Lipids Flashcards
What is the basic structure of fatty acids?
A hydrophilic carboxylate group is attached to one end of the hydrocarbon chain, which contains typically 12 to 24 carbons.
What is a saturated fatty acid?
All of the carbons of the tail are saturated with hydrogen atoms.
What is an unsaturated fatty acid?
The carbon chains contain at least one double bond
What is the orientation about double bonds in naturally occurring unsaturated fatty acids?
Usually cis rather than trans.
Each cis bond inserts a bend in the hydrocarbon chain
What is the alpha carbon? What is the omega carbon? (in context to fatty acids)
The alpha carbon is the COO- carbon
The omega carbon is the last C atom in the chain
What is the system of abbreviations for fatty acids?
1) The number before the colon gives the totally number of carbons
2) The number after the colon gives the count of double bonds
3) The configurations of double bonds are indicated by c (cis) or t (trans)
4) The carbon atoms where each double bond starts is designated by Delta followed by the number of the carbon (relative to omega carbon)
Example – 18:1cDelta9
What is a polyunsaturated fatty acid?
An unsaturated fatty acid with several double bonds
What happens if you shake fatty acids with water?
The fatty acids make spherical micelles, in which the hydrocarbon tails cluster within the structure and the carboxylate heads are in contact with the water
What happens when you mix fatty acids with water and an oily (for example hydrocarbon) substance?
The micelles will form around the oil droplets, emulsifying them. In this way soaps and synthetic detergents solubilize grease.
What are triacylglycerols in terms of structure?
Triesters of fatty acids and glycerol
What are triacylglycerols good for?
They are good for energy storage because they contain carbon in a reduced form and will therefore yield a large amount of energy on oxidation.
Also referred to as fats
Much more efficient as energy stores compared to carbs. (because they are anhydrous)
What are simple fats?
Simple fats are triacylglycerols with the same fatty acid esterified at each position
What are mixed fats?
Mixed fats are triacylglycerols with a mixture of fatty acids, often including unsaturated ones.
More common than simple fats.
What does is the consequence of having glycerol esterification in fats (within the context of hydrophilicity)?
The glycerol esterification diminishes the hydrophilic character of the fatty acid head groups, meaning that triacylglycerols are NOT water soluble.
How do cells/organisms store fats?
- They form oily droplets in the cytoplasm.
- Adipocytes are animal cells specialized for fat storage and almost the entire volume of each cell is filled by a fat droplet.
What are the functions of fat storage in animals?
- Energy production (oxidation of bonds for generation of ATP)
- Heat production (brown fat oxidizes triacylglycerols for heat production, rather than to make ATP)
- Insulation (layers of fat cells under the skin keep us warm)
How is a soap produced?
- Fats are hydrolyzed with strong bases such as NaOH or KOH to produce a soap
- This process is called saponification
- The fatty acids are then released as either sodium or potassium salts, which are fully ionized
What are waxes?
Long-chain fatty acids esterified to a long-chain alcohol
Yields a head group that is only weakly hydrophobic, attached to two long hydro-carbon chains
Waxes are completely water-insoluble (often serve as water repellents)
What are the major lipid components of biological membranes?
Glycerophospholipids, sphingolipids, glycosphingolipids, and glycoglycerolipids
What are phospholipids?
Lipids with phosphate-containing head groups
What are glycerophospholipids?
The major class of naturally occurring phospholipids.
Contain glycerophosphates.
What are some common head groups of glycerophospholipids?
Phosphatic acid (H) ionized at neutral pH
PE, positive charge
PC, positive charge
What is sphingosine?
A type of amino alcohol
What is a sphingolipid?
A class of lipids containing a backbone of sphingoid bases, a set of aliphatic amino alcohols that includes sphingosine.
What is a ceramide?
Consists of sphingosine and a fatty acid.
What is sphingomyelin?
A type of ceramide that has a phosphocholine group attatched to the C3 carboxyl.
What are glycolipids?
Lipids containing saccharide groups.
What are glycosphingolipids?
Ceramide with an added sugar to the head
What are gangliosides?
Anionic glycosphingolipids containing one or more sialic acid residues.
What is cholesterol?
- Cholesterol is a member of a large group of substances called steroids, it is found in higher animals
- Is weakly amphipathic because of the hydroxyl group at one end of the molecule.
- Bulky and rigid, thus disrupts regular packing of fatty acid tails in membrane structure – affecting membrane stiffness and permeability.
- At low concentration it incorporates into the membrane, at high, it forms conglomeraes of cholesterol.
What are the two individual layers of phospholipids called?
leaflets
What are vesicles? How are they used to study proteins in membranes?
Vesicles are fragments of membrane that have resealed to form hollow shells with an inside an outside
By seeing which reactants act where, you can figure out which portions of the protein were on the inner face and which were on the outer phase
Are membranes in equilibrium?
No, they are not. They are dynamic, steady-state structures.
As a rule of thumb, what is the makeup of a typical membrane in terms of lipids/proteins?
- 60% protein
- 40% lipid
What is the fluid mosaic model?
A model that postulates that a membrane is a fluid mixture of lipids and proteins
What are peripheral membrane proteins?
They are associated with one side of the bilayer and can be separated from the membrane without disrupting the bilayer.
What are integral membrane proteins?
They are deeply embedded in the bilayer and can only be extracted under conditions that disrupt membrane structure.
What happens when you mix human and mouse cells, each carrying distinctive fluorescent markers, and they fuse together?
- The two kinds of markers gradually become intermixed, demonstrating lateral diffusion can occur in the membrane.
What happens to synthetic membranes when temperature is changed from cold to hot?
At cool temperatures, the membrane is in a nearly solid geld state.
At hot temperatures, the membrane “melts” to adopt a semifluid liquid crystalline state.
The temperature that this happens at is called the transition temperature
Bilayers: structure? dimensions? what types of lipids?
Phospholipid bilayer
Phospholipids are cylinder shaped
6nm total, with 3nm being the hydrophobic core
Micelles: structure, what types of lipids?
Spherical structure with hydrophobic tail in the center
Phospholipids are more wedge shaped
What is a phospholipase?
A phospholipase is an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances.
What are lysophospholipids?
Lysophospholipids are small bioactive lipid molecules characterized by a single carbon chain and a polar head group.
The lysolipid structure renders these lipids more hydrophilic and versatile than their corresponding phospholipids.
