2a plasma membrane Flashcards
epithelia
sheets of tissue that cover all body surfaces
amphipathic
molecule with both polar and nonpolar regions
ex of amphipathic
phosphatidylcholines are common in animal cell membranes)
when the melting point is low, is it going to be more or less fluidity?
more
Would you expect a thermo-conforming animal to have
more unsaturated bonds (as a phosphatdyethanolamines) which is more than phophatidylcholines
integral
permanently embedded in the membrane
peripheral
connected to the membrane, but removable
aqueous pores
channels through which aqueous solutions
can pass from one side of the membrane to the other.
type of channel protein
Channel proteins
Control
diffusion of aqueous solutes
osmosis of water
Transporter (carrier) proteins
Move specific molecules across a membrane by reversibly (non-covalently) bonding with them to facilitate transport
-can be active or facilitative
Membrane-bound Enzymes
Protein catalysts of various types embedded in membranes
Receptor proteins
– exact def of carrier proteins but can cause signal transduction
– signal transduction: 1. primary messenger, which may be a chemical signal, electrical pulse, or even physical stimulation. Then, the receptor protein embedded in the cellular membrane must accept the signal. Upon receiving the signal, this protein goes through a conformational change. This changes its shape and thus, how it interacts with the molecules around it.
- Some proteins activate other molecules, called second messengers, which carry the message to the nucleus or other organelles. Other proteins use the energy from ATP to activate enzymes, which carry out metabolic reactions.
–responsible for mediating responses to chemical signals arriving at the cell membrane.
Structural proteins
- anchor intracellular elements to the cell membrane
- form cell junctions
- form the protein infrastructure of the membrane
epithelium
- –lines a cavity in an organ or body
- –forms boundaries between body regions
- –forms boundaries between an animal and its external environment
apical (mucosal) surface
facing the side of an open membrane
basal (serosal) region
towards the tissue to which the epithelium is attached
basement membrane or basal lamina
- — thin, permeable, non-living, non-cellular fibrous matrix
- — allow gas exchange
name 3 of the simple and stratified epithelia
- squamous epithelium (cell width > height)
- cuboidal epithelium (cell width = height)
- columnar epithelium (cell width < height)
simple vs stratified
stratified has more than one layer
pseudo stratified
really one layer but looks like more than one layer because nuclei are on opp sides
What is the functional significance of microvilli? (How do they increase transport efficiency?)
increase surface area for transport across membranes
brush border
microvilli often resemble the bristles of a brush when viewed under the microscope, a row of microvilli
tight junctions
Found only in vertebrates.
Block the interstice between two adjacent cells
Prevent interstitial movement of solutes from apical to basal regions. ( sealed together)
Substances must enter via cell membrane channels.
serve as barriers and prevent leaks
Septate junction
used as tight junctions for invetebrates
isoenzymes
as multiple forms of enzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. These enzymes usually display different kinetic parameters (e.g. different KM values), or different regulatory properties.
covalent modulation
activation or inactivation of enzymes, either by phosphorylation/dephosphorylation or by proteolytic cleavage. A major means of regulation of enzyme action by hormones.
