Overview • Basic unit of life • 75 Trillion cells in human body • Vary in size and shapes Varieties • Over 260 types of cells in body • i.e. neurons, muscle, bone, blood cells • All types are derived from just 1 fertilized egg • Differentiation • Forming specialized cells from unspecialized cells
Overview • Maintains integrity of cell • Fluid – flexible • Selectively permeable• allows only select substances into and out of cell • Signal transduction – • communication between cell & environment
Structure of cell membrane •Bilayer of phospholipids •Cholesterol •Membrane proteins
Phospholipid Bilayer
Phospholipid Bilayer Nonpolar Hydrocarbon tails •Phosphlipids align so that tails are hidden from water •Nonpolar tails form the interior of membrane
Polar Phosphate heads •Polar groups align to face water •Polar heads are exposed to surfaces of membrane
Phospholipid bilayer forms a fluid, yet stable boundary.
Hydrophobic Interior of Membrane
1. Integral Proteins • Spans cell membrane • Forms ion channels & pores • Examples include: Na + channels and K + channels • Aquaporins = water channels
Transmembrane Proteins • Integral protein, where one end extends outside cell, and the other end dips into cytoplasm. • Many function as receptors
2. Peripheral Proteins • Projects from surface of membrane • May be a glycoprotein (protein + sugar) • Includes Cellular Adhesion Molecules (CAM)
Cellular Adhesion Molecules (CAM)
•Guides moving cells to targets •Establishes cell-to-cell connections •Forms new neural connections in learning and memory •Guides cells surrounding an embryo towards uterus •Guides white blood cells to injury
Selectin •Covers the surface of white blood cells (WBC) •Selectin binds to carbohydrates on surface of damaged capillaries •Allows circulating WBCs to anchor near site of injury
Transmembrane Protein Receptor •A molecule (ligand) binds to portion of receptor outside cell •Transmembrane Protein changes conformation •Portion inside cell sends a signal into cell
3 Parts of the nucleus
Nuclear Envelope •Double-layered membrane = 2 lipid bilayers. •Nuclear Pores •Channel proteins allow specific molecules across nuclear envelope •Ribosomes & RNA leaves nucleus through pores