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Part 1: The Cell Theory

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The Discovery of the Cell

In 1665, Robert Hooke used an early microscope to look at a thin slice of cork, a plant material.

Cork looked like thousands of tiny, empty chambers.

Hooke called these chambers “cells.” (THINK PRISON CELLS)

Cells are the basic units of life.

Hooke’s Drawing of Cork Cells

• Anton van Leeuwenhoek used a microscope to observe tiny organisms (microorganisms) in pond water

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The Cell Theory

In 1838, Matthias Schleiden concluded that all plants were made of cells.

In 1839, Theodor Schwann stated that all animals were made of cells.

These conclusions led to the first two parts of the cell theory:

1) All living things are composed of cells

2) Cells are the basic unit of structure and function in living things

The Cell Theory

In 1855, Rudolph Virchow concluded that new cells

were created only from division of existing cells.

This led to the third part of the cell theory:

3) New cells are produced from existing cells

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Exploring the CellElectron Microscopes

Electron microscopes reveal details 1000 times smaller than those visible in light microscopes.

Electron microscopy can be used to visualize only nonliving, preserved cells and tissues.

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Exploring the CellTransmission electron microscopes (TEMs)

• Used to study cell structures and large protein molecules

• Specimens must be cut into ultra-thin slices

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Exploring the Cell

Scanning electron microscopes (SEMs)• Produce three-dimensional images of cells• Specimens do not have to be cut into thin slices

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Exploring the Cell

Scanning Electron Micrograph of Neurons

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Prokaryotes and Eukaryotes

Cells come in a variety of shapes and sizes.

2 Types: Prokaryotic and Eukaryotic

All cells:– are surrounded by a barrier called a cell

membrane.– at some point contain DNA.

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Prokaryotes and Eukaryotes

Cells are classified into two categories, depending on whether they contain a nucleus.

The nucleus is a large membrane-enclosed structure that contains the cell's genetic material in the form of DNA.

The nucleus controls many of the cell's activities. (The Brain of the Cell!)

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Eukaryotes are cells that contain nuclei.

Prokaryotes are cells that do not contain nuclei.

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What are the characteristics of prokaryotes and eukaryotes?

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Prokaryotes Prokaryotic cells have genetic material that is not contained in a nucleus.

•Prokaryotes do not have membrane-bound organelles (cell parts surrounded by membrane).

•Prokaryotic cells are generally smaller and simpler than eukaryotic cells.

•Example Organism: Bacteria

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Eukaryotes 

Eukaryotic cells contain a nucleus in which their genetic material is separated from the rest of the cell.

Eukaryotic cells generally contain dozens of cell parts (organelles) and internal membranes

They are generally larger and more complex than prokaryotic cells.

• Cells contain internal structures called organelles

• Organelles carry out specific functions for the cell (like organs in the body!)

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•Many eukaryotic cells are highly specialized (Ex: leaf cells in plants, nerve cells, muscle cells)

•Example Organisms: Plants, animals, fungi, and protists are eukaryotes.

Just for Fun

Guess the cell type for each cell:

Options are:

plant cell, neuron (nerve cell), skin cell, sperm cell, bone cell, bacterium, blood cell, muscle cell

#1 #2

#3

#4 #5

#6

#7

#8

How are Cells Different From Each Other?

1) Size

2) Shape

3) Internal Organization

Fun Fact: In the human body, there are at

least 200 different cell types!

Size

• Big Enough for the Unaided Eye?Example: Giraffe Nerve Cells (2 Meters)

• Small Enough to Need a Microscope?Examples:

1) Plant / Animal Cells (10-50 Micrometers)

2) Bacteria (0.2 Micrometers)

Shape• Remember: Form Follows Function!

Question: How does the shape of these cells help them perform their functions?

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Part 2: Eukaryotic Cell Structures

Review

• Organelle: A cell component that performs specific functions for the cell

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

• The Cytoplasm is the portion of the cell outside the nucleus.

Cytoplasm

• Definition: The region of a cell between the cell membrane and the nucleus

• Contains a variety of organelles in a jelly-like, watery fluid called the cytosol

Cell Membrane

• Also called the plasma membrane

• A barrier that surrounds the cytoplasm

• Separates the inside of cells from the outside environment

• Regulates passage of materials into and out of the cell

• Found in both plant and animal cells

Nucleus

The nucleus is the control

center of the cell.

The nucleus contains nearly all the cell's DNA and with it the coded instructions for making proteins and other important molecules.

Red = Nucleus

Green = Nucleolus

Ribosomes

One of the most important jobs carried out in the cell is making proteins.

Proteins are assembled on ribosomes.

Ribosomes are small particles of RNA and protein found throughout the cytoplasm.

Endoplasmic Reticulum• A system of

membranous tubes and sacs

• Used to make proteins and as a “highway for cell materials”

Rough ER Smooth ER

Structure Has Ribosomes No Ribosomes

Function Makes Protein Regulates calcium level in muscle,

makes steroids in glands, breaks

down toxins in liver

Golgi Apparatus

• Function: the processing and packaging organelle; works with the ER; modifies proteins to be sent out of the cell

• Structure:

1) System of membranes

2) Flattened sacs

Lysosomes• Structure: small, spherical

organelles that enclose hydrolytic enzymes within single membranes

• Function: these enzymes can digest carbs, lipids, DNA, RNA, old organelles, viruses, bacteria

• Not found in plant cells or prokaryotes

• Role of lysosomes in development?

Mitochondria

• Function: powerhouse of the cell; produces energy!

• Structure: 2 membranes, have their own DNA

• Question: In what types of cells would mitochondria be the most numerous?

Chloroplasts• Function: the organelles in a plant cell in

which the energy of sunlight is converted into chemical energy (photosynthesis)

• Structure: 2 membranes, contains DNA, chlorophyll (green color!)

Vacuole

• Found in plants and animals

• Large central vacuole in plant cells

• Function: fluid-filled organelle that stores enzymes and wastes

Cell Wall

• Not found on animal cells; on plant cells and bacteria

• Function: supports and protects the cell

• Structure: cellulose, pores

Cytoskeleton• Function: a structure to

maintain the shape and size of cells (like our skeletons!)

• Structure: a network of long protein strands located in the cytosol; 2 types

1) Microfilaments (thinner)

2) Microtubules (thicker)

Cilia / Flagella

• Structure/Function: hair-like organelles that extend from the surface of the cell, where they assist in movement

• Made of microtubules!

• Differences between cilia and flagella