Flashcards in Lesson 3-4 Deck (28)
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.
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
if instead of choline there is a cholamine in the molecule
Phosphatidic acid is:
When there is neither choline nor cholamine in the structure
18-carbon amino alcohol with an unsaturated hydrocarbon chain.
Sphingosine + fatty acid
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:
- 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.)
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
- Molecules can diffuse passively through the lipid components of cellular membranes.
- Oxygen, carbon dioxide, ammonia, ethanol, urea etc.
- 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
Transport of solvent throug the cellular membrnae from the less concentrated solution in the direction of more concentrated solution.
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