Biological Membrane Flashcards
Ch 8
fluid mosaic model
accounts for the presence of lipids, proteins, and carbohydrates in a dynamic, semisolid plasma membrane that surrounds the cell
plasma membrane contains what
contains proteins embedded within the phospholipid bilayer
fatty acids
carboxylic acids that contain a hydrocarbon chain and a terminal carboxyl group
-can be saturated or unsaturated
triacylglycerols (triglycerides)
storage lipids involved in human metabolic processes
-contain three fatty acid chains esterified to a glycerol molecule
unsaturated fatty acids
- regarded as “healthier” fats
- have more double bonds and exist in liquid form at room temperature
what are two important essential fatty acids for humans
alpha linolenic acid
linolenic acid
saturated fatty acids
main components of animal fats and tend to exist as solids at room temperature
-when incorporated into phospholipid membranes, saturated fatty acids decrease the overall membrane fluidity
glyercerophospholipid structure
- also known as a phospholipid
- by substituting one of the fatty acid chains of triacylglycerol with a phosphate group
- polar head, nonpolar tails
phospholipids can assemble into
-micelles (small monolayer vesicles)
-liposomes (bilayered vesicles)
due to hydrophobic interactions
phospholipid function
- membrane synthesis and can produce a hydrophilic surface layer on lipoproteins
- primary component of cell membranes
- second messengers in signal transduction
- attachment point for water-soluble groups
waxes
class of lipids that are extremely hydrophobic and are sometimes found in the cell membranes of plants
transmembrane proteins
pass completely through the lipid bilayer and function as receptors or channels
-have both extracellular and intracellular domain
embedded proteins
associated with only the interior or exterior surface of the cell
involved in cellular communication
desmosomes
bind adjacent cells by anchoring to their cytoskeleton
-found at the interface between two layers of epithelial tissue
hemidesmosomes
attach to epithelial cells to underlying structures, especially the basement membrane
flippases
specific membrane proteins that maintain the bidirectional transport of lipids between the layers of the phospholipid bilayer in cells
cholesterol
present in large amount and contributes to membrane fluidity and stability
what are the three types of proteins within the cell membrane
transmembrane proteins
embedded proteins
membrane associated proteins
membrane associated proteins
as as recognition molecules or enzymes
what is carbohydrates function in the membrane?
form a protective glycoprotein coat function in cell recognition
extracellular ligands function in the membrane
bind to membrane receptors, which function as channels or enzymes in second messenger pathways
cell-cell junctions function in the membrane
regulate transport intracellularly and intercellularly
gap junctions
allow for rapid exchange of ions and other small molecules between adjacent cells
tight junctions
prevent paracellular transport but do not provide intercellular transport
concentration gradients
help to determine appropriate membrane transport mechanisms in cells
osmotic pressure
- colligative property
- pressure applied to a pure solvent to prevent osmosis
- used to express the concentration of the solution
- “sucking” pressure in
passive transport
- does not require a transporter
- molecule is moving down its concentration gradient from an area of low concentration until equilibrium is achieved
simple diffusion
- does not require a transporter
- small, nonpolar molecules passively move from an area of high concentration to an area of low concentration until equilibrium is achieved
osmosis
-describes the diffusion of water across a selectively permeable membrane
facilitated diffusion
-uses transport proteins to move impermeable solutes across the cell membrane
active transport
requires energy in the form of ATP or an existing favorable ion gradient
-may be primary or secondary depending on the energy source
primary active transport
uses ATP or another energy molecule to directly power the transport of molecules across a membrane
-involves the use of a transmembrane ATPas
secondary active transport (coupled transport)
uses energy to transport particles across the membrane
-gets energy from the energy released by one particle going down its electrochemical gradient to drive a different particle up its gradient
symport
when both particles flow the same direction across the membrane
antiport
when particles flow in the opposite direction
what is one example of primary active transport
in many tissues
primary active transport maintains the membrane potential of neurons in the nervous system
what is one example of secondary active transport
the kidneys
usually driven by sodium
reabsorb and secrete various solutes into and out of the filtrate
endocytosis
occurs when the cell membrane invaginate and engulfs material to bring it into the cell
exocytosis
occurs when secretory vesicles fuse with the membrane, releasing material from inside the cell to extracellular
pinocytosis
endocytosis of fluids and dissolved particles
phagocytosis
ingestion of large solids such as bacteria
what will initiate endocytosis
substrate binding to specific receptors embedded within the plasma membrane
what is an example of exocytosis
important in the nervous system and intercellular signaling
ex: exocytosis of neurotransmitters from synaptic vesicles
membrane potential
maintained by the sodium-potassium pump and leak channels
nerst equation
calculate the electrical potential created by one ion
goldman-hodgkin-katz voltage equation
calculate the resting potential of membrane eat physiological temperature
how does the mitochondrial membrane differ from the cell membrane
- outer mitochondrial membrane is highly permeable
- inner mitochondrial membrane does not contain cholesterol
the movement of any solute or water by diffusion or osmosis is dependent on what
only on the concentration gradient of that molecule and on membrane permeability
sphingolipids
- contain a hydrophilic region and two fatty hydrophobic tails
ex: gangliosides, ceramide, sphingomyelin, cerebrosides
resting membrane potential depends on
- the differential distribution of ions across the membrane
- active transport process
- selective permeability of the phospholipid bilayer
what will contribute to membrane fluidity?
compounds that will lower the melting point or disrupt the crystal structure
ex: cholesterol and unsaturated lipids
hypotonic
the concentration of soluce inside the cell is higher than the surround solution
hypertonic
a solution that is more concentrated than the cell
water will move out of the cell
isotonic
the solutions inside and outside are equimolar
-prevents the NET movement of particles
