UNIT 1: THE CELL

Hans and Zacharias Janssen (father and son), late 16th century

- Dutch spectacle makers, inventors of the first microscope (simple, and compound). - Also associated with the invention of the first telescope.

simple (single-lens) microscope

Robert Hooke (1635-1702)

- observed cork under the microscope

- 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 (1804-1881)

- German botanist.

- Observed plants under the microscope, and concluded:

“All plants are made of cells” (1838)

Friedrich Theodor Schwann 1810-1882)

- German physiologist and anatomist.

- He studied animal tissues under the microscope, and concluded:

“All animals are made of cells” (1839)

Rudolf Carl Virchow (1821-1902)

- German doctor and pathologist.

- He studied cell reproduction andconcluded:

“All cells come from pre-existing cells”(1858)

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 PRE-EXISTING CELLS

Santiago Ramón y Cajal (1852-1934)

- 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

Levels of Organization of the Living Beings

Bulk Elements:

They form aprox. 99% of living matter

They are found in ALL living things

Trace Elements:

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

C H O N

P S

Ca Na K

Cl Fe Cu

ZnIF

The Elements of Life:

Elements in the living beings:

The Molecules of Life (Biomolecules):

WATERInorganic: (common to non-living and

living matter)

MINERALS

CARBOHYDRATES

LIPIDS (only in living matter

they all contain C)

PROTEINS

NUCLEIC ACIDS

Organic:

WATER:

Most abundant molecule in the cells.

Important biological functions:

“Universal Solvent”

Substance exchange between cell/medium,

transport, removal.

Temperature buffer: moderates the temperature changes

in the cell

MINERALS:

Present in two forms:

Precipitated (solid): bones, shells, etc.

Ions (dissolved): regulating several cellular

processes

CARBOHYDRATES (I):

- Formed by C, H and O: Cn(H

2O)

n 1: 2: 1

- Three main types:

MONOSACCHARIDES DISACCHARIDES

Sweet and soluble Sweet and soluble

Only one molecule: Two molecules of monosaccharides

Glucose

Sucrose

Lactose

Ribose

SUGARS

ENERGETIC

ENERGY STORAGE

POLYSACCHARIDES

Not sweet, not soluble

Many molecules of monosaccharides

Starch Cellulose

Chitin

STRUCTURAL

PLANTS

GlycogenANIMALS

CARBOHYDRATES (II):

LIPIDS (I):

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)

Phospholipids

Types of lipids Waxes

Terpens

Steroids

Contain FATTY ACIDS

Do NOT contain FATTY ACIDS

Fatty Acids: long chains of C, H and O

Triglicerids (fats and oils): 3 fatty acid chains attached to a glycerol molecule

They store energy.

Phospholipids: They contain P.

They constitute the cell membranes

(structural)

.

LIPIDS (II):

LIPIDS (III):

Waxes:Protect the leaves and fruits in plants, and skin, hair and feathers in

animals. (structural)

Terpenes: - Aromatic oils and pigments in plants.

- Some vitamins: A,E and K are terpenes.

Steroids:- Some vitamins: D

- Some hormones: sex hormones (testosterone, estrogens)

and other hormones (cortisone, aldosterone)

- Biliar acids

- Cholesterol

(regulatory)

(structural)

PROTEINS (I):

Formed by C, H, O, N (and S)

Long chains (polymers) of basic

units (monomers) called AMINO

ACIDS

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 tri-

dimensional structure.

PROTEINS (II):

Functions:

Structural: cell membranes, cell organelles.

Catalytic: enzymes make possible cell reactions.

Transportation of oxygen (hemoglobin) and other

substances.

Regulatory: some hormones are proteins (insulin)

Muscular contraction: actin, myosin

Defense: some proteins belong to the IS: antibodies

(energetic)

NUCLEIC ACIDS (I):

- Formed by C, H, O, N and P.

- They are chains (polymers) of basic units

(monomers) called nucleotides.

nucleotide polinucleotide

NUCLEIC ACIDS (II):

DNA (DeoxyriboNucleic

Acid)

- carries the hereditary

information of the cell

RNA (RiboNucleic Acid)

- takes the information in the

DNA and helps to make

proteins with it

Parts of a Compound Light Microscope

Prokaryotic cellNo nucleus

Circular DNA floating in the cytoplasm

No membranous organelles

Ribosomes

Mesosomes

Cell wall covering

the Cell Memebrane

Capsule

Flagellum

Eukaryotic Cell: Plant Cell

Eukaryotic Cell: Animal Cell

Influenza TMV

Bacteriophage

VirusesNot cells

DNA or RNA + protein capsid

Some have an envelope

Obligatory parasites of animals,

plants or bacteria.

Cell Membrane

A phospholipid bilayer with

proteins.

Isolates the cell and controls the

substance exchange with the

medium.

Cytoplasm

Content of the cell:

Cytosol (liquid): water and soluble substances.

Cell Organelles

Nucleus

Controls the cell activity.

Double membrane, with pores.

Nucleoplasm.

Nucleolus (RNA+proteins): where

ribosomes are formed.

Chromatin (DNA+proteins)

transforms into chromosomes

when the cell is going to divide.

Cell Wall

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.

MitochondriaDouble 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.

Chloroplasts

Only present in plant cells.

Like mitochondria, they have a double

membrane (outer and inner).

Like mitochondria, they have DNA and

ribosomes.

The inner membrane forms a system of

sacs piled up forming structures called

thylakoids. The stacks of thylakoids are

called grana.

The space inside the inner membrane is

called stroma.

They contain pigments like chlorophyll,

that make photosynthesis possible.

Endoplasmic ReticulumSystem of membranes that

extend over the cytoplasm.

Two types:

ROUGH ER: with ribosomes

attached. Produces, stores and

trasnports proteins

SMOOTH ER: no ribosomes.

Produces, stores and

transports lipids.

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

cell.

LysosomesVesicles formed in the Golgi

Complex.

They contain digestive enzymes

that break down large

molecules or cell organelles.

If they broke, the cell would be

destroyed by them.

Vacuoles

Vesicles that store substances.

Plant cells usually have 1 or 2 big vacuoles.

Animal cells have many small vacuoles.

RibosomesPresent in all types of cells (prokaryotic and eukaryotic)

Composed of RNA and proteins. Produced in the nucleolus.

Not membranous.

May be floating free in the cytoplasm or attached to the RER

They synthesize (=produce) proteins.

Cytoskeleton

Only present in animal cells.

Composed of protein filaments of two types:

Microfilaments

Microtubules

Functions:

Helps the cell to divide (mitosis)

Contraction

Cell movement (form pseudopodia)

Transport inside the cytoplasm.

Form the centriols, cillia and flagella.

Centrosome

Only present in animal cells.

Composed of two centrioles,

one perpendicular to the other.

It organizes the cytoskeleton

and helps the cell to divide

(mitotic spindle)

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

than flagella.

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)

Transport through the Cell Membrane

Cells need to exchage substances with their environment, in order to get

materials for nutrition and remove wastes.

This exchage can be:

PASSIVE:

ACTIVE:

does NOT require ENERGY

down a gradient (high to low)

requires ENERGY

up a gradient (low to high)

Passive Transport (I): DIFFUSIONSmall molecules like gases (O

2, CO

2), water, nutrients move through

the cell membrane from the area of higher concentration to the area

of lower concentration, until the gradient disappears (concentration

equals)

Permeable to the solute

Passive Transport (II): FACILITATED DIFFUSIONSome molecules need the help of a carrier, a protein in the cell

membrane, to enter or exit the cell.

Passive Transport (III): OSMOSISSpecial 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

solution.

Semi-permeable membrane

ACTIVE TRANSPORTMovement 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.