rsf lecture 1 sides

8/3/2019 RSF Lecture 1 Sides

1/23

LIPIDS

(Diverse class of compounds defined by their insolubility in water)

A. Fatty Acids

B. Neutral Fats (Triglycerides)

C. Steroids

D. Phospholipids

E. Micelles

F. The phospholipid Bilayer

Dr. Ross Feldberg

Tufts University,Medford, MA (near Boston)

Questions on the lectures? Send them to class e-mail so everyone can seethe answers

Edited by Foxit ReaderCopyright(C) by Foxit Software Company,2005-2007For Evaluation Only.


2/23

CH3CH2CH2CH2CH2CH2CH2CH2CH2COOH

CH3(CH2)8COOH

The Building Blocks: Isoprene and the Fatty Acids

Charged at one end,but long nonpolar tail....

it this hydrophobic orhydrophilic?


3/23

FattyAcids

(LONG HYDROCARBON CHAIN WITH CARBOXYLIC ACID AT ONE END)

CH2-CH

2-(CH

2)13

-CH2-CH

2-COOH

stearic acid C18 saturated (No double bonds)

CH2-CH2-(CH2)5-CH2-CH=CH-CH2-(CH2)5-CH2-COOH

oleic acid C18 1 cis double bond

A cis double bond introduces a kink inthe molecule - a bend in its structureThis is an unsaturated fatty acid


4/23

Neutral Fats form when the carboxyl groups of three fatty acids

condense with the hydroxyl groups of glycerol.

Q. What do we call the functional group that is formed?

what does this zigzag line represent?

Neutral fats are your major long-term energy reservoir(stored in adipocytes a specialized fat storage cell that makes up fat tissue)



5/23

Neutral Fats consist of three fatty acids linked to glycerol. This is

the storage form that excess calories take in your adipose tissue.

Saturated fatty acids have no double bonds and neutral fats with no double bonds form

solids (grease) found in animals

Unsaturated fatty acids with cis double bonds disrupt the compact structure and neutral

fats with such fatty acids form liquid structures (oils) - found in plants)



6/23

H

O

H

+ -Water is a dipole, making it a goodsolvent for charged or polar solutes

Water Structure and solvent properties


7/23

Electronegativity

-C=O - -N-H + -C-H

+ - no in chargeacross bond

In biological systems, oxygen, nitrogen and sulfur have high electron affinity.

When they form bonds to C or H the covalent bond tends to have an unequalcharge across it (POLAR COVALENT BONDS)

In contrast, Bonds between C and H are NONPOLAR

Molecules that are made up mainly of Carbons and Hydrogens tend to beHYDROPHOBIC - they associate with one another when placed in waterrather than with the water molecules. They are insoluble in water.


8/23

8

http://scholar.hw.ac.uk/site/chemistry/activity3.asp

Fats with cis double bonds cannot pack together to form solids

Fats with trans double bonds alsoshow close packing - these aresynthetic and used in baking, butnow thought to be unhealthy

Saturated fats and trans fats tend toform tightly packed solids(margarine)

Unsaturated cis fats form oils(olive oil, canola oil)



9/23

CH3

CH3

H3C CH3

CH3

HO

STEROIDS

Steroids have a four-membered fused ring system

Cholesterol

Testosterone

Q. What does thisindicate?

Fused isoprene unitsmake up a steroid (a 4-membered ring system)


10/23

C

C

CH2

H

H

H

C CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

O

C CH2

CH2

CH2

CH2

CH

O

O

O

OP

O

O-

OR

CHCH2

CH2

CH2

CH3

PHOSPHOLIPIDS

GLYCEROL ESTERIFIED TO TWO FATTY ACIDS AND A PHOSPHORIC ACID

Where R = glycine,serine, ethanolamine,choline or a variety ofother small molecules

The cell membrane is made up of a phospholipid bilayer

charged head group

Hydrophobic tail groups


11/23

soaps form these!

(animal fat + lye to giveCH3(CH2)nCOO- Na+)insoluble fats will be trapped in thecenter of the micelles

Phospholipids associate to form micelles or lipid bilayers


12/23

ARTIFICIAL MEMBRANES: 1. LIPOSOMES

Lipid Bilayers can also form small droplets called liposomes in which there isan aqueous interior.These fuse with cell membranes and can be used to carry into cellshydrophilic molecules that would not normally cross the membrane.



13/23

13

Doxorubicin: An anticancer agent used in treatment of metastatic breast cancerand delivered to cells by being packaged in liposomes



14/23

Q. What is the most fundamental characteristic of a cell ?


15/23

Phospholipid bilayers are Selectively Permeable

These requireprotein carriers toget them across

the membrane


16/23


17/23

In diffusion

1. The net movement of molecules is always down its concentration gradient

2. Since this is a spontaneous process, it is possible to capture some of the energydecrease in moving to equilibrium as work

3. The rate of diffusion is proportional to the concentration difference, thetemperature and the size of the molecules (Einstein was the first to derive anaccurate equation for diffusion!)



18/23

Osmosis is the diffusion of water that takes place when a membrane impermeable

solute is present at different concentrations on either side of a membrane

We actually measure this bydetermining how much pressure wouldhave to be exerted on compartment 2

to keep its volume constant = OsmoticPressure

1 2

Molecules in compartment 2 can NOTcross the membrane


19/23

Osmosis: The diffusion of water down its concentration gradient

high salt solution water balanced salt solution

During profound dehydration, you need to rehydrate with a balanced salt solution, not water


20/23

20

What are some of the properties of biological membranes?

1. Are they rigid or fluid?2. What is the position of membrane proteins in the membrane?3. How do polar and charged molecules get across the membrane?

4. What roles do membrane proteins and carbohydrates play?

In addition to the membrane that defines a cells outer boundary (the plasma

membrane), in eukaryotic cells there are a number of membrane boundedinternal compartments.

The various cell membranes have different lipid components and different proteinsthat determine the structure and function of that membrane.


21/23

21

Human Cell

Mouse Cell

Hybrid cellT = 0

Fuse the twocell types

Hybrid CellT = 60 min

Mouse Membrane Protein

Human Membrane Protein

Use specific fluorescent antibodies to identify mouse-specific and human -specificmembrane proteins

Q. What might you conclude from this experiment?


22/23

The Fluid Mosaic Model of the Cell Membrane

Cholesterol

1. The lipid bilayer (fatty acids and groups attached to phosphate vary from membrane tomembrane)

2. Saturated Fatty Acids & Cholesterol (animal membranes) both reduce fluidity


23/23

The Fluid Mosaic Model of the Cell Membrane

1. Proteins: Peripheral (easy to remove) and Integral (requires dissolving membrane to

remove)

2. Carbohydrates bound to proteins (glycoproteins) and to lipids on exterior surface. Thedifferent blood groups (A, B and O) reflect different sugars on the cell surface of bloodcells

rsf lecture 1 sides

Documents