Topic 1.3 and 1.4 Membrane structure and transport Flashcards
What was the davson-danielli model?
Phospholipids were in the centre with a layer of protein on either side.
Reasons for the D-D model?
It composed of phospholipids and protein
enough red blood cells for there to be twice as many phospholipids
layer of protein acted like a barrier
Electron microscopes showed that there were two dark bands separated by a lighter one and proteins came up darker.
What was the evidence that did not fit the D-D model?
Freeze fracture showed globular proteins inside bilayer.
proteins showed parts of their surfaces were hydrophobic
fission of cells with membrane proteins showed proteins could not move
What was the new model called?
Singer-Nicolson model or fluid mosaic model
What did the fluid mosaic model look like
Had a phospholipid bilayer with different proteins in-between
What are characteristics of phospholipid
They are amaphitic - hydrophobic and hydrophilic
when mixed in water form a bilayer
very stable due to bilayer
it is the basic component of all biological membranes
Characteristics and function of cholesterol?
it is to stabilise the membrane component of animal cell membrane have hydrophilic and hydrophobic parts restricts movement of phospholipids reduces fluidity of membrane reduces permeability of membrane
What are integral proteins?
intrinsic - Ones that are embedded in phospholipid bilayer they go all the way through or are inside the membrane.
What are peripheral proteins?
extrinsic - ones that are attached on an outer surface of membrane outside the membrane or go part way through.
What are glycoproteins?
Sugar proteins attached on the outer surface
Different membrane proteins?
Insulin receptor Cytochrome c calcium pump Cadherin Cytochrome oxidase Nicotinic acetylcholine receptor
What is the insulin receptor?
Integral protein, hormone receptor
What is the Cytochrome c?
peripheral, electron transportation
What is the calcium pump?
Integral, active transport of calcium ions
What is the Cadherin?
integral, cell to cell adhesion
What is the cytochrome oxidase?
integral, immobilised enzyme
What is Nicotinic acetylcholine receptor?
Integral, receptor for neuro transmitter, channel for facilitated diffusion of Na+ ions.
What is diffusion?
It is passive movement of particles from a region of higher concentration to a region of lower concentration as a result of the random motion of particles, until equilibrium is established.
What does it mean to be partially permeable?
That the membrane allows some substances through but not others.
What is simple diffusion?
Process where a substance passes through the membrane without aid from a protein within the membrane.
What is facilitated diffusion?
Process where substances pass through the membrane but with help from integral proteins. Channel proteins.
What is passive transport?
movement of biochemicals and other molecular substances across cell membranes without ATP.
What is osmosis?
The passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane.
Why is the plasma membrane usually permeable to water?
Water is a solvent (liquid in which particles dissolve).
What do channel proteins allow through?
Anything with charge
What are receptor proteins for?
Electron transport to produce ATP
What is ATP?
energy used for a chemical reaction
What go directly through the membrane?
alcohol and fats.
What is the sugar side chain for?
Cell recognition (glycoprotein)
What is cell adhesion?
neighbouring cells stick together
What does hypertonic mean?
It is a solution that the cells are in which has a higher concentration than the cell.
What dies hypotonic mean?
A solution that the cells are in which has a lower concentration than the cells.
What is turgor pressure?
Pressure inside the cell.
When is there a risk of Plasmolysis and what is it?
When in a hypertonic solution. It is the shrinking of a cell.
When is there a risk of cytolysis and what is it?
In a hypotonic solution is the breaking of a cell when turgor pressure increases.
What is active transport?
Movement of molecules across the membrane with the cells providing ATP.
What does the protein pump do?
Pumps molecules in and out of a cell.
each pump only pumps certain substances
particles are released on the high concentration side.
What proteins are found in the membranes of neurones?
Na+ and K+ channel proteins. they open and close depending on voltage across membrane.
What is endocytosis?
The taking in of matter by a living cell to create a vacuole.
What is exocytosis?
Process by which the contents of a cell vacuole are released through fusion.
What is antiponer?
When Na+ and k+ ions are pumped in different directions.
What does ATP cause?
State changes.
How much energy does 1 ATP have?
enough to pump 2Na+ and 3K+ ions in or out of a cell.
