Lipids Flashcards
(24 cards)
What is a lipid?
Water insoluble biomolecules that are highly soluble in organic solvents
Membrane constituents
What is the key constituent of lipids?
Fatty acids- give lipids hydrophobic properties
What do fatty acids build that are components of biological membranes?
Phospholipids and glycolipids
What allows proteins to target to membranes?
Covalent attachments of fatty acids to proteins
What are derivatives of fatty acids?
Hormones, signal molecules and intracellular messengers
How do you number the carbon atoms in lipids?
You start numbering at the carboxyl terminus
Carbon 2 and 3 are called alpha and beta carbons
The methyl carbon at the distal end of the chain is called the omega carbon
How do you number number bonds?
The position of the double bond is denoted by the delta and then a superscript number
Ex. Cis-delta ^9 = a cis double bond between atoms 9 and 10
OR
Can count from the omega carbon and number from there
Ex. Omega-3 fatty acid
What is the ending of a fatty acid with no double bonds? One double bond? Two double bonds? Three double bonds?
No double bonds= anoic
One double bond = enoic
Two double bonds= dienoic
Three double bonds= trienoic
18: 0 = C18 with no double bonds
18: 2 = C18 with 2 double bonds
How many carbons does a typical fatty acid have?
Even number of carbons anywhere between 14 and 24 but most common is 16 to 18
What is the most common configuration of double bonds in most unsaturated fatty acids?
Cis
Why can we refer to fatty acids according to their carboxylate form?
Because fatty acids are ionized at physiological pH
What happens to fatty acids as the chain length increases?
The melting point also increases
Which have a higher melting point? Saturated or unsaturated fatty acids?
Saturated have a higher melting point
What are the three essential fatty acids?
Omega-6 : linoleate
Omega- 3: linolenate
Omega-6: Arachidonate
What are the three major membrane lipids?
- Phospholipids
- Glycolipids
- Cholesterol
What are the 4 components of phospholipids?
- Fatty acid (provides a hydrophobic barrier)
- A backbone to which fatty acids are attached
- A phosphate
- An alcohol attached to phosphate
What allows phospholipids to interact with their environment?
The hydrophilic properties of the phosphate and alcohol groups
What is the simplest phosphoglyceride?
Phosphatidate (diacylglycerol 3-phosphate)
What are examples of phosphoglyceride so derived from Phosphatidate and what is their importance?
- Phosphatidylserine: important for memory and cognition
- Phosphatidylcholine: major constituent of cell membrane and pulmonary surfactant
- Phosphatidylethanolamine: composing 25% of all phospholipids, they are found in nervous tissue such as the white matter of the brain
- Phosphatidylinositol: important signaling and other functional activities in eukaryotic cell
- Disphosphatidylglycerol (cardiolipin): important component of inner mitochondrial membrane
What classification is sphingosine?
An amino alcohol
What is sphingomyelin?
A phospholipid with sphingosine as the backbone
- amino group of backbone is linked to fatty acid by an amide bond
- found in animal membranes (myelin sheath)
What are glycolipids?
- Sugar-containing lipids
- derived from sphingosine
- different from sphingomyelin because unit linked to primary hydroxyl group on backbone
- sugar residues always on extracellular side of membrane
What is cerebroside?
- Simplest glycolipid
- contains one sugar residue
- important in animal muscle and nerve cell membranes
What is cholesterol?
- most abundant steroid found in eukaryotes made of 4 fused saturated hydrocarbon rings
- sterol
- major component of eukaryotic plasma membrane
- not found in prokaryotes
- oriented parallel to fatty acid chains of phospholipids- hydroxyl group interacts with nearby phospholipid heard group to inhibit tight packing of FA chains
