Lecture 7: Lipids and Organizers of the Cell

Lipids are composed of:

• Carbs

• Hydrogen

• Oxygen

• + more

Lipids are NOT:

• Macromolecules (but interact with MM to form cell structures and organelles)

  • No Monomers/Polymers

Lipids are _____ molecules

diverse biological

Lipid functions that change with structure:

• Solubility

• Rigidity

• Signaling

Lipids provide function via: 

hydrophobic interactions 

Lipids are amphipathic due to structural variants:

• Fatty acids

• Phospholipids

• Sterols

• Glycolipids

• Sphingolipids 

Lipids are composed of: 

Many hydrocarbon units (aliphatic or aromatic) 

Aliphatic

Single bonds

Aromatic

Double bond, strong

Biological roles of Lipids

• Structure 

• Provide/Store energy 

• Signaling

Structural Lipids

Sequester and maintain cellular environments

Ex. of Structural Lipids 

Cholesterol stabilizes membranes of cells and organelles

Energy providing/storing lipids 

Store energy to be released when needed

Ex. Lipids Providing/Storing Energy

Palmitic acid is oxidized to acetyl-CoA to capture ATP energy 

Signaling Lipids

Communicate and signal between cells 

Ex. Signaling Cells

Prostacyclins initiate inflammation in target calls

Glycerolipids formed by:

combining Fatty acids and glycerol

Fatty Acids

• Carboxylic acid (hydrophilic) 

• Aliphatic tail (hydrophobic) 

  • Chain of carbons w/ single bonds

• Oxidized for energy 

Glycerol

• Three C structure with OH groups 

• NOT a carb 

• OH groups form covalent bonds with FAs 

• Can be oxidized for energy 

Glycerolipids

• Mono/Di/Triglycerides 

• Storage form of fat for energy in adipose tissue 

FA Length

• Determines fit with hydrophobic molecs.

• Short FAs (<6 C) easily evaporate 

• Long tail stable, harder to evaporate

• Most common 16-18 C 

FA Saturation

• Determines fluidity when grouped (like membrane)

• Saturated packs closely

• Unsaturated packs loosely

• Trans FA act like saturated

• Single bond = Saturated

• Double bond = Unsaturated

  • More central DB = More fluid

Saturated Glycerolipid 

• Solid at room temp

• Butter 

Unsaturated Glycerolipid

• Liquid at room temp

• Bent/has kink 

• Oil

Phospholipids

• Lipids with phosphate (mostly glycero) 

• Phosphate head (hydropholic) 

• Aliphatic tail (hydrophobic) 

• Primary part of cell memb. 

• Molecule on opp. side of phosphate determines sub type (choline common) 

Glycolipids

• Any lipid with carb group 

• Serves as specificity markers 

• Facilitate cell-cell interactions 

• ~3% of cell memb. 

Sphingolipids

• Contain sphingosine as the backbone (instead of glycerol) 

• Creates barriers in cells and tissues 

• Coordinate vital cellular processes 

Sphingolipid barriers in cells and tissues 

• Sphingomyelin and Ceramides

• Highly abundant in nervous and gastrointestinal tissues

Sphingolipid coordinate vital cellular processes

• Initiate inflammation and cellular differentiation 

• Regulate cell cycle (proliferation, apoptosis) 

Steroids

• C skeleton for four fused rings (aromatic)

  • Three 6 C

  • One 5 C

• Modifications determine subtypes 

Sterols

• Steroids with OH (alcohol) groups 

• Basic sterol is cholesterol (in mammals) 

• Serve structural and signaling roles 

  • Reduce memb. fluidity (tight packing) 

  • Act as hormones