Plasma Membrane Flashcards
ICF (5 things)
- intracellular fluid: fluid inside cells
- 40% body weight
- 2/3 body water
- maintains shape of cell
- moves across membrane via osmosis
ECF (4 things)
- extracellular fluid: fluid outside cells
- 20% body weight
- 1/3 body water
- made up of: ISF, plasma volume and lymph, and transcellular fluid
Plasma volume and lymph (three things)
- in blood and lymphatic vessels
- 1/4 ECF
- 5% body weight
How is plasma volume and lymph separated from ISF?
separated by capillary wall
Where do the exchange between plasma, lymph, and ISF occur?
capillary beds
Transcellular fluid (three things)
- in specialized areas
- very small % of body weight
- stable volume
Examples of transcellular fluid
- cerebral spinal fluid
- aqueous humor
Where is most of the body weight?
ICF
Most important cation in ICF?
K+
Important cation for cell function?
Ca2+
Most important anion in ISF?
Cl-
Important ECF buffer
HCO3-
What do proteins act like in the ICF?
act as major anions
What does the cell membrane separate?
ICF and ECF
Functions of the cell membrane
- regulate exchange w/ environment
- cell communication
- structural support
How does cell membrane regulate exchange w/ environment?
provides permeability barrier and highly selective filter
How does cell membrane help w/ cellular communication?
receptors and signal transduction pathways for hormones and neurotransmitters
Cell membrane contains:
adhesion molecules and surface antigens
Adhesion molecules allow for:
- anchoring
- tissue organization
- intracellular communication
- cell shape
Types of junctions (3 types)
- gap
- tight
- anchoring
Major adhesion molecules (4 of them)
- cadherins
- integrins
- immunoglobulin superfamily CAMs
- selectins
Cadherins:
- cell-cell junctions
- adherens junctions
- desmosomes
- Ca2+ dependent
Integrins:
- mostly found in cell-matrix junctions
- help w/ cell signaling
Example of immunoglobulin superfamily CAMs and its function
nerve cell adhesion molecules (NCAM): responsible for nerve cell growth during nervous system development
Selectins:
temporary cell-cell adhesion
Surface antigens function
important for recognition of “self” vs. “nonself”
Model of plasma membrane structure
fluid mosaic model
Plasma membrane is made of
lipids (50%), proteins (50%), and carb
Phospholipids:
- core structure
- organized in bilayer
- have polar head and nonpolar tail
Why are phospholipids of plasma membranes amphipathic?
has polar (hydrophilic) phosphate head and nonpolar (hydrophobic) tails
Orientation of phospholipids in plasma membrane?
polar heads on the outside and nonpolar fatty acyl tail chains are on the inside
Nonpolar tail of plasma membrane forms what?
permeability barrier to H2O soluble molecules
Cholesterol
- hydrocarbon ring structure
- about 20% of total membrane lipid
Functions of cholesterol in plasma membrane
- stabilizes membrane at body temp (37 C)
- increases membrane fluidity
- reservoir of precursor molecules for steroid hormones
Protein types:
- integral / intrinsic
- peripheral / extrinsic
Integral / intrinsic proteins:
- 70% of membrane proteins
- embedded in membrane
- transmembrane protein: spans membrane completely
Functions of integral / intrinsic proteins:
- carriers
- enzymes
- channels
- receptors
Peripheral / extrinsic:
- either on outside or inside of plasma membrane
- often are enzymes
T/F: phosphatases remove phosphate group from protein.
T
T/F: kinases remove phosphate group from protein.
F
Carbohydrates:
- 2-3% of membrane lipid
- glycoproteins: made of carb and proteins
- glycolipids: made of carb and phospholipids
Functions of glycoproteins / glycolipids:
- cell-cell communication
- structural stability
- immune response
Example of membrane transporters
- carriers
- channel proteins
T/F: Carriers change conformation
T
Channel proteins form:
- open channels
- closed channels
Types of gated channels:
- mech
- voltage
- chem
Structural proteins are found in:
- cell junctions
- cytoskeleton
Membrane enzymes:
- activated by membrane receptors
- functions in: metabolism and signal transfer
Functions of membrane receptors:
- receptor mediated endocytosis
- signal transfer
- open and close chem gated channel
Order of concentration of ions in ECF (highest to lowest)
Na+, Cl-, K+
Order of concentration of ions in ICF (highest to lowest)
K+, Na+, Cl-
