Cell Theory

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Cell TheoryThis theory is one of the foundations of biology.

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Antonie van LeeuwenhoekThe first man to witness a live cell under a microscope was Antonie van Leeuwenhoek, who in 1674 described the algae Spirogyra and named the moving organisms animalcules, meaning “little animals.”

In 1678, Antoni van Leeuwenhook reported that he had observed “little animals” -- protozoa -- through a microscope, he also called them “little beasties.”

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Robert HookeThe cell was first discovered by Robert Hooke in 1665. He observed dead cork (cork comes from the bark of a cork oak0 tree) and named the structures he observed “cells” which means small room.

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Theodor SchwannMatthias Jakob Schleiden Rudolf Virchow In 1839, Schwann and Schleiden suggested that cells were the basic unit of life.

In 1858, Rudolf Virchow concluded that all cells come from pre-existing cells, thus completing the classical cell theory.

Theodor Schwann, Matthias Jakob Schleiden, and Rudolf Virchow are credited with developing cell theory.

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Schwann

Schleiden

Virchow

Traditional rules of the Cell Theory 1. All life forms are made

from one or more cells.

2. Cells only arise from pre-existing cells.

3. The cell is the smallest form of life.

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Modern rules of the Cell Theory — 1

1 All known living things are made up of cells. All organisms are made up of one or more cells.

2 The cell is structural & functional unit of all living things.

3 All cells come from pre-existing cells by division. (Spontaneous Generation does not occur).

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Modern rules of the Cell Theory — 2

4 Cells contains hereditary information (DNA) which is passed from cell to cell during cell division.

5 All cells are basically the same in chemical composition.

6 All energy flow (metabolism & biochemistry) of life occurs within cells.

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Living?Characteristics of Life

HomeostasisOrganizationMetabolismGrowthAdaptationResponse to stimuliReproduceHereditary molecule is DNA

Viruses Bacteria are living organisms but

opinions vary on whether viruses are.

A virus is an organic structures that interacts with living organisms.

It does show characteristics of life such as having genes, evolving by natural selection and reproducing by creating multiple copies of themselves through self-assembly.

But viruses don't have a cellular structure or their own metabolism; they need a host cell to reproduce.

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Viruses Viruses are the smallest and

simplest life form known. They are 10 to 100 times smaller than bacteria.

Viruses must have a living host - like a plant or animal - to multiply.

Viruses are intracellular organisms (they infiltrate the host cell and live inside the cell). They change the host cell's genetic material from its normal function to producing the virus itself.

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Two basic cell typesProkaryotes

&Eukaryotes

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Two basic cell typesProkaryotes

&Eukaryotes

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ProkaryotesProkaryotesThe lack of a nucleus gives prokaryotes their name.

ProkaryotesProkaryotes

The prokaryotes are a group of organisms that lack a cell nucleus, or any other membrane-bound organelles.

They differ from the eukaryotes, which have a cell nucleus.

Most are unicellular, but a few prokaryotes such as myxobacteria have multicellular stages in their life cycles.

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Prokaryotes The prokaryotes are divided into

two domains: the bacteria and the archaea.

Archaea were recognized as a domain of life in 1990.

These organisms were originally thought to live only in inhospitable conditions such as extremes of temperature, pH, and radiation but have since been found in all types of habitats.

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Eukaryotes

Greek Meaning

eu good, noble, true

karyon nut, kernel

The presence of a nucleus gives eukaryotes their name.

Eukaryotic

A eukaryotic is an organism whose cells contain complex structures inside the membranes.

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The most important membrane-bound structure setting eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried.

Most eukaryotic cells also contain other membrane-bound organelles such as mitochondria, chloroplasts and the Golgi apparatus.

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Eukaryotic

OrganellesFound only in eukaryotic cells

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NucleusThe “control center,”

it maintain the integrity of these genes and to control the activities of the cell by regulating gene expression.

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Nucleolus

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Function:

Ribosomal RNA (rRNA) is transcribed and assembled within the nucleolus.

Cell Membrane or Plasma Membrane

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Function:

It separates the interior of a cell from the outside environment. The cell membrane surrounds all cells and it is semi-permeable, controlling the movement of substances in and out of cells.

Cell Wall

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Provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell. They are found in plants, bacteria, fungi, algae, and some archaea.

Ribosome Make proteins from amino acids.

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Vesicle

Membrane-enclosed

sac that stores or

transports substances

within a cell.

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Rough Endoplasmic Reticulum (RER)

Ribosome to bind to

the RER and pass the

new protein through

the ER membrane.

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Smooth Endoplasmic Reticulum (SER) Several metabolic processes,

including synthesis of lipids and

steroids, metabolism of

carbohydrates, regulation of calcium

concentration, drug detoxification,

attachment of receptors on cell

membrane proteins, and steroid

metabolism.

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Golgi apparatusProcesses and packages

macromolecules, such as

proteins and lipids, after their

synthesis and before they

make their way to their

destination; it is particularly

important in the processing of

proteins for secretion

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Cytoskeleton It is a dynamic structure that

maintains cell shape, protects the

cell, enables cellular motion (using

structures such as flagella, cilia and

lamellipodia), and plays important

roles in both intracellular transport

(the movement of vesicles and

organelles, for example) and cellular

division.

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Mitochondria Generate most of the cell’s supply of

adenosine triphosphate (ATP), used

as a source of chemical energy. In

addition to supplying cellular

energy, they are involved in a range

of other processes, such as signaling,

cellular differentiation, cell death, as

well as the control of the cell cycle

and cell growth.

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Vacuole The function and importance of vacuoles varies greatly

according to the type of cell in which they are present, having much greater prominence in the cells of plants, fungi and certain protists than those of animals and bacteria. In general, the functions of the vacuole include: Isolating materials that might be harmful or a threat to

the cell Containing waste products Maintaining internal hydrostatic pressure or turgor

within the cell Maintaining an acidic internal pH Containing small molecules Exporting unwanted substances from the cell Allows plants to support structures such as leaves and

flowers due to the pressure of the central vacuole

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Cytoplasm Are filled with liquid that is kept separate

from the rest of the cytoplasm by

biological membranes. The cytoplasm is

the site where most cellular activities

occur, such as many metabolic pathways

like glycolysis, and processes such as cell

division.

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Lysosome

Lysosomes digest

excess or worn-out

organelles, food

particles, and

engulfed viruses or

bacteria.

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Centrioles within Centrosome These are involved in the organization of

the mitotic spindle and in the completion

of cytokinesis (the process in which the

cytoplasm of a single eukaryotic cell is

divided to form two daughter cells).

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Chloroplasts

Chloroplasts capture light

energy to conserve free

energy in the form of ATP

and reduce NADP to

NADPH through a complex

set of processes called

photosynthesis.

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OrganellesPlantsPlants

Cell MembraneCell wallsChloroplastsVacuoles LysosomesGolgi BodiesMitochondriaEndoplasmic Reticulum

(ER)Ribosomes

AnimalsAnimals

Cell MembraneCentrioles (used in cellular

reproduction) Vacuoles LysosomesGolgi BodiesMitochondriaEndoplasmic Reticulum

(ER)Ribosomes

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Cell Theory RapListen close to the story I tell.

It’s the rapping story of the living cell.

It’s a happy tune that’s sort of cheery.

About a real tough topic called the cell theory.

All animals, plants, and protists too,

Are made of cells with different jobs to do.

They’re the basic units of all organisms,

And I hope by now you got the rhythm.

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It all started with one dude named Hooke.

Who at some cork cells took a look.

He used a scope and took his time.

‘Cause a cell is small and thinner than a dime.

Say 1, 2, 3, 4,

Are you ready to learn some more?

The animal cell has many parts,

And you must know each one by heart.

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Like the farmer man in the dell.

The nucleus controls the cell.

its gives the orders -- kind of like a brain.

And it’s protected by a nuclear membrane.

Around the cell, you’ll find another “skin,”

The cellular membrane holds the whole cell in

But its job isn’t simple there’s no doubt,

It lets some particles go in and out.

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Now please don’t lose your science enthusiasm,

Listen to the story of the cytoplasm.

All around the cell this thick fluid does go,

But in the nucleus it will not flow.

And don’t forget those ribosomes -

This is where proteins come from.

These protein factories are so small, you’ll agree,

You need an electron microscope to see.

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Just when you thought you weren’t having any fun,

Along comes teh endoplasmic reticulum.

These tubelike structures serve as a track,

To carry stuff to the membrane and back.

Now have you ever seen any doughnuts without holes?

In a cell, they’re called vacuoles.

They’re filled with stuff like H2O

And they carry food so the cell can grow.

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Las of all, but not the very least,

Mitochondria - mighty cellular beasts,

Since they turn sugars into energy so well,

We call them the powerhouse of the cell.

Now my friend, you know it well,

The unforgettable story of the living cell.

“Science World”

10-5-90

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