A%20Tour%20of%20the%20Cell

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• A Tour of the Cell
• Friday Sept 16, 2005
• BCOR 011
• Lecture 8

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• Common features of all cells

Plasma Membrane defines inside from outside
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• Plasma membrane
• Functions as a selective barrier
• Specific portals for selective transport of
• materials in and out of cell

Carbohydrate side chain
Figure 6.8 A, B
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• Common features of all cells

Plasma Membrane defines inside from outside
Cytosol - Semifluid inside of the cell
DNA chromosomes - Genetic material
hereditary instructions
Ribosomes factories to synthesize proteins
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Cytosol
Free ribosomes
ER

• Carry out protein synthesis

Membrane Bound ribosomes
Proteins To be exported
Large subunit
Figure 6.11
TEM showing ER and ribosomes
0.5 µm
Small subunit
Ribosome RNA Protein Complex
Diagram of a ribosome
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Two Broad Classes of Cells
Prokaryotes
Eukaryotes
Pro before
Eu true
karyon nucleus
HAVE A NUCLEUS membrane-bound organelles
DO NOT HAVE A NUCLEUS NO internal membranes
bacteria, cyanobacteria archaebacteria
Plants, Animals, Fungi, protists
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No internal membranes
Bacterial Cell (Prokaryotic)
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Figure 6.6 A, B
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On the same size scale
Bacterial cell (Prokaryotic
Animal Cell (Eukaryotic)
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Relative Sizes
Typical 1-2 ?M Bacterium

Typical 5 to 20 ?M diameter Animal Cell

Typical 5 to 50 ?M diameter Plant Cell

?M micrometer or micron 10-6 meter
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Internal membrane-bound organelles
Animal Cell (Eukaryotic)
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Why Internal Membranes?
Compartmentalization (Division of Labor)
Im playing my sax
Im watching TV
Im cooking dinner
Im sleeping
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Animal Cell
endoplasmic reticulum
ENDOPLASMIC RETICULUM (ER)
nucleus
NUCLEUS
Rough ER
Smooth ER
Plasma membrane
cytosol
Centrosome
CYTOSKELETON
Microfilaments
Intermediate filaments
ribosomes
Ribosomes
Microtubules
Golgi apparatus
Golgi apparatus
Peroxisome
In animal cells but not plant cells Lysosomes Cen
trioles Flagella (in some plant sperm)
lysosome
Lysosome
Figure 6.9
Mitochondrion
mitochondrion
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Nucleus Information storage
DNA housed, copied, read
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The NUCLEUS
Double membrane
Nucleolus
Nuclear pores
DNA RNA protein lipid (membrane)
Nuclear Lamina
Euchromatin Heterochromatin
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• nuclear envelope

Figure 6.10
Nuclear lamina
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Nucleolus Site of Ribosome Subunit Assembly
Note No membrane
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Euchromatin region Site of mRNA synthesis
Expression Of Informational RNAs
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Endoplasmic reticulum (ER)

• Rough ER

• Smooth ER

1 ?m
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Endoplasmic reticulum (ER) Reticulum network
Continuous network of flattened sacs tubules,
vesicles, throughout eukaryotic cytoplasm
Smooth ER

• Synthesizes membrane lipids
• Synthesizes steroids
• Stores calcium
• Detoxifies poison

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Example detoxification in smooth ER
Benzo(a)pyrene charred meat, cigarette smoke
Oxidations more soluble
Some metabolites are more toxic
Chronic use of barbiturates, alcohol- SER
proliferation, resistance
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• Rough ER
• ribosomes attached to cytoplasmic face
• Large flattened sheets
• Synthesizes secreted proteins, membrane proteins
  exported
• Protein modification
• initial steps of
• carbohydrate addition
• - glycoproteins

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Rough ER Slips proteins Through ER
membrane Glycosylation Adds oligosaccharides
added as protein being made
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Figure 6.16
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Golgi Apparatus protein secretion Processing,
packaging and sorting center
Cis Golgi Close To RER
Trans Golgi Far side Away From RER
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Functions of the Golgi Apparatus
Present wrapping Service modifies proteins
Fed Ex Central Sorts for delivery To specific
compartments
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Functions of the Golgi Apparatus

• Trimming of Oligosaccharide side chains on
• glycosylated proteins

• Addition of new Oligosaccharide residues to
• existing side chains of glycosylated proteins

• Maturation Cleavages of specific proteins
• e.g., insulin

• Phosphorylation of specific sugar residues on
• oligosaccharide side chains of
• glycosylated proteins
• molecular zip codes

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Molecular tags route proteins to proper
destination
P added in cis Golgi
Proteins with M-6-P tag bind receptor in trans
Golgi
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Lysosomes Recycling Center sacs of
digestive enzymes
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Endocytosis And Phagocytosis
Figure 6.14 A
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In phagocytosis, a cell engulfs a particle by
Wrapping pseudopodia around it and packaging
it within a membrane- enclosed sac large enough
to be classified as a vacuole. The particle is
digested after the vacuole fuses with a
lysosome containing hydrolytic enzymes.
PHAGOCYTOSIS
Figure 7.20
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• Autophagy

Figure 6.14 B
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Vesicles move thru the endomembrane system
exocytosis
endocytosis
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Mitochondria Powerhouses of the cell
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Mitochondria singular mitochondrion

• powerhouse of the animal cell
• produces 90 of ATP

• Carries out oxidative reactions

• Believed Derived from prokaryotic ancestor

- DNA - ribosomes - double membrane inner
and outer
define two functional spaces
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• Mitochondria are enclosed by two membranes
• A smooth outer membrane
• An inner membrane folded into cristae

Mitochondrion
Intermembrane space
Outer membrane
Free ribosomes in the mitochondrial matrix
Inner membrane
Cristae
Matrix
Mitochondrial DNA
Figure 6.17
100 µm
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Cell organelles Cytosol Gel Important
chemical reactions cytoskeleton - eukaryotes
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• The cytoskeleton
• Is a network of fibers extending throughout the
  cytoplasm
• Structural Support
• Movement of Materials and Organelles

Figure 6.20
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Microtubules
Microfilaments
Intermediate Filaments
Tubulin 25 mM dia
Actin 7 mM dia
various 8-15 mM dia

• There are three types of fibers that make up the
  cytoskeleton

Cell shape Organelle movt Chromosome
separation Flagellar movt
Cell shape Cell cleavage Cytoplasmic
streaming Muscle contract
Nuclear lamina Tension bearing
elements Anchors
Motors Dynein Kinesis
Motors Myosin
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• Movement of Vesicles along Microtubules

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Motor MAPs transport vesicles
Dynein inbound
outbound kinesin
MTOC
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• Contains a pair of centrioles

microtubule-organizing center
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• Animal cells
• Lack cell walls
• Are covered by an elaborate matrix, the ECM

• The ECM Is made up of glycoproteins

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• Functions of the ECM include
• Cell-Cell adhesion
• Cell-Cell recognition
• Regulation of cellular processes

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• plant cell

Ribosomes (small brown dots)
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
NUCLEUS
Golgi apparatus
Central vacuole/Tonoplast
Microfilaments
Intermediate filaments
CYTOSKELETON
Microtubules
Mitochondrion
Peroxisome
Plasma membrane
Chloroplast
Cell wall
Wall of adjacent cell
Plasmodesmata
Figure 6.9
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• Plant Central vacuoles - Tonoplasts
• Are found in plant cells
• Hold reserves of important organic compounds and
  water
• Regulates Turgor

Figure 6.15
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In plant cells, chloroplasts capture energy from
the sun
Photosynthesis
Figure 6.18
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Chloroplasts

• Contain DNA
• Contain bacterial-like ribosomes
• Believed derived from prokaryotic ancestor
• cyanobacterium blue-green alga
• -Double membrane organelle
• defines three functional spaces

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Inner Chlorplast Membrane
3 Central Players
OuterChlorplast Membrane
Stroma
Thylakoid Space
Intermembrane Space (transports things in and out
of the chloroplast, but not central to
photosynthesis itself
Thylakoid Membrane
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Cell Walls of Plants

• The cell wall
• Is an extracellular structure of plant cells that
  distinguishes them from animal cells

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• Plant cell walls
• Are made of cellulose fibers embedded in other
  polysaccharides and protein
• May have multiple layers

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• Plasmodesmata
• Are channels that perforate plant cell walls

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Summary Features of all cells Features of
Prokaryotes Organelles of Animal
Cells Organelles of Plant Cells