Complete and in-depth TERM TEST 2 Notes for BCH210 for EXAM prep. Kevin has combined notes from his peers and his own work to provide the most complete and comprehensive study guide for all types of students. He has achieved an overall cumulative GPA of 3.95 during his undergrad at the University o...
Why are membranes important?
-‐ Protection
-‐ Selectively permeable (No nutrition in, no O2 in, no waste out – all permeable not good either)
-‐ Specialization
-‐ Compartmentalize genetic material so it stays distinct
Lecture 1 Overview – Lipid structure and properties
-‐ Review structure and properties of fatty acids
-‐ Review structure and properties of the most common lipid found in membranes
o Glycerophospholipids
o Sphingolipids
o Cholesterol
-‐ Describe the role of lipids in health and disease
Biological Lipids!
Biological lipids
LIPIDS
Fatty Acids Steroids
Waxes Eicosanoids Triglycerides
Glycerophospholipids* Sphingolipids* Cholesterol*
* Primary lipids in biological membranes
-‐ Fatty acids is a much more diverse family
*Primary lipids in biological membranes
6!
General properties of lipids
-‐ Solubility
o Low in water and high in non-polar solvents
-‐ Hydrophobic and/or amphipathic
o Contain both polar and non-polar groups Saturated Fatty Acid Structure!
-‐ Self-assemble in water
Polar
o Hydrophobic effect and van der Waals interactions Non-polar Carboxylic
Hydrocarbon tail acid
Saturated fatty acid structure H H H H H H H H H H H H H H H O
=
H!C!C!C!C!C!C!C!C!C!C!C!C!C!C!C!C
!
OH
-‐ Alkane adopts lowest energy form based on steric clash H H H H H H H H H H H H H H H
-‐ Physiological pH most acids are deprotonated ∴ makes (CH2)n H H H H H H H H
them more polar H H
H3C
-‐ Extended conformation = zigzag H H
H H H H H H H H
CH3
‘Anti’ conformation Extended conformation
Saturated fatty acid nomenclature
Unsaturated Fatty Acids!
is most stable is most stable 8!
-‐ 4 ways to name a fatty acid but only talk about 3 H H
1. Symbol
Oleic Acid
a. [#C]:[# of double bonds]
b. 18:0 O
2. Systematic name OH
a. Octadecanoic acid
3. Common name
a. Steric acid
• Double bonds almost always in cis conformation
• Results in a kink in structure
10!
,Unsaturated fatty acids
-‐ Double bonds almost always in cis conformation
-‐ Results in a “kink” in structure
Mono-unsaturated fatty acids
-‐ Symbol
o 18:1
-‐ Systematic name
o 9-octadecenoic acid
-‐ Common name
o Oleic acid
Poly-unsaturated fatty acids (PUFAs)
-‐ Symbol
o 18:2
-‐ Systematic name
o 9,12-octadecadienoic acid
-‐ Common name
Packing
o Linoleicofacid
Fatty Acids
Packing of fatty acids
Fatty Acid Properties!
3 stearate 2 stearate + 1 oleate Carbons: Common Melting
-‐ Disrupted packing in 2 stearate + 1 oleae double bonds Name point
13! C16:0 Palmitate 63 °C
Fatty acid properties
C18:0 Stearate 70 °C
-‐ Understand and know that an introduction of a double bond
can cause significant decrease in melting point C16:1 Palmitoleate -0.5 °C
-‐ Melting point reflects how stable the structure is C18:1 Oleate 13 °C
C18:2 Linoleate -9.0 °C
Fatty acids in health and disease
-‐ Fatty acid intake impacts cardiovascular health 14!
Partial Hydrogenation!
o Saturated fatty acids =↑ disease
o Unsaturated fatty acids =↓ disease Melting Temp
O
-‐ Not all unsaturated fatty acids are good
OH
o Hydrogenation of unsaturated fats during food -9°C
Vegetable Oil
processing produces unhealthy fatty acids Healthy but impractical for (fast) food industry
o Healthy but impractical for (fast) food industry O
45°C
o Melting temperature -9°C OH
-‐ Elaidic acid – trans fatty acid Elaidic Acid – Trans Fatty Acid
o Good for baking and long shelf life but Great for baking + long shelf-life but unhealthy
*worse than saturated fatty acids*
unhealthy 16!
, o Worse than saturated fatty acids
o Melting temperature 45°C
-‐ Converting vegetable oil into elaidic acid by partial hydrogenation limiting H2 goes from a cis bond to a
trans dramatically increases the melting temperature
Some Fatty Acids are Essential!
Some fatty acids are essential
• Required forfor
-‐ Required normal
normalhealth butcannot
health but cannot
be be made
made
– We cannot
o Wesynthesize doubledouble
cannot synthesize bonds pastpast
bonds C9*C9*
o Thus, must acquire from diet O
-‐ Animals
• Animals need
need twoEFAs
two EFAsfrom
from diet
diet: Fish Oil
HO
!-Linolenic acid (18:3 "3)
3
O
Eicosapentaenoic acid (20:5 "3)
"-Linolenic Acid = Omega-3 Fatty Acid 3
HO
O O
Docosahexanoic acid (22:6 "3)
* !2
HO 3
-O
!3 ! - anti-inflammatory
Linoleic Acid = Omega-6 Fatty Acid
O
Linoleic acid (18:2 !6)
O Vegetable Oil
!6 6
*
HO
O
-O Arachidonic acid (20:4 !6)
! 17! 6
HO
- pro-inflammatory
Fatty acids are the “tails” of membrane lipids
-‐ In membranes fatty acids are attached to
A healthy diet has a balance of ω3 to ω6 18!
phosphate containing head group
1. Glycerophospholipids
Glycerophospholipids
2. Sphingolipids
General Structure!
Glycerophospholipids general structure
Glycerophospholipids
Headgroup
• Glycerophospholipids are the most
abundant membrane lipids in cells 20!
Glycerophospholipids
Glycerophospholipids
– Based on structure of glycerol
-‐ Glycerophospholipids are the most abundant membrane lipids in cells
o Based on structure of glycerol Fatty Acyl Chains
HO HO Glycerol backbone
CH2 CH2
HO C H HO C H O
H2C OH H2C O P O-
O-
Glycerol Glycerol-3-Phosphate
21!
Glycerophospholipid properties Phosphate Head Group
-‐ Constant
o Glycerol & phosphate 22!
-‐ Variable
, o Fatty acid tails (length, degree of unsaturation)
o Head groups (size, charge)
Neutral Glycerophospholipids Anionic Glycerophospholipids
Neutral glycerophospholipids Anionic Glycerophospholipids
-1 +1
Sphing
-1 +1
• Sphingolipids are the
of membrane lipids
– Based on structure of s
PC and PE are zwitterionic (net neutral) 25!
26!
Sphingolipids Cholesterol
-‐ Sphingolipids are the second major class of membrane lipids
o Based on structure of sphingosine (not glycerol)
Sphi
o Sphingosine backbone – 18 carbon amino • alcohol backboneis the third major component o
Cholesterol 18 Carbon
Sphingolipid biosynthesis membranes
-‐ Important in nerve tissue cell membranes – Most common steroid in animals
Sphingolipid Biosynthesis
-‐ Genetic defects in DL metabolism à many disease
– Precursor for all other animal steroids
-‐ Sphingomyelin highly abundant in nervous system
H3C
CH3
CH3
Cholesterol
Sphingosine Ceramide
Cholesterol
(85% of all SL) Properties & Function
Sphingomyelin* HO
*Important in nerve tissue cell membranes
Cholesterol
third major• component
Cholesterol is amphipathic OH
Genetic defects inisSL
-‐ Cholesterol themetabolism # many diseases
of membranes
28!
o Most common steroid in – animals
Small hydrophilic OH head group
o Precursor for all other animal steroids
– Rigid and planar CH3
Cholesterol properties and function
-‐ Cholesterol is amphipathic
o Small hydrophilic OH• head
Modulates
group membrane fluidity
CH3
o Rigid and planar – Disrupts packing of hydrocarbon tails
-‐ Modulates membrane fluidity
– Slows motion of hydrocarbon tails
o Disrupts packing of hydrocarbon tails
CH3
o Slows motion of hydrocarbon tails
Lipid distribution is membrane specific
30!
-‐ Has a lot to do with the function
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