Lipids & Cell Membranes

Honors Biology

Recall: Macromolecules

BIG biological molecules◦ Made of smaller

parts Monomers

Carbon-based (organic)◦ Carbohydrates◦ Nucleic acids◦ Proteins◦ Lipids

Monomer◦ Glycerol head◦ Fatty acid tail

Used for:◦ Long term energy storage◦ Insulation◦ Major component of

membranes◦ Signaling molecules and

hormones Examples:

◦ Fats, oils, waxes Found in:

◦ All the good tasting foods

Lipids

Cell Membranes

All cells have cell membranes Some cells (eukaryotes) have membranes

surrounding organelles◦ Example: nucleus

All cells need to import and export molecules in order to function properly and maintain homeostasis

Cellular Biology Review

1. Regulate passage of nutrients, wastes, gases, and water into and out of cell

1. Selectively permeable – “picky” about what passes

2. Separate cell from the environment3. Allow cells to communicate with other

cells via receptors on the surface

Cell Membrane Function: Homeostasis!

Cell membranes are fluid mosaics of lipids and proteins

Made of phospholipid bilayer ◦ Phosphate (hydrophilic) “head” ◦ Lipid (hydrophobic) “tail”

Structure of the Cell Membrane

Phospholipid bilayer

Channel protein◦ Allow large molecules to pass through

Structure of the Cell Membrane

Protein channels

Receptor Protein ◦ Receives messages from outside the cell◦ Cell communication is key for homeostasis!

Structure of the Cell Membrane

Receptor Protein

Cholesterol ◦ Lipids that prevent freezing◦ Helps membrane remain fluid (flexible)

Structure of the Cell Membrane

Cholesterol