Lipids and cellular membrane structure and function Flashcards
What are sphingolipids?
Sphingolipids are lipids that do not contain glycerol. Instead they contain the long chain amino alcohol sphingosine, from which this class of compounds takes its name.
Where are sphingolipids most abundant?
They are most abundant in the nervous system
What are the simplest compounds of the class of sphingolipids? Describe this compound
Ceramides
They consist of one fatty acid linked to the amino group of sphingosine by an amide bond.
How are sphingomyelins structured?
In sphingomyelins, the primary alcohol group of sphingosine is esterified to phosphoric acid, which, in turn, is esterified to another amino alcohol, choline
What are the functions of complex sphingolipids?
Complex sphingolipids in cell membranes are thought to serve several functions, including protection from harmful environmental factors, signal transmission, and adhesion sites for extracellular proteins
What are the functions of lipids (name a function for each of the three types of lipids)
Triglycerides: Storage form of lipids
Sphingolipids: Signaling, protein targets
Phospholipids: make up biological membranes
What are phospholipids derived from?
phosphatidic acid
Give an example of simple lipids?
Triglycerides
Give an example of complex lipids
Sphingolipids and glucerophospholipids
Give an example of a polar lipid
Phospholipid
What is the cell membrane composed of? (name all the molecules)
Phospholipids Cholesterol Proteins Other lipids Carbohydrates
Which substances are impermeable to the phospholipid bilayer of the cell membrane?
Water soluble molecules such as ions, glucose and urea
Which substances are permeable to the phospholipid bilayer?
Oxygen, carbon dioxide, and alcohol
What are the functions four functions of cholesterol in the cell membrane?
- It immobilizes the outer surface of the membrane, reducing fluidity.
- Reduces permeability to very small water-soluble molecules that would otherwise freely cross.
- Separate phospholipid tails thus preventing crystallization of the membrane.
- Secures peripheral proteins by forming high density lipid rafts capable of anchoring the proteins
What are sphingomyelins made up of?
Ceramide + choline
Where are sphingomyelins mostly found?
Nerve tissues, red blood cells, and other ocular lenses
True or false:
Sphingomyelins are incapable of forming hydrogen bonds
FALSE
Sphiingomyelins have hydrogen bonding capabilities
True or false:
Hydrophobic chains of sphingomyelin are more saturated than other phospholipids
True
Why are omega 3 and omega 6 considered essential?
Omega 3 (DHA) and Omega 6 (AA) are polyunsaturated fatty acids that are most prominent in brain cells
What is optimum ratio between Omega 3 and 6?
1:1 to 4:1
What is optimum ratio between Omega 3 and 6?
1:1 to 4:1
Describe integral glycoproteins
Protrude all the way through the membrane Structural channels (or pores) Carrier proteins (active transport)
Describe peripheral glycoproteins
Attached only to one surface
Receptors for water soluble chemicals
Enzymatically activate the intracellular part of the protein
List 4 functions of the cell membrane
Identification
Communication
Transport
Isolation of cytoplasm from the external environment
What are the chemical characteristics of the cell membrane?
- Amphiphilic
- Semipermeable
- Fluid
Define fluidity
Ability or ease of molecules to move in the membrane. It refers to the viscosity of the cell membrane
What factors influence fluidity of the membrane?
- Alcohol consumption: increase fluidity
- Cholesterol composition: less fluidity
- Phospholipid (unsaturated, saturated)
- Temperature
Why do unsaturated fatty acids increase membrane permeability?
Unsaturated FAs have kinks that lead to lesser van de Waals interaction with other lipids
Why do short chain FAs increase the membrane’s permeability?
Less surface area because the interaction between hydrocarbons is reduced
Define permeability
Permeability of a membrane is the rate of passive diffusion of molecules across the membrane. It’s the ease with which molecules pass through the membrane barrier.
List factors influencing permeability
- Temp
- Solvent concentration
- Chain length
- Whether the membrane lipids are saturated/unsaturated
List and explain the factors affecting drug delivery
-Physicochemical properties of the drug:
Molecular size
Concentration gradient
pKa
-Properties of the membrane Thickness Surface area Permeability (drug-specific) Solution pH on either side of the membrane
-Type of transport
Paracellular, in which case it diffuses through extracellular fluid
Diffusion through membranes
Active transport by facilitated diffusion or transport proteins
What are the considerations for drug delivery?
Small molecule cargo – conjugate to known carrier
Peptide cargo – cyclizing peptides, methylating nitorogen
Protein cargo – membrane disruption, pores/channels, virus based, lipid/polymer carriers, nano-carriers
How does pH affect drug solubility?
The lipid solubility of drugs is determined by the degree to which they are ionised in the body fluid, which in turn depends on their pKa and on the pH of the body fluid
Nme the lipid-soluble vitamins
Vitamin A (Retinol, retinoic acid): vision, growth, cell division, reproduction, antioxidant and immunity
Vitamin D : help the body absorb and retain calcium and phosphorus
Vitamin E (Alpha-tocopherol): Antioxidant, immune protection, works with vit K
Vitamin K: blood clotting and wound healing
