heredity, genes are made up of DNA and contain the set of instructions to produce a specific molecule in the body, often protein.
• Genome: The entire set of DNA instructions (genes) found in a cell.
• Glucose: The major source of energy in plants and animals, a 6-carbon monosaccharide.
• Glucose Transport: A carrier protein that changes its shape when bound by glucose, Increases diffusion rate into cells significantly.