Chapter 3

Cells
 Cytology – the study of cells
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Cells vary greatly in size and structure
Cells have two main parts – nucleus and cytoplasm
 Enclosed in a cell membrane (also called plasma membrane)

Cell Characteristics
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Extremely thin
Outpouchings and infoldings
Porous
Selectively permeable = controls what enters and leaves the cell.
 It allows some things to pass, but not others
 This is the MAIN FUNCTION of the cell membrane

Cytoplasm
 Cytoplasm – the area between the plasma membrane and the nucleus.
 Where most metabolic reactions / activities take place
 Filled with a clear fluid called cytosol
 Contains many structures called organelles

Organelles
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Endoplasmic Reticulum (ER) – complex system of internal membranes, canals, or channels.
Function = transport system
 Rough ER – where ribosomes are located, protein manufacture
 Smooth ER – no ribosomes, lipid synthesis

Organelles
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Golgi Apparatus (Bodies) – series of flattened, membranous sacs near the nucleus
Function = Packaging and delivery of proteins
 Mitochondria – usually numerous, double layer membrane
 Function = Chemical energy transformed into
ATP (adenosine triphosphate) through the process of cellular respiration

Organelles
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Lysosomes – variable in size and shape
Function = digestion and destruction of foreign particles, microorganisms, and damaged or worn out cells and cell parts
 Centrosome – composed of numerous microtubules
 Function = forms spindle fibers during cell division

Organelles
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Vesicles – small sacs
Function = transport of substances
 Microfilaments & Microtubules – threadlike structures
 Function = cell movement and cell shape and structure

Organelles
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Nucleus – large sphere usually in the center of the cell
Function = directs the activities of the cell, contains genetic information
 Nucleolus – small, dense structure within the nucleus
 Function = produces ribosomes

Organelles
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Chromatin – loosely coiled “fibers” in nucleus, composed mainly of DNA and protein
Function = contains information for protein synthesis