Transcript Cell Structure and Function

2.1
The 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
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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
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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
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Non-membrane bound
Contains RNA & proteins
Most cells have 2 or more.
Directs synthesis of RNA
Forms ribosomes
End of Part 1!