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Membrane fluidity The property by which most of the plasma membrane lipids and proteins easily rotate and move side ways in their own half of the lipid bilayer. THis property allows the membrane to self seal if torn; proteins seldom flip-flop from one half of the bilayer to to the other. Cholesterol A steroid molecule which makes up 20% of the membrane lipids; it has the typical four-ring structure of the steroid molecule; it helps stabalize the lipid bilayer. Cytosol the fluid portion of the cytoplams containing water, dissolved solutes and suspended particles. Lipid bilayer two-back-to-back layers made up of three types of lipid molecules, primarily phospholipid. Cytoplasm all the cellular contents between the plasma membrane and the nucleus Chromosomes a single molecule of DNA associated with several proteins and containing thousands of hereditary units called genes. Permeable means that a structure permits the passage of substances through it. Transmembrane proteins Integral proteins which span the entire lipid bilayer and protrude into both the cystosol and the extracellular fluid Nucleus A large of organelle which holds most of the cell's DNA in the form of chromosomes; it is theorganelle which controls the functions of the cells. Carriers are integral membrane proteins which selectively move polar molecules or ions from one side of the plams to the other Hydrophilic water-loving, polar part of an amphipathic molecule Glycolipids molecules which make up 5% of membrane lipids; they have attached carbohydrates groups and are only found in the part of the bilayer facing the extracellular fluid. Genes the hereditary units which control most aspects of cellular structure and function. Phospholipids molecules which make up 75% of membrane lipids; they contain phosphorus at their hydrophilic end and fatty acids at their hydrophobic end. Receptors integral proteins which are cellular recognition sites;each type of receptor recognizes and binds to a specific type of molecule called a ligand. Amphipathic molecules which have both polar and nonpolar parts; phospholipids are an example Glycocalyx formed by the glycolipids and glycoproteins at the extracellular fluid side of the plasma membrane forming an extensive sugary coat for cells; this sugary coat has many functions. Organelles small structures found in the cytoplasm which have characteristic shapes and specific functions. Glycoproteins proteins with carbohydrates groups attached to the end of the protein which protrudes into the extracellular fluid Selectively permeable means that a structure permits some substances to pass through it but not others; the lipid bilayer is permeable to nonpolar, uncharged molecules but impermeable to ions and large polar molecules. Impemeable means that a structure does NOT permit the passage of substances through it PLasma membrane a cell's flexible selectively-permeable outer surface Integral proteins proteins which extend into or through the lipid bilayer and are firmally embedded in it Enzymes are either integral or peripheral protein molecules which catalyze specific chemical reactions at the inside or outside surfaces of the plasma membrane of the cell. Identity markers are membrane glycoproteins anbd glyco lipids which enable a cell to recognize other cells of the same typeduring tissue formation or to respond to potientially dangerous foreign cells; the ABO blood type markers are a good example. Hydrophobic water-hating, nonpolar part of an amphipathic molecule Peripheral proteins proteins which are not firmly embedded in the membrane; they are loosely associated with the polar heads of membrane lipids or with integral proteins at the inner or outer surface of the membrane. ion channels integral membrane proteins which form pores or holes in the membrane through which specific ions can move into or out of the cell; most of there are selective for a specific ion Ligand a specific molecule which binds to a receptor protein within the plasma membrane. Linkers integral or peripheral protein molecule which anchor proteins in the plamsa membranes of neighboring cells to one another or to protein filaments inside or outside the cell Antiporters carrier proteins which can move two substances opposite directions across the plasma membrane using the concentration gradient of one of the two substances. Channel-mediated facilitated diffusion a process in which a solute moves down its concentration gradient through a membrane channel (mostly ion channels) which may be gated or not gated; this process is slower tha simple diffusion Aquaporins integral membrane proteins which serve as water channels Hypertonic solution the solution outside the cell has a higher concentration of solutes than the cytosol inside the cell causing water to move out of the cell and shrinking or shriveling of the cell Symporters carrier proteins which can move two substances the same direction across the plasma membrane using the concentration gradient of one of the two substances Sodium-potassium pump a very important type of primary active transportpump; all body cells have thousands of them facilitated diffusion the process by which solutes which are too polar or highly charged can cross the plasma membrane assisted by an integral membrane protein. Crenation when the solution outside the cell has a higher concentration of solutes than the cytosol inside the cell causing water to move out of the cell aned shrinking the cell Hypotonic solution the solution outside the cell has a lower concentration of solutes than the cytosol inside the cell causing water molecules to enter the cell and rupture Carrier-mediated facilitated diffusion a process in which the solute binds to a carrier protein to move down its concentration gradient and the protein changes shape to move the solute into or out of the cell Primary active transport is the process in which some solutes, which must enter or leave cells against their concentration gradients, can be moves by use of ATP specifically for energy by the cell Vesicle a small, spherical sac composed of a lipid bilayer Electrical gradient a difference in electrical charge between one side of the plasma membrane to the other side Passive transport the processs by which substances move down their concentration or electrical gradients to cross the plasma membrane using their own kinetic energies Transport maximum Once all of the carrier proteins are occupied, the number of solute molecules that can move across the membrane is limited Concentration Gradient a difference in the concentration of a chemical from one side of the plasma to the other side Isotonic solution the concentration of solutes that cannot cross the plasma membrane are the same on both sides of the membrane Active transport the process in which some solutes which enter or leave cells, moving"uphill" against their concentration gradients, can be moved by use of energy by the cell. Trancytosis the process that moves materials across a cell in a vesicle hemolysis the process in which cell membranes are ruptured because the solution outside the cell has a lower concentration of solutes than the cytosol inside the cell causing water molecules to enter the cell Primary active transport pumps carrier proteins which mediate primary active transport; they use 40% of the ATP produces ina typical body cell Tonicity the measure of a solution's ability to change the volume of cells by altering their water content Secondary active transport the process that uses energy stored in an ionic concentration gradient to move substances against their concentration gradients Exocytosis the process that moves materials out of the cell by fusion of a vesicle with the plasma membrane Receptor mediated endocytosis a highly selective process in which cells take up specific ligands Endocytosis the process that moves materials into a cell in a vesicle formed from the plasma membrane Osmosis A type of diffusion in which there is a net movement of solvent (usually solvent) down its concentration gradient through a selectively permeable membrane; a passive process Diffusion a passive process in which the random mixing of particles in a solution occurs because of the particles kinetic energy; both the solute and the solvent particles undergo this process Rates of diffusion depends on many factors such as steepness of a concentration gradient, temperature, the mass of a diffusing substance, the surface area for the diffusion and the diffusion distance. Simple diffusion a passive process in which substances move freely through the lipid bilayer without the help of membrane transport proteins Phagocytosis a form of endocytosis in which the cell engulfs large solid particles such as worn-out cells, whole bacteria or viruses Pinocytosis the process by which tiny droplets of extracellular fluid are taken into a cell; no receptor proteins are involved and all the solutes in the extracellular fluid are brought into the cell Phagocytes macrophages and neutraphils Pseudopods extensions of the plasma membrane of a phagocyte which are used to surround a solid partile such as a worn-out cell, whole bacterium or virus particle Phagosome a vesicle formed by pseudopods to engulf a solid particle Organelle specialized structures within a cell that have characteristic shapes and perform specific functions in cellular growth, maintenance and reproduction Microfilaments composed of the protein, actin, and are the thinnest elements of the cytoskeleton; found mostly at the edge of the cell to generate movement and provide mechanical support as in microvilli, they anchor the cytoskeleton to integral proteins in the plasma Intermediate filaments composed of several different proteins and they are thicker than microfilaments; found in parts of the cell subject to mechnical stress, they help stabilize positions of organelles such as the nucleus and help attach cells to another Microtubules long, unbranched hollow tubes composed mainly of the protein, tubilin; they help determine cell shape and function in movement of organelles adn chromosomes during cell division; they also move cilia and flagella. Centrosome located near the nucleus and it consosts of two components: a pair of centrioles and a pericentriolar material Pericentriolar material surrounds the centrioles and contains hundreds of ring-shaped complexes composed of the protein, tubulin; the complexes are the organizing centers for the growth of the mitotic spindle. Centrioles cylindrical structures each of which is composed of 9 clusters of 3 microtubules arranged in a circular pattern; the two centrioles lie at right angles to one another; they are essential for cell division because they organize the mitotic spindle. Tubulin the protein which is found in microtubules. Cilia numerous, short, hairlike projections that extend from the surface of cells and function to move fluids and mucous along the apical surfaces of the cells. Flagella longer than cilia; their function is to move entire cells; in humans, found only on sperm cells. Ribosomes the sites of protein synthesis; they contain RNA and consist of 2 subunits which are produced in the nucleus; some are attached to the outer surface of the rough endoplasmic reticulum; others are free in the cytoplasm. Rough endoplasmic reticulum a network of membranes in the form of flattened sacs continous with the nuclear membrane and studded with ribosomes; it produces secretory proteins, membrane proteins and organelle proteins. smooth endoplasmic reticulum extends from the rough endoplasmic reticulum but does not contain ribosomes on its outer surface; it synthesizes fatty acids and steroids, detoxifies drugs, and releases glucose into the blood stream. Golgi Complex consists of 3 to 20 flattened membranous sacs called cisternae; its function is to modify, sort and package proteins, which it has received from the rough ER, for transport Cisternae flattened membraneous sacs which form the golgi complex Transfer Vesicles bud from the edges of the cisternae of the golgi complex; they function to move enzymes back toward the entry face of the golgi complex and to move proteins toward the exit face. Secretory Membranes leave the exit face of the golgi complex carrying proteins which are delivered to the plasma membrane where they undergo exocytosis into the extracellular fluid. Membrane vesicles carry processed proteins from the exit face of the gogi complex to the plasma membrane for incorporation into the plasma membrane itself Lysosomes membrane-enclosed vesicles that form from the golgi complex and contain as many as 60 kinds of powerful digestive and hydrolytic enzymes; they helnp recycle worn-out cell components or even destroy entire cells Autophagy the process by which entire worn-out organelles are digested Autophagosome a vesicle formed around a worn-out organelle; this vesicle then fuses with a lysosome which digests the organelle Autolysis the process in which entire cells are destroyed due to a pathological condition or after death of an organism Interphase When the sell replicates its DNA, produces additional organelles and cytosolic components in anticipation of cell division; this phase is a time of high metabolic activity and growth Cristae the folds in the inner mitochondrial membrane Transfer RNA binds to an amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation; one end carries the amino acid and the opposite end is the anticodon which attaches to the messenger RNA Telophase begins after the chromosomal movement stops and the chromosomes, now at opposite poles of the cell, uncoil and revert to the chromatin form; the nuclear envelope and nucleoli reappear and the mitotic spindle breaks up Sex chromosomes an homologous pair which does NOT contain all of the same genes; the X chromosome from the female is larger than the Y chromosome from the male; the X chromosome contains more genes than the Y chromosome. Anaphase when the centromeres split, separating the 2 members of each chromatid pair ( now called chromosomes) which then are pulled toward opposite poles of the cell by the spindle microtubules. Peroxisomes similar to lysosomes, but smaller; they contain several enzymes which protect cells from harmful or toxic chemicals; they can self replicate. Transcription the copying of the DNA sequence of base triplets from one strand of the DNA to form one of 3 types of RNA; this process occurs in the nucleus. Nuclear pores large openings that extend through the nuclear membrane; small molecules pass through by diffusion; large molecules are transported throug active transport Prophase the phase in which the chromatin fibers condense and shorten into chromatids which are identical and held together by a centromere; late in this phase, the centrosomes begin the formation of the mitotic spindle; the nucleolus disappears and the nuclear envelope breaks down. Metaphase when the spindle microtubules align the chromatid pairs at the exact center of the mitotic spindle. Mitosis the distribution of 2 sets of chromosomes into 2 separate nuclei resulting in the exact partitioning of genetic information; also called nuclear division Homologus chromosomes a pair of chromosomes which contain similar genes arranged in the same ( or almost the same) order along the chromosome Matrix the central fluid-filled cavity that lies inside the inner mitochondrial membrane Translation the process by which the nucleotide sequence in a messenger RNA molecule specifies the amino acid sequence in a protein; this process is carried out by ribosomes in the cytoplasm. Messenger RNA directs the synthesis of a protein at the ribosome Nucleoli small spherical bodies which are the sites of synthesis of ribosomal RNA and assembly of the rRNA and proteins into the ribosomal subunits Nuclear membrane a double membrane that separates the nucleus from the cytoplasm; both layers are bilayers similar to the plasma membrane Proteasomes barrel-shaped structures which use enzymes to destroy unneeded, damaged faulty proteins in the cytosol; thousand are found in both the cytosol and nucleus Genome the total genetic information carried in a cell or organism Mitochondria the powerhouses of the cell generating most of the ATP used by the cell by aerobic (cellular) respiration; they have a 2 layered membrane; the inner membrane consists of folds which surround a central fluid-filled; they self-replicate and have their own circular DNA Mitotic phase consists of a nuclear division and a cytoplasmic division Cell cycle an orderly sequence of events by which a somatic cell duplicates its contents and divides into 2 daughter cells Chromatids the replicated DNA in nucleosomes which is even more condensed; a pair of these form a chromosome. Chromatin fiber consists of coiled nucleosomes which form a larger diameter fiber Nucleosome one bead of the beads-on-a-string structure of chromatin; each one is a doublestranded DNA wrapped twice around a core of 8 histone proteins Ribosomal RNA together with proteins forms the segment of the ribosome Chromatin a loosely coiled complex of DNA, proteins called histones and some RNA; it is found in the nucleus