Cells
-Cells discovered in ca.1660 by
Antonie van Leeuwenhoek.
-word Cell coined in 1665 by
Robert Hooke (latin for small room).
--Cell Theory:
1. All organisms composed of 1 or
more cells.
2. Cells are the basic unit of
organization in life.
3. All cells arise from pre-existing
cells.
Why Organize into Cells?
-individual cells can be lost and replaced
-organisms can outlive the cells that
compose them.
-Cells are always small (10-100 microns).
--WHY?
--Surface-to-Volume Ratio
--as size increases, volume grows
more rapidly than surface area.
--Area increases as A2
--Volume increases as V3
--everything must enter/exit across
the surface area.
--a given surface area can only
maintain a limited volume.
Cell Classification: --2 Types of Cells:
1. Prokaryotic cells (bacteria)
-lack (true) membrane bound
organelles, and have no distinct
nucleus. (No internal membranes).
2. Eukaryotic cells (all other
organisms, plant, animal, etc.)
-have true membrane bound
organelles and a distinct nucleus.
(Has internal membranes).
Eukaryotic Cell Organelles:
--Plasma Membrane
-contains the cell
-regulates transport
-consists of a phospholipid bilayer
--Cell Wall
-Only present in Plants & Fungi
-protects and supports cell
-located outside of membrane
-composed of=
--Cytoplasm
-fluid inside membrane
- 50% cell volume
--Nucleus
-composes 5-10% of cell’s volume.
-contains the cell’s DNA (chromatin).
-nucleolus
-nuclear envelope
-nucleoid
--Endoplasmic Reticulum (ER)
-system of folded membranes.
-surrounds the nucleus
-composed of 2 parts:
Rough ER =
-ribosomes
-functions in protein synthesis
Smooth ER = no ribosomes
-functions in lipid synthesis.
--Golgi Complex
-flattened stacks of folded membranes.
-functions in the packaging & distribution
-Cisternae=
-Vesicles=
-Lysosome=
--Mitochondria
- “Power house” of the cell
-site of ATP synthesis in the cell.
Chloroplasts=photosynthesize to
produce sugars.
-most abundant in leaf cells
-appear green in color due to pigment
chlorophyll.
--Cytoskeleton
-functions in anchoring organelles
& maintaining cell shape.
-3 components/ all protein fibers:
1. Actin filaments=longest
-function in contraction of cell.
-very abundant in muscle cells.
2. Microtubules=hollow tubes
-provide shape to the cell.
3. Intermediate fibers=protein
ropes (many woven strands).
-connection of…
--Centrioles =
--function is unknown
--animal cells only
--Locomotion Structures
-Flagella=long thread-like
structures.
-occur alone or in a pair.
-Cillia=short thread-like structures
-occur in mass number over
large surface
-both function in forward propulsion
and in food gathering.
-Pseudopodia=
--Central Vacuole
-large water storage structure of
plant cells—NOT present in animals