Transcript Tour Of The Cellx

Tour Of The Cell
Chapter 6
https://www.youtube.com/watch?v=cj8dDTHGJBY&
list=PLb3m_5kPlQwPK22qq6tBsUt_pkt4UQUvQ
https://www.youtube.com/watch?v=9UvlqAVCoqY
Microscopy
• What is the difference between magnification
and resolving power?
• Magnification is how much larger the object
can now appear
• Resolving power is the ability to distinguish
between two points It is limited by the
wavelength of visible light
The different microscopes
 Light microscope - resolving power is limited by the
wavelengths of light
 Specimen should be stained, but can be alive
◦ compound microscope (light shines under and through the
specimen-one eyepiece-multiple objectives)
◦ Stereomicroscope (dissecting/reflects light from above –two
eyepieces-single objective)
 Electron microscope - resolving power is greater since
wavelengths of electrons are smaller than those of light
◦ SEM (Scanning Electron Microscope) - 3D image
◦ TEM (Transmission Electron Microscope) - flat internal
ultrastructure of cell image
 Electron microscopes cannot use live specimens
Scientist used cell fractionation
to separate the cell organelles so
their particular functions can be
determined.
Pellets sink to the bottom and
supernatant floats on top based
on the density (size and weight)
of particles. Cells treated with
increasingly rapid spins will
contain nucleus, mitochondria,
membranes, and then
ribosomes.
As organisms get larger, why do
they become multicellular?
It’s all about the
surface area to
volume ratio! A
higher surfaceto-volume ratio
facilitates the
exchange of
materials
between a cell
and its volume.
Prokaryotic vs. Eukaryotic Cells
Prokaryotic cells
Eukaryotic cells
• Bacteria, Archaea
• Protists, Plants, Fungi
• genetic material not in a
and Animals
nucleus
• true nucleus with genetic
• no membrane bound
material
organelles: DNA,
• has membrane bound
ribosomes, plasma
organelles
membrane, and a cell
wall
The Prokaryotic Cell
The Plasma
Membrane
General Eukaryotic Cells
Two Areas of the Eukaryotic Cell
• What is the space between the cell membrane
and the nucleus called?
• The cytoplasm. This includes the organelles and
the cytosol
• The cytosol is the fluid medium found in the
cytoplasm
• The volume enclosed by the plasma membrane
of plant cells is often much larger than the
corresponding volume in animal cells, because
plant cells contain a large vacuole that reduces
the volume of the cytoplasm.
The nucleus
Nuclear Components
• Envelope = double layered membrane that has
pores for molecular transport
• Chromatin = DNA + protein complex of
threadlike fibers that make up the eukaryotic
chromosome
• Chromosome = Contain genetic information
and chromatin fibers condense into visible
chromosomes during cell division
Ribosomes
• Attached ribosomes make proteins that transported out of the cell
• Free ribosomes make proteins that are used within the cell
• Ribosomes can change between free and attached
• Cells lacking in glycoproteins also lack extracellular matrix and Golgi
The Endomembrane System
• Related through direct continuity or by transfer
on membrane segments through vesicles
• Smooth ER makes lipids (oils, steroids, etc)
• Rough ER is the site of protein synthesis
exported out of the cell
• Structure of membranes is not identical
• Common route for membrane flow is
rough ER → vesicles → Golgi → plasma membrane
Transport vesicle
from ER
New vesicle
forming
Transport vesicle
from Golgi
Functions of Golgi apparatus
• Modifies stores and routes products of ER
• Golgi apparatus produces and modifies
polysaccharides that will be secreted
• Alters membrane phospholipids
• Targets products for parts of the cell
Vacuoles
• Larger than vesicles
• food vacuoles = formed by phagocytosis
• contractile vacuole = found in fresh water
protozoans, keeps water balance
• central vacuole = found in most plant cells stores
organic compounds, compartment that often
takes up much of the volume of a plant cell, has
enzymes to break macromolecules, has
poisonous and unpalatable compounds, etc.
Lysosome
• Contains hydrolytic enzymes
• Helps to recycle the cell's organic material
• In animal cells, hydrolytic enzymes are
packaged to prevent general destruction of
cellular components. Lysosomes function in
this compartmentalization.
Mitochondria and Chloroplasts
• Mitochondria are one of the main energy
transformers of cells
• not part of endomembrane system
• their membrane proteins are made by free ribosomes
and their own ribosomes
• both have small amount of DNA, ribosomes, ATP is
formed and produced
• grow and reproduce on their own within the cell
• Mitochondria produce ATP in the dark; Chloroplasts
produce ATP (chemical energy) with light.
Plastids
• amyloplasts - store starch, in roots and tubers
• chromoplasts - non-chlorophyll pigments
responsible for non-green colors
• chloroplasts - chlorophyll containing plastids
Chloroplasts contain grana,
thylakoids, and stroma.
Peroxisome
 Contains enzymes that transfer hydrogen
from substrates to oxygen producing
hydrogen peroxide
 Some use oxygen to fuel the breakdown of
fatty acids to smaller molecules that can be
used in the mitochondrion
 In liver they detoxify alcohol and other
poisons by transferring hydrogen from poison
to oxygen
 Hydrogen peroxide is toxic. What enzyme can
be used to break this down?
Cytoskeleton
•
•
•
•
Provides structural support
Maintains the shape of the cell
Functions in motility and motion
Parts of cytoskeleton include microtubles,
microfilaments, intermediate filaments, and
actin
Microtubules
• cellular support
• provides tracks for movement within the cell:
e.g. transport vesicles
• composes cilia and flagella, locomotive
appendages of certain cells
• separation of chromosomes during cell
division (spindle fiber)
• composes centrioles in animal cells which are
used in cellular division
Microfilaments
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•
•
•
smaller than microtublues
participates in muscle contraction
support
localized cell contractions
The Cell Surface
• External support and protection for plant
cells is cell walls
• membrane linked channel - plasmodesmata
that connects cytoplasm between cells
Animal Cell Surfaces
• glycocalyx - strengthens cell surface, helps glue
animal cells together
• tight junctions - holds cells together to block
transport
• desmosomes - rivets cells together into strong
sheets but permits transport
• gap junctions - analogous to plasmodesmata in
plant cells and allows ions can travel directly
from the cytoplasm of one cell to the cytoplasm
of an adjacent cell
Common Structural Features of an
Animal Secretory Cell and a
Photosynthetic Plant Cell
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•
•
•
•
•
Golgi Apparatus
Mitochondria
Plasma Membrane
Nucleus including DNA
Enzymes
Ribosomes
Associated with Movement of Cells
• Microtubules
• Microfilaments
• Actin
Let’s Review
• Name the cell structure and its function
• Be able to tell if this structure is found in
prokaryote, eukaryote, plant and/or animal
cells