Cell Notes (Take 2)
•Prokayotes: No nucleus, nucleoid
•Eukaryotes:
Nucleus
Cell Structure
•Plasma
Membrane - Encloses cell and separates contents from surroundings.
•Nucleus
of eukaryotes contains DNA.
•Cytoplasm
- Semi-fluid matrix filling cell interior.
Cell Theory
•All
organisms are composed of one or more cells.
–Metabolism
and heredity occur within these cells.
•Cells
are the basic units of organization for all organisms.
•Cells
arise only by division of a previously existing cell.
Cells Are Small
•Advantage
of small cell size is explained by surface area-to-volume ratio.
–As
a cell’s size increases, its volume increases much more rapidly than surface
area.
–Cell
membrane plays a key role in controlling cell function.
•Small cells have more surface area
per unit volume thus more effective communication.
Prokaryotic Cells
•Bacterial
cells are small, consisting of cytoplasm surrounded by a plasma membrane
enclosed within a rigid cell wall.
–Categorized
by cell wall structure:
–Many
propelled by flagellum (flagella).
–Lack
internal organization.
Eukaryotic Cells
•Interior
of eukaryotic cells contain numerous membrane-bound structures (organelles) that close off
compartments to allow multiple simultaneous biochemical processes.
–Vesicles - Storage and Transport
–Nucleus - Chromosomes (DNA)
–Cytoskeleton - Internal Structure
–Central Vacuole - Storage (Plants
Only)
Nucleus
•Nucleus
is the repository of genetic information. (DNA)
–Nuclear
envelope bound by two membranes.
•Covered with nuclear pores that permit passage
of material in and out of the cell.
–DNA
divided into chromosomes.
Organelles With DNA
•Mitochondria
–Bound
by smooth outer membrane and an inner membrane folded in ridges called cristae.
–Contain
own DNA.
Organelles With DNA
•Chloroplasts
–Contain
photosynthetic pigment chlorophyll that gives most plants their green color.
Endosymbiosis
•Theory
of endosymbiosis proposes some eukaryotic organelles
evolved by symbiosis.
–One
species of prokaryote was engulfed and lived inside another.