Lesson 3-4 Flashcards
What is the main components of cell (biological) membrane?
lipoids 40% and proteins 60%
Important lipoids in the cell membrane:
Mainly phospolipids: sphingomyelin, lecithin, cephalin.
Cholesterol
What is Glycerolphspatide?
If the phospholipids have a glycerol backbone
What type of small molecules, usually polar can be linked to the phsophate group?
Lecithine and cephaline. Forms a variety of phospholipids
Cephaline is:
if instead of choline there is a cholamine in the molecule
Phosphatidic acid is:
When there is neither choline nor cholamine in the structure
Sphingolipids is:
A phospholipid.
18-carbon amino alcohol with an unsaturated hydrocarbon chain.
Ceramine is:
Sphingosine + fatty acid
Sphingomyelin is:
Ceramide + phosphate + choline
What is characteristic of an unsatturated fatty acid
Has generally one to three double bonds.
The fatty acid will have a kink in its shape wherever a double bond occurs that result in looser packing and lower melting points.
What is the characteristics of cholesterol?
They are steroids.
they are characterized by a carbon skeleton consisting of four fused rings.
Function to stabilize the membrane.
Precursor from witch other steroids are synthesized.
High levels in blood = atherosclerosis.
(NOT in prokaryotes)
Types of movement of lipids in the membrane:
- rotation
- lateral diffusion
- transversal diffusion (flip-flop)
- energy is needed, flippase protein is needed.
What is Integral proteins?
- Transmembrane proteins with hydrophobic regions that completely span the hydrophobic interior of the membrane.
- Dynamic function, serve as ion-channels.
What is Peripheral proteins?
- loosely bound to the surface of the membrane (not embedded in the lipid bilayer)
often to the exposed part of the integral proteins. - static function, receptor function.
What are the membrane carbohydrates?
- branched oligosaccharides with fewer than 15 sugar units (glucose, galactose, mannose, fucose = deoxyhexose and the N-acetylated sugars like N-acetylglucosamine, N-acetylgalactosamine and mannosamine + pyruvate = neuraminic acid.)
- glycolipids
- glycoproteins
Oligosaccharides functions as?
markers that distinguish one cell from another.
What is Lipid raft?
Spingolipid and cholestrol rich microdomain, ordered assemblies of specific proteins = lipid raft.
- important role in the cellular machinery
Membrane fluidity (elasticity) increases if:
- increased temperature
- decreased amount of cholestrol
- increased proportion of cis-unsaturated fatty acids in the phospholipids.
Describe Passive transport:
- Direction: down the concentration/electro chemical gradient.
- Energy: no
- Carrier: generally no (but at facilitated yes)
- Specific inhibition: no
describe Active transport:
- Direction: Against concentration/electrochemical gradient.
- Energy: yes
- Carrier: yes
- Specific inhibition: yes
Types of passive transport:
Simple diffusion, Facilitated diffusio, Osmosis
Simple diffusion:
- Molecules can diffuse passively through the lipid components of cellular membranes.
- Oxygen, carbon dioxide, ammonia, ethanol, urea etc.
Facilitated diffusion:
- Molecules can diffuse passively through proteins of cellular membranes which act as carrier and transport molecules or produce pores, gates.
- glucose, glucose transportes, carnitine and translocase
Osmosis:
Transport of solvent throug the cellular membrnae from the less concentrated solution in the direction of more concentrated solution.
Gibbs-Donnan-Equilibrium
Unequal ion distribution on both side of the semipermeable membrane –> membrane potential
Types of active transport:
They differ in their source energy:
- Primary active transport: involves a transport protein that directly hydrolyzes ATP to drive the transport process
- Secondary active transport (cotransport): utilizes energy stores in electromechanical gradients of ions to drive transport.
Types of primary active transport:
- Sodium-potassium pump
- Proton pump
a) in the respiratory chain
b) in the epithelial cells of stomach mucous membrane - ABC transporter protein family
Types of Secondary active transport:
- SGLT-1 and SGLT-2 transporters
