Lipids Flashcards
What is a lipid?
water insoluble biomolecule that is highly soluble in organic solvents
membrane constituents
made up of fatty acids which provide the hydrophobic properties
How is the solubility of a fatty acid/lipid determined?
The longer the hydrocarbon tail the more insoluble the lipid/fatty acid.
What are fatty acids?
contain hydrocarbon chains of various lengths and degrees of unsaturation that terminate with carboxylic acid group
building blocks of phospholipids and glycolipids
Which regions of a phospholipid are hydrophobic/hydrophilic?
hydrocarbon tails - hydrophobic
polar heads (carboxylic acid group) - hydrophilic
Describe a triglyceride (TAG).
3 fatty acid molecules covalently bonded to a glycerol backbone
What are the 2 ways to number a fatty acid?
Start from the the carboxyl terminus with the number 1, and on down the chain
or
start with the methyl carbon at the distal end of the chain
Which configuration are the double bonds in most unsaturated fatty acids?
cis
Are fatty acids usually even or odd numbered carbon atoms?
even; usually ranging from 14-24
What length of carbon atoms is most common for fatty acids?
16-18
True or False, fatty acids are ionized at physiological pH?
Do we refer to them in their acid state or their carboxylate state?
True
carboxylate form
What determines the properties of fatty acids?
length of chain and degree of saturation
True or False, unsaturated fatty acids have a lower melting point than compared to saturated fatty acids.
True
True or False, the melting points of saturated fatty acids increases with the chain length.
True
List the essential fatty acids.
Linoleate, Linolenate, Arachidonate
How does an archaeon membrane lipid differ from a human membrane phospholipid?
Archaeon has saturated branched fatty acid chains (instead of nonbranched chains) which are linked to glycerol backbone via ether linkages (instead of ester linkages).
List the 3 major types of membrane lipids.
Phospholipids, glycolipids, cholesterol
What are the 4 components of a phospholipid?
- 1 or more fatty acids
* Provides hydrophobic barrier - Platform where fatty acids attach
* Glycerol = Phosphoglycerides
* 2 fatty acid chains
* Phosphorylated alcohol
* Simplest = phosphatidate
* Common alcohol moieties are: amino acid serine, ethanolamine, choline, glycerol, and inositol
* 3 carbon alcohol
* Sphingosine
* Sphingomyelin; backbone linked to fatty acid via amide bond - Phosphate
- Alcohol attached to phosphate
What enables the interaction with the environment of a phospholid?
The hyrdophilic properties of the phosphate and alcohol groups
What is the simplest phospholipid containing a glycerol backbone?
phosphatidate
What is an example of a phospholipid containing a shingosine backbone?
shingomyelin
What is the simplest glycolipid containing a shingosine backbone?
cerebroside
What is a glycolipid?
derived from sphingosine;
differs from sphingomyelin:
replaced -OH group with sugar on amino alcohol
group of sphingosine
oriented with sugar on the extracellular side of the membrane
What is cholesterol?
steroid
4 fused saturated hydrocarbon rings
also classified as a sterol
Why is cholesterol classified as a sterol?
because of its C3-OH group and its branched aliphatic side chain of 8-10 carbon atoms at C-17
True or False, cholesterol is present in most eukaryotes and prokaryotes.
False: cholesterol is present in most eukaryotes, but not in most prokaryotes.
What is the most abundant steroid in animals?
cholesterol
True or False, cholesterol is a major component of a eukaryotic plasma membrane.
True
How is cholesterol oriented to the fatty acid chains of the phospholipids?
parallel
True or False, cholesterol is not the metabolic precursor of steroid hormones.
False: it is the precursor of steroid hormones
What are the roles of lipids?
- Fuel molecules
- Highly concentrated energy stores
- Signal molecules
- Messengers in signal-transduction pathways
- Components of membranes
What are the functions of lipids?
> Energy storage
> Information transduction
