1.2 Ultrastructure of Cells1.2 Ultrastructure of Cells

This electron micrograph shows the complexity of cells in the panceas

Two Fundamentally Different Cell Architectures

A prokaryotic cell

A eukaryotic cell

1.2.U1 Prokaryotes have a simple cell structure without 1.2.U1 Prokaryotes have a simple cell structure without compartmentalizationcompartmentalization

Prokaryote means “before nucleus”

http://www.wiley.com/college/boyer/0470003790/animations/cell_structure/cell_structure.htm

ProkaryoticProkaryotic

Cell wallCell wall pilipili Plasma membranePlasma membrane FlagellaFlagella Ribosomes (70 S)Ribosomes (70 S) NucleoidNucleoid

(region containing DNA)(region containing DNA)

Prokaryotic Structures & Prokaryotic Structures & FunctionsFunctions

Cell WallCell Wall protects and maintains shapeprotects and maintains shape Composed of peptidoglycan (carb-protein)Composed of peptidoglycan (carb-protein) Some have additional layer to adhere to Some have additional layer to adhere to

structures (teeth, skin)structures (teeth, skin)

Plasma MembranePlasma Membrane Controls movement of materials in and Controls movement of materials in and

outout Role in binary fissionRole in binary fission Cytoplasm is the complete interiorCytoplasm is the complete interior No compartmentsNo compartments DNA most visible structureDNA most visible structure

Prokaryotic Structures & Prokaryotic Structures & FucntionsFucntions

PiliPili These hollow, hairlike structures made of These hollow, hairlike structures made of

protein allow bacteria to attach to other cellsprotein allow bacteria to attach to other cells and specialized pili have a role in conjugationand specialized pili have a role in conjugation

FlagellaFlagella The purpose of flagella (sing., flagellum) is The purpose of flagella (sing., flagellum) is

motility.motility. Flagella are long appendages which rotate by Flagella are long appendages which rotate by

means of a "motor" located just under the means of a "motor" located just under the cytoplasmic membrane.cytoplasmic membrane.

Bacteria may have one, a few, or many Bacteria may have one, a few, or many flagella in different positions on the cell.flagella in different positions on the cell.

http://highered.mcgraw-hill.com/sites/007337525x/student_view0/exercises_35-90/bacterial_locomotion.html

Prokaryotic Structures & Prokaryotic Structures & FunctionsFunctions

RibosomesRibosomes site of protein synthesissite of protein synthesis small made up of two parts that come together, can be in small made up of two parts that come together, can be in

large numberslarge numbers 70S 70S

Note: S Svedberg unit, a measure of the rate of sedimentation in centrifugation rather than size and accounts for why fragment names do not add up (70S is made of 50S and 30S).

Prokaryotic Structures & Prokaryotic Structures & FunctionsFunctions

Nucleoid regionNucleoid region DNA in the bacterial cell is DNA in the bacterial cell is

generally confined to this generally confined to this central region. central region.

Though it isn't bounded by a Though it isn't bounded by a membrane, it is visibly membrane, it is visibly distinct from the rest of the distinct from the rest of the cell interior.cell interior.

PlasmidPlasmid

A A plasmidplasmid is a DNA molecule that is separate from, and can replicate is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double stranded independently of, the chromosomal DNA. They are double stranded and, in many cases, circular. Plasmids usually occur naturally in and, in many cases, circular. Plasmids usually occur naturally in bacteria, but are sometimes found in eukaryotic organismsbacteria, but are sometimes found in eukaryotic organisms

1.21.2.A2.A2 Pr Prokaryotes divide by binary fissionokaryotes divide by binary fission

http://www.classzone.com/books/hs/http://www.classzone.com/books/hs/ca/sc/bio_07/animated_biology/ca/sc/bio_07/animated_biology/bio_ch05_0149_ab_fission.htmlbio_ch05_0149_ab_fission.html• asexual reproduction

• semiconservative replication (unit 2.7 U1)

•2 DNA loops attach to membrane

•Membrane elongates and pinches off forming two cells

•Daughter cells are clones (genetically identical)

Drawing #1 Please complete in your Drawing #1 Please complete in your sketchbook.sketchbook.

You must be able You must be able to draw and label a to draw and label a diagram of the diagram of the ultrastructure of a ultrastructure of a prokaryotic cell prokaryotic cell based on electron based on electron micrographsmicrographs..

The organelles The organelles previously discussed previously discussed must be included in must be included in your drawing.your drawing.

Similarities Between Similarities Between Prokaryotes & EukaryotesProkaryotes & Eukaryotes

1.1. DNADNA

1.1. Plasma membrane Plasma membrane (a.k.a. “cell (a.k.a. “cell membrane”)membrane”)

3.3. CytoplasmCytoplasm

4.4. RibosomesRibosomes

DifferencesDifferencesProkaryoteProkaryote EukaryoteEukaryote1.1. DNA ring no proteinDNA ring no protein chromosomeschromosomes

2.2. DNA freeDNA free nucleusnucleus

3.3. No mitochondriaNo mitochondria mitochondriamitochondria

4.4. 70 S ribosomes70 S ribosomes 80 S80 S

5.5. No internal compartmentalizationNo internal compartmentalization organellesorganelles

6.6. Less than 10 micrometersLess than 10 micrometers greater than 10 greater than 10 micrometersmicrometers

1.2.U2 Eukaryotes have a 1.2.U2 Eukaryotes have a compartmentalized structurecompartmentalized structure

Electron micrograph of a mammalian cell

Why compartmentalize?

An idealized animal cell.

Eukaryotic cells

An idealized plant cell

Eukaryotic:Animal, algae, Eukaryotic:Animal, algae, protozoa, fungi and Plant cellsprotozoa, fungi and Plant cells

This shows the This shows the organelles of a liver organelles of a liver cellcell

Eukaryotic cells are usually 5 to 100 micrometers, nucleus is membrane bound, have membrane bound organelles

1 micrometer= 0.001mm

1nanometer= 0.001 µ m

1.2.A1 1.2.A1 Structure and function of organelles within exocrine Structure and function of organelles within exocrine

gland cells of the pancreas (animal cell) and within palisade mesophyll gland cells of the pancreas (animal cell) and within palisade mesophyll cells of the leaf (plant cell)cells of the leaf (plant cell)

Pancreas cell

Palisade mesophyll cells

The Nucleus

Two meters of human DNA fits into a nucleus that’s 0.000005 meters across!

• Generally spherical with double membrane

• Pores in membrane• Contains genetic

information in chromosomes/chromatin (DNA + histone proteins)

The MitochondrionThink of the mitochondrion as the powerhouse of the cell.

• Has a double membrane (smooth outer and folded inner)

• Folds are called cristae• Shape varies• Site of energy production (ATP) during

cellular respiration• they have their own DNA• large surface for cellular metabolism• produces and contains its own ribosomes

(70S type)• Can reproduce independently

Worn out mitochondria may be an important factor in aging

Free ribosomesFree ribosomes

Bound ribosomes are attached to another organelle called the endoplasmic reticulum and their protein products are shipped out of the cell

The Endoplasmic Reticulum (ER)

• Consists of flattened membrane sacs called cisternae

• Often located near the nucleus• 80 S ribosomes attached to

outside• Synthesizes proteins which are

transported by vesicles to the golgi apparatus before secretion out of the cell

• Pancreatic exocrine cells would have an abundance of these do to the constant production of digestive enzymes

Rough ERSmooth ER-no ribosomes-lipid synthesis- Fewer of these exist in pancreatic cells

Endoplasmic Reticulum

The Golgi collects, packages, modifies and distribute materials the cell makes (especially protein)

Golgi in the cytoplasm of a macrophage in lung tissue

• Like the ER it is composed of flattened sacs called cisternae

• However, it has no ribosomes and is often near the plasma membrane

• Cisternae are shorter and more curved than those on ER

Golgi apparatus

VesiclesVesicles

A single membrane with A single membrane with fluid insidefluid inside

Very smallVery small Used to transport Used to transport

materials outside of cellmaterials outside of cell

http://bcs.whfreeman.com/thelifewire/content/chp04/0402002.html

The Lysosome•Intracellular•arise from golgi•Spherical with a single membrane

Many diseases (e.g. Tay-Sachs) are caused by lysosome malfunction http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__lysosomes.html

Functions: Contain digestive enzymes•Breakdown ingested food•Breakdown damaged or unwanted organelles•Cell suicide (a.k.a “suicide sac”)

Stains dark in micrographs due to high concentration of enzymes

The Lysosome

This bacterium about to be eaten by an immune system cell will spend the last minutes of its existence within a lysosome.

VacuolesVacuoles

• Store food, waste, toxins, water

• Increase SA to volume ratio

• Allow plants to be rigid

Cilia and FlagellaCilia and Flagella

CiliaCiliatiny hair like projectionstiny hair like projectionscontains microtubulescontains microtubulesused to move the cell or used to move the cell or move the fluids next to the move the fluids next to the cellcell

Flagella•Thin projection from cell surface•Contains microtubules•Used for movement

Mature plant cells do not contain these structures but some plant gametes do

Lung cilia

Microtubules and CentriolesMicrotubules and Centrioles

The ChloroplastThink of the chloroplast as the solar panel of the plant cell.

Only plants and algae have chloroplasts

• Contain double membrane• same size as bacteria• Has own DNA• has 70 S ribosomes• can reproduce on own• Inside are stacks of

thylakoids (discs of flattened membrane)

• Usually oval in shape• Site of photosynthesis

(production of carbohydrates)

Starch granules maybe present if producing lots of food!

IN PLANTS NOT ANIMALS!

Granum-flattened sacs like solar panels (increase SA)

Stroma-fluid, contains enzymes and chemicals

Cell WallCell Wall

• Extracellular component not an organelle

• Secreted by all plant cells (also fungi and some protists)

• In plants it contains mostly cellulose

• Cellulose is permeable, strong and hard to digest (little maintenance required)

IN PLANTS NOT ANIMALS!

DifferencesDifferencesPlant Plant vs. vs. AnimalAnimal

Cell wall noneChloroplasts noneLarge vacuoles small or noneCarbs stored as starch glycogenNo centrosome centrosomeFixed angular shape flexible, rounded

http://library.thinkquest.org/C003763/flash/gaia1.htm

http://www.youtube.com/watch?v=LP7xAr2FDFU&feature=related

http://www.youtube.com/watch?v=GigxU1UXZXo&feature=fvwrel

Magnification- is how large the object will appear compared to its actual size

Electron MicrographsElectron Micrographs

A rat liver cell (with color enhancement to show organelles).

PerioxsomePerioxsome Similar to Similar to

lysosomes except lysosomes except peroxisomes bud peroxisomes bud off from the off from the endoplasmic endoplasmic reticulumreticulum

Have many roles Have many roles and/or involvement and/or involvement in producing bile, in producing bile, fatty acid fatty acid breakdown, breakdown, cholesterol, myelin cholesterol, myelin production, getting production, getting rid of Hrid of H22OO2 2 etc…etc…

Extracellular MatrixExtracellular Matrix-animal cells-animal cells

composed of collagen and glycoproteins (sugar and protein)composed of collagen and glycoproteins (sugar and protein)

form fibres, anchor to the plasma membrane to strengthen it,form fibres, anchor to the plasma membrane to strengthen it,

cell to cell interactioncell to cell interaction

possible altering of gene expression,possible altering of gene expression,

leads to coordination of cell actionleads to coordination of cell action

may be involved in directing stem cells,may be involved in directing stem cells,

and possibly cell migration and movementand possibly cell migration and movement

An animal cell cytoskeleton

The name is misleading. The cytoskeleton is the skeleton or scaffolding of the cell, but its also like the muscular system as well, able to change the shape of cells in a flash.

The Cytoskeleton

A Cytoskeleton Gallery

A macrophage using the cytoskeleton to “reach out” for a hapless bacterium.

The Cytoskeleton in Action

The Cytoskeleton in Action

Membrane ruffles on a crawling cell.

CentrosomeCentrosome

- usually a pair of centriolesusually a pair of centrioles-Assemble microtubules for structure and Assemble microtubules for structure and movementmovement-cell divisioncell division- higher plants produce microtubules even higher plants produce microtubules even though they do not have centriolesthough they do not have centrioles