Chapter 7: Membrane Structure and Function Flashcards
integral proteins
transmembrane proteins that completely span the hydrophobic interior of the bilayer
phospholipid bilayer
large part of fluid mosaic model
hydrophobic and hydrophilic interactions hold membrane together
most lipids and some proteins can drift randomly in the bilayer (some are attached to the cytoskeleton)
peripheral proteins
loosely bonded to the surface of the membrane and some are attached to the extra cellular matrix
oligosaccharides
short sugar chains attached to the membrane
15 sugar units long
oligo
short (Greek)
glycolipid
sugar chains bonded directly to the membrane (phospholipid layer)
glycoprotein
sugar chain directly bonded to a protein
oligosaccharide usages
markers that distinguish one cell from another
vary from species to species and distinguish blood types using varying oligosaccharides
blood types
O, A, B, AB
6 functions of proteins in membrane
1) Transport
2) Enzymatic activity
3) Signal transduction
4) Cell-cell recognition
5) Intercellular joining
6) Attachment to the cytoskeleton and extra cellular matrix (ECM)
cholesterol in the membrane
steroid or lipid in the membrane that reduces membrane fluidity
reduce phospholipid movement by stabilizing the membrane
kinks in phospholipid tails
where double bonds (unsaturated bonds) are located
why do unsaturated bonds increase fluidity?
more porous, spaced farther apart (see diagram)
saturated bonds
single bonds that make membrane more viscous
heads close together, tails straight
passive transport
does NOT require adenosine triphosphate
moves with concentration gradient
diffusion
when any substance moves from an area of higher concentration to an area of lesser concentration without the use of energy
concentration gradient
when there is an area of high and low concentration
no equilibrium is when
diffusion is still occurring. when diffusion is done, there is no high/low concentration
equilibrium
when a substance is equally spaced throughout a container
osmosis
the diffusion of water across a selectively permeable membrane
isotonic environment
having the same amount of water and dissolved diluted as the cell
75% water 25% solutes in
75% water 25% solutes out
hypertonic environment
having less water and more dissolved solutes as the cell
75% h2o 25% solutes in
(more dilute)
(lose water, cell shrinks---->)
70% water 30% solutes out
(more stuff)
hypotonic environment
having more water and less dissolved solutes as the cell
75% h2o 25% solutes in
(less h2o)
(gains water, cell swells ---->)
80% h2o 20% solutes out
(more h2o)
ocean water is
isotonic to most marine invertebrates
extracellular fluid is
isotonic in land dwelling animals
fresh water invertebrates live in a
hypotonic environment
osmoregulation
the control of water balance using adaptations
example of osmoregulation
paramecium (hypotonic (fresh water))
example of osmoregulators in paramecium
contractile vacuole
pellicle
pellicle
intricate cell membrane that slows water gain into the organism (less permeable than average cell membrane)
ex of osmoregulators in paramecium
turgor pressure
in plant cell; (turgid environment)
when a plant cell is turgid, this is a healthy condition in the plant- it’s gained enough water where the cell membrane is pushed against the cell wall
turgor pressure helps plants:
support; keeps them straight
flaccid
low turgor pressure- limp
plasmolysis
when cell is actively losing water
herbaceous plants
soft plants (will wilt)
woody plants
not enough water —-> dies
lyse
(in animal cell) cell gains too much water that it breaks open
facilitated diffusion
flows WITH concentration gradient
many polar molecules and ions are impeded by the lipid layer so they must be transported with the help of transport proteins. these transport proteins are specialized for the solute
main molecule moved by facilitated diffusion
glucose
main example of solute with specialized transport proteins
glucose
gated channels
stimulus causes these to open or close (electrical or chemical)
ex of gated channels
nerve cell (neurotransmitter used to open a gated channel that allows sodium into the cell)
active transport
any cellular transport that requires cellular energy and moves AGAINST the concentration gradient
sodium-potassium pump
ATP transfers it’s terminal (last) phosphate directly to the transport protein. this changes the protein’s conformation and translocation the solute
how sodium-potassium pump works
sodium is being pushed out of the cell against it’s concentration gradient (10% more sodium outside than inside the cell). potassium is being pushed inside the cell against it’s concentration gradient (10% more K inside than outside)
Na to K ratio in sodium potassium pump
3 Na for every 2 K
endocytosis
when materials are moving into the cell
phagocytosis
form of endocytosis (type of AT)
when a cell engulfs food by wrapping pseudopods around it and forming a food vacuole (cell eating)
pinocytosis
form of endocytosis (type of AT)
a pocket forms in the cell membrane trapping extracellular fluids and it’s contents. the vesicles pinches off and enters the cell (cell drinking)
receptor - mediated endocytosis
form of endocytosis (type of AT)
receptor proteins in the cell membrane are clustered in regions of the membrane called coated pits. the cell is collecting a desired substance called a ligand. the ligands bind to these receptors and are pulled into the cell forming vesicles (called coated vesicles)
exocytosis
cell removing materials
the vesicles fuses with the cell membrane and dumps it’s contents outside of the cell
ex of exocytosis
pancreas secreting insulin
