Ch.7: Membranes Flashcards
The plasma membrane is composed of
phospholipid and proteins
contain hydrophobic and hydrophilic regions that maintain a bilayer
phospholipid
states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it
An ocean of phospholipids with islands of protein
fluid mosaic model
What maintain the membrane structure.?
The properties of the phospholipids
determine most of the membrane’s specific functions
membrane-protein
are bound to the surface of the membrane
peripheral protein
penetrate the hydrophobic core
XXXXXx that span the membrane are called trans-membrane proteins
Integral proteins
Six major functions of membrane proteins
Transport Enzymatic activity Signal transduction Cell-cell recognition Intercellular joining Attachment to cytoskeleton
is the tendency for molecules to spread out evenly into the available space
Molecules naturally try to XXXX in and out of cells
Cells are constantly fighting XXXX to maintain internal homeostasis
diffusion
From high concentration to low concentration
concentration gradient
The diffusion of a substance across a biological membrane is ______ ______
It requires no energy to make it happen
Water is always diffusing into and out of cells
passive transport
is the diffusion of water across a selectively permeable membrane
Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration
osmosis
Solute concentration is the same; no net water movement
isotonic
Solute concentration is greater; cell loses water
hypertonic
Solute concentration is less; cell gains water
hypotonic
transport proteins speed the passive movement of molecules across the plasma membrane
Transport proteins are often needed to move large molecules across a membrane
Remember, these proteins serve to maintain selective permeability of the membrane
facilitated diffusion
moves substances against their concentration gradient
XXXXX requires energy, usually in the form of ATP
________ ______is performed by specific proteins embedded in the membranes
Na / K pump
active transport
However, large polysaccharides and proteins, cross the membrane differently
by?
bulk transport
the cell takes in macromolecules by forming vesicles from the plasma membrane
endocytosis
There are three types of endocytosis
Phagocytosis (“cellular eating”)
Pinocytosis (“cellular drinking”)
Receptor-mediated endocytosis
transport vesicles migrate to the membrane, fuse with it, and release their contents
exocytosis
Many secretory cells use exocytosis to export their products
Examples include:
protein hormones
