Midterm paper

CELL BIOLOGY LAB Plasma Membrane

Pre-lab Resources Dr. Lisa Brinn

The Plasma Membrane

■ Also called: – Cell membrane – Plasmalemma

■ Functions: 1. Physical isolation 2. Regulation of exchange with the environment 3. Sensitivity 4. Cell-to-cell communication, adhesion, and structural support

Fluid Mosaic Model

■ Describes the structure of the cell membrane as: – Dynamic – Flexible – With diverse components ■ Phospholipids ■ Proteins ■ Cholesterol

Move freely

Phospholipid Bilayer

■ Made of two layers of phospholipids

■ Phospholipid – Head ■ Hydrophilic ■ Polar

– Tail ■ Hydrophobic ■ Non-polar

Amphipathic

Proteins

1. Peripheral proteins

2. Integral proteins (transmembrane)

Glycolipids

■ Lipids with a carbohydrate attached to them

■ Function: – Maintain stability of cell membrane – Facilitate cellular recognition ■ Immune response ■ Cell connections – tissue formation

Sterols

■ Cholesterol

■ Function: – Stabilize the membrane structure – Regulate membrane:

■ Fluidity ■ Permeability ■ Rigidity

– Membrane remodeling ■ Endocytosis

Cholesterol Synthesis ■ Cholesterol levels

– Dietary intake – Biosynthesis

■ Enzyme – HMG-CoA (3-hydroxy- 3-methylglutaryl-CoA) reductase ➙ cholesterol Blood vessels blockage

Heart attackinhibitors

Statins

Bind to enzyme’s active sites Changes enzyme’s structure

Prevents receptor binding

Reduces cholesterol production

Cytoskeleton ■ Microfilaments

– Slender strands – Made of protein (actin) – Functions:

■ Anchor proteins of the plasma membrane ■ Actin might interact with other proteins (myosin)

■ Microtubules – Thin, hollow tubes – Made of protein (tubulin) – Functions:

■ Forms the main components of the cytoskeleton ■ Allow cell movement or shape change ■ Help to move organelles within the cell ■ Help during cell division ■ Form structural components of organelles:

– Centrioles – Cilia – Flagella

Centrioles

■ Cylindrical structures composed of microtubules

■ Location – Centrosome ■ Clear region of cytoplasm that contains this pair of centrioles

■ Function: – Organize microtubules to move the chromosomes during cell division

Cilia and Flagella

■ Cilia – Also made of nine groups of microtubules – Beat rhythmically to move fluids or secretion across the cell surface.

■ Flagella – Present in some bacteria – Sperm – only human cell that has flagellum – Helps cell to move or propel itself