Chapter 11: Introduction to the course and Lipids Flashcards
Lipids
defined as water-insoluble molecules that are highly soluble in organic solvents
lipids do not form
polymers
Biochemical roles of lipids (3)
- key components of membranes
- play a variety of roles in signal transduction pathways
- used to store energy
Free Fatty Acids (4)
What it is+commonly used as+structure
- simplest type of lipid
- most commonly used as a fuel
- building blocks for membrane lipids
- chains of hydrogen-bearing carbon atoms, called hydrocarbons, that terminate with carboxylic acid groups
Triacylglycerols (2)
WHat it is+the structure
- This class of lipid is the storage form of
fatty acids - formed by linking 3 fatty acids chains with an ester linkage to three alcohol groups in glycerol
Phospholipids
- consist of fatty acids attached to a scaffold that also bears a charged phosphoryl group, creating a macromolecule with a polar head and
nonpolar tail
Glycolipids
- lipids bound to carbohydrates
Steroids
- polycyclic hydrocarbons
Fats Vs Carbohydrates
Fats are good fuels because they are more reduced than carbohydrates; that is, the carbon atoms are bonded to hydrogen atoms and other carbon atoms rather than to oxygen atoms, as is the case for carbohydrates. Because of this greater reduction, fats yield more energy than
carbohydrates do when undergoing combustion to carbon dioxide and water, they have more hydrogen-carbon bonds, which release more energy when broken.
Oleic acid
a C18 fatty acid
The notation 18:0 denotes a C18 fatty acid with
no double bonds
ionized forms of fatty acids
Loses the H
Palmitate is a
16-carbon saturated fatty acid
oleate is a
18-carbon fatty acid with a single cis double bond.
The configuration of the double bonds in most unsaturated fatty acids is —-.
cis
The double bonds in polyunsaturated fatty acids are separated by at least one
methylene group
The properties of fatty acids and of lipids derived from them are markedly dependent on (2)
chain length and degree of saturation
Unsaturated fatty acids have — melting points
than those of saturated fatty acids of the same length
lower
Explain why cis double bonds lower melting temp in lipids
The presence of a cis double bond introduces a kink in the fatty acid and makes tight packing between the chains impossible. The lack of tight packing limits the van der Waals interactions between chains, lowering the melting temperature.
The fat that accumulates in the pan as bacon is fried is composed primarily of —- fatty acids and solidifies soon after the burner is turned off.
saturated
Olive oil, on the other hand, is composed of high concentrations of oleic acid and some —- fatty acids and remains liquid at room temperature.
polyunsaturated
Thus, —– and —— enhance the fluidity of fatty acids and of their derivatives.
- short chain length
- cis unsaturation
Despite the fact that fatty acids are our principal energy source, the concentration of free fatty acids in cells or the blood is —- because free fatty acids are —-. High concentrations of free fatty acids would ——.
- low
- strong acids
- disrupt the pH balance of the cells
How are triacylglycerols used?
When energy is required during a fast (for instance, while
sleeping), the fatty acids are cleaved from the triacylglycerol and carried to the cells. The ingestion of food replenishes the triacylglycerol stores.
triacylglycerols are stored in a
- anhydrous form
containing no water
adipose tissue
- ## the major site of accumulation of triacylglycerols
adipose cells (Fat cell) (2)
What happens inside cell+what they do
- droplets of triacylglycerol coalesce to form a large
globule in the cytoplasm - specialized for the synthesis and storage of triacylglycerols and for their mobilization into fuel molecules that are transported to other tissues by the blood.
Three major kinds of membrane lipids, be specific
Phospholipids, sphingolipids (of which glycolipids are a subclass), and cholesterol.
Phospholipid molecule is constructed from four components:
- one or more fatty acids
- a platform to which the fatty acids are attached
- a phosphate
- an alcohol attached to the phosphate
Phosphoglycerides (2)
- Phospholipids derived from glycerol
- composed of a glycerol backbone to which are attached to fatty acid chains and a phosphorylated alcohol
In phosphoglycerides, the hydroxyl groups at C-1 and C-2 of glycerol are ——. The C-3 hydroxyl group of the glycerol backbone is —–
- esterified to the carboxyl groups of the two fatty acid chains
- esterified to phosphoric acid
The simplest phosphoglyceride
phosphatidate
Sphingosine (2)
What it is+what its used as
- an amino alcohol that contains a long, unsaturated hydrocarbon chain
- backbone for sphingolipids
Sphingomyelin (3)
What it is+ structure (2)
- a common sphingolipid and phospholipid found in membranes
- the amino group of the sphingosine backbone is linked to a fatty acid by an amide bond.
- the primary hydroxyl group of sphingosine is attached to phosphorylcholine through an ester linkage.
Sphingolipids
what it is+ where it is found
A lipid having sphingosine rather than glycerol as its backbone. Sphingolipids are found in the plasma membranes of all eukaryotic cells, although the concentration is highest in the cells of the central nervous system.
Glycolipids
- play a role in cell–cell interactions
- glycolipids in animal cells are derived from sphingosine.
Difference between Glycolipid and sphingomyelin
Glycolipids differ from sphingomyelin in the identity of the unit that is linked to the primary hydroxyl group of the sphingosine backbone. In glycolipids, one or more sugars (rather than phosphorylcholine) are attached to this group.
The simplest glycolipid, called a —-, contains a single sugar residue, either glucose or galactose
- cerebroside
How are glycolipids orientated?
Glycolipids are oriented in an asymmetric fashion in membranes with the sugar residues always on the extracellular side of the membrane
All steroids have a
- tetracyclic ring structure called the steroid nucleus
- The steroid nucleus consists of three cyclohexane rings and a cyclopentane ring joined together
Where are cholesterol stored?
- Free cholesterol does not exist outside of membranes. Rather, it is esterified to a fatty acid for storage and transport.
Membrane anchors
hydrophobic groups that are covalently attached to proteins (in blue) and tether the proteins to the membrane
