Chapter 12 : Lipids Flashcards
The monomer of lipids is
fatty acids
What are fatty acids
Long hydrocarbon chains with a carboxylic acid on one end
What are the two types of fatty acids ?
Saturated or unsaturated
Saturated fatty acids are made of
Single carbon to carbon bonds
Unsaturated fatty acids are made of
One or more C-C double bonds
Which type of fatty acid is more abundant in nature?
Unsaturated fatty acids
The double bonds in unsaturated fatty acids cause
a cis conformation , causing them to kink by packing closely together. It also gives a lower melting range temperature .
What are the functions of lipids ?
- energy storage
- insulation and heat regulation
- membrane composition
- cell messengers
What are the four types of lipids
- triglycercides
- phospholipids
- steroids
- waxes
What is the most common type of lipid ?
Triglyceride
Where are triglycerides most commonly found ?
butter, lard, margarines and oils
What is the structure of a triglycerol ?
1 glycerol molecule and three fatty acids
True or false, triacylglycerols take up more space than polysaccharides
False, because triacylglycerols are hydrophobic, they take up less space
What are the three types of membrane lipids
- phospholipids
- glycolipids
- cholesterol
Phospholipids
-forms the cell membrane , phospholipid bilayer
Structure of phospholipid
Hydrophilic phosphate head , hydrophobic tails
How is the glycerol bonded to the fatty acids in phospholipids ?
The hydroxyl group the glycerol sis bonded to the carboxyl group of the fatty acids.
The phosphatidate is phospholipids is made up of
The glycerol backbone, fatty acid, and phosphoric acid
Sphingomyelin is a type of
membrane phospholipid
Instead of glycerol, sphingomylein uses :
spingosine
To form sphingomyelin :
sphingosine is linked to the fatty acid though an amide bond
What is the primary hydroxyl group of spingosine ?
phosphorylcholine
Glycolipids
Contains a sphingosine backbone, fatty acid , and one or more sugar residues
The fatty acid is joined to the sphingosine backbone through what type of bond?
amide linkage
The primary hydroxyl group in glycolipids is linked to a
Sugar
Ex) cerebroside or gangliosides
Cerebrosides
A glycolipid which contains simple sugar attatchments such as glucose or galactose
Gangliosides
A glycolipid that have more complex sugar attachments of branched sugar molecules
Cholesterol serves as a type of
steroid
Functions of steroids
- Hormones for chemical messaging
- No fatty acids, C and H are in rings
Cholesterol is synthesized from molecules called
terpenes
Terpenes
Any large group of large volatile unsaturated hydrocarbons found in essential oils of plants
Polyprenols
natural long chain of isoprenoid alcohols that function as natural bioregulators, found in various plant tissues
Most steriods are found in the form of
5 or 6 membered rings
The most common steroid found in nature is
cholesterol
What are the 5 classes of steroids ?
- Androgens
- Estrogens
- Progestins
- glucocorticoids & mineralocorticoids
- bile acids
Function of androgens and estrogen
- Mediate the development of sexual characteristics and functions in animals
Progestins
Participate in the control of the menstrual cycle and pregnancy
Bile Acids
Detergents produced by the gall bladder and added to bile to assist in absorption of lipids in the intestine
Glucocorticoids
Participate in the control of carbohydrate protein and lipid metabolism
Mineralcorticoids
Regulates the balance of salts such as Na , K and Cl in tissues
Other than the backbone, what is the difference between glycolipids and phospholipids
Phospholipids have a phosphate group esterified to the hydroxyl group on the 3rd carbon while glycolipids have at least one sugar esterfied to the hydroxyl group on the 3rd carbon
Amphipathic
Having both a hydrophobic and hydrophilic end
ex) cell membranes
Hydrocarbon tails which are nonpolar are considered to be
hydrophobic
The phosphate and choline heads are considered to be
hydrophilic
In the cell membrane, the hydrophilic heads are facing which direction
The hydrophilic heads are in contact with the water while the hydrophobic sides avoid contact with the water
Micelles
Hydrophobic tails of the phospholipids face the center while the polar heads face towards the outside
Are lipid bilayers spontaneously or non-spontaneously formed ?
Spontaneously formed
How are lipid bilayers stabilized ?
- Hydrophobic interactions from fatty acids
- Van der Waals attractive forces between hydrocarbon tails
- Electrostatic and hydrogen bonding between the polar heads of molecules
Lipid bilayers are impermeable to
most ions and polar molecules
Based on the type of membrane, the ratio of ___ to _____ differs
lipid to protein
What are the two type of protein associations ?
Peripheral and integral
Peripheral
Extrinsic, proteins that do not penetrate far into the bilayer
How can peripheral proteins be dissociated from the membrane
Salt solutions or changes in pH
Integral proteins
Intrinsic, proteins that extend all the way across the membrane
How can integral proteins be dissociated from the membrane?
They can be removed only by disrupting the lipid bilayer itself
α-helical membrane proteins
Most common transmembrane protein
Example of a α-helical membrane protein
Bacteriohodopsin which is found in bacteria to help transport protons across the membrane
prostaglandin
H2-synthase-1
Example of an α-helical membrane protein that is used as a membrane anchor , not spanning across the entire membrane
β-barrel membrane Proteins
Found on the outer membranes of bacteria , mitochondria for ion transport , passive nutrient intake, membrane anchor
β-barrel membrane Proteins are arranged in a
antiparallel fashion
On the inner surface of the β-barrel, there is ___ and on the outer surface , there is a ____ __
water , hydrophobic surface
What are the four types of lipid anchors
- amide -linked myistoyl anchors
- thioester- linked fatty acyl anchors
- thioether- linked prenyl anchors
- glycosyl phosphartidylinositol anchors
Amide- linked myristoyl anchors
myristic acid ( a lipid) that may be linked by an amide bond to the α-amino
group of the N-terminal
glycine of certain proteins.
Thioester-linked Fatty Acyl Anchors
palmitoyl group ( a lipid_ attatched through a thioester linkage to the side chained of cysteine and sometimes serine or threonine
Thioether-Linked Prenyl Anchors
Long chains of isoprenoid groups which occurs at the cysteine residue which is then cleaved by a protease leaving the C terminus on the anchor
Glycosyl Phosphatidylinositol Anchors
The phophatidylinositol (lipid) is attached to an oligiosaccharide which is attatched to an ethanolamine. The enthanolamine is atatched to the C terminal of the amino acid
What features of the phospholipid molecules cause them to form a bilayer membrane spontaneously when placed in an aqueous environment
The phospholipid structure has both a hydrophilic head and a hydrophobic tail allowing the tails to be placed away from water and the heads toward water
What are two common secondary structures often found in transmembrane proteins
The α-helix and the β-sheet are often found in
transmembrane proteins.
How can bacteria change the fluidity of the cell membrane
By adjusting the number of double bonds and the chain length of its lipids
How can eukaryotes change the fluidity of the cellmembrane
Changing the amount of cholesterol inserted into the membrane
Most proteins move ___ through the membrane
laterally or can flip flop from one side to the other
Membranes have what type of symmetry
Transverse asymmetry.
* Sugars are only on the extracellular side of the membrane
Amine containing phospholipids are only on which side
cytoplasmic side
Choline containing phospholipids and sphingolipids are only on the
outer side of the membrane
If there is a loss of lipid asymmetry
It could trigger apoptosis
Flippases
ATP dependent that flip the PS and sometimes the PE from the outer layer to the inner layer
Floppases
ATP dependent that transport lipids, PC and sphingomyelin from inner to outer membrane
In what ways can the membrane be asymmetric ?
- Proteins on either side could be different or phospholipids could be different compared from the inner to the outer membrane
Can lipids be moved from one side to the other
Phospholipids can be moved by using enzymes called flippases and floppases . proteins cannot be moved from one side to the other.
