Download Chapter 3: Cell Structure and Function

Chapter 3: Cell Structure and Function
Processes of Life
1. Growth2. Reproduction3. Responsiveness4. Metabolism5. Cellular Structure*The activity of any of these functions can vary over time.
Eukaryotic and Prokaryotic Cells: An Overview
Cell Theory-
Eukaryotes- can be single celled or part of a multicellular organism, and share
general characteristics:
Prokaryotes- single celled organisms and share general characteristics:
Prokaryotes are divided into two major groups based on the sequence of base
pairs in their ribosomal RNA; bacteria and archaea
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External Structures of Bacterial Cells
Glycocalyces-Functions of the Glycocalyx:
1.
2.
3.
Flagella (bacterial)
-A long whip-like structure that allows the bacteria to be motile
-Composed of three major parts:
1.
2.
3.
-The hook and the rod and rings of the basal body allow the filament to
rotate 360o.
-Differences in the proteins that make up the flagella allow for
classification of species into groups called serovars (strains of a single
species).
-Flagella can be arranged on the bacterial cell in various ways
-polar-peritrichous-Spirochetes (spiral shaped bacteria)-The major function of the flagella is locomotion
-these actions are in response to external stimuli:
1. phototaxis2. chemotaxis3. positive taxis4. negative taxis2
Fimbriae and Pili- proteinaceous filamentous extensions of the cell
Fimbriae-
Pili-
Prokaryotic Cell Walls
Bacterial cell walls
-the primary polymer of the bacterial cell wall is peptidoglycan, a
polysaccharide.
-this polymer consists of alternating monomer units, both similar to
glucose:
NAG: N-acetylglucosamine
NAM: N-acetylmuramic acid
-chains of NAG and NAM are attached to other chains by crossbridges of
four amino acids (tetrapeptides)
-there are two basic types of bacterial cell walls; gram negative and gram
positive.
-Gram Positive Cell Walls
-Gram Negative Cell Walls
-Bacteria without Cell Walls
-Mycoplamsa-
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Bacterial Cytoplasmic Membranes
Structure-composed of a phospholipid bilayer which can contain various other types
of molecules.
Function- controls what enters and leaves the cell, selective permeability
-Passive processes
1. diffusion-
2. osmosis1. isotonic2. hypertonic3. hypotonic-Active processes- substances move across the membrane using cellular
energy (ATP)
1. active transport2. group translocation-
Cytoplasm of Bacteria
Cytosol- liquid portion of the cytoplasm
InclusionsEndospores and Sporulation-
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Nonmembranous Organelles
-ribosomes-differentiated by sedimentation rate (S= Svedberg units)
-prokaryotes have 50S and 30S subunits which make a 70S
ribosome
-eukaryotes have 60S and 40S subunits which make a 80S
ribosome
-cytoskeleton-formed by the internal fibers of the cell
-some round cells may not have a cytoskeleton.
Archaeal External and Internal Structures
Glycocalyces-
Flagella-Differences between archaea and bacteria flagella
Fimbriae and HamiCell Walls and Membranes-Archaeal cell walls lack peptidoglycan
Both Gram (+) and Gram (-) forms exist
-Archaeal membranes lack phosphate groups on lipids, and have stronger
hydrocarbon linkages.
CytoplasmRibosomes and enzymes are similar to eukaryotes
Endosymbiotic Theory
Because of the similarities of mitochondria and chloroplasts to bacteria, it is
thought that larger anaerobic prokaryotes engulfed smaller aerobic prokaryotes,
and began a symbiotic relationship which evolved into eukaryotic cells.
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