PROKARYOTIC CELLS and EUKARYOTIC CELLS

Prokaryotic Cells

          - Greek, pro 'before' and karyon 'kernel'
          - unicellular organisms
          - lack nucleus and other membrane-bounded structures
          - bacteria and blue-green algae
          - DNA is coiled into a nucleus-like region(nucleoid)


Eukaryotic Cells

          - Greek, eu 'true' and karyon 'kernel'
          - plants, animals, protists, fungi
          - multicellular organisms
          - well-defined nucleus
          - DNA is bounded within a nucleus
          - with membrane-bounded organelles
          - with cytoskeleton

THREE BASIC PARTS of a EUKARYOTIC CELL

1. Plasma Membrane or Cell Membrane
2. Cytoplasm
3. Nucleus

CELLULAR STRUCTURES and FUNCTIONS

> The Cell Membrane

          - a thin layer of lipid and protein molecules held by noncovalent bonds
          - separates the cell contents from the surrounding medium
          - ranges from 5-10 nanometers
          - controls the entrance and release of substances in the cell
          - mainly composed of phospholipid molecules

PHOSPHOLIPID MOLECULE
          - composed of glycerol, two fatty acids, and one phosphate group
Polar or Amphipatic
          - 2 ends have different properties in water

• head - hydrophilic
• tail - hydrophobic

> The Nucleus

          - the control centre of the eukaryotic cell
          - surrounded by nuclear envelope (double layer)
          - contains the DNA
          - 2 main functions
               - directs chemical reactions in cells
               - acts as storage of genetic information and transfers such information

> The Cytoplasm

         - includes everything between the cell membrane and the nucleus
         - 2 main parts
               - Cytosol
                    - viscous colloidal substance of the cytoplasm
                    - where organelles are suspended
                    - site of major biological processes
               - Organelles

| THE ORGANELLES

Mitochondrion

• rod-shaped
• carries out process of cellular respiration
• "power-centre of the cell"
• has two compartments

           : Intermembrane Space
                 - inner and outer membranes
                 - highly folded (cristae)
           : Matrix

Endoplasmic Reticulum

• extensive network of membranes
• connects the nuclear envelope to the cell membrane
• 2 kinds :

      R.E.R

• has ribosomes attached on its surface
• makes more membranes
• transport proteins within a cell

      S.E.R.

• lacks ribosomes
• synthesizes lipids (fatty acids, phosholipids and steroids)

Ribosomes

• the protein factories of the cell
• attached to the E.R. (R.E.R.)

Golgi Apparatus

• from Camillo Golgi
• consists of a series of flat, membrane-bound sacs
• parallel to each other
• packages and secretes products of E.R.
• "packaging counter of the cell"
• one side receives from the E.R.
• inner sacs modify molecule
• other side transports out of the cell

Lysosomes

• is derived from the Greek word "breaking body"
• "suicidal bags of the cell"
• fuse with food vacuoles and digest the cell contains with the enzymes

     Lysosomal Storage Disease

• Pompe's Disease - accumulation of glycogen
• Tay-Sach's Disease - accumulation of lipids

Vacuoles

• fluid-filled cavities in the cytoplasm containing crystals, inorganic salts, sugars, insoluble particles, and excess water
• bounded by a membrane
• usually acts as storage organelles

Food Vacuoles
Contractile Vacuoles

In Plants:
     Centarl Vacuole - for growth
- contain pigments that attract insects
- contain toxic substances to protect from plant-eating insects

Peroxisomes
     - catalase
              - breaks down hydrogen peroxide
Hydrogen Peroxide
     - very toxic
     - product of cellular metabolism

ORGANELLES PECULIAR TO PLANT CELLS

1. Cell Wall
          - protection
          - 3 layers : primary layer
                              middle lamella
                              secondary layer
2. Plastids
          - pigment-containing storage organelles
Chloroplasts: red, yellow, green, violet, orange
Leucoplasts: colorless

Thylakoids  - disk-shaped structures
                     - stroma
                     - grana