Transcript A Tour of the Cell

A Tour of the Cell
Tools of Biology
• Microscopes
– Light Microscope
– Electron
Microscope
– Scanning Electron
Microscope
– Transmission
Electron
Microscope
Tools Of Biology
• Cell Fractionation
– takes cells
apart and
separates
organelles from
one another
– Done by
centrifuge
Eukaryotes vs. Prokaryotes
• Similarities between these two types of cells
include:
– Enclosed in plasma membrane that is filled
with cytosol
– Contain chromosomes that hold the genetic
information for the cell
– Have ribosomes that make proteins according
to instructions from genes
Eukaryotes vs. Prokaryotes
• Differences include:
– Location of DNA: Eukaryote found in
Nucleus; Prokaryote found in Nucleoid
(not bound by membrane)
– Eukaryotic cells have membrane bound
organelles with specialized form and
function; Prokaryotes do not
– Eukaryotes tend to be larger in size
(related to the functions that take place)
Eukaryotes vs. Prokaryotes
You will be required to draw
and/or annotate pictures of
E. coli and the liver cell as an
example of these cell types.
Eukaryotes: Plants and Animals
Know the differences
between plant, animal and
prokaryote cell structure
p81-83 in textbook
Eukaryotic Cell Parts
• Nucleus – contains the genetic
information within the cell; enclosed by
the nuclear envelope
• Nuclear envelope – double membrane
(2 lipid bilayers) with pores to allow
movement in and out of the nucleus
• Nucleolus – dense region inside the
nucleus where rRNA is synthesized
using instructions from the DNA
Eukaryotic Cell Parts
• Nuclear side
of nuclear
envelope
contains the
nuclear
lamina which
maintains the
shape
• Also evidence
for a nuclear
matrix
Eukaryotic Cell Parts
• Ribosomes
– Made of rRNA and protein
– Carry out protein synthesis
– Are found floating freely in the cytosol or attached to the ER
or nuclear envelope
– These ribosomes are structurally identical, but may perform
slightly different jobs
• Free floating tend to make proteins used within the cytosol
• Bound tend to make proteins for membranes or that will be
exported out of the cell (associated with ER)
Eukaryotic Cell Parts
• Endomembrane system
– Tasks include synthesis and transport of proteins within and
outside the cell; metabolism and movement of lipids; detox
of poisons
– Membranes of the system related through physical proximity
or via vesicles
– System includes: nuclear envelope (NE); ER (rough and
smooth); GA; lysosomes; vacuoles; (sometimes plasma
membrane)
Eukaryotic Cell Parts
• Endoplasmic Reticulum
(ER)
– Membrane continuous with
the NE
– Consists of smooth and
rough ER
– Smooth ER – not covered in
ribosomes; synth. of lipids,
metablism of carbs and
detox of drugs and poisons
– Rough ER – covered in
ribosomes; produces many
secretory proteins (insulin)
and membrane proteins
Eukaryotic Cell Parts
• Golgi Apparatus (GA) – proteins from the
ER are modified, stored and then sent to
another location
• Polar sides known as cis and trans vary in
membrane thickness and function
Eukaryotic Cell Parts
• Lysosomes – a sac that holds digestive
enzymes in animal cells
• Lysosome membrane and enzyme made
by rough ER and processed by GA
• Plays role in phagocytosis and autophagy
Eukaryotic Cell Parts
• Vacuoles – storage
vesicles with a variety
of functions
– Food vacuoles
– Contractile vacuoles –
involved in maintaining
homeostasis
– Central vacuole - can
hold cell sap, toxins,
pigments
Eukaryotic Cell Parts
• Mitochondria – Site of cellular respiration which generates ATP
(usable energy) from fats and sugars
–
–
–
–
Is membrane bound, but not a part of the endomembrane system
Found in nearly all eukaryotic cells
Often have hundreds or thousands per cell
Composed of 2 membranes that create an outer cavity called the
intermembrane space and an inner cavity called the mitochondrial
matrix, which holds enzymes, mitochondrial DNA and ribosomes
Eukaryotic Cell Parts
• Chloroplasts – photosynthetic organelle that
holds the pigment chlorophyll
– Built similarly to mitochondria: 2 membranes
separated by an intermembrane space. Inside
there are flattened sacs called thylakoids that can
be stacked into grana. The stroma (fluid outside
the thylakoids) contains the chloroplasts DNA,
enzymes and ribosomes
Eukaryotic Cell Parts
Peroxisomes – similar to lysosomes, but are
not a part of the endomembrane system
– Contain enzymes that
transfer hydrogen from
various substrates to oxygen,
producing hydrogen
peroxide, but also contains
enzymes that can break this
down into water
– Some aid mitochondria by
breaking down fats into
usable sizes, but also works
in detoxification
Eukaryotic Cell Parts
• Cytoskeleton – has a variety of roles
including support, movement and
regulation of biochemical activities.
– Microtubules – shape and support the
cell and help in organelle movement
– Centrosomes and Centrioles – aid in cell
division
– Cilia and Flagella – aid in movement
– Microfilaments – helps the cell bear
tension and keep its shape (muscles)
– Intermediate Filaments- Aid in bearing
tension and reinforcing cell shape
Additional Structures
• Cell Wall – protects cell,
maintains shape and prevents
excessive water uptake.
– Found in plants, fungi,
prokaryotes and some protists.
– Primary Cell Wall – secreted by
young plants; relatively thin and
flexible to allow for growth
• Adjacent cells are “stuck” together
with a sticky polysaccharide
called pectin in a space called the
middle lamella
– Secondary Cell Wall – a cell wall
between the primary cell wall and
plasma membrane often
deposited in several layers (wood)
Additional Structures
• The Extracellular Matrix (ECM)
– Made of glycoproteins that form strong fibers on
the exterior of the animal cell.
• Glycoproteins are usually collagen or fibronectin
– There are surface receptors imbedded in the
plasma membrane called integrins
• Integrins are used to communicate between the ECM and
the cytoskeleton of the cell and are integral in changes to
the cell inside and out
Additional Structures
• Intracellular Junctions – cells are
able to communicate with each
other through these means
– Plants
• Plasmodesmata – a channel between
two adjacent cells that creates a path
through cell walls
– Animals
• Tight Junctions – neighboring cells are
bound together by specific proteins
(tight seal – ie. skin)
• Desmosomes (anchoring junctions) –
fasten cells together (muscles)
• Gap Junctions (communicating
junctions) – provide channels between
cells