anph 12 unit e - plasma membrane
PM is
boundary that separates living cells from non living surroundings
PM 3 facts
1. in all cells
2. separates internal/external enviornments
3. controls molecular traffic in and out of cell by being selectively permeable
Fluid mosaic model is
collage of different proteins in fluid matrix and made up of 4 components
4 components of fluid mosaic model
phospholipids, membrane proteins, carbs, and cholesterol
Phospholipids are
main lipid of PM because of amphipathic nature meaning it has hydrophilic and hydrophobic regions
Phospholipid bilayer is
fluid and held together by hydrophilic bonds which are weaker than covalent bonds
Phospholipids will
drift laterally but rarely flip flop to other side during creation or merging of vesicles
Cholesterol is
Lipid steroid wedged between phospholipid molecules in animal PM to stabilize membrane fluidity
Membrane Proteins + Two facts
Amphipathic and individually dispersed into bilayer with hydrophilic regions protruding outwards facing H2O and hydrophobic regions facing non-aqueous enviornments
Will draft laterally at a slow pace and determine most of PM's specific functions
Enzymatic proteins deactivate at...
extreme temperatures/pH which alters permeability of PM
Two types of membrane proteins
Peripheral and integral proteins
Peripheral proteins are
Partially embedded in bilayer and most attached to membrane surface, held together by cytoskeleton filaments to stabilize membrane structure
Integral proteins are
Mostly/fully embedded in bilayer but may protrude outwards causing molecules/ions to move
Carbs are
Restricted to exterior surface
Two types of carbs
Glycolipids and glycoproteins
Glycolipids
carb attached to phospholipid head
Glycoproteins
carb attached to protein
Glycolipids and glycoproteins are both
ID cells that identify self and non-self cells and reject non self cells
Five types of integral proteins
channel, carrier, receptor, cell recognition, and enzymatic proteins
Channel proteins
Span membrane and provide hydrophilic membrane which allow specific ions and polar molecules such as O2 and CO2 to freely cross following concentration gradient and may have a gate that opens when specific ions/molecules bind to it
Two examples of channel protein involvement
1. H+ ions flow into inner mitochonrial membrane to help w ATP creation
2. Cystic fibrosis - Genetic disorder in CFTR gene that disrupts Cl- channels and builds mucus in airways
Carrier proteins
Bind to specific passenger molecules/ions and transport them across PM - used during facilitated and active transport
Cell-recognition protein
carb chain attached to protein in animals --> forms a glycoprotein and contains glycocalyx
Glycocalyx is
sugar coat in cell-recogniton protein that protects and glues cells together --> found on external side of PM
Glycoproteins are
ID tags that get recognized by other cells during cell-cell recognition
Example of glycoprotein involvement
ABO blood system with four blood types
Carb chains usually have...
15 monosaccharides but can have up to 100 - which is what makes cells unique to each other and enable them to identify pathogens and trigger immune response
Receptor proteins
protein that has a specific binding site that fits chemical messenger/signal molecule such as a hormone which gets recieved by a cell, making the cell grow and sends message to the inside of it
Example of receptor protein involvement
Liver stores glucose after receiving signal from insulin
Enzymatic proteins
Membrane protein that may be an enzyme with active site exposed to substances/substrates and may act as a team to carry out steps of metabolic pathway
PM is selectively permeable but has a
hydrophobic interior
Permeability of bilayer prevents
charged molecules, hydrophilic ions, and uncharged hydrophilic polar (macro) molecules from crossing
Permeability of bilayer allows
hydrophobic hydrocarbons and non polar O2 and CO2 to dissolve and cross membrane + allow uncharged hydrophilic polar molecules to pass between hydrophilic heads
Active transport
Requires chemical energy such as ATP and carrier protein and includes endocytosis and excytosis
Passive transport
requires kinetic energy in molecules and ions and includes diffusion, osmosis, and facilitated transport
Diffusion is the
movement of molecules from an are aof high to low concentration until equilibrium is reached
Equilibrium is
the state of stability
Each substance goes through diffusion
individually and dont affect each other
Diffusion applies to
small, noncharged molecules such as O2, CO2, H2O, and alcohol (gases and liquids)
Osmosis is the
Diffusion of H2O across a semipermeable membrane
Direction of osmosis is determined by
solute differences in solutions on either side of membrane
Osmotic pressure gradient makes
H2O move form an area of low to high solute AKA opposite diffusion gradient
Example of opposite diffusion gradient
H2O absorbed by kidneys, taken in by capillaries in tissue due to osmotic pressure
Isotinc solution is
Solute in cells typically the same as in extracellular fluid which makes cells isotonic to its surroundings
Tonicity is the
osmotic pressure or solute of solution
Osmosis in animal cells
No net osmosis occuring as equilibrium is reached and cell maintains its size
2 examples of osmosis in animal cells
IV solutions at hospitals and red blood cells having 0.9% tonicity
Osmosis in plant cells
Will wilt because central vacuole isn't fully saturated
HYPOtonic solution
Outside solution has lower solute than that of a cell
HYPOtonic solution in animal cells
H2O enters faster than it leaves, cell swells, cytolysis occurs
Cytolysis
Bursting of cells
Hemolysis
RBCs bursting
HYPOtonic solution in plant cell
H2O enters via osmosis, filling central vacuole and pusing PM against cell wall which prevents bursting AKA tugor pressure
HYPERtonic solution
Outside solution has higher solute than that of a cell
HYPERtonic solution in animal cell
will shrivel/crenate and lose H2O
2 examples of HYPERtonic solution in animal cells
1. Increase in salt in lake may kill animals
2. Salt on slug
HYPERtonic solution in plant cell
Will shrink and lose H2O, making PM move away from cell wall AKA plasmolysis
Facilitated and active transport both involve
Carrier proteins
Facilitated transport follows the
concentration gradient
Facilitated transport/diffusion is the
diffusion of solutes through carrier proteins in PM
Facilitated transport does not use __ because ___
energy because substances follow the concentration gradient
In facilitated transport, carrier proteins...
alternate between 2 shapes
In faciliated transport, solutes can be transported...
in either direction as long as concentration gradient is followed
Facilitated transport can occur around
100 times per second
In facilitated transport, glucose can be transported...
hundreds of times faster than other sugars
In faciliatated transport, the speed of glucose may be slowed by...
imposter molecules which inhibits actual solute from binding
in faciliated transport, substrate molecule...
enters carrier protein's binding site which undergoes conformation increase and then is releassed to other side and carrier protein returns to original conformation
Active transport goes against the...
concentration gradient
active transport is the
pumping of ions/molecules/solutes against concentration gradient from low to high area
active transport requires
ATP and carrier proteins
active transport is needed to
maintain internal concentration of small ions/molecules that differ from ones surroundings
active transport example involving iodine
iodine pumped into thyroid gland
active transport example involving sodium
sodium-potassium pump in which is active in animal cells for nerve impulse conduction
2 types of active transport
endocytosis and exocytosis
during exocytosis, a cell
secretes macromolecules by fusing vesciles in PM
during exocytosis, a vesicle is
budded from GA and moved by microtubule cytoskeleton to PM where the phospholipids and proteins of it is rearranged with PM to become continous and contents spill outside of cell
example of exocytosis
pancreatic cells make insulin but only secrete it via exocytosis when insulin is needed to decrease blood glucose
during endocytosis, a cell
takes in macromolecules by forming vesicles derived from PM around substances which is called invagination
2 types of endocytosis
phagocytosis and pinocytosis
Phagocytosis AKA
cellular eating
phagocytosis is when
a cell engulfs a particle by wrapping pseudopoding around it and packing it within a larger vesicle in which the particle is digested when fused with lysosome
phagocytosis is categorized as
specific
pinocytosis AKA
cellular drinking
pinocytosis is when
a cell "gulps" droplets of extracellular fluid in tiny vesicles and any solutes in which are dissolved in droplets are taken in
pinocytosis is categorized as
non specific
receptor mediated endocytosis (RME)
membrane proteins with specific receptor sites are exposed to extracellular fluid
ligands in receptor mediated endocytosis are
substances that bind to sites such asa vitamins, peptide hormones, and lipoproteins
RME: receptor proteins clustered in membrane regions are called
coated pits
RME: coated pits are deepened by
a lining of a fuzzy protein layer called a cytoplasmic site AKA invagination which forms a vesicle
RME: formed vesicle fuses with
lysosome when formed and RME enables cell to acquire bulk quantities of specific substances
RME is more efficient than __ because of __
pinocytosis because of HIGH selectivity
example of RME
humans take in cholesterol for membrane synthesis and as a steroid/precursor
people with familial hypercholesterolemia (FH) have
high blood cholesterol levels because lipoprotein's receptor proteins are defective meaning that lipoproteins can't enter cells
FH: lipoproteins cause
atherosclerosis
atherosclerosis
caused by lipoproteins in which fatty buildup called plaque is formed on blood vessel lining
atherosclerosis means the occurrence of
high blood pressure, blocked/occluded arteries, heart attacks, and strokes