THE LIVING CELL

Discovery of the cell

Robert Hooke (1665) – examined a thin section of cork under the microscope and saw boxlike structure which were the outermost coverings of plant cell later called as cell wall.

Robert Brown (1830) – found the central part of the cell called the nucleus

Matthias Schleiden and Theodore Schwann found out that all living things are made up of cells

Rudolf Virchow discovered that exixting cells give rise to new cells.

Cell Theory states that:

1. the cell is the basic unit of structure and function in living organisms.
2. plants and animals are made up of one or more cells.
3. existing cells give rise to new cells

ANIMAL CELL

1. 

PLANT CELL

General Parts of the Cell:

1. nucleus – central part of the cell

nucleolus – contains the chromosomes; made up of DNA material and proteins which carry the hereditary information; synthesizes the ribosomes

nuclear membrane – separates the nucleus from the other parts of the cell

2. cytoplasm – semi-fluid substance in which the organelles are suspended
3. plasma membrane or cell membrane

v continuous double-layered membrane enclosing the cell

v made up of phospholipids molecules with proteins that are embedded within or located on the surface of the membrane

v selectively permeable or semi-permeable

cell wall – made up of cellulose which is responsible for making the plant cells rigid and sturdy

Cell organelles

1. golgi bodies

· modify proteins that are synthesized and packaged in endoplasmic reticulum

· facilitates transport of materials like glycoproteins

2. ribosomes – small granular structures involved in protein synthesis

2. endoplasmic reticulum

· smooth endoplasmic reticulum – branching canals and act as calcium ions reservoir in skeletal muscles

· rough endoplasmic reticulum – synthesize and packaged proteins which are sent to be synthesized in the golgi apparatus

· associated with ribosomes

4. mitochondria

· “powerhouse of the cell”

· This is where chemical energy of food such as glucose is converted into energy in the form of ATP (Adenosine triphosphate)

5. chloroplast – contains green pigment chlorophyll which is used to convert light energy to ATP

5. lysosomes

· “suicide bags” of the cell”

· Digest complex nutrients and broken down organelles

7. centrosomes / centrioles – duplicate during interphase and prophase and move apart

7. cytoskeletons - “bone and muscle” of the cell

a.) microtubules – skeletons of cells; help provides anchorage for organelles in the cell

b.) intermediate filaments – give support to the cytoplasm of cells; detect some disaorders

c.) microfilaments – muscles of cells; give shape to the cell and are involved in the construction of cytoplasm during mitosis

9. Vacuoles – serve as storage of food and water

Unicellular – single-celled organisms and can survive in their own

Multicellular – different kinds of cells exists; all cells carry on the basic activities of life; each kind of cell often specializes in a particular function in addition to itas basic activities.

Colonial – made up of similar cells; cells are organized into working unit different from individual cells

Prokaryotes

• organisms where the cells have no true nucleus and lack some organelles
• nuclear materials are not enclosed by a nuclear membrane
• the DNA is a single circular structure (plasmid)
• do not have mitochondria, endoplasmic reticulum, lysosomes, vacuoles and golgi bodies; ribosomes are small
• examples are bacteria and blue-green algae

Eukaryotes

• have well-defined nuclear membrane and distinct nucleus
• multiple chromosomes are present and can be seen during cell division
• membrane-bound organelles can be found
• division of labor among organelles enabled them to be multicellular and grow larger than prokaryotes