SNC 2D1
The Cell Theory
&
Structure &
Function of the Cell
Cellular Organization
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Cell
Tissue – group of cells functioning together.
Organ – group of tissues functioning together.
Organ System – group of organs functioning
together.
Organism – group of organ systems
functioning together.
The History of the Cell

The Cell
The basic unit of an organism
 Discovery made possible by the invention of the
microscope
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Microscopes and Cells
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1600’s.
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Anton van Leeuwenhoek
first described living cells
as seen through a simple
microscope.
Microscopes and Cells
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Robert Hooke used the
first compound
microscope to view thinly
sliced cork cells.
•Hooke was the
first to use the term
“cell”.
•Compound scopes
use a series of
lenses to magnify in
steps.
Microscopes and Cells
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1830’s
Mathias Schleiden
identified the first plant
cells and concluded that
all plants are made up of
cells.
Thomas Schwann made
the same conclusion
about animal cells.
The Cell Theory
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All living things are composed of one or more
cells.
The cell is the smallest entity that retains the
property of life.
New cells arise only from pre-existing cells.
The life properties of an organism depend on
the life properties of its individual cells.
Two Basic Cell Types
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Prokaryote
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Lacks internal compartments.
No membrane bound
organelles.
No true nucleus.
Most are single-celled
(unicellular) organisms.
Single circular loop of DNA
Ribosomes
Examples: bacteria
nucleoid (DNA)
ribosomes
food granule
prokaryotic
flagellum
plasma membrane
cytoplasm
cell wall
Two Basic Cell Types
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Eukaryote
Has several internal structures (organelles). Most
organelles are enclosed by a membrane
 True nucleus. Larger nucleus.
 DNA is organized into linear chromosomes
 Can be either unicellular or multicellular.
 Unicellular example: yeast
 Multicellular examples: plants, animals and fungi
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chromatin (DNA)
nucleus
nucleolus
nuclear envelope
flagellum
rough endoplasmic
reticulum
cytoplasm
intermediate
filaments
plasma
membrane
ribosome
lysosome
microtubules
smooth endoplasmic
reticulum
Golgi
complex
free ribosome
vesicle
mitochondrion
vesicle
microtubules
(part of cytoskeleton)
mitochondrion
chloroplast
Golgi complex
central vacuole
smooth endoplasmic
reticulum
vesicle
cell wall
rough endoplasmic
reticulum
plasma
membrane
nucleolus
nucleus nuclear pore
chromatin
nuclear envelope
intermediate
filaments
ribosomes
free ribosome
Similarities of Plants and Animal Cells
 Both
constructed from eukaryotic cells
 Both
contain similar organelles
 Both
surrounded by cell membrane
Differences of Plants and Animal
Cells
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Plants have
Cell wall made of cellulose provides strength & rigidity
 Have chloroplasts, so are photosynthetic
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Animals have
Other organelle not found in plants (lysosomes
formed from Golgi Bodies)
 Centrioles, important in cell division
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Fungi have
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Cell wall made of chitin
The Parts of The Eukaryotic Cell
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Plasma Membrane (Cell Membrane)
 Serves as a boundary between the cell
and its external environment.
 Allows materials to pass in and out of
the cell.
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Cell Wall
Surrounds the plasma membrane of the cells
of plants, bacteria, and fungi.
 Plant cell walls contain cellulose while fungi
cell walls contain chitin.
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Nucleus
Regulates cell function, is the control centre of the
cell.
 Surrounded by a double-layered membrane (nuclear
enveloped) with large pores that allow materials to
pass in and out of the nucleus.
 Contain nucleoli: synthesizes ribosomal RNA
 Contains chromatin – long tangles of DNA.
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Nucleolus
 Darker structure inside the nucleus.
 Responsible for ribosome production.
 Ribosomes are the sites of protein
production.
nuclear
envelope
nucleolus
nuclear
pores
chromatin
nucleus
nuclear
pores
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Cytoplasm
 The jelly-like polysaccharide (sugar)
material that surrounds the organelles.
 Mostly made of water.
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Endoplasmic reticulum
 Folded membrane that acts as the cell’s
delivery system. Attached to nucleus.
 Smooth E.R. contains enzymes for lipid
synthesis.
 Rough E.R. is studded with ribosomes
for protein synthesis and secretion.
rough endoplasmic reticulum
ribosomes
0.5 micrometers
smooth endoplasmic reticulum
0.5 micrometers
vesicles
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Ribosomes
 Assemble amino acids into polypeptide
chains
 Associated with the E.R.
 Composed of nucleic acids (DNA-like
material)
Ribosomes
(small dots)
rough endoplasmic reticulum (tubes)
0.5 micrometers
vesicles
smooth endoplasmic reticulum
0.5 micrometers
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Golgi apparatus (or Golgi body)
 A series of flattened sacs where newly
made fats and proteins from the E.R. are
repackaged and shipped to the plasma
membrane.
 (Lysosomes are Golgi-derived vesicles,
containing digestive enzymes.)
vesicles
from ER
Golgi
complex
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Vacuoles
 A sac of fluid surrounded by a membrane
used to store food, fluid, or waste products.
 In plants, a large water vacuole takes up much
of the space inside the cell
 These water vacuoles provide water pressure
(Turgor pressure) that helps keep the cells
rigid – without it, plants would wilt.
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Lysosomes
 Contain a digestive enzyme.
 Can fuse with vacuoles to digest food, or
can digest worn cell parts.
 Also known as “suicide sacs” because
they can also destroy the whole cell.
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Mitochondria
 Produce the energy for the cell.
 Also known as the “powerhouse of the cell”.
 Has a highly folded inner membrane (cristae).
 Have their own DNA and ribosomes; self
replicate
 Found in cells of all eukaryotes (plants,
animals and fungi)
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Chloroplasts
Found in plant cells and some protists.
 Transforms light energy into chemical energy which
is stored in food molecules.
 Contain chlorophyll – a green pigment that traps
light energy and gives plants their green color.
 stroma/grana (thylakoid stacks)
 Have their own DNA and ribosomes; self – replicate
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Cilia
 Short,
numerous, hair-like projections
from the plasma membrane.
 Move with a coordinated beating action.
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Flagella
 Longer, less numerous projections from
the plasma membrane.
 Move with a whiplike action.
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Centrioles
 made
of protein.
 play a role in the splitting of the cell into two
cells.
 found in animal and fungi cells.
Cell Size
 Range
from 1–100µm
 Why is there a limit to cell size?
 Surface area-to-volume ratio gets too small
– a point will be reached where there is not
enough surface are to service all of the
cytoplasm
 Materials cannot diffuse into center of cell
such as oxygen, and food (glucose) and
wastes cannot get out
Cells must divide
 For
reproduction
 Asexual
reproduction
 Sexual reproduction
 For
growth
 For repair