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Discovery of the Cell
Robert Hooke: 16651stperson to see a cell
Used a microscope to
look at a piece of cork
Saw small, empty
“boxes”which reminded
him of the small rooms
monks lived in called
cells.
These “cells”weren’t
alive.
From Robert Hooke's
Micrographia (1667 ed.).
National Library of Medicine
1st Living Cells
Anton van Leeuwenhoek
1st person to see and
describe living cells: 1673
Made his own microscopes
Could magnify 200 times!
Described the things he
observed as “Animalcules”
Wrote many description of
his discoveries to the Royal
Society in LondoMany of
his drawings and
descriptions are very
accurate even today
Cell Theory Developement
From the 1stobservation of the cell by Hooke and
Leeuwenhoek it took 150 years to develop a theory that
explained them.
A lot of reasons for the length of time.
Not many people had access to microscopes.
Problems with making lenses.
Previous knowledge/thoughts about where life came from
(spontaneous generation).
Development of technology to make lenses allowed for more
people to study cells.
The Cell Theory
 1.All Living things contain a cell or cells.
 2.Cells are the basic unit of structure and function of life
 Anything smaller than a cell can’t be alive
 3.Cells come only from other cells.
 Disproved spontaneous generation.
Two Basic Types of Cells
Prokaryotes
&
Eukaryotes
PROKARYOTIC CELLS
 Only Unicellular (Single Celled)
 DO NOT have a NUCLEUS
 Examples include:
 The Kingdom Monera – Bacteria Only
PROKARYOTIC CELLS
 DO NOT have a NUCLEUS
 DO NOT have membrane bound
organelles
Information about Prokaryotics
 Important Facts
 Evolved 4 billion years ago
 No membrane bound nucleus or organelles
 Some have flagella – whip like tail
 Some have cilia – short, hair like extension
 Pro = Before Karyon = Nucleus
Eukaryotic Cells
 Only Unicellular or Multicellular
 DO HAVE a NUCLEUS
 Examples include:
 The Kingdom Protista, Fungi, Plantae, and
Animalia
Eukaryotic Cell
Information about Eukaryotics
 Important Facts
 Evolved 3 billion years later than bacteria
 Have membrane bound nuclei and organelles
 More complex than Prokaryotes
 Some unicellular organisms can have flagella or cilia
 Eu = True
Karyon = Nucleus
There are two main types of eukaryotic
cells
animal and plant cells
What is inside of animal and plant cells?
What is inside the eukaryotic cell?
 Cell Organelles
 Organelle= “little organ”
 Found only inside
eukaryotic cells
 Everything in a cell except
the nucleus is cytoplasm
Cell Membrane
 Boundary of the cell
 Made of a phospholipid bilayer
 Part is hydrophobic (water fearing) and part is hydrophillic (water
loving)
The Nucleus
 Control center of the cell
 Contains DNA
 Surrounded by a double
membrane
 Usually the easiest
organelle to see under a
microscope
 Usually one per cell
What is inside the nuclear envelope?
Inside the Nucleus
 Chromatin
 granular material inside nucleus
 Consists of DNA bound to
proteins
 Chromosomes –
 what chromatin condenses to
form
 Contains the genetic nformation
 Nucleolus
 Small dense region where
assembly of ribosomes begins
Endoplasmic Reticulum
 A.k.a. “ER”
 Connected to nuclear
membrane
 Highway of the cell
 Rough ER: studded with
ribosomes; it makes
proteins
 Smooth ER: no ribosomes;
it makes lipids
Ribosome
 Site of protein synthesis
 Found attached to rough
ER or floating free in
cytoplasm
 Produced in the nucleolus
 Two parts to the ribsome
 Large and small subunits that
act together
 “reads” messagner RNA and
makes polypeptides (proteins)
Golgi Apparatus
 Looks like a stack of plates
 Acts like the post office of
the cell
 Modifies, stores and sorts
packages (proteins)
Lysosomes
 Garbage disposal of the cell
 Contain digestive enzymes
that break down wastes
Mitochondria
 “Powerhouse of the cell”
 Structure – organelle
with double membranes;
the inner membrane has
many folds
 Cellular respiration occurs
here to release energy for the
cell to use
 Bound by a double membrane
 Has its own unique strand of
DNA
Vacuoles
 Large central vacuole
usually in plant cells
 Many smaller vacuoles in
animal cells
 Storage center for the cell
 container for water, food,
enzymes, wastes, pigments,
etc.
Cytoskeleton
 Acts as skeleton and
muscle
 Provides shape and
structure
 Helps move organelles
around the cell
 Made of three types of
filaments
 Microtubules
 Actin filaments
 Intermediate filaments
Centriole
 Aids in cell division
 Usually found only in
animal cells
 Made of microtubules
There are additional organelles in
plant cells not found in animal cells
Chloroplast
 Found only in plant cells
 Structure – thylakoid
membranes are stacked;
they contain pigments
such as chlorophyll
 Contains the green pigment
chlorophyll
 Convert solar energy into
chemical energy through
photosythesis (makes
glucose)
 Bound by a double membrane
CHLOROPLAST
Cell Wall
 Found in plant and bacterial
cells
 Rigid, protective barrier
 Located outside of the cell
membrane
 Made of cellulose
Movement of Molecules
 Diffusion –movement of molecules from HIGH to LOW concentrations
 Does not require energy
 Osmosis – the diffusion of water
Movement through a membrane
 Facilitated diffusion -when substances move across a membrane
through specialized protein channels
Active transport
 Active
transport –
movement
of molecules
in the cell
against the
gradient
(from LOW
to HIGH)
 Requires
energy
Vocabulary to Know
Isotonic = same solute as water
Hypotonic = less solute, more wtaer
Hypertonic =more solute, less water
Concentration Determination
Molecules will move until
they are equal on each side
of the membrane
They will continue to pass
back and forth and forth
across the membrane
staying equal on both sides
hypertonic/hypotonic
solutions are determined by
comparison of solute on
each side of the membrane
Why are cells so small?
The
surface of a cell, its membrane, is the site of exchange between its
interior and its external environment. This surface must allow sufficient
exchange to support the contents of the cell. As an object increases in size its
volume increases as the cube of its linear dimensions while surface area
increases as the square. As these cubes illustrate the surface area to volume
ratio of a small object is larger than that of a large object of similar shape.
This ratio limits how large cells can be.
Cell Specialization
 Cells develop in
different ways to
perform different
tasks
 Stem cells
 Levels of
organization




Cells
Tissues
Organs
Organs systems