B2.1 membrane and membrane transport Flashcards
phospholipid bilayer
consists of phosphate and fatty acids
( hydrophilic polar head and hydrophobic non polar tail)
micelle
phospholipid bilayer shaped in a circle, wth hydrophobic area in the centre and membrane enclosed structures
libosome
circular membrane
enclosed structure
hydrophobic area and hydrophilic area
2 circles
amphiapathic properties
both polar and non polar properties in the same structure
why do phospholipids clump together
non polar regions clump together on the inside of the bilayer,polar regions (head) move towards the outside of the bilayer where they contact with water
fluid mosaic bilayer
flexible, resistant and ability to change shape
composition of many structural molecules embeded in the bilayer such: proteins carbs and cholesterol
structure of plasma cell membrane
1) phospholid bilayer
2) polar head and tail
3) cholesterol
4) carbohydrate group
5) glycolipid
6) integral transmembrane protein
7) integral protein
8) peripheral protein
9) glycoprotein
what does cholesterol do
regulates the fluidity of the membrane
what does glycolipid do
acts as cell receptors and/or recognition
what does integral transmembrane protein and integral protein do
function as channels pumps and enzymes
integral means permently associated with cell membrane
receptor protein
these membrane proteins recognize and respond to chemical signals from outside the cell. when the chemical signal binds, the membrane protein triggers a response by the cell
example of receptor protein
insulin receptor protein is a hormone released by the pancreas when blood sugar levels are high. inslulin binds to the isulin receptor protein, which then allows glucose to enter cell from blood
adhesive proteins
proteins that achor the cell membrane to:
the inner cytoskeleton
proteins outside the cell
other cells
examples of adhesive proteins
desmone proteins are found in muscles tissue where they bind muscle cells to one another
recognition protein
these membrane proteins serve as identification tags on the surface of the cell. these are often “glycoproteins” with the carbohydrate portion projecting out of the cell and into the extracellular space. these give the cell a biochemical personality and are important in cell-to-cell recognition
regocnision protein examples
imunoglobulins or antibodies b cells carry antibodies embeded by the tail in the outer cell membrane, with the binding sites facing outwards. this enables the b cells to bind to antigens
channel protein
these membrane allow small molecules to pass through the cell membrane by creating a pore through the membrane.
channel protein examples
proteins called aquaporin allows water molecules to move through the cell membrane single file
pump protein
.these proteins function to move small molecules or ions across the cell membrane by creating a pore through the membrane.
crate concentration gradient- energy from low to high
pump protein examples
the calcium pump allows muscles to relax after contraction y moving calcium ions back into th
enzyme protein
Membrane proteins show enzymatic activity and catalyse reactions.
example of enzyme protein
ATP sythase builds atp by adding phosphate group to adp
exocytosis
the secretion of macromolecules produced within the cell ( inside the RER) to the extracellular fluid without going through the phospholipid bilayer
examples of exocytosis
- secretion of neurotransmiter at synapse
- secretion of hormones from endocrine gland, such as insulin
- secretion of digestive juices from exocrine glands in the mouth and stomach
- secretion of blood plasma protein such as fibronogen from liver
- release of cortical granuled from egg cell during fertilization
step 1 exocytosis
macromolecules synthesized in the RER moves towards the golgi complex by being packed within a transport vesicle.
these vesicles contain the same membrane composition as plasma membrane
step 2 of exocytosis
transport vesicles fuse with the embrane of the golgi complex, that modifies macromolecules. from the gogi, a new vesicle is formed by budding of the membrane and releasing secretory vesicle
step 3 of exocytosis
secretion of the macromolecule happens when the sceretory vesicle fuses with the cell membrane, releasing its contents to the outside of the cell.
+ a increase in the plasma membrane as the membrane of the vesicle fuses with it
endocytosis
the intake of macromolecules from the extracellular fluid to the cytoplasm without passing through the phospholipid bilayer
examples of endocytosis
-phagocytosis- engulfing f any pathogen by a phagocyte
- pinocytosis-intake of liquid macromolecules such as tissue fluid
- receptor-mediated endocytosis: specific intake of macromolecules that will bind to a receptor at the plasma membrane. chlatin in the protein membrane allows specific molecules to be engulfed regulating a more specific intake of macromolecule
endocytosis step 1
macromolecules in the extracellular fluid are engulfed by the plasma membrane, one this pinches off and packages the macromolecule inside an endosome. these vesicles contain the same mebrane composition of the protein membrane.
endocytosis step 2
the endosome moves through the cytoplasm and fuses with the lysome
endocytosis step 3
the lysome digests the contents using its enzymes. the products are used as building blocks for the cell
simple diffusion
down concentration gradient from high to low
osmosis
movement of water down concentration gradient from high to low water potential
what are the membrane proteins used in osmosis
only in kidneys and ileum (aquaporin: problem channel)
facilitated diffusion
down concentration gradient, uses selectively permable membrane
channels or carriers
what molecules are moved through facilitated diffusion
channels: small hydrophobic molecules
carriers: small ionic molecules
active transport
against concentration gradient, uses pump membrane protein
how are non polar molecules moved
simple diffusiom
how are polar molecules moved
facilotated diffusion
how are macromolecules moved
active transport
types of pumps
- uniport= 1 movement in 1 direction
-symport= more than 1 molecule in 1 direction - antiport= more than 1 molecule in both direction simeltaneously
direct movement
energy is used to move molecule through the plasma membrane
indirect movement
energy is used to move only 1 molecule while other molecule is cotransported just flows together along movement
CAM’s
cell adhesion molecules: mostly cabrs, that link one cell to another by the formation of pores. they increase the communication between cells
channel protein function
tube that lets small and hydrophilic molecules pass
cholesterol function
membrane stiffener
carrier protein function
gate lets small charged molecules and ionic molecules pass
cytoskeleton function and composed of
microfiliments, microtubules
structural framework
what happens with the change of temperature to the membrane
low temperature= hel, solif ordered phase
high temp= liquid disorders phase
phospholipid molecule
major membrane molecule
summary of proteins:
transport
receptor
adhesion
cell recognition
enzymes
transport- transport molecules across membrane
receptor-specifically binds to a molecule outside the cell, triggering a cell change
adhesion-anchors the cell membrane to protein outside the cell
cell recognition-acts on identifying cells
enzymes-break down substrates into products
