2010 Foundations - Cells, organelles and cell boundaries
Note - This current page is not yet completed see also the earlier 2008/2009 Lecture
The 2 major classes of cells are defined by the presence or absence of a nucleus; Eukaryotic (with nucleus) and Prokaryotic (without nucleus).
Eukaryotes can be further divided into unicellular (only one cell, like prokaryotes) and multicellular (like us) organisms.
A major difference between eukayotes and prokaryotes is the presence of physical compartments (membrane bound) and organelles within the cell. These compartments allow the separation/specialization of processes within the cell.
About Human Body
- 210+ cell types in body
- total number of estimated cells in the body - 1013 (American Ten trillion/British Ten billion)
- bacteria, fungi and archaea
- found on all surfaces exposed to the environment
- skin and eyes, in the mouth, nose, small intestine
- most bacteria live in the large intestine
- 500 to 1000 species of bacteria live in the human gut
- total number of estimated flora ten times as many bacteria 1014 (American One hundred trillion/British One hundred billion)
Divisions of Life
- archaea (single-celled microorganisms)
- no cell nucleus or any other organelles within their cells
- organisms that can live in extreme habitats http://www.ucmp.berkeley.edu/archaea/archaea.html
MBoC - Figure 1-12 Procaryote sizes and structures (Note image scale should be microns mot millimetres)
DNA (gene): storage, gene regulation, gene expression, messenger RNA processing.
Humans have cells both with a single nucleus, with several nuclei and without a nucleus. Are still considered eukaryotic cells?
In general these fully differentiated (adult) cells started out quite differently, always with a nucleus, as they developed (differentiated) this changed.
- Red blood cells which as they develop in the bone marrow had a nucleus, that is lost as they mature, and exist in the circulation without a nucleus.
- Heart cardiomyocytes may have 2 nuclei, bone osteoclasts may have several nuclei and a single skeletal muscle fiber may have several hundred nuclei.
Metabolism: absorbtion (endocytosis), secretion (exocytosis), messenger RNA translation (ribosomes), protein processing (rough endoplasmic reticulum, Golgi appraratus), transport (transport vesicles), energy production (Mitochondria), digestion (lysosomes), lipid synthesis and detoxification (smooth endoplasmic reticulum).
Is this all these organelles do?
The list above is very generalised, as many organelles have many different functions, and interact with other organelles and structures.
Do all these organelles just "float" in the cytoplasm?
The cytoskeleton, which are 3 separate filament systems (microfilament, intermediate filament, microtubules), regulate cell shape, motility and the position of organelles within the cytoplasm.
Within eukaryotic cells exist physical compartments (separated by membranes) and functional compartments where specific processes may occur or are restricted too. This lecture is also an introduction to compartments within the cell and membranes. The key components are: cell compartments, membrane structure. The lecture slides and textbook alone contain enough information as an introduction to the subject for this level of study. If you are interested in further reading, I have also included below links to more detailed textbooks with further information and images.