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THE DISCOVERY OF THE CELL

• It was not until the mid-1600’s

that scientists began to use

microscopes to observe cells.

• In 1665, Englishman Robert

Hooke used an early compound

microscope to look at a slice of

cork, plant material.

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CORK CELLS

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• Hooke saw thousands of empty chambers

which he called cells. They reminded him

of a monastery’s tiny rooms, which were

called cells.

• In Holland around the same time, Anton

van Leeuwenhoek used a single-lens

microscope to observe pond water and

other things.

• He discovered that living things seemed to

be everywhere, even in the water he was

drinking.

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Paramecium

Spirogyra

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THE CELL THEORY

• In 1838, German botanist

Matthias Schleiden concluded

that all plants were made of cells.

• In 1839, German biologist

Theodor Schwann stated that all

animals were made of cells.

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• In 1855, German physician

Rudolf Virchow concluded that

new cells could be produced only

from the division of existing cells.

• These discoveries, confirmed by

other biologist, are summarized

in the cell theory.

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• CELL THEORY STATES…

1. All living things are composed of

cells.

2. Cells are the basic units of

structure and function in living

things.

3. New cells are produced from

existing cells.

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THE CHANGE OF THE

MICROSCOPE

• Hooke, Virchow, and others

used crude microscopes to study

the cells.

• Today scientist can use a variety

of different techniques.

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• High resolution video to make

movies of cells as they grow.

• Transmission electron

microscope

–electrons pass through thin slices of

cell parts

–Cells must be dead and in a

vacuum

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CONFOCAL

LIGHTTEM

TEM

CHLOROPLAST

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• Scanning electron microscope

–produces three-dimensional images

of cells

–Do not have to cut cells into slices

–Vacuum

TEM is more powerful than SEM

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MARINE DIATOM

SEM

pea weevil egg

SCANNIING

ELECTRON

MICROSCOPE

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White pine sheath mite

on eastern white pine Scanning electron microscope

image of white pine sheath mite

24Sheet metal as seen with an SEM

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PROKARYOTES and

EUKARYOTES

• Cells fall into two categories, depending on whether they contain a nucleus.

1. Eukaryotes (YOUkaryotes)-have a nucleus.

2. Prokaryotes (Pro=NO)-

no nucleus.

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PROKARYOTIC CHARACTERISTICS

• Smaller than eukaryotic cells

• Genetic information is not contained by a

nuclear membrane

• NO internal membranes

• Less complex compared to eukaryotic

cells

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• Some glide and swim through

liquids.

• Forms of locomotion are:

• Cilia – hair like structures

• Flagella – whip like structure.

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Example of Prokaryotes: Bacteria

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EUKARYOTIC CHARACTERISTICS

• Larger than prokaryotes

• They usually contain dozens of structures

and internal membranes = organelles

• Genetic info is carried by a nucleus.

• Some live solitary lives while other form

large multicellular organisms.

• Examples: plants, animals, fungi, and

protist.

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PARTS OF THE CELL

• Cell biologists divide eukaryotic cell into two parts: the nucleus and the cytoplasm.

• The cytoplasm is the portion of the cell that is outside the nucleus. (includes the organelles)

• Cytosol = is the internal fluid of the cell, and a large part of cell metabolism occurs here

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THE NUCLEUS• The nucleus is the control center

of the cell.

• It contains the cell’s DNA and the

code for making proteins and

other important molecules.

• The nucleus is surrounded by a

nuclear envelope composed of

two membranes.

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• The envelope is dotted with

thousands of pores, which allow

materials to leave the nucleus to

other parts of the cell.

• Inside of the nucleus is a granular

material called chromatin.

• Chromatin consists of DNA

bound to protein (histones).

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Structure of DNA

• http://www.johnkyrk.com/chromosomestru

cture.html

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• When a cell divides, the chromatin condenses to form chromosomes.

• These are the distinct structures that are passed from cell to cell…generation to generation.

• Deep inside the nucleus is the nucleolus which is where assembly of ribosomes begins.

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? QUESTION ?

• WHAT KIND OF INFORMATION IS

CONTAINED IN CHROMOSOMES ?

• ANSWER: Genetic Information known

as DNA

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RIBOSOMES

• One of the most important jobs

carried out in the cell is making

proteins.

• Proteins are assembled in

ribosomes.

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• Ribosomes are small particles of

RNA and protein found

throughout the cell (mostly

cytoplasm).

• Ribosomes produce proteins by

following coded instructions that

come from the nucleus.

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? QUESTION ?

• WHAT DO RIBOSOMES

PRODUCE ?

• ANSWER: PROTEINS

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ENDOPLASMIC RETICULUM

• The endoplasmic reticulum also

known as ER. It is the site where

lipid components of the cell

membrane are assembled, along

with proteins and other materials.

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• The portion of the ER involved in synthesis of proteins is called Rough ER.

• Rough ER = ribosomes found on the surface.

• Newly made proteins leave ribosomes and are inserted into the Rough ER, where they can be chemically modified.

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• There are other portions of the

ER called Smooth ER because

no ribosomes are embedded.

• Smooth ER contains enzymes

that synthesize lipids and the

detoxification of drugs. (liver cells

contain a lot of Smooth ER)

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? QUESTION ?

• WHAT IS THE ROLE OF THE

Rough ER ?

• ANSWER: to synthesize proteins

& chemically modify them

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GOLGI APPARATUS

• The Golgi Apparatus receives

proteins from the Rough ER.

• The job of the Golgi Apparatus is

to modify, sort, and package

proteins for storage or secretion

outside the cell.

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• The Golgi Apparatus is like a

customizing shop that puts on the

final touches before proteins are

shipped out.

• It is also like the UPS of the cell.

It doesn’t make anything, but it

sorts and packages items.

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Golgi Animation

• http://www.johnkyrk.com/golgiAlone.html

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? QUESTION ?

• WHAT IS THE ROLE OF THE

GOLGI APPARATUS ?

• ANSWER: It modifies, sorts, and

packages proteins, lipids, and

other materials/chemicals.

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VACUOLES

• Vacuoles are saclike structures that store materials such as water, salts, proteins, and carbohydrates in all organisms.

• Plant cells have vacuoles. They help each cell maintain water pressure to hold up heavy structures such as leaves and flowers.

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• Central Vacuole = holds water and waste materials for plants

• Some single-celled organisms & plants have contractile vacuoles which regulates the water inside the cell.

• Contractile vacuoles help cells maintain Homeostasis or “internal balance”

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? QUESTION ?

• WHAT IS THE ROLE OF A

VACUOLE ?

• ANSWER: They store materials

and help plants maintain their

structure

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LYSOSOMES

• Lysosomes are the clean up

crew of the cell.

• They are small organelles filled

with enzymes that break down

and digest lipids, carbohydrates,

and proteins.

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? QUESTION ?

• WHAT IS THE ROLE OF THE LYSOSOME ?

• ANSWER: clean up the cell and get rid of material & breaks down lipids, carbohydrates, and proteins

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CELLS AND THEIR POWER

• Nearly all eukaryotic cells,

including plants contain

Mitochondria.

• Mitochondria are organelles that

convert the chemical energy

stored in food into compounds

that are more convenient.

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• In humans, all or nearly all our

mitochondria come from the

cytoplasm of the ovum, or egg

cell.

• In plants, chloroplasts are the

organelles that capture the

energy from the sunlight and

convert it into chemical energy in

a process called photosynthesis.

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• Both mitochondria and

chloroplast are the only

organelles that have small DNA

molecules.

• Scientist have evidence that these

two organelles may have been

descendants of ancient

prokaryotes at one time.

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CYTOSKELETON

• The cytoskeleton is a network of

protein filaments that help the cell

maintain its shape.

• Microfilaments and Microtubules

make up the cytoskeleton.

• Microfilaments are threadlike made

of a protein called actin.

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• Microtubules are hollow

structures that are made up of

proteins called tubulins.

• In animal cells, tubulin helps in

the development of centrioles.

• Centrioles are located near the

nucleus and help in cell division.

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• Cell membrane = phospholipid

double layer with protein,

carbohydrates, and other

molecules embedded.

• Cell wall (plants, fungus, and

some protists) = tough outer

covering

–Plants – made of cellulose

–Fungus – made of chitin

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