Lipids And Membranes Flashcards
What are lipids
Non polar organic compounds
Not soluble in water, soluble in non polar solvents
Used in membrane formation, energy storage, precursors of signalling molecules
What does a fatty acid contain
Carboxylic acid which is polar and hydrophilic
Unbranched hydrocarbon chain which is non polar and hydrophobic
How does c=c bond affect melting point
As the number of C=C bonds increase, the melting point of the lipid decreases
Why does a c=c affect melting point
Alkene= geometric isomerism (cis/trans)
Chains are bulky and bend
More C=C means more bending
Affects the ability of hydrocarbon chains to pack together
Low mp
What are polyunsaturated fatty acids
Precursors for biosynthesis of important signal molecules
What are triacylglycerols
Energy storage in fat cells and released by hydrolysis for energy productions
One molecule of fatty acid to form 3 ester links
What are phospholipids
Used in biological membranes= phospholipid bilateral
Amphipathic= both hydrophilic and hydrophobic
Phosphate group
What is cholesterol
Used for structural=c part of cell membranes to increase membrane fluidity
Used as a biosynthesis precursor for bit D, bile acids and steroid hormones
What do membranes do
Provide structure and control localisation of nutrients
Control the internal conditions of each compartment
Control which molecules can come in and out (nutrients+ waste)
Cellular communication
What type of self assembled structures can form lipids
Miscelles
Phospholipid bilayer
Liposomes= hollow aq centre which can be used for drug delivery
Characteristics of lipid bilayer
Fluid= gives bilayers flexibility
Impermeable to anything charged/polar= allows cell to retain things it needs to function/ stops leakage of essential nutrients
Transport proteins= allows access for a specific molecule
What are integral proteins
Embedded in the bilayer and only removed by disruption of the membrane by detergents
Transmembrane proteins
What are peripheral proteins
Loosely attached to one face of the membrane
Removed by mild changed of ph or ionic strength
What are transmembrane proteins
Allow entry/exit of polar molecules which cannot cross the bilayer
Big proteins allowing polar compounds to lass without coming in contact with fatty acid tails
Passive diffusion
Transfer of solutes or ions down conc gradient
No energy expenditure
Can be facilitated by a specific carrier proteins
Ligand gating
Ion channel opens in response to the binding of a particular molecule
Voltage gating
Where the channel opens in response to a change in membrane potential
Types of carrier proteins
Uniporters transport only one type of solute
Co-transporters transfer 2 different solutes
Types of co transporter
Symporters= carries 2 solutes across the membrane in the same direction
Anti-porters= transport one solute in one direction and a different solute in the opposite direction (countertransport)
Glucose transport
1) epithelial cell/blood surface, the Na+/K+ ATPase anti potter uses ATP to drive the active transport of K+ into the epithelium and Ns+ out of it, decreasing the concentration of Na+
2) Na+ moves down its concentration gradient from the gut lumen into the cell via the Na+ glucose symporter, providing the free energy to bring glucose into the cell from the gut lumen against its concentration gradient. This creates Hugh glucose concentration inside the epithelial cell
3) glucose flows down its conc gradient into the blood via a glucose uniporter
Ion pump
1) Ca2+ bonds closed channel on cytoplasmic side
2) atp binds nucleotide binding site
3) atp hydrolysis, releasing energy
4) energy dependent conformational changes releases ca2+ into er
5) phosphate hydrolysis
6) channel reverts to closed state
Pinocytosis
Uptake of fluid in vesicles
Phagocytosis
Uptake or large particles forming a vacuole
Receptor mediated endocytosis
Some molecules are selectively taken up in vesicles when bound by a specific receptor proteins on the cell surface
