Download 3-Cell - Discovery

Discovery of cells


Cells 1st discovered
in 1665 by Robert
Hooke
Viewed dead cork
cells with simple
light microscope
Discovery of cells

1st live cells seen
by Anton van
Leeuwenhoek
Cell Theory

About 150 years
after 1st
observations,
scientists developed
cell theory
Three parts of the theory:
1) All living things are
composed of one or
more cells
2) Cells are the basic
units of structure and
function in an
organism
3) Cells come only from
the reproduction of
existing cells
Cell Diversity

Size


Lots of variation in
size; from bacteria
to eggs. Some
giraffe nerve cells
can be 6.5 feet long!
However, most are
microscopic
Cell Diversity



Although there is
variation, most cells
are microscopic
Cells are limited by
their surface area
to volume ratio
Please turn to page
70 of text
Cell Diversity

Shape


Shapes of cells vary
according to their
function
“form follows
function”
Cell Diversity

Shape


Shapes of cells vary
according to their
function
“form follows function
Internal Organization


Internal structures of
cells are called
organelles
Organelles perform
specific functions
of the cells
Two types of cells



Prokaryotes
(bacteria) lack
membrane bound
organelles
Eukaryotes have
membrane bound
organelles
We will only study
eukaryotes in this
course(ZOO ONLY)
Organelles

Cell membrane


Membrane must
regulate what
wastes and
nutrients leave or
enter the cell
Because of this the
membrane is said to
be selectively
permeable
Organelles

Structure



Made of a bilayer of
lipids and proteins
Proteins and lipids
move, creating a
fluid mosaic
Composition of
membrane varies
according to cell
function
Organelles

Cytoplasm


Located between cell
membrane and
nucleus
Jelly-like substance
in which other
organelles are
located
Organelles

Mitochondria


Large organelles
located in
cytoplasm
Manufactures ATP
Organelles

Mitochondria



Have double
membrane
Have own DNA
Has lead scientists to
believe that
mitochondria
evolved as
symbionts with
another cell
Organelles

Ribosomes



Most numerous
organelle in the
cytoplasm
No membrane. They
consist of proteins
and RNA.
Important in
production of
proteins in the cell.
Organelles

Ribosomes

2 kinds
 Those in cytoplasm
produce proteins used in
the cytoplasm. They are
“free floating” in the
cytoplasm
 Those attached to the
endoplasmic reticulum
produce proteins for the
membrane and those to be
exported from the cell
Organelles

Endoplasmic
Reticulum (ER)


Made up of
membranous
tubules and sacs.
Cellular highway for
molecules to move
from one area of the
cell to another
Organelles

Endoplasmic
reticulum

Rough ER--dotted
with ribosomes. Lot
of rough ER in cells
that produce proteins
to be exported from
the cell or inserted
into the membrane
Organelles

Endoplasmic reticulum
 Smooth ER--not
covered with
ribsomes
 Responsible for
synthesis of steriods
in glands, regulation
of calcium in
muscles, and
breaking down of
toxins in liver
Organelles

Golgi apparatus-
Processing,
packaging,
secreting organelle
of the cell. Like ER,
is a network of
membranes
Organelles

Lysosomes-
Small spherical
organelles that
enclose certain
enzymes within
membranes
(digestive and
breaking down
types)
Organelles

Cytoskeleton



Network of long
protein strands in the
cell.
Provide the cell with
support and
structure
Move organelles
around the cell
Organelles

Cilia


Hair like organelles that
extend from cell surface
Assist in cellular
movement


Ex: moving unicellular
organisms through water
Lining respiratory tract to
move particles to throat for
swallowing
Organelles

Flagella
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Similar to cilia,
though fewer in
number
Propel cells though
solution
Made of
microtubules similar
to those of the
cytoskeleton
Organelles

Nucleus

Contains genetic
material of the cell
and directs most of
it’s activity
Organelles

Nucleus

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Nuclear matrix-similar to
cytoskeleton
Double membrane-called nuclear
envelope
Chromatin--fine
strands of DNA and
protein
Organelles

Nucleus

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Chromosomes-chromatin that coils
and packs densely
prior to reproduction
Site where DNA is
copied into RNA.
RNA is exported
from nucleus and
made into proteins
Organelles

Nucleus

Has at least one
spherical area called
nucleolus. This
area synthesizes and
partially assembles
ribosomes.
Multicellular Organization-tissues


In most multicellular
organisms, cells
combine to form
tissues
Tissue-group of
cells that carries out
a specific function
Tissue Examples

Epithelial tissue-closely packed cells
that cover the
surface of things
such as skin or
lining of the nose
Tissue examples

Connective tissue-loosely scattered
arrangement of cells
that serves to
support and link
together other
tissues.
Multicellular organization-organs


Organs--several types
of tissues that interact
to perform a specific
function
Example-stomach.
Made up of

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epithelial tissue(lining)
Muscle tissue
(movement)
Connective tissue (holds
it all together)
All work toward one
function; digestion
Multicellular organization:
organ systems

Organ systemsgroups of organs
that carry out a set
of related tasks

Example: stomach is
part of the digestive
systems which also
includes the mouth,
esophagus, small
and large intestines,
and other organs.
Evolution of multicellularity


Fossil evidence suggests
that the first life on Earth was
unicellular, prokaryotic
organisms similar to bacteria
Eukaryotes though to have
evolved through symbiosis
with prokaryotes
(mitochondria have their own
DNA and membranes--they
could have originally been
symbionts inside another
cell!)
Evolution of Multicellularity

Eventually some
unicellular organisms
started to live together
in colonies. Over time,
certain cells began to
specialize in certain
functions. Eventually,
this lead to the
development of tissues
What to know for quiz

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Cell theory
Why cells are small
Organelles and their
function
Multicellular
organization
Evolution of
multicellularity