Biology
A Tour of the Cell
http://www-micro.msb.le.ac.uk/MBChB/bloodmap/Blood.gif
• A cell is the smallest
unit of life.
• They can vary in size,
shape and function
(structure
determines
function).
• The light
microscope led the
way to knowledge of
the cell.
http://www.microscope-microscope.org/basic/microscopeimages/138-microscopes-lg.jpg
Microscopes:
• A light
(COMPOUND)
microscope
magnifies objects
(specimens)
~1000x their size.
Most cellular
structures
CANNOT be seen.
• You will work with
a light microscope
in the lab.
http://www.dsbn.edu.on.ca/schools/Westlane/Scien
ce/simon/SBI3C1/micro.gif
• Electron microscopes give more detail and
magnify a million times the object’s size.
• However, the organism dies when using an
electron microscope.
There are 2 types of electron microscopes:
• A scanning electron microscope (SEM) gives
a 3D image of a specimen/object.
• A transmission electron microscope (TEM)
transmits electrons to view the interior of an
object.
SEM
http://w3.salemstate.edu/~pkelly/sem/image003.jpg
http://www.nims.go.jp/htm21/MA/tem.jpg
http://img72.imageshack.us/img72/2392/071003100546198ddedh5.jpg
http://www.st-andrews.ac.uk/~dclogan/Fig3.jpg
A history lesson:
• Robert Hooke (1665) named the cell
after looking at cork under the
microscope.
http://www.google.com/imgres
• Anton van Leeuwenhoek (LAY-vonhohk) (1670’s) developed a simple light
microscope & discovered unicellular
organisms and called them “little
beasties”.
http://www.google.com/imgres
• Rudolf Virchow (1855) stated that all
cells came from pre-existing cells (a.k.a.
Cell Theory).
The Cell Theory (Virchow) has 3 basic
principles:
1. Cells are the basic
units of life.
2. All organisms are
made of 1 or more
cells.
3. All cells arise from
existing cells.
http://www.leksikon.org/images/virchow_rudolf.jpg
http://www.dmturner.org/Teacher/Pictures/Cell%20reproduction.jpg
Cell Structures:
• All cells have an
enclosure called a cell,
or plasma membrane.
• This functions as the
gate keeper and
controls what enters
and exits the cell.
• It is mainly composed
of phospholipids and
proteins.
http://www.google.com/imgres
• Within the cell is the
cytoplasm. This is a
semifluid substance
that contains the
organelles.
• The organelles are
small structures that
have specific
functions within the
cells.
http://www.google.com/imgres
• The cytoskeleton is a protein network within the
cytoplasm that helps support the cell and helps the
cell maintain or change its shape. It also
– Anchors organelles
– Enables the cell to move
– Allows materials to move throughout the cell
– Composed of microtubules & microfilaments
http://www.google.com/imgres
http://www.google.com/imgres
• The nucleus is the control center of the cell
– It is surrounded by the nuclear envelope
– It contains the chromosomes. There are 46
chromosomes in the human nucleus (in every cell
of the human body). The chromosomes are the
DNA (genetic material).
• The nucleus is only found in eukaryotic cells!
• The nucleus
contains the
nucleolus
(if more than 1,
nucleoli).
• Nucleolus:
makes
ribosomes
• Ribosomes
make proteins.
http://www.google.com/imgres
2 Types of Cells
Prokaryotic Cells
• Bacteria
• NO organelles
(membrane-bound
structures)
• Contained w/in cell
membrane & cell wall,
contain ribosomes, 1
circular chromosome in
nucleoid region (NO
nucleus) & plasmids
(extra pieces of DNA)
Eukaryotic Cells
• Protists, Fungi, Plants,
& Animals
• Contained w/in cell
membrane (may have a
cell wall)
• Contain nucleus &
other membrane-bound
organelles
• Means ‘true kernel’
There are 2 types of cells:
1. Prokaryotes:
These are bacteria
(in Kingdoms
Archaebacteria
and Eubacteria).
–
–
They are unicellular
organisms.
These were the first
cells. They are very
small cells and are
very simple cells.
http://www.singleton-associates.org/gifs/cell.jpg
2. Eukaryotes: found in
all other kingdoms.
– These have a nucleus
(as well as a cell
membrane and the
majority of the
organelles being
discussed, depending
on the type of
organism).
http://www.google.com/imgres
Animal Cell: http://www.animalport.com/img/Animal-Cell.jpg
http://micro.magnet.fsu.edu/cells/plants/images/plantcell.jpg
• Ribosomes make proteins from amino acids;
can be found suspended within the
cytoplasm or attached to the endoplasmic
reticulum. (not really organelles; these are
cellular components)
• The endoplasmic reticulum (ER) is a network
of membrane that produces materials for the
cell. There are 2 types:
– The rough ER contains ribosomes and functions
in protein synthesis and makes new cell
membrane.
– The smooth ER makes lipids, process
carbohydrates and breaks down toxins.
http://www.google.com/imgres
• The golgi apparatus is composed of flat
membranous save that modify, package and
distribute molecules (warehouse of the cell).
http://www.google.com/imgres
Vacuole
• Vacuoles are membranebound organelles that
have various functions.
– Some store food, water,
proteins, ions, or wastes.
Generally these are large
and centralized.
• Lysosomes contain
digestive enzymes that
break down large
molecules and old
organelles that the cell no
longer needs.
http://www.google.com/imgres
• Chloroplasts, doublemembrane-bound
organelles, perform
photosynthesis.
– This is the process of
making sugar
(synthesis) in the
presence of light
(photo).
– Plants (some bacteria
& protists) make their
own food (a.k.a.
autotrophic).
http://www.daviddarling.info/images/chloroplast.jpg
• The mitochondria is the “powerhouse of the
cell” b/c it changes stored enter from food into
useable chemical energy (ATP) for chemical
reactions.
– ATP = adenosine triphosphate (energy ‘currency’
of cells)
– The chemical reactions are cellular respiration.
http://scienceblogs.com/worldsfair/Mitochondria.jpg
Cellular Structures
• Cilia are short hairlike projections
that are in the
surface on the cell
usually in large
number. (NOT
organelles)
– Beat in unison and
aid in the cell’s
movement or in the
movement of fluid
over the cell.
http://www.google.com/imgres
• Flagella are long tail-like
projections that are on
the surface of the cell.
(NOT organelles)
– Usually 1 to 3 of these.
– In prokaryotic cells, they
spin like propellers.
– In eukaryotic cells, they
move like whips.
http://www.google.com/imgres
Plants differ from animal
cells. In plants:
Cell Wall
• A cell wall surrounds the
cell membrane.
• The cell wall is a rigid outer
covering that protects and
maintains the shape of the
plant cell.
• Fungi, algae (a type of
protist) and bacteria also
have cell walls but the
composition is different.
http://www.google.com/imgres
• Plants LACK lysosomes and centrioles.
• Animals are heterotrophic, meaning
they must consume food.
Animal cells:
• LACK a cell wall but have cytoskeletons
for structural support.
• LACK chloroplasts
• Contain small vacuoles (instead of a
large centralized one)
• Have lysosomes
BOTH Animal and Plant Cells Contain:
• Organelles previously mentioned
(nucleus, ER, mitochondria, ER,
ribosomes, etc)
• Cell membranes
• DNA (in chromosomes)
SEMI-PERMEABLE MEMBRANE
• Cell/plasma
membrane is
composed of a
phospholipid bilayer
(2 layers of
phospholipids) with
proteins
interspersed.
• Phospholipids have
a hydrophilic head &
hydrophobic tail
• Fluid & flexible
http://www.bioteach.ubc.ca/Bioindustry/Inex/graphics/phospholipid.gif
Cell Membrane
http://www.hallym.ac.kr/~de1610/histology/cell-3.jpg
Membrane Functions
• Cell membranes are semipermeable. This
means that some things pass through the
membrane while others cannot pass through
(this depends on the size & charge of the
molecule).
• Passive transport is the movement of a
substance across a membrane without
energy input.
• Active transport is the movement of a
substance across a membrane with the input
of energy.
• http://www.sumanasinc.com/webcontent/ani
mations/content/diffusion.html
• Concentration=[ ].
• Molecules move from a higher [ ] gradient to a lower [ ]
gradient.
• A [ ] gradient is the difference between the [ ] of a particular
molecule in 1 area and its [ ] in an adjacent area.
• The rate of diffusion depends on temperature and size of
molecules involved (molecules move faster at higher temperatures
and smaller molecules move faster than larger molecules).
• Once molecules are dispersed evenly, DYNAMICequilibrium is
reached and diffusion stops.
CLICK ON LINK:
http://highered.mheducation.com/sites/007249585
5/student_view0/chapter2/animation__how_diffu
sion_works.html
Passive Transport
• Diffusion is the movement of molecules from
a higher concentration to a lower
concentration.
http://www.google.com/imgres
http://www.google.com/imgres
• Facilitated diffusion is the diffusion of
molecules with the help of a carrier
protein embedded within a cell
membrane. CLICK ON LINK:
• http://highered.mheducation.com/sites/00
72495855/student_view0/chapter2/animat
• Osmosis is the diffusion of water.
• Diffusion, facilitated diffusion and osmosis
are all type of passive transport. These do
NOT require energy (occur spontaneously).
http://www.biologycorner.com/resources/osmosis.jpg
• Active transport in cells usually occurs
with the help of carrier proteins but
REQUIRE energy. An example is the
sodium-potassium pump (Na+/K+ pump).
http://web.ahc.umn.edu/~mwd/cell_www/images/Na-Kpump.png
• When comparing 2 solutions with a membrane
between them, there are 3 types of solutions:
• Hypertonic: the fluid outside a cell has a
higher [solute] than the cytoplasm inside the
cell. In this case, water diffuses out of the
cell.
• Isotonic: the [solute] outside the cell= the
[solute] inside the cell. In this case, no
osmosis will occur.
• Hypotonic: the fluid outside a cell has a
lower [solute] than the cytoplasm inside the
cell. In this case, water will move inside the
cell.
http://kentsimmons.uwinnipeg.ca/cm1504/Image130.gif
http://road-to-rn.tumblr.com/post/127238852030/hypotonichypertonic-isotonic-solutions-videos
Bulk Transport:
1. Exocytosis:
exo=exit; cyto=cell
• Wastes and cell
products are
packaged in
vesicles by the
golgi apparatus.
• The vesicles fuse
with the cell
membrane and
leave the cell
http://www.octc.kctcs.edu/gcaplan/anat/images/Image152.gif
2. Endocytosis: endo=within; cyto=cell
• A portion of the cell membrane
surrounds a substance outside of the
cell & pinches off to form a vesicle
• The vesicle moves inward and fuses
with other organelles
• This includes
– Pinocytosis: cell drinking
– Phagocytosis: cell eating
http://www.gla.ac.uk/~jmb17n/Teaching/L2teaching/Agpres/Figures/Endocytosis.jpg