AP Biology The Cell Theory AP Biology Some Random Cell Facts The average human being is composed of around 100 Trillion individual cells!!! It would.

AP Biology

The Cell Theory

AP Biology

Some Random Cell Facts The average human being is composed

of around 100 Trillion individual cells!!! It would take as many as 50 cells to

cover the area of a dot on the letter “i”

WOW!!!

AP Biology

Discovery of Cells 1665- English Scientist, Robert Hooke,

discovered cells while looking at a thin slice of cork.

He described the cells as tiny boxes or a honeycomb

He thought that cells only existed in plants and fungi

AP Biology

Anton van Leuwenhoek 1673- Used a handmade microscope to observe

pond scum & discovered single-celled organisms He called them “animalcules”

He also observed blood cells from fish, birds, frogs, dogs, and humans

Therefore, it was known that cells are found in animals as well as plants

AP Biology

150-200 Year Gap??? Between the Hooke/Leuwenhoek

discoveries and the mid 19th century, very little cell advancements were made.

This is probably due to the widely accepted, traditional belief in Spontaneous Generation.

Examples:

-Mice from dirty clothes/corn husks

-Maggots from rotting meat

AP Biology

19th Century Advancement Much doubt existed around Spontaneous

Generation Conclusively disproved by Louis Pasteur

Pasteur: Ummm, I don’t think so!!!

+

=?

AP Biology

Development of Cell Theory 1838- German Botanist, Matthias Schleiden,

concluded that all plant parts are made of cells

1839- German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.

AP Biology

Development of Cell Theory 1858- Rudolf Virchow, German physician,

after extensive study of cellular pathology, concluded that cells must arise from preexisting cells.

AP Biology

The Cell Theory Complete The 3 Basic Components of the Cell

Theory were now complete: 1. All organisms are composed of one or

more cells. (Schleiden & Schwann)(1838-39) 2. The cell is the basic unit of life in all living

things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of

preexisting cells. (Virchow)(1858)

AP Biology

Modern Cell Theory Modern Cell Theory contains 4 statements, in

addition to the original Cell Theory: The cell contains hereditary information(DNA)

which is passed on from cell to cell during cell division.

All cells are basically the same in chemical composition and metabolic activities.

All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc)

Cell activity depends on the activities of sub-cellular structures within the cell(organelles, nucleus, plasma membrane)

AP Biology

How Has The Cell Theory Been Used?

The basic discovered truths about cells, listed in the Cell Theory, are the basis for things such as: Disease/Health/Medical Research and Cures(AIDS,

Cancer, Vaccines, Cloning, Stem Cell Research, etc.)

It’s all about:Surface Area-to-Volume Ratio

Cell radius (r) 1 unit 10 unitsSurface area (4╥r2) 12.57 units2 1257 units2

Volume (4/3╥r3) 4.189 units3 4189 units3

Large Cells

vs.

Small Cells

Why Are Cells So Small?Size Matters!

As a cell get larger, its volume increases at a faster rate than its surface area!SA/V= 2.98 0.30

______ ______

AP Biology

Archaebacteria&

Bacteria

Classification Old 5 Kingdom system

Monera, Protists, Plants, Fungi, Animals

New 3 Domain system reflects a greater

understanding of evolution & molecular evidence Prokaryote: Bacteria Prokaryote: Archaebacteria Eukaryotes

Protists

Plants

Fungi

Animals

Prokaryote

Eukaryote

AP Biology

KingdomProtist

KingdomFungi

KingdomPlant

KingdomAnimal

KingdomArchaebacteria

KingdomBacteria

AP Biology 2007-2008

Prokaryotes

Domain Bacteria

Domain Archaebacteria

DomainBacteria

DomainArchaea

DomainEukarya

Common ancestor

AP Biology

Bacteria live EVERYWHERE! Bacteria live in all ecosystems

on plants & animals in plants & animals in the soil in depths of the oceans in extreme cold in extreme hot in extreme salt on the living on the dead

Microbes alwaysfind a way to

make a living!

AP Biology

Bacterial diversityrods and spheres and spirals… Oh My!

AP Biology

Prokaryote Structure Unicellular

bacilli, cocci, spirilli

Size 1/10 size of eukaryote cell

1 micron (1um)

Internal structure no internal compartments

no membrane-bound organelles only ribosomes

circular chromosome, naked DNA not wrapped around proteins

prokaryotecell

eukaryote cell

AP Biology 2007-2008

Eukaryotes

Domain Eukarya

DomainBacteria

DomainArchaea

DomainEukarya

Common ancestor

AP Biology

Eukaryote Structure Unicellular or Multicellular

Plant, animal, fungi, protist

Size 10X larger than a prokaryote cell

10-100 micron (1um)

Internal structure Far more complex (compartmentalized)

nucleus containing DNA other membrane-bound organelles ribosomes (no membrane)

Linear chromosome wrapped around proteins

prokaryotecell

eukaryote cell

AP Biology

Prokaryote vs. Eukaryote Chromosome

double helix

Prokaryote

Eukaryote

AP Biology

Variations in Cell Interior

internal membranesfor photosynthesislike a chloroplast(thylakoids)

internal membranesfor photosynthesislike a chloroplast(thylakoids)

internal membranes

for respiration

like a mitochondrion

(cristae)

internal membranes

for respiration

like a mitochondrion

(cristae)

aerobic bacterium

mitochondria

cyanobacterium(photosythetic) bacterium

chloroplast

AP Biology

Prokaryote Cell Wall Structure

peptide sidechains

cell wallpeptidoglycan

plasma membrane

protein

Gram-positive bacteria

Gram-negative bacteria

peptidoglycan

plasmamembrane

outermembrane

outer membrane of lipopolysaccharides

cell wall

peptidoglycan = polysaccharides + amino acid chainslipopolysaccharides = lipids + polysaccharides

That’simportant foryour doctorto know!

AP Biology

Prokaryotic metabolism How do bacteria acquire their energy &

nutrients? photoautotrophs

photosynthetic bacteria chemoautotrophs

oxidize inorganic compounds nitrogen, sulfur, hydrogen…

heterotrophs live on plant & animal matter decomposers & pathogens

AP Biology

Genetic variation in bacteria Mutations

bacteria can reproduce every 20 minutes binary fission

error rate in copying DNA 1 in every 200 bacteria has a mutation you have billions of E. coli in your gut!

lots of mutation potential!

Genetic recombination bacteria swap genes

plasmids small supplemental

circles of DNA

conjugation direct transfer of DNA

conjugation

AP Biology

Bacteria as pathogens Disease-causing microbes

plant diseases wilts, fruit rot, blights

animal diseases tooth decay, ulcers anthrax, botulism plague, leprosy, “flesh-eating” disease STDs: gonorrhea, chlamydia typhoid, cholera TB, pneumonia lyme disease

AP Biology

Bacteria as beneficial (& necessary) Life on Earth is dependent on bacteria

decomposers recycling of nutrients from dead to living

nitrogen fixation only organisms that can fix N from atmosphere

needed for synthesis of proteins & nucleic acids plant root nodules

help in digestion (E. coli) digest cellulose for herbivores

cellulase enzyme

produce vitamins K & B12 for humans

produce foods & medicines from yogurt to insulin

AP Biology

How big are cells?

Microscopic (mostly)

Measured in microns µm

(micrometers).

A µm is one millionth of a meter =

10-9 m = one thousandth of 1 mm.

AP Biology

How big are cells?

Smallest free-living cell = Mycoplasma genitalium

Size = 0.2 to 0.3 µm

AP Biology

How big are cells? Bacteria e.g. Eschericia coli (aka

E.coli) Size=1 µm by 3 µm

AP Biology

How big are cells? Human red blood cell = 8 µm in

diameter

AP Biology

How big are cells?

Largest cell on the human body =

ovum Size= 1000 µm in

diameter

(1 mm)

AP Biology

How big are cells? Smallest cell in the human body =

sperm cell.

AP Biology

How big are cells?

Largest cell with a metabolism =

Chaos chaos

Size=1-5 mm in length.

common name =

Giant Amoeba

Chaos diffluens, is an amoeba closely related to the giant amoebae

AP Biology

How big are cells? Largest cell = yolk of an ostrich egg

AP Biology

Ostrich, egg, humans

AP Biology

Ostrich emerged from egg

AP Biology

How can we study cells?

Problem:

They are microscopic!

Solution:

Use a microscope!

AP Biology

Types of Microscopes

1. Compound light microscope

Light passes through lenses to magnify image up to 1000X

Can observe living cells

AP Biology

Types of Microscopes

2. Electron microscope

Uses a beam of electrons to magnify image

> 1000X Kills cells being

observed