Wednesday, 29 August 2012

Cell Structures


Typical model of an animal Cell:

Typical model of a Plant Cell:

Organelles in cells:

Cell Wall

o  Found in plant cells and bacteria
o  Surrounds the cell membrane
o  Rigid structures that maintain the shape, supports and protects cells
o  Fully permeable
 
Cell Membrane

o  Partially/selectively permeable


Nucleus

o  Contains chromatins that control cell activities
o  Chromatin contain DNA, genetic material
o  DNA contains instructions for traits and characteristics and to carry out the cell’s function
o  Separated from cytoplasm by nuclear membrane
 
Cytoplasm

o  Gel-like mixture
o  Surrounded by cell membrane
o  Contains organelles

Mitochondria

o  “Powerhouse” of the cell
o  Food we eat is transformed into energy (ATP) for the cell and our bodies.
 
Endoplasmic reticulum

o  An interconnected network of tubes and vesicles
o  Involved in synthesis of proteins, fats and steroids (e.g. cholesterol)
o  Transports materials around in cell.
o  Smooth type: lacks ribosomes
o  Rough type: ribosomes embedded in surface
o  Allows protein to assume correct form/shape


Ribosomes

o  Each cell contains thousands
o  Make/forms proteins using instructions from chromatin.
o  Found on ER and floating throughout the cell.

Golgi Bodies

o  Works closely with ER.
o  Processes and packages complex molecules like proteins an fat by the cell.
o  Brings these products to the surface of the cell where they can be secreted.
o  Other secretions include hormones, antibodies and enzymes.

Lysosomes

o  Contains digestive enzymes
o  Digests excess/worn-out organelles, food particles and engulf bacteria or viruses.
o  Also helps repair worn-out plasma membrane
o  Provides sugars, amino acids, and bases which are the foundation of macromolecules
o  Cell breaks down if lysosome explodes.

Vacuoles

o  Membrane-bound sacs for storage, digestion and water removal (multi-purpose)
o  Animal cells- many vacuoles, small
o  Central, large vacuoles help plants maintain shape.
o  Food vacuoles are formed by phagocytosis.
o  Contractile vacuoles (formed in freshwater protists) pump excess water out of the cell.
 
Chloroplast

o  Usually found in plant cells
o  Contains green chlorophyll
o  Where photosynthesis takes place
o  Converts light energy into chemical energy in glucose.



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