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2.1The Structure & Functions of
Eukaryotic Cells
Cells
• Smallest living unit• Most are microscopic
Defining a Cell
• A cell is a confined system of potentially self perpetuating linked organic reactions that are catalyzed step-wise by enzymes.
Principles of The Cell Theory
• All living things are made of 1 or more cells
• Smallest living unit of structure and function of all organisms is the cell
• All cells arise from pre-existing cells
(this principle discarded the idea of
spontaneous generation)
Cell Size
Small Cells have a large Surface Area-to-Volume Ratio. Why?
Why are S.A./Vol. Ratios Important?
• Surface area represents the “access” available to and from a cell for supplies.
• Volume represents how much has to be supplied.
• The more “access” you have to supply each unit of volume, the more efficient the cell is.
Characteristics of Living Cells
• Very complex• Very small• Self-replicating• Autonomous/semiautonomous• Homeostatic
There are 2 Cell Types
• Prokaryotic
• Eukaryotic
Prokaryotic Cells• First cell type on earth
(chemosynthetic)• All are single celled (ie Bacteria)
Prokaryotic Cells
• No membrane bound structures inside• Nucleoid instead of nucleus (region of DNA
concentration).• Organelles not bound by membranes
Eukaryotic Cells
• Internal membrane bound organelles• Cytoplasm (cytosol, organelles +
molecule & ions ) for metabolism• Cell Membrane (Phospholipid bilayer)• Can be Single or Multi-celled
Protozoan
Eukaryotic Animal Cell
Animal Cell Micrograph
Eukaryotic Plant Cell
Plant Cell Micrograph
Cytoplasm
• Viscous fluid containing organelles• components of cytoplasm
– Interconnected protein filaments & fibers – Fluid = cytosol– Organelles (not nucleus)– storage substances
Nucleus • Control center of the cell
• Contains nucleoplasm
• Wrapped by a nuclear envelope which is a double membrane.
• Nuclear pore complexes form openings in nuclear envelope
• Contains
– Chromosomes (DNA)
– Nucleolus
Nucleus Micrograph
Chromosomes (DNA)• Hereditary material• Chromosomes - DNA + proteins
– Short, thick strands– form for cell division
• Chromatin - DNA + proteins
– long, thin strands– form for interphase
• DNA is transcribed & translated into protein to express hereditary traits
Nucleolus
•Non-membrane bound•Contains RNA & proteins•Most cells have 2 or more.•Directs synthesis of RNA•Forms ribosomes
End of Part 1!