BIOCH200 Lecture Notes - Lecture 6: Van Der Waals Force, Melting Point, Membrane Lipids
1 May 2018
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Reaction Regulates enzyme activity through change in protein shape.
❏Kinase → phosphorylates → can not remove phosphate!! (Protein Kinase
❏Phosphatase → removes phosphate
Addition of Phosphate groups result in
1. Large increase in size, polarity/hydrophilicity
2. Addition of two negative charges
3. New H-bonds
4. Phosphorylation changes enzyme activity by changing 3-D shape.
Fatty Acids
❏Carboxylic Acid group with a pKa of 5 → Deprotonated at physiological pH
❏Saturated → No double bonds
❏Cis → Big groups on same side
❏Trans → opposite
❏Monounsaturated → 1 double bond
Fatty Acid Characteristics
❏Long Chains (can be short) → Hydrocarbon carboxylic acids
❏16 and 18 most common → General formula CH3(Ch2)nCOO-
❏Amphipathic/Amphiphilic (polar/non-polar portions)
❏Saturated or unsaturated → usually cis (naturally occuring)
Types of Lipids (Hydrophobic)
1. Fatty Acids
2. Triacylglycerols (TAGs/Fat)
3. Membrane lipids → (glycerophospholipids, cholesterol and sphingolipids)
4. Cholesterol → By itself for synthesis of water, hormones and vitamin D
a. Small polar head, with thick hydrophobic part
b. Mostly Hydrophobic → 27 carbons, 1 OH (very weak amphipathic)
c. Membrane lipid → maintains fluidity and rigidity
i. High temperature → Fluid, Low temperature → Rigid.
d. Not in plants or bacteria!
e. Fatty acids are added to cholesterol through ester bond to the OH group.
f. Embedded in membrane and interacts with the head groups.
❏Alpha is the first carbon after carboxylic acid.
❏Beta is third carbon
❏Omega (w) is the last carbon on the chain.
❏Naming = Number of Carbons:Number of double bonds (Triangle location)
❏Need to write trans, if you don’t write trans its assumed to be cis.
Saturated versus Unsaturated
❏Saturated → Align close to one another to increase van der waals (maximum) interaction → Pack
closely.
❏Unsaturated → two tails do not align → minimum van der waals interactions → Can not pack
closely.
Melting Point Affected by
1. Number of Carbon (Length) → Longer melt at higher temperatures, shorter at lower temperatures
2. Degrees of Unsaturation → Saturated melt at high temperatures, unsaturated melt at lower
temperatures.
Document Summary
Reaction regulates enzyme activity through change in protein shape. Kinase phosphorylates can not remove phosphate!! (protein kinase. Addition of phosphate groups result in: large increase in size, polarity/hydrophilicity, addition of two negative charges, new h-bonds, phosphorylation changes enzyme activity by changing 3-d shape. Carboxylic acid group with a pka of 5 deprotonated at physiological ph. Cis big groups on same side. Long chains (can be short) hydrocarbon carboxylic acids. 16 and 18 most common general formula ch3(ch2)ncoo- Saturated or unsaturated usually cis (naturally occuring) High temperature fluid, low temperature rigid: not in plants or bacteria, fatty acids are added to cholesterol through ester bond to the oh group, embedded in membrane and interacts with the head groups. Alpha is the first carbon after carboxylic acid. Omega (w) is the last carbon on the chain. Naming = number of carbons:number of double bonds (triangle location) Need to write trans, if you don"t write trans its assumed to be cis.
