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A Tour of the Cell
Chapter 6
Overview: The Importance of Cells
Cell Theory: All organisms are made of cells
The cell is the simplest collection of matter that can live
Cells
All cells have several basic features in common
They are bounded by a plasma membrane
They contain a semifluid substance called the cytosol (cytoplasm is the physical area between membrane and nucleus which contains the cytosol)
They contain chromosomes made of DNA
They have ribosomes
The Cell
Prokaryotic cells
Do not contain a nucleus or other membrane bound organelles
Have their DNA located in a region called the nucleoid
Two Types of Cells
Pili
Nucleoid
Ribosomes
Plasma membrane
Cell wall
Capsule
Flagella(a) A typical rod-shaped bacterium
(b) A thin section through the bacterium Bacillus coagulans (TEM)
0.5 µm
Prokaryotic Cell
Eukaryotic cells
Contain a true nucleus, bounded by a membranous nuclear envelope
Contain many other specialized membrane bound organelles
Are generally quite a bit bigger than prokaryotic cells
Two Types of Cells
In animal cells but not plant cells:•Lysosomes•Centrioles•Flagella (in some plant sperm)•ECM•Desmosomes, tight junctions, gap junctions
Eukaryotic Cells: Animal
In plant cells but not animal cells:•Chloroplasts•Central vacuole and tonoplast•Cell wall•Plasmodesmata
Eukaryotic Cells: Plant
Endomembrane system is a related series of membrane bound structures responsible for protein and lipid synthesis. Includes:
Plasma/cell membrane
Nuclear membrane
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles and vesicles
Endomembrane System
Outside of cell
Hydrophilicregion
HydrophobicregionHydrophilicregion
Phospholipid
Proteins
0.1 µm
Inside of cell
Plasma membrane: Selective Barrier
Carbohydrate
Pore complexes Nuclear lamina
Nucleus
NucleusNucleolus
Nuclear envelope:
Nuclear porePorecomplex
1 µm
1 µm
0.25 µm
Nucleus and its Envelope: Contains DNA
Ribosomes ER Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Largesubunit
Smallsubunit
TEM showing ER and ribosomes Diagram of a ribosomerRNA and proteins
0.5 µm
Ribosomes: Protein Factories
Smooth ER
Rough ER
ER lumenCisternae
RibosomesTransport vesicle
Transitional ER200 µm
Endoplasmic reticulum (ER): Series of Membranes
Rough ER:
Contains bound ribosomes so manufactures proteins
These proteins often destined to be exported from cell
Smooth ER:
No ribosomes so no protein synthesis
Lipid synthesis such as making fatty acids, steroids
Metabolizes carbohydrates
Detoxification of drugs by adding hydroxyl groups (makes water soluble)
Roles of Rough and Smooth ER
Golgiapparatus
cis facereceiving”
Cisternae
trans face“shipping” side
TEM of Golgi apparatus
0.1 0 µm
5
3
Golgi apparatus: “Post Office” of the Cell
Lysosome
1 µm
1 µ m
Vesicle containingdamaged mitochondrion
Digestion
Food vacuole
Plasma membraneLysosome
Digestiveenzymes
Phagocytosis: lysosome digesting food Autophagy: lysosome breaking down damaged organelle
Lysosome
Digestion
Lysosome
Lysosomes: Digestive Enzyme Packets
Central vacuole
Tonoplast
Centralvacuole
5 µm
Plant Cell Vacuole
Intermembrane spaceOuter
membrane
Freeribosomesin the mitochondrialmatrix
MitochondrialDNA
InnermembraneCristae
Matrix
100 µm
Mitochondrion: Site of Cellular Respiration (ATP Synthesis)
Endosymbiosis?“living within”
Granum
Chloroplast
ChloroplastDNA
RibosomesStromaInner and outermembranes
Thylakoid1 µm
Chloroplast: Site of Photosynthesis
Also endosymbiosis?
Network of fibers in cytoplasm that organize and anchors organelles and gives structural support
3 types of cytoskeleton
Microtubules
Microfilaments
Intermediate filaments
Cytoskeleton
StructureThickest of 3 types, hollow
Made of tubulin
Dynamic structure
Microtubules
Microtubules Function
Provides organelle tracks
Moves chromosomes during cell division
Forms structure of locomotive appendages cilia and flagella
StructureThinnest of 3 types, solid
Made of actin
Twisted, double chain
Dynamic stucture
Microfilaments
Function
Interacts with myosin for muscle contraction
Creates cleavage furrow during cell division
Responsible for gel-sol state
Pseudopodia
Cytoplasmic streaming
Microfilaments
• Structure
• Intermediate in size
• Made of keratin
• Permanent structure
Intermediate Filaments
• Function
• Organelle anchor
• Comprises nuclear lamina
• Desmosomes
Intermediate Filaments
Plasma membrane
1 µmCentral vacuole
Plant cell walls
Plasmodesmata
Plant Cell Walls: Made of cellulose
Tight junctions prevent fluid from moving across a layer of cells
Tight junction
0.5 µm
1 µm
Spacebetweencells
Plasma membranesof adjacent cells
Gap junction
Tight junctions
0.1 µm
Intermediatefilaments
Desmosome
Gapjunctions
.
“Communicating”
TIGHT JUNCTIONS
DESMOSOMES
GAP JUNCTIONS
Intercellular Junctions in Animal Tissues
“Rivets”
“Seals”