basic unit of life, yet many different shapes and functions

80% water

                                     19% protein, lipid and carbohydrate

                           1% nucleic acid and minerals

     FUNCTION:

Cell membrane is the major regulatory component of the cell.

                    Maintains homeostasis

           a) boundary – separates intracellular and extracellular

           b) cell recognition - receptors,antigens.

           c)  regulates transport – selectively permeable

           d) maintains voltage – membrane potentials

7%Protein

            90% Phospholipids and cholesterol

            3% Carbohydrate

a) Phospholipids form a bilayer, with hydrophobic (water fearing) ends to inside and hydrophillic (water loving) ends to outside.

Cholesterol - other lipid component - stabilizes and lends flexibility.

b)              Proteins  Integral and peripheral 

                    1.  pumps and channels:  transport

                    2.  structural - integrity of membrane

                    3.  receptors - identification

                    4.  enzymes - chemical reactions

                    5.  junctions – CAM’s

c)  Carbohydrates are attached to proteins and lipids - forming glycoproteins and     glycolipids – glycocalyx.  Part of receptors for cell recognition.

Microvilli - folds of cell membrane - increases surface area

a)    Diffusion - random movement of molecules from a high to low concentration until equilibrium.  (with the gradient)

                    Brownian motion:

                      examples:  ions, O2, CO2, lipid soluble molecule 

affected by size of molecules, medium & temperature and gradient

                    Facilitated diffusion:  use of protein carriers in membrane 

               b)  Osmosis - movement of water through a selectively permeable                           membrane from  a high to low concentration until equilibrium. solutes lower water concentration. 

                    responsible for osmotic pressure.

                          solutes ­ ↑ osmotic pressure ­↑

                          solutes ¯  osmotic pressure ¯

uses energy (40% of energy made by cell). Uses proteins in membrane as carriers. Transport against the gradient-low to high concentration.

                    Sodium / Potassium pump (antiport)

                       examples:  glucose, amino acid

          Can utilize as cotransport mechanisms (symport)

engulfing of particles by cell

formation of endosome (vesicle)

                     - Important for hormones & proteins

                     -  Method of immunity for fetus

receptor-mediated pinocytosis

1. Cytosol- liquid matrix of cell - gel

            70 -90% water, rest protein, lipid & glycogen 

2.     Cytoskeleton-Shape, transport, movement

Microtubules   .02   mm

Structure long thin tubes made of protein - no membrane.

            found throughout cytoplasm as scaffolding.Assembles on one end & disassembles on other end.  Made from MTOC. 

Function

            Cell support and intracellular movement (cytokinesis).

            formation of spindle.

           Forms centrioles, source of basal body for cilia, flagella

Structure

           thin filaments of protein called actin (similar to muscle) - no membrane, part of scaffolding, especially in outer part of cytoplasm.

Function

           cell movement - especially in muscle cells.

            cell shape - cytoplasmic streaming.

           support for microvilli.

           contractile ring in cell division during cytokinesis.

Structure intermediate size - examples are keratin, neuro-filaments, etc.

 Function mechanical strength, varying other functions.