B2.1 membrane and membrane transport Flashcards
explain scenario 2, phospholipids in micelle
Miceele contains a hydrophobic core, can carry lipid base susbtances eg.cholesterol
membrane enclosed compartment
explain scenario 3, liposome
liposome is a hydrophilic core, that can carry soluble based susbtances (eg.insulin or fsh) Membrane enclosed compartment
what happens when phospholipids are placed in water
they spontaneaously arrange into a bilayer. The shape can change accordingly to the nature/ property of the fatty acid, tails will always arrange in a way that they are protected from water contact whilst heads touch the water
amphipathic property
whats the phospholopid bilayer also called
fluid mosaic model
whats meant by fluid in fluid mosaic model
constantly in flux, shifting components back and forth to help the cell take in food remove waste let special molecules in and out gather info about the enviornment and communicate with other cells and repais itself. Cholesterol maintain fluidity at right level, can move
whats meant by mosaic in fluid mosaic model
composition of phospholipid molecules in 2 layer sheet it is studded with other types of molecules such as proteins, carbs and cholesterol either floating or embedded
whats meant by model in fluid mosaic model
conceptual framework most accepted
what is the plasma membrane composed of
phospholipid bilayer
cholesterol
proteins: peripheral protein, integral transmembrane protein, glycoproteins
glycolipids
glycolipid
little tree out of phospholipid
acts as a receptor
integral protein
square in between phospholipids not entirely throguh
usually acts as an enzyme, or an adhesive protein
glycoproteins
whole through rectangle with tree in top
tree is a carb
acts as protein receptors
cholesterol
little squares in fatty acid tails
peripheral proteins
rectangle attched to polar head, only bind to plasma membrane at certain times, it temporarily attaches to the plasma membrane
integral transmembrane protein
big rectangle that goes through phospholipid bilayer
can have functions of a protein channel or a protein ion acceptor or a protein pump
integral and integral transmembrane proteins are temporarily or permenantly embrdded in plasma membrane
permenantly
what are the protein fucntions
TRACE
transport; channel or pump
receptor
adhesion
cell recognition
enzyme
explain role of protein as a receptor
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
explain role of protein for adhesion
proteins that anchor the cell membrane to 1)inner cytoskeleton, 2) proteins outside the cell, 3) other cells
in essence, these membrane bound proteins help cells stick to each other and to their surroudings
explain role of protein for cell recognition
serve as id tags on surface of a cell, often glycoproteins with the carbohydrate portion projecting out of the cell and into extracellular space. These give the cell a biochemical personality and are important in cell to cell recognition
explain role of protein for channel
these membrane proteins allow small molecules to pass through the cell membrane by creating a pore through the membrane
explain role of protein for pump
move small molecules or ions across the cell membrane from low concentration region to high. They use energy from ATP to transport against the concentration gradient
explain role of protein for enzyme protein
promote “catalyze”chemical reactions that synthesize or break apart biological molecules
what type of protein is used for neurotransmission explain
receptor
acetylcholine receptor recognizes and responds to the neurotransmitter acetylcholine
acetylcholine released from vesicles of a neuron and the acetylholine receptors bind the acetylcholine which then triggers a response in the receiving cell
what type of protein is desmosome protein explain
adhesion,they are found in muscle tissues where they bind muscle cells to one another
what type of protein is used for immune systems explain
recognition, molecules are located on surface of cells, interact with immune systems cells to tell them that your cells are your cells and not invading cells
what type of protein is used for aquaporins explain
channel
aquaporin allows water molecules to move through the cell membrane single file
what type of protein is used for muscle relaxation or contraction explain
pump
calcium pimp, allows muscles to relax after contraction by moving calcium ions back into the sarcoplasmic reticulum of muscle cells
what type of protein is used for atp synthatse explain
enzyme protein
atp synthase builds atp by adding a phosphate group to adp
explain RECEPTOR
insulin receptor protein
insulin is a hormone by the pancrease when blood sugar levels are high insulin binds to the insulin receptor proteins whicht hen causes cell to open the typically closed glucose transport protien, alows glucose to enter cell from blood
explain ADHESION
cadherins
a type of transmembrane protein in the presence of calcium binds cells within tissue together
explain RECOGNITION
immunoglobulins or antibodies
beta cells carry antibodies embedded hy the tail in their outer cell membrane with the binding sites facing outwards this enables the beta cells to bind to antigens that fit the binding sites in the antibodies it carries on its surface
explain CHANNEL
glucose channel protein
glucose is too large and too hydrophilic to diffuse naturally through the phospholipid bilayer. Glucose needs a channel protein in order to do this. no energy recquired
explain PUMP
sodium potassium pump
both sodium and potassium are moving against their concentration gradients which recquires energy in form of ATP
why is cholesterol important
regulate degree of fluidity
membranes need to be fluid enough that recquired substances can move across the membrane
if too fluid membrane could not effectively restrict the movement of substances across itself
what can change membrane fluidity
temperature
amount of cholesterol
type of fatty acid (saturated or unsaturated)
if an amino acid goes through a membrane what are its properties
in cytosol= hydrophilic
inside phospholipid bilayer = hydrophobic
out in fluid= hydrophilic
what happens when a phospholipid made of saturated fatty acids is put in a low temp
how does cholesterol fix this
gel solid ordered phase, molecules cant penetrate phospholipid bilayer
presence of cholesterol increases permeability to hydrophilic molecules and ions
what happens when a phospholipid made of unsaturated fatty acids is put in a high temp
how does cholesterol fix this
fluid liquid disordered phase, too many molecules can pass through
more cholesterol presence of cholesterol in membrane reduces permeability to hydrophilic molecules and ions
cams
cell adhesion molecules, molecules mostly carbs, that link one cell to other by the formatin of pores, they increase the communication between cell
adhesive proteins present these present in plasma membrane can use CAMS to support their anchorage
explain simple diffusion
donw conc gradient
eg. gases and hydrophobic molecules
explain osmosis
down conc gradient, across selectively permeable mebrane
memebrane proteins only in kidneys and ileum (aquaporins protein channel)
example, water
explain facilitated diffusion
down conc gradients
across selectively permeable membrane
uses channels or carriers
examples, channels= small hydrophilic molecules
carriers= small ionic molecukes
explain active transport
against concentration gradient
uses pump membrane protein
uses ATP
examples, any molecule against conc gradient and all macromolecules
what are the 3 types of pumps for active transport
uniport, symport and antiport
explain uniport
direct movement, only 1 type of molecules
energy is used to move molecules through the plasma membrane
explain symport
only one way= unidirectional
2 types of molecules are transported
explain antiport
bidirectional= 2 ways
2 types of molecules are transported
explain both antiport and symport
both are cotransporters
carry 2 types of moelcules
indirect movement, energy is used to move only one molecule while the other molecule cotransported just flows together along the movement
whats endocytosis
engulfement or invagination of macromolecules through the plasma membrane, forming a endoyotic vesicle
whats exocytosis
secretion of macromolecule through the formation of exyotic secretoy vesicles
explain frist step of exocytosis
protein synthesised for secretion in the rough endoplasmic riticulum (responsible for protein synthesis) moves using the cytoplasm of the cell towards the golgi inside transport vesicle
explain second step of exocytosis
the transport vesicle memebrane fuses with the membrane of golgi complex the macromolecules diffuse inside the complex and suffer some post translation modification they are packed inside secretory vesicles that pinches off the golgi
explain third step of exocytosis
secretory vesicle membrane fuse with plasma membrnae increasing the length of the plasma membrane. Since all emmebrane contain soem components (phospholipid bilayer). removal or addition of phospholipid does not affect the intergrity of the plasma memrbane (membrane is flexible) macromolecules isnide the vesicles are released to the extracellular fluid without corssing plasma membrnae
explain first step of endocytosis
plasma membrane folds inwards (invagination) ofrming a cavity that fills with extracellular fluid dissolved molecules food particles, foreign matter,pathogens etc. plasma membrane folds back on itself until the ends of the in folded mmebrnae meet, this traps the fluid inside the vesicle, which pinches off from memebrane as the ends of the in folded membrane fuse togehter, the vesicle breaks away from the cell membrane and moves into the cytoplasm the cell membrane has gotten smaler
explain second step of endocytosis
an endoyotic vesicle or endosane is formed, moving in teh cytoplasm through the contraction fot he cytoskeleton
explain third step of endocytosis
the endosome fuses with a lysome (organelle that performes cellular digestin) the contents inside the endosome mixes with the enzymes present in the lysosome. The products of digestion (simple organci molecules) cross the lysosome membrane and diffuse in the cytoplasm
what are the three types of endocytois
phagocytosis
pinocytosis
receptor mediated endocytosis
explain phagocytosis
engulfment of solid particles or molecules
explain pinocytosis
engulfemment of liquid molecules
explain receptor mediated endocytosis
collects specfic molecules by binding it to a receptor protein at the cell membrane
the vesicles formed is coated with clathrin pits, that infroms the cell to recruit lysosomes to the area
