Cellular Level (235 #3, 230 #2) Flashcards
plasma membrane
forms the cell’s flexible outer shell, separating the internal environment from the external environment - selective barrier that regulates flow of materials in/out of cell. Plays key role in communication among cells and between cells and external environment.
cytoplasm
cellular contents between plasma membrane and nucleus - cytosol and organelles
cytosol
Composed of water, solutes, suspended particles, lipid droplets, and glycogen granules. Within the cytoplasm is the cytoskeleton, a network of microfilaments, intermediate filaments, and microtubules. - Fluid in which many of cell’s metabolic reactions occur. Maintains shape and general organization of cellular contents; responsible for cellular movements.
organelles
little organs - specific shape and function - cytoskeleton, ribosomes, endoplasmic reticulum, Golgi complex, lysosomes, peroxisomes and mitochondria
nucleus
large organism that houses most of a cell’s DNA.
chromosome
a single molecule of DNA associated with several proteins containing thousands of hereditary units called GENES that controls most aspects of cellular structure & function.
fluid mosaic model
a continually moving sea of fluid lipids that contains a mosaic of different proteins - some float freely while others are anchored. Membrane lipids allow passage of lipid-soluble molecules, but act as a barrier to charged or polar substances.
lipid bilayer
two back-to-back layers made up of three types of lipids - phospolipids (75%), cholesterol (20%) and glycolipids (5%). Phospholipid heads (hydrophilic) face the outside, tails face inside. Glycolipids are in membrane layer facing extracellular fluid, cholesterol are among other lipids in both membranes.
integral proteins
extend into or through the lipid bilayer among fatty acid tails and are firmly embedded. Most are TRANSMEMBRANE, protruding into both cytosol and extracellular fluid. AMPHIPATHIC
peripheral proteins
attached to polar heads of membrane lipids, or to integral proteins at the inner or outer surface of the membrane.
cholesterol
AMPHIPATHIC and are inspersed amonth the other lipids in both layers of the membrane
glycolipids
appear only in the membrane layer that faces the extracellular fluid which is why the bilayer is asymmetric.
glycoproteins
proteins with carb groups attached to the ends that protrude from into ECF. They are coated with glycocalyx (sugary coat) that varies from one cell to another - molecular signature for cell recognition. Also enables cells to adhere to one another and protects cells from being digested by enzymes in ECF. Hydrophilic properties allow a film of fluid to attach to somes (makes RBCs slippery).
Ion Channels
allow specific ions to pass through water-filled pores - selective! Integral! Small-diameter (0.8 nm) may be open or closed to its specific ion as a result of changes in channel shape in response to a controlling mechanism.
Carriers/Transporters
transports specific substances across membranes by changing shapes (polar substances or ions) - integral!
Receptors
recognizes specific ‘ligands’ and alters cells’ function in some way - cellular recognition sites - integral!
Enzyme
catalyzes reaction inside or outside cell depending on side it faces. integral or peripheral
Linker - Cell Adhesion Molecules (CAMs)
anchors filaments inside and outside the plasma membrane, providing structural stability and shape of the cell. may also participate in movement of cell or link two cells together - integral and peripheral. Form loops or hooks that the cells use to grip each other and grasp connective tissue fibres between cells.
CADHERINS - on the surface of adjacent cells interlock in zipper fashion
INTEGRINS - span the plasma membrane, connecting inner membrane surfaces to intracellular cytoskeltal scaffolding. Also ‘signalling molecules’
Cell Identity Marker - Glycoprotein
distinguishes your cells from anyone else’s. Allow cells to recognize others of the same type during tissue formation or recognize and respond to potentially dangerous foreign cells.
membrane fluidity
membrane lipids and many membrane proteins easily rotate and move sideways in their own half of the lipid bilayer. Depends on the number of double bonds in the fatty acid tails (more kinks mean more fluidity) and on the amount of cholesterol present. Cholesterol fills space between tails and makes it stronger at normal body temp, lower temps it increases fluidity.
selective fluidity
allowing some substances to pass more readily through the membrane than others. Permeable to nonpolar uncharged particles (O2, CO2, steriods) but impermeable to large uncharged polar molecules and ions. Slightly permeable to H2O, urea.
concentration gradient
difference in the concentration of a chemical from one place to another. ‘Down’ the gradient is going to the lower concentration, ‘Up’ is going towards higher concentration (requires energy)
electrical gradient
the difference in electric charges between two areas. Across the plasma membrane, this is known as the membrane potential.
electrochemical gradient
the combined influence of concentration and electrical gradients on movement of a particular ion
passive transport processes
substance moves DOWN concentration or electrical gradient to cross the membrane using only kinetic energy - no input of energy from the cell.
active transport processes
cellular energy is used to drive the substance UP it’s concentration or electrical gradient, usually in the form of ATP.
diffusion
a passive process in which the random mixing of particles in a solution occurs because of the particles’ kinetic energy. affected by 1)steepness of gradient, 2) temp, 3) mass of diffusing substance, 4) surface area, 5) diffusion distance
simple diffusion
passive movement of substance DOWN its concentration gradient without any help of membrane tx proteins
facilitated diffusion
passive movement of a substance down its concentration gradient through the bilayer by transmembrane proteins that function as channels or carriers TXS= polar or charged solutes, glucose, fructose, galactose, some vits, ions
osmosis
passive movement of H2O across selectively permeable membrane from higher to lower water conc. until equilibrium. txs = water
tonicity
a measure of the solution’s ability to change the volume of cells by altering H2O content - isotonic = the concentration of solutes are the same on either side of the membrane. hypotonic = the solution has lower concentration of solute, so H2O enter cells faster than they leave (cells swell, hemolysis/lysis
), hypertonic = solution has higher conc of solute, so H2O leaves cells (crenation).
active transport
active processes in which a cell expends energy to move a substance across the membrane against its conc. gradient by transmembrane proteins that function as carriers. txs = polar or charged solutes.
primary active transport
active process in which a substance moves across the membrane UP its conc. gradient by pumps (carriers) that use energy supplied by ATP hydrolysis. Na+, K+, Ca2+, H+, I-, Cl-
Na+/K+ ATPase
primary active transport mechanism expels Na+ from cells and bring K+ into cells. a part of the sodium-potassium pump acts as an ATPase (enzyme that hydrolizes ATP) - maintains low conc. of Na+ in the cytosol, by pumping Na+ into ECF while bringing in K+. Work non-stop, thousands in each cell’s plasma membrane. Crucial form maintaining cell volume and for cells to generate electrical signals (action potentials). Maintain normal tonicity on each side of membrane so cells neither shrink or swell.
secondary active transport
coupled active transport of two substances across the membrane using energy supplied by Na+ or H+ conc. gradient maintained by primary active transport pumps. Antiporters move Na+ (or H+) and another substance in opposite directions, Symporters move them in the same direction. Anti = Ca2+ and H+ out of cells. Sym = glucose, amino acids
transport in vesicles
active process in which substances move into or out of cells in vesicles that bud from plasma membrane, requires energy from ATP
endocytosis
movement of substances INTO a cell in vesicles
receptor-mediated endocytosis
ligand-receptor complexes trigger infolding of a clathrin-coated pit that forms a vesicle containing ligands. Ligands: transferrin, LDLs, some vits, hormones and antibodies.
