4

The The Characteristics Characteristics

of a Cellof a CellChapter 4Chapter 4

Section 1Section 1

Key ConceptKey Concept Cells function similarly in all living Cells function similarly in all living

organismsorganisms

So What’s a Cell?So What’s a Cell? Would you believe Would you believe

that a chicken egg or that a chicken egg or ostrich egg is a cell?  ostrich egg is a cell? 

Look at the relative Look at the relative sizes of these cells sizes of these cells (human cell is (human cell is actually much actually much smaller)smaller)

Most cells are so Most cells are so small they could only small they could only be seen with a be seen with a microscopemicroscope

CellsCells

A cell is the simplest living thing A cell is the simplest living thing that can have a "life of its own." that can have a "life of its own."

Cells were only discovered after the Cells were only discovered after the invention of the microscope in the invention of the microscope in the mid-1600smid-1600s

Scientists and CellsScientists and Cells

Robert Hooke – 1665 Robert Hooke – 1665 built a microscope to built a microscope to look at tiny objectslook at tiny objects

Saw cork (bark of Saw cork (bark of cork tree) made of cork tree) made of “little boxes” (cells)“little boxes” (cells)

He also looked at He also looked at plants, feathers, fish plants, feathers, fish scales, and housefly scales, and housefly eyeseyes

Scientists and Cells Scientists and Cells Cont…Cont…

1673 – Anton van Leeuwenhoek saw small organisms in 1673 – Anton van Leeuwenhoek saw small organisms in water (“animalcules”)water (“animalcules”)

Actually was seeing single-celled protistsActually was seeing single-celled protists Also looked at blood of different kinds of animals:Also looked at blood of different kinds of animals:

Fish, bird, frog blood cells were ovalFish, bird, frog blood cells were oval Human and dog blood cells were round and flatHuman and dog blood cells were round and flat

First person to see bacteriaFirst person to see bacteria

Contributors to the Cell Contributors to the Cell TheoryTheory

1838- Matthias 1838- Matthias Schleiden found that all Schleiden found that all plant parts were made of plant parts were made of cellscells

1839 – Theodor Schwann 1839 – Theodor Schwann found that all animal found that all animal tissues were made of tissues were made of cellscells

1858 – Rudolf Virchow 1858 – Rudolf Virchow stated that all cells could stated that all cells could only come from other only come from other cellscells

The Cell TheoryThe Cell Theory

All organisms are All organisms are made up of one or made up of one or more cellsmore cells

The cell is the The cell is the basic unit of all basic unit of all living thingsliving things

All cells come from All cells come from existing cellsexisting cells

Parts of a CellParts of a Cell Cells have different functions and come in Cells have different functions and come in

different shapes and sizesdifferent shapes and sizes ALLALL cells have some parts in common: cells have some parts in common:

Cell membrane (barrier Cell membrane (barrier between cell & between cell & environment)environment)

Cytoplasm (fluid inside)Cytoplasm (fluid inside) Organelles (“mini organs”)Organelles (“mini organs”) Genetic Material (DNA)Genetic Material (DNA)

Two Kinds of CellsTwo Kinds of Cells Cells that have a nucleus are eukaryotic Cells that have a nucleus are eukaryotic

cellscells Cells that do not have a nucleus are Cells that do not have a nucleus are

prokaryotic cellsprokaryotic cells

Prokaryotes:Prokaryotes: Eukaryotes:Eukaryotes:

Single celledSingle celled No nucleusNo nucleus DNADNA No membrane No membrane

bound organellesbound organelles RibosomesRibosomes Have strong cell Have strong cell

wallswalls Bacteria, ArchaeaBacteria, Archaea

MulticellularMulticellular NucleusNucleus DNADNA Membrane bound Membrane bound

organellesorganelles RibosomesRibosomes Some have cell Some have cell

wallswalls Plants, Animals, Plants, Animals,

Fungi, ProtozoaFungi, Protozoa

Pop QuizPop Quiz

Question: Who was the first person to see Question: Who was the first person to see bacteria?bacteria?

Answer: Anton van LeewenhoekAnswer: Anton van Leewenhoek Question: According to the cell theory, Question: According to the cell theory,

where do cells come from?where do cells come from? Answer: Other cellsAnswer: Other cells Question: What parts do all cells have in Question: What parts do all cells have in

common?common? Answer: Cell membrane, cytoplasm, Answer: Cell membrane, cytoplasm,

organelles, DNAorganelles, DNA