Hans and Zacharias Janssen
(father and son), late 16th century
- Dutch spectacle makers, inventors
of the first microscope (simple, and
- Also associated with the invention
of the first telescope.
Robert Hooke (1635-1702)
- observed cork under the
- used the word CELLS for the first
time, to describe the tiny, empty
chambers he saw.
Anton van Leeuwenhoek (1632-1723)
- Dutch cloth merchant.
- “father of microbiology: he used a
simple microscope to observe pond
water... and discoverd a whole new
world of living microorganisms!
- he was the first one to observe
living cells, among them: bacteria,
sperm cells, blood cells, protozoa...
Robert Brown (1773-1858)
- he discovered the cell nucleus,
in plant cells.
Matthias Jakob Schleiden
- German botanist.
- Observed plants under the
microscope, and concluded:
“All plants are made of cells” (1838)
Friedrich Theodor Schwann
- German physiologist and anatomist.
- He studied animal tissues under the microscope,
“All animals are made of cells” (1839)
Rudolf Carl Virchow (1821-1902)
- German doctor and pathologist.
- He studied cell reproduction and
“All cells come from pre-existing cells”
Louis Pasteur refuted one year later for
good the “Spontaneus Generation”
The CELL THEORY is the result of the discoveries
of Schleiden, Schwann and Virchow, and consists
on 3 principles:
ALL ORGANISMS ARE MADE OF CELLS
THE CELL IS THE BASIC UNIT OF LIFE IN ALL
LIVING THINGS (structural and functional unit)
ALL CELLS COME FROM THE DIVISION OF
Santiago Ramón y Cajal
- Spanish doctor, who
studied the Nervous System
- He proved that neurons were independent cells,
which finally confirmed the Cell Theory.
- He was awarded the Nobel Prize in
Physiology and Medicine
The Elements of Life:
C H O N
They form aprox. 99% of living matter
They are found in ALL living things
Ca Na K
Cl Fe Cu
They form <1% of living matter (if <0.1%
they are called oligo-elements
Some of them are common to all living
beings, some others are specific
The Molecules of Life (Biomolecules):
(common to non-living and
(only in living matter
they all contain C)
Most abundant molecule in the cells.
Important biological functions:
Substance exchange between cell/medium,
Temperature buffer: moderates the temperature changes
in the cell
Present in two forms:
Precipitated (solid): bones, shells, etc.
Ions (dissolved): regulating several cellular
- Formed by C, H and O:
- Three main types:
Sweet and soluble
Only one molecule:
1: 2: 1
Sweet and soluble
Two molecules of monosaccharides
Not sweet, not soluble
Many molecules of monosaccharides
All of them formed by C, H and O.
Some of them contain N and P.
None of them are soluble in water.
Triglicerids (fats, oils)
Types of lipids
Do NOT contain FATTY ACIDS
long chains of C, H and O
Triglicerids (fats and oils):
3 fatty acid chains attached to a glycerol molecule
They contain P.
They constitute the cell membranes
Protect the leaves and fruits in plants, and skin, hair and feathers in
- Aromatic oils and pigments in plants.
- Some vitamins: A,E and K are terpenes.
- Some vitamins: D
- Some hormones: sex hormones (testosterone, estrogens)
and other hormones (cortisone, aldosterone)
- Biliar acids
Formed by C, H, O, N (and S)
Long chains (polymers) of basic
units (monomers) called AMINO
There are 20 types of amino acids.
Proteins are different depending
on their sequence (order)
Proteins are folded in space. Their
function depends on this tridimensional structure.
Structural: cell membranes, cell organelles.
Catalytic: enzymes make possible cell reactions.
Transportation of oxygen (hemoglobin) and other
Regulatory: some hormones are proteins (insulin)
Muscular contraction: actin, myosin
Defense: some proteins belong to the IS: antibodies
NUCLEIC ACIDS (I):
- Formed by C, H, O, N and P.
- They are chains (polymers) of basic units
(monomers) called nucleotides.
NUCLEIC ACIDS (II):
- carries the hereditary
information of the cell
RNA (RiboNucleic Acid)
- takes the information in the
DNA and helps to make
proteins with it
DNA or RNA + protein capsid
Some have an envelope
Obligatory parasites of animals,
plants or bacteria.
A phospholipid bilayer with
Isolates the cell and controls the
substance exchange with the
Content of the cell:
Cytosol (liquid): water and soluble substances.
Controls the cell activity.
Double membrane, with pores.
Nucleolus (RNA+proteins): where
ribosomes are formed.
transforms into chromosomes
when the cell is going to divide.
Only present in plant cells.
It covers and protects the cell membrane.
It gives the cell a fixed shape.
Formed by a matrix of cellulose molecules.
Double membrane (outer and inner
The inner membrane forms cristae.
The inner space (matrix) contains
DNA and ribosomes!
They produce energy in a metabolic
process called cellular respiration.
Only present in plant cells.
Like mitochondria, they have a double
membrane (outer and inner).
Like mitochondria, they have DNA and
The inner membrane forms a system of
sacs piled up forming structures called
thylakoids. The stacks of thylakoids are
The space inside the inner membrane is
They contain pigments like chlorophyll,
that make photosynthesis possible.
System of membranes that
extend over the cytoplasm.
ROUGH ER: with ribosomes
attached. Produces, stores and
SMOOTH ER: no ribosomes.
Produces, stores and
Golgi Apparatus (or Complex)
Composed of membranous flat sacs piled
up forming stacks.
It modifies the substances that receives
from the ER, and secrets them outside the
Vesicles formed in the Golgi
They contain digestive enzymes
that break down large
molecules or cell organelles.
If they broke, the cell would be
destroyed by them.
Vesicles that store substances.
Plant cells usually have 1 or 2 big vacuoles.
Animal cells have many small vacuoles.
Present in all types of cells (prokaryotic and eukaryotic)
Composed of RNA and proteins. Produced in the nucleolus.
May be floating free in the cytoplasm or attached to the RER
They synthesize (=produce) proteins.
Only present in animal cells.
Composed of protein filaments of two types:
Helps the cell to divide (mitosis)
Cell movement (form pseudopodia)
Transport inside the cytoplasm.
Form the centriols, cillia and flagella.
Only present in animal cells.
Composed of two centrioles,
one perpendicular to the other.
It organizes the cytoskeleton
and helps the cell to divide
Cillia and Flagella
Only found in animal cells (unicellular or multicellular organisms).
Extensions of the cell membrane that are able to move.
They have the same structure, but cillia are shorter and more numerous
They allow the cells to move (protozoa, sperm cells...); they also help the
cell to capture nutrients from the environment, and move the liquids on the
surface of the cells (respiratory epithelia)
Cells need to exchage substances with their environment, in order to get
materials for nutrition and remove wastes.
This exchage can be:
does NOT require ENERGY
down a gradient (high to low)
up a gradient (low to high)
Passive Transport (I): DIFFUSION
Small molecules like gases (O2, CO2), water, nutrients move through
the cell membrane from the area of higher concentration to the area
of lower concentration, until the gradient disappears (concentration
Passive Transport (II): FACILITATED DIFFUSION
Some molecules need the help of a carrier, a protein in the cell
membrane, to enter or exit the cell.
Passive Transport (III): OSMOSIS
Special term used for the diffusion of water through a semi-permeable cell
membrane (= only allows the solvent -water – to go through it)
Water moves frome the HYPOTONIC solution to the HYPERTONIC
Movement occurs against the concentration
gradient (from low to high concentration)
A carrier protein in the membrane is required, as
well as energy.
ENDOCYTOSIS / EXOCYTOSIS
Transport of large particles through the cell membrane, using vesicles.
and requiring energy.
EXOCYTOSIS: waste products are placed in vesicles that then fuse
with the cell membrane, releasing their contents outside the cell.
ENDOCYTOSIS: the cell membrane engulfs a large molecule outside
the cell and releases it inside. There are two types of endocytosis:
PHAGOCYTOSIS: the cell takes solid food particles.
PINOCYTOSIS: the cell takes nutrients dissolved in fluids.