Download Unit 2: Cell theory

UNIT 2: CELL THEORY
7th Grade
CELLS ARE EVERYWHERE!!
Cells are the fundamental units of life.
All living organisms are composed of and depend
on cells to function normally.
Scientists estimate that our bodies contain anywhere
from 75 to 100 trillion cells.
CELL THEORY
Before 330+ years ago, there was no knowledge of cells. Cells
were too small to be seen. But with the invention of the microscope,
an entirely new world was discovered, where very large objects
like humans are in fact made up of billions of tiny individual pieces
called cells.
1665 – CELL FIRST OBSERVED
Robert Hooke, an English scientist, discovered a
honeycomb-like structure in a cork (tree) slice using
a primitive compound microscope. He only saw cell
walls as this was dead tissue. He coined the term
"cell" for these individual compartments he saw.
1670 – FIRST LIVING CELLS SEEN
Anton van Leeuwenhoek, a Dutch biologist, looks at pond water
with a microscope he made lenses for.
1683 – MINIATURE ANIMALS
Anton van Leeuwenhoek made several more discoveries on a
microscopic level, eventually publishing a letter to the Royal Society
in which he included detailed drawings of what he saw. Among
these was the first protozoa and bacteria discovered.
150 YEAR GAP
Between the Hooke/Leuwenhoek discoveries and the mid 19th
century, very little cell advancements were made.
This is due to the widely accepted, traditional belief in
Spontaneous Generation.
Examples:
-Mice from dirty clothes/corn husks
-Maggots from rotting meat
1833 – THE CENTER OF THE CELL SEEN
Robert Brown, an English botanist, discovered the nucleus in plant
cells.
1838 – BASIC BUILDING BLOCKS
Matthias Jakob Schleiden, a German botanist, proposes that all
plant tissues are composed of cells, and that cells are the basic
building blocks of all plants.
This statement was the first generalized statement about cells.
1839 – CELL THEORY
Theodor Schwann, a German botanist reached the conclusion that
not only plants, but animal tissue as well is composed of cells. This
ended debates that plants and animals were fundamentally
different in structure.
He also pulled together and organized previous statement on cells
into one theory, which states:
1 - Cells are organisms and all organisms consist of one or more
cells
2 - The cell is the basic unit of structure for all organisms
1840 – WHERE DOES LIFE COME FROM?
Albrecht von Roelliker discovers that sperm and eggs are also cells.
1845 – BASIC UNIT OF LIFE
Carl Heinrich Braun reworks the cell theory, calling cells the basic
unit of life.
1855 –
RD
3
PART OF THE CELL THEORY ADDED
Rudolf Virchow, a German physiologist/physician/pathologist
added the 3rd part to the cell theory. The original is Greek, and
states Omnis cellula e cellula. This translates as all cells develop
only from existing cells. Virchow was also the first to propose that
diseased cells come from healthy cells.
COMPONENTS OF BASIC CELL THEORY
1. All organisms are composed of one or more cells.
(Schleiden & Schwann)(1838-39)
2. The cell is the basic unit of life in all living things.
(Schleiden & Schwann)(1838-39)
3. All cells are produced by the division of preexisting cells.
(Virchow)(1858)
MODERN CELL THEORY
Modern Cell Theory contains 4 statements, in addition to the original Cell
Theory:
- The cell contains hereditary information (DNA) which is passed on from cell to
cell during cell division.
- All cells are basically the same in chemical composition and metabolic
activities.
- All basic chemical & physiological functions are carried out inside the
cells.(movement, digestion,etc)
- Cell activity depends on the activities of sub-cellular structures within the
cell(organelles, nucleus, plasma membrane)
SINGLE OR MULTI-CELLED ORGANISMS
PROKARYOTES
a microscopic single-celled organism that
has neither a distinct nucleus with a
membrane nor other specialized
organelles.
Prokaryotes include the bacteria
DNA is free-floating in the cell
Move thorough the use of flagella (tail) or
cilia (little hairs)
TYPES OF PROKARYOTES
Paramecium
Euglena
Amoeba
EUKARYOTES
A eukaryote is any organism whose cells
contain a nucleus and other organelles
enclosed within membranes
Are usually part of a greater organism
DNA found in nucleus
Not known to move by themselves
ORGANELLES
Means “little organ” and
refers to a specialized cell
part
Found only in eukaryotic
cells
CELL MEMBRANE
Two main purposes:
1. Boundary of the cell
2. Facilitates passage of
items in and out of the
cell
NUCLEUS
Control center of the cell
Location of DNA
Surrounded by a double
membrane
Easiest organelle to see under a
microscope
Usually only one per cell
Nucleolus is found inside the
nucleus and produces ribosomes
CYTOSOL
Empty space found
between the
organelles is
considered the cytosol
and is comprised of
the jelly-like substance
called the cytoplasm
CYTOSKELETON
Provides shape and
structure
Helps move
organelles around
the cell
ENDOPLASMIC RETICULUM
Also known as the “ER”
Connected to the nuclear
membrane (nucleus)
Highway of the cell
Two Parts:
1. Rough ER: studded with
ribosomes (it makes proteins)
2. Smooth ER: no ribosomes (it
makes lipids)
RIBOSOMES
Site of protein synthesis
Found attached to the
rough ER and floating in
the cytosol
Produced by the nucleolus
GOLGI APPARATUS
Stores, modifies and
packages proteins
Molecules transported
to and from the Golgi
by means of vesicles
(containers or shipping
boxes)
LYSOSOMES
Garbage disposal of
the cell
Contains digestive
enzymes that break
down waste and worn
out or old cell parts
MITOCHONDRIA
Powerhouse of the cell
Site of cellular
respiration where
energy is converted
Bound by a double
membrane
Has its own DNA
CHLOROPLAST
Found only in plant cells
Contains the green pigment
Chlorophyll
Site of food (glucose)
production
Bound by a double membrane
Look like little stacks of
pancakes!
CELL WALL
Found in plant and some
bacteria cells
Rigid, protective barrier
Located outside the cell
membrane
Made of cellulose (fiber)
VACUOLES
Large central vacuole
usually in plant cells.
Animal cells have many
smaller vacuoles called
vesicles.
Storage container for water,
food, enzymes, wastes, etc.
TAXONOMY
Usually Unicellular
ARCHAEA
Cell Walls
Autotroph &
Heterotroph
“Extremophiles”