Chpt 12 Lipids

Question 1

Lipids Definition

Answer 1

Defined on the basis of chemical properties, not chemical structure
-Heterogenous groups of water insoluble (hydrophobic)organic molecules that can be extracted from tissues by non polar solvents (Chloroform)

Question 2

Fatty Acids

Answer 2

Long hydrocarbon chain of various lengths (C12-C24) and degree of saturation terminated with carboxylic acid group

Saturated-no double bonds
Unsaturated- contains double bonds (cis or trans)Fat

Alpha carbon-carbon 2
Beta Carbon- Carbon 3
Omega Carbon-Terminal Carbon

Question 3

Fatty Acid Solubility

Answer 3

The longer the chain the less solube (solubility decreases)

-was less solube than carbohydrates

Question 4

Nomenclature: Simplified System

Answer 4

of C: # of double bonds cis or trans Delta, Delta

Question 5

Fatty Acids to Know

Answer 5

Fuck All Principle BioChem Lecture
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Formic Acid- 1 carbon
Acetic Acid-2 Carbons
Propionic acid- 3 Carbons
Butyric acid-4 carbons
Capric Acid- 10 C's
Lauric Acid- 12 C's

Palmitic acid 16:0
Palmit(ole)ic acid 16:1 cis 9

Stearic acid 18:0
Oleic Acid 18:1 cis 9
Linole(ic) 18:2 cisx2 9,12
Linole(nic) 18:3 cisx3 9,12,15
Arachidonic Acid 20:4 cisx4 5, 8, 11 ,14
Lignoceric acid 24:0
Nervonic Acid 24:1

Question 6

Two essential Fatty Acids in humans

Answer 6

Linoleic Acid (Omega 6 FA)

• 18:2 cis, cis (delta 9,12)
• cis, cis-9,12 octadecadienoic acid
• Precursor of arachidonic acid
• Deficiency lead to making arachidonic acid essential

Linolenic Acid (Omega 3 FA)

• 18:3 cis, cis (Detal 9, 12, 15)
• cis, cis, cis-9,12,15-octandecatrienoic acid
• Precursor for other omega 3 fatty acids
• Deficiency leads to decreased vision, altered learning behavior

Question 7

Functions of lipids

Answer 7

Cellmembranes:
Phospholipids, glycolipids, sterols

Energy Storage:

• Triacylglycerol or fat
• stores 2.5 x more energy than equal weight of carbohydrates

Cell Signaling:
steroid hormones

Question 8

Phospholipids

Answer 8

or Phosphoglycerides
Amphipathic

contain a:

• Glycerol
• polar head group (phosphate)
• two non polar tails (fatty acids)

Question 9

Amphipathic

Answer 9

molecule with both hydrophobic and hydrophilic regions

Question 10

Common Phospholipids

Answer 10

Head groups: Serine, ethanolamine, choline, inositol

Sphingoymylin

Question 11

Sphingomylin

Answer 11

• a non glycerol containing phospholipid

- contains sphigosine (modified serine)

Question 12

Glycolipids

Answer 12

contain

• substituted Serine (like sphingosine)
• 2 fatty acids
• Carbohydrate (ex glucose)

Question 13

Triacylglycerol (fats)

Answer 13

Glycerol

-three fatty acids-> accumulates as fat droplets in cytoplasm

Question 14

Cholesterol

Answer 14

Multi ring, non polar structure with a hydroxyl

• component of cell membrane
• precursor of steroid hormones
• 27 carbons
• four Rings A, B, C ,D called steroid nucleus

Substituted with

• Hydroxyl group- may be substituted by addition of ester
• two methyl groups
• a branched 8 carbon side chain
• one double bond

Question 15

Micelle

Answer 15

Formed by ionized fatty acids

-steric constants prevent formation of micelle by phospholipids and glycolipids, which usually form vesicles

Question 16

Phospholipid bilayer

Answer 16

(or vesicle)
Liposome (lipid vesicle) aqueous compartment surround by a phospholipid bilayer
-contains phospholipids, glycolipids, cholesterol

Question 17

Formation of Phospholipid bilayer

Answer 17

(or vesicles)
Phospholipids spontaneously form bilayers in aqueous environment
-Energy consideration-> hydrophobic interactions between fatty acid tails. Electrostate and hydrogen bonding between head group and water molecules.

1) Suspend liquid in aqueous solution
2) Sonicate
- agitating with high freq sound waves
3) Vesicles form
4) gel filtration- to seperate particles on size

Question 18

Phospholipid bilayer: Membrane proteins

Answer 18

Vary in percentage of proteins

Two types of proteins:
Trasmembrane (integral) proteins
-protein passes through both layers of the bilayer
-extraction requires detergent or organic solvent
-cross the membrane by hydrophobic alpha helixes
-some cross the membrane by hydrophobic beta sheets (BETA BARRELL)

Peripheral proteins

• attached to one side of the membrane. Associations with polar head groups or membrane proteins
• extraction requires increase in ionic strength or change in pH

Question 19

Bacteriorhodopsin

Answer 19

Aracheal protein

• uses light energy to transport protons out of cell to create a proton gradient
• seven alpha helixes span membrane

Question 20

Hydropathy Index

Answer 20

• Hydrophobic alpha helixes can be identified by plotting the hydrophthy index
• Plot sliding 20 amin acid average of free energy change
• once it meets a critical/criterion level is transmembrane protein

Plotting hydropathy index is not able to detect BETA BARRELS

Question 21

Glycophorin

Answer 21

Red blood cell membrane protein

-single alpha helix spans membrane

Question 22

Porin

Answer 22

E. coli and Rhodobacter capuslatus

-allows movement of material across the membrane

Question 23

Peripheral proteins

Answer 23

Peripheral proteins are anchored to the membrane by:

• lipid anchors
• GPI anchors
• sometimes Hydrophobic alpha helixes

Question 24

Solubility of membranes

Answer 24

Continium not all or non process

Question 25

Fluid Mosaic model of membrane

Answer 25

Membrane are 2D solutions oriented lipids and globular proteins (transmembrane and peripheral) -"rigid" Fluid that separates two fluid filled compartments Movement of phospholipids within bilayer: - Lateral is rapid - Transverse (flip flop) is VERY slow Movements of proteins varies greatly: - Lateral movements: some proteins move as fast as lipids, others do not due to being anchored to cytoskeleton - transverse (flip flop)-does not happen for proteins- orientation of proteins is established at time of protein synthesis Membrane Fluidity: Solid like vs fluid like controlled by fatty acid composition and cholesterol content. -fatty acids exist in rigid state or fluid state. -changes of state changes abruptly at Tm: degrees of unsaturation and length of Fatty acid Shorter fatty acids=Lower Tm More double bonds=Lower Tm Cholesterol-membrane antifreeze and coolant Membranes are asymmetric -membranes contain different lipids and protein components on the different surfaces (faces) of the membrane