AP Biology Chapter 5 - Membrane Structure and Function

amphipathic molecule

having both a hydrophilic and hydrophobic region ex: phospholipid

describe how a cell would react to a hypertonic or hypotonic solution:

in a hypotonic solution the cell swells or even bursts, due to an intake of water. in a hypertonic solution the cell shrinks or shrivels due to loss of water

glycolipids

lipids with a carbohydrate attached by a glycosidic (covalent) bond; maintain stability of the cell membrane

adhesion junctions

mechanically attach adjacent cells ex: desmosome

active transport

moves molecules against their concentration gradient; requires energy in the form of ATP

plasmodesmata

numerous narrow, membrane-lined channels that pass through the cell wall

pinocytosis

occurs when vesicles form around a liquid or around very small particles

osmosis

the diffusion of water across a selectively permeable membrane from high to low concentrations

describe the composition of the extracellular matrix of an animal cell:

the extracellular matrix of an animal cell is a meshwork of proteins and polysaccharides in close association with the cell that produced them. collagen and elastin are important structural protein in ECM; collagen resists stretching and elastin gives ECM resilience. fibronectin is an adhesive protein inECM that binds to integrin, protein in the plasma membrane. amino sugars in the ECM form multiple polysaccharides that attach to a protein, therefore called proteoglycans.

turgor pressure

the force within the cell that pushes the plasma membrane against the cell wall

contrast diffusion with facilitated transport:

the major difference between diffusion and facilitated transport is that facilitated transport used carrier proteins to move molecules with the concentration gradient, while diffusion does not

diffusion

the movement of molecules from a higher to a lower concentration until equilibrium is achieved

osmotic pressure

the pressure that develop in a system due to osmosis; the greater the osmotic pressure, the more likely it is that water will diffuse in that direction

tonicity

the strength of a solution

sodium-potassium pump

the transport of sodium and potassium linked through the same carrier protein

explain why a cell would be connected by a tight junction rather than a gap junction or an adhesion junction:

a cell would be connected by a tight junction because it brings cells even closer than adhesion junction and an impermeable barrier is formed that doesn't allow molecules to pass, making it preferred in cells (ex: cells in the intestine or in kidneys)

summarize why a cell would use bulk transport rather than active transport:

a cell would use a bulk transport rather than active transport because certain molecules, such as proteins, polysaccharides, or nucleic acids, are too large to be transported by carrier proteins (active transport), so bulk transport is preferred to move these molecules in and out of the cell by vesicles

receptor-mediated endocytosis

a form of pinocytosis that is specific because it uses a receptor protein to recognize compatible molecules and take them into the cell

extracellular matrix

a meshwork of proteins and polysaccharides in close association with the cell that produced them

fluid mosaic model

a model used to describe the plasma membrane; fluidity is describe by the lipid content of the membrane and the mosaic is described by the presence of many proteins

cell wall

a porous layer that varies in thickness, depending on the function of the cell

plasmolysis

a shrinking of the cytoplasm due to osmosis

aquaporins

a type of channel protein that allows water to cross the plasma membrane

bulk transport

a way that large particles can exit or enter a cell

explain why active transport requires energy:

active transport requires energy because the molecules are going against their concentration gradient in this case both carrier proteins and ATP is needed

gap junction

allows cell to communicate; formed when two identical plasma membrane channels join

exocytosis

an intracellular vesicle fuses with the plasma membrane as secretion occurs

tight junction

another type of adhesion which brings cells even closer than desmosome, by connecting plasma membrane between adjacent cells together, producing a zipper like fastening

glycoproteins

any of a class of proteins that have carbohydrate groups attached to the polypeptide chain

endocytosis

cells take in substances by forming vesicles around the material

facilitated transport

explains how molecules are rapidly transported across the plasma membrane; movement with concentration gradient; requires no energy; uses carrier protein

explain why phospholipids play such an important role in the structure of the cell membrane:

phospholipids play an important role because since they are amphipathic molecule (both hydrophilic region and hydrophobic region); they create the membrane ( a phospholipids bilayer) which separates the cell and external environment as well as compartments within the cell itself

compare how cells transport polar and non polar molecules across a membrane:

substances that are hydrophobic (similar to the phospholipids center of the membrane) are able to defuse across membrane at energy cost (passively. polar molecules, however, are incompatible with the center of the membrane and so require an expenditure of energy to drive their transport

hemolysis

term used to describe cytolysis in red blood cells

crenation

when red blood cells are in a hypertonic condition

phagocytosis

when the material taken in by endocytosis is large ex: food particle