Cellular Organization

Characteristics of lifeAll organisms (uni- & multicellular) carry out the same

functions of life:

1) All life is made of cells.2) Reproduction: life comes from life (biogenesis).

3) Heredity directed by DNA: growth & development.

4) Metabolism: energy utilization and transformation.

5) Homeostasis: maintenance of steady-state conditions.

6) Response to stimuli: organisms sense and react to their environment.

7) Evolutionary adaptation: life changes in response to

interactions between organisms and environment.

Cell theory

Robert Hooke first described cells in 1665 using a microscope he made himself.

Cell theory

The cell theory has developed since Robert Hooke’s work beginning in 1665.

There are three components:All organisms are composed of one or more cells;Cells are the smallest units of life;All cells come from pre-existing cells.

Evidence for the cell theory

1) All organisms are com- posed of one or more cells:

Hooke’s observations of cork cells in 1665:

Hooke coined the term “cell”, since the com-partments reminded

him of the rooms (or cells) of monks.

Evidence for the cell theory

1) All organisms are composed of one or more cells:

Antonie van Leeuwenhoek observed the first living

cells (the alga Spirogyra) in the 1670s.

Evidence for the cell theory

1) All organisms are composed of one or more cells:

In 1838 Mathias Schleiden observed that plants are made of cells.

Evidence for the cell theory

1) All organisms are composed of one or more cells:

In 1839 Theodor Schwann observed that animals are made of cells.

http://www.youtube.com/watch?v=dscY_2QQbKU

Evidence for the cell theory

2) Cells are the smallest units of life:To date, no one has found a living thing on Earth that is not made of at least one cell.

But viruses are not made of cells. Are they alive?

Bacteriophages infecting a bacterium

Evidence for the cell theory

3) All cells come from pre-existing cells. Spontaneous generation is the idea that life can be generated from non-living matter.

The concept goes back to Aristotle ~330 BC; if meat were left out, maggots would appear in a few days. Francesco Redi disproved this in 1668.

Maggot eggsseen on cloth

The size of cells and other things

Although cells can be seen with a light microscope, viruses are too small to be seen that way.

The electron microscope bounces electrons off targets, so smaller things can be seen.

The size of things

The electron microscope

The size of things

The electron microscope shows the relative sizes of molecules, cell membrane thickness, and viruses.

Molecules from 1 nm Membranes about 10 nm

The size of things

Viruses: up to 100 nm

HIV budding from infected cell

Bacteriophage

Tobacco mosaic virus

The size of things

But cells and most organelles can be seen with the light microscope.

Cells are up to 100 μm(100 micrometers).Organelles up to 10 μm.

Chloroplast

Calculating magnification

Images must contain a scale bar to indicate size.

Scale is indicated on photo or in text.Multiply to find the actual size of material.

From text, bar = 1 micron, so width of strand = 2 x 1 = 2 μm.

Photo states bar = 20 nm, so lengthof molecule = 8 x 20 = 160 nm.

The size of life

A comparison of sizeshttp://www.cellsalive.com/howbig.htm

Limits to cell size

Why are cells so small?As a cell increases in size,

volume increases faster than surface area. Smal-ler cells have a greater ratio of surface area/volume .Cube a Cube b Cube c

Emergent properties of multicellular organisms

New properties emerge in multicelled organisms.

Differentiation allows for specialization of cells.

for digestion, reproduction, sensing the environment, etc.

Cell differentiation

Multicellular organisms differentiate to carry out specialized func- tions by expressing some of their genes but not others.

*After birth many genes are “turned off” permanently.

*Think how puberty causes new developments to occur

that were not therepreviously - other DNA is “turned on”.

Cell differentiation

Some cells retain the capacity to divide, as well as their ability to differentiate.

Example: cuttings from plants produce whole plants.

Stem cells

Stem cells retain the capacity to divide and have the ability to differentiate along different

pathways.One type (em-bryonic stem

cells) must beharvested from aborted embryos.

Stem cellsAdult (somatic) stem cells are unspecialized cells that are found in different parts of the body (like bone marrow).

Umbilical cord blood from newborns also has a potential for the harvesting of stem cells.

Stem cells

Therapeutic uses of stem cells:

Cellular Organization

Prokaryotes

Objectives

2.2.1 – Draw & label a diagram of Escherichia coli (E. coli) as an example of a prokaryote.

2.2.2 – Annotate the diagram from 2.2.1 with the functions of each named structure.

2.2.3 – Identify structures from 2.2.1 in electron micrographs of E. coli.

2.2.4 – State that prokaryotes divide by binary fission.

Prokaryotic cells

Prokaryotes are in the kingdoms Archaebacteria and Eubacteria.

Unicellular bacteria.No membrane-boundorganelles.DNA is not separated

from cytoplasm (no nucleus).

Usually very small in size (~1 μm).

(Bacteria on a pinhead)

Prokaryotic cells

An example of a prokaryote is Escherichia coli (E. coli), a symbiotic bacterium

that lives in the human gut and helps us digest

our food.Draw & label:

No nucleus or other organelle

Escherichia coli

Functions of bacterial structuresNucleoid (or chromosome): the structure of DNA that contains the

heredity of the bacterial life.

Escherichia coli

Functions of bacterial structuresRibosomes: granules of RNA that translate the original DNA code into protein.

Escherichia coli

Functions of bacterial structuresPlasma membrane: a lipid bilayer with proteins re- sponsible for transport of ions, nutrients & waste.

Escherichia coli

Functions of bacterial structuresCell wall: A barrier of sugars and proteins (peptido- glycan) that produces the shape of the bacterium.

2 types – Gram pos.

(purple)

Gram neg. (pink)

Escherichia coli

The Gram stain is a way to partially identify bacteria based upon their cell wall characteristics.

E. coli are gram negative bacilli (left below).

Gram negative Gram positive

Prokaryotic cells

Shapes of bacteria:coccus (2 cocci) – roundbacillus (2 bacilli) – rodspirillum (2 spirilla) - spiral

Staphylo- = grapeStrepto- = chainDiplo- = pair

Prokaryotic cellsElectron micrographs of E. coli

show more detail than is possible with a light micro-

scope.

Prokaryotic cell division

Prokaryotes divide by binary fission.

The cell grows, DNA is copied, then it splits into 2 daughter cells.

Cellular Organization

Eukaryotes

Objectives

2.3.1 – Draw and label a diagram of the ultra-structure of a liver cell as an

example of an animal cell.

2.3.2 – Annotate the diagram from 2.3.1 with the functions of each named structure.

2.3.3 – Identify structures from 2.3.1 in electron micrographs of liver cells.

Eukaryotic cellsEukaryotes are found in the kingdoms Protista,

Fungi, Plantae, and Animalia.Cells are subdivided by internal membranes into compartments called organelles.The DNA is segregated inside a nucleus.They are ~1000 times bigger than prokaryotes.

Unicelluler eukaryotes (protists)Single cells and colonies

Giardia (l) &Trichomonas

Diatoms (l)& Volvox

Multicellular eukaryotes

Top left – human cheek cellsTop right – fungal cellsBottom – plant cells

Eukaryotic cells

Unlike prokaryotes, eukaryotes have a nucleus and other organelles.

All cells have: cell membrane, cytoplasm, & ribosomes.

All cells have: cell membrane, cytoplasm, & ribosomes.

Eukaryotic cells

A comparison of animal cells and plant cells

(Things in magenta areunique to that type of cell.)(Things in magenta areunique to that type of cell.)

AnimalAnimalcellcell

PlantPlantcellcell

Eukaryotic cell

The cell membrane separates a living cell from its nonliving surroundings.

A mosaic of proteins in two layers of fatty material.8 nm thick; controls traffic into and out of the cell.Selectively permeable: only certain substances pass.

Eukaryotic cells

The cytoplasm is everything inside the cell membrane

The cytosol is the watery solution alone.

Cytoplasm

Eukaryotic cell

The nucleus contains most of the genes in a eukaryotic cell (some are located

in mitochondria and chloroplasts).

Control center for the cell.The nucleolus man-

ufactures parts to make ribosomes.

Nuclear pores allowmaterials to exit.

Eukaryotic cells

Ribosomes build a cell’s proteins.Ribosomes are made of RNA and protein.Cells that make more proteins have more ribosomes.

Eukaryotic cells

Ribosomes build a cell’s proteins.Proteins form as the ribosome translates a piece of messenger RNA.

Eukaryotic cells

The endoplasmic reticulum manufactures membranes and performs many other

biosynthetic functions.Continuous with the nuclear envelope.

Two regions:Smooth ER lacks ribo-somes; rich in enzymes

that synthesize lipids.Rough ER has ribosomes

attached to the outside.abundant in cells that secrete proteins.

Eukaryotic cells

The Golgi apparatus finishes, sorts, and ships cell products.

Many vesicles from the ER travel to the Golgi apparatus for modifica-tion of their contents.The Golgi is a center of manufacturing, ware-housing, sorting, and shipping.The Golgi apparatus is extensive in cells spe-cialized for secretion.

Eukaryotic cells

Lysosomes are digestive compartments in animal cells

A membrane-bound sac ofenzymes that digests large molecules.

The enzymes work best at pH 5.

Recycle protein, fat, poly-sacharide, nucleic acids.Rupturing lysosomes can autodigest a cell, called autophagy.

Eukaryotic cells

Mitochondria are the powerhouses of the cell.The number of mitochondria (100s or 1000s) is greater in cells with more metabolic activity.They have a smooth

outer membrane, and a highly folded

inner membrane with all of the

enzymes neededto make ATP.

Typically 1-10 μm.Contain DNA;

self-reproducing.

Plant cells vs. animal cells

Plant cells vs. animal cells

Differences between plant & animal cells:The plant cell wall.

Contains cellulose and other polysaccharides.A plant’s cell wall provides rigidity against water loss.

Plant cells vs. animal cells

Differences between plant & animal cells:Chloroplasts contain the green pigment chlorophyll.

They have a double membrane system that contains the enzymes for photosynthesis.They can reproduce themselves by pinching in two.Measure ~2μm by ~5μm.

Plant cells vs. animal cells

Differences between plant & animal cells:Vacuoles store water,

proteins, inorganic ions, metabolic by-

products, pigments, and

compounds that defend against her- bivores.

Plant cells vs. animal cells

A final comparison of animal cells and plant cells

(Organelles in magenta areunique to that type of cell.)(Organelles in magenta areunique to that type of cell.)

AnimalAnimalcellcell

PlantPlantcellcell

Definition of a cellSo what is a cell?

Cells are the smallest unit of life, containing a membrane that encloses cytoplasm with DNA and all the machinery for reproduction, metabolism, heredity, homeostasis, response to stimuli, and the ability to evolve.