CellsLectures #4 & #5, Chapter 4

by John Cozza, Biology Dept.(some material modified from Raven, Biology 9th ed.)

Cells outline

• What is a cell?• Types of cells• Cytoplasm

– Cytosol – Organelles– Cytoskeleton

• Cell wall and ECM– Cell junctions

Cells outline

• What is a cell?• Types of cells• Cytoplasm

– Cytosol– Organelles– Cytoskeleton

• Cell wall and ECM– Cell junctions

What is a cell?

How did the first cell originate?

• Genetics first: RNA world

• Metabolism first• Proteins first• Membrane first• Hybrid world• Intelligent design?

http://pandasthumb.org/archives/2010/02/primordial-soup-1.html

Interactive question #1

Intelligent design is not a scientific hypothesis because it is not

A.an educated guess

B.possible

C.controversial

D.testable

One hypothesis of life’s origin…

• Micro-caves of undersea volcanic vents

• Metabolism first• Then RNA• Then proteins• Then DNA

…and the first prokaryotic

cells (bacteria &

archaea)

• Then lipids & membranes

• Then cell walls

Martin, W. and M. Russell 2003. On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells. Phil. Trans. R. Soc. Lond. B 358: 59–85.

Cell size

Cells outline

• What is a cell?• Types of cells• Cytoplasm

– Cytosol – Organelles– Cytoskeleton

• Cell wall and ECM– Cell junctions

Types of cells

Prokaryotic

Eukaryotic

Prokaryotic cell

http://classes.midlandstech.com/carterp/Courses/bio225/chap04/sld003.htm

Nitrosomonas sp. (Proteobacteria)Dirtland: http://commtechlab.msu.edu/sites/dlc-me/zoo/zdrs0232.html

Anabaena variabilis(Cyanobacteria)http://genome.jgi-psf.org/anava/anava.home.html

Some prokaryotes have internal membranes!

Prokaryotic cell

E. coliBy David GoodsellScripps Institute

Yellow = DNA, RNA, & proteinsBlue = Cytoplasmic proteinsPurple = ribosomesGreen = membranes + proteins

http://mgl.scripps.edu/people/goodsell/illustration/public

TEM of eukaryotic cell

http://www2.estrellamountain.edu/faculty/farabee/BIOBK/biobookcell2.html

Eukaryotic cell

Prokaryotic cell

Interactive question #2The definitive difference between prokaryotic and eukaryotic cells is that prokaryotes

A.are smaller

B.are pathogens

C.do not have a nucleus

D.have a cell wall

E.lack internal membranes

Eukaryotic cell sectionYellow & green = cell membrane and proteins

Blue = proteins

Blue filaments = cytoskeleton

Pink = ribosomes

Tan = mRNA, tRNA

From: Inside a Eukaryotic Cellby David GoodsellScripps Institutehttp://mgl.scripps.edu/people/goodsell/gallery/patterson.html

Eukaryotic cell sectionYellow (L) = Golgi apparatus

Yellow (R) = mitochondrion

Blue = proteins

Green = glycosylation

Blue “Buckyball” = coated vesicle

Pink = ribosomes

Tan = mRNA, tRNA

Eukaryotic cell section

Yellow = nuclear membrane

Blue = proteins

Orange “spaghetti” = mRNA being synthesized (R) and then spliced in nuclear pore (L)

Pink (R) = DNA

Origin of eukaryotic cell: endosymbiosis

fermentation

photosynthesis

respiration

Origin of the nucleus: alternative hypotheses

Martin, W. 2005. Archaebacteria (Archaea) and the origin of the eukaryotic nucleus. Current opinion in microbiology 8(6): 630-637.

Origin of the nucleus: alternative hypothesis

Margulis, L. 2000. The chimeric eukaryote: Origin of the nucleus from the karyomastigont in amitochondriate protists. PNAS 97(13): 6954-6959

According to the various hypotheses, the nucleus may have evolved from any of the following except:

A.A merger of a community of cells

B.A merger of a liposome and a chromosome

C.A spore

D.An engulfed cell

E.Infoldings of the cell membrane

Interactive question #3

Cells outline

• What is a cell?• Types of cells• Cytoplasm– Cytosol – Organelles– Cytoskeleton

• Cell wall and ECM– Cell junctions

Cytosol

• Water (~70%)• Ions• Building blocks ,

nutrients, etc.• Proteins (>20%)• Other

macromolecules• DNA (prokaryotes)

http://en.wikipedia.org/wiki/Cytosol

http://www.scripps.edu/news/scientificreports/sr2008/mb08olson.html

Cytosol:E. coli

by David GoodsellThe Machinery of LIfeFig. 4.3

Think—pair—share

What are the advantages to a eukaryotic cell of having organelles?

Organelles (with membrane)Organelle Main features Function

Nucleus

Endoplasmic reticulum (ER)

Golgi apparatus

Mitochondrion

Chloroplast

Storage plastid

Vacuole

Lysosome

Microbody

Nucleus and endomembrane system

Why are we considering them together?

White blood cellby David GoodsellThe Machinery of LIfeFig. 5.3

Nuclear pore

by David GoodsellThe Machinery of Life, Fig. 5.3

Endoplasmic reticulum (rough ER)

by David GoodsellThe Machinery of Life, Fig. 5.4

Golgi apparatus

by David GoodsellThe Machinery of Life, Fig. 5.4

Secretory vesicles leaving the cell

by David GoodsellThe Machinery of Life, Fig. 5.6

Energy organelles

• Mitochondria (red)

• Chloroplast (deep green)

Euglena gracilis

Mitochondrion

by David GoodsellThe Machinery of Life, Fig. 5.1

Artemesia chloroplast

TEM by George Chapman

Chloroplast

Artemesia chloroplast

TEM by George Chapman

Chloroplast internal membranesby David Goodsellhttp://cbm.msoe.edu/markMyweb/SUN-chlorophyllEbookWorking/chloroplast.html

Chloroplast

Storage plastids

Cazzonelli, C. & Pogson, B. 2010. Source to sink: regulation of carotenoid biosynthesis in plants. Trends in plant science 15(5): 266-274.

Plastids may function in all of the following except

A.photosynthesis

B.fruit ripening

C.food storage

D.cell respiration

Interactive question #4

Vacuole

http://amit1b.wordpress.com/the-molecules-of-life/10-the-living-cell-gallery/

“Organelles” with no membraneaka macromolecular assemblies

“Organelle” Location Main features

Function

Pyruvate dehydrogenase complex Replisome (DNA polymerase)

RNA polymerase

Spliceosome

Ribosome

Fill this table out as we go along…

Ribosome

• rRNAs• Proteins

Prokaryotic vs. eukaryotic ribosomes

Melnikov, S. et al. 2012. One core, two shells: bacterial and eukaryotic ribosomes. Nature Structural & Molecular Biology, 19(6), 560-567.

Blue = rRNARed = proteinLight = conservedDark = unique

Eukaryote cytoskeleton

• Microtubules• Intermediate

filaments• Actin filaments

(microfilaments)• Motor proteins

Modified from David GoodsellThe Machinery of Life, Fig. 5.6

Bacterial cytoskeleton!

The bacterial cytoskeleton. The only cytoskeletal element present in spherical bacteria such as S. aureus (top left) is the tubulin-like cell division protein FtsZ (green), which localizes in a ring at the onset of cell division, recruits other cell division proteins, and defines the division plane. Most rod-shaped bacteria (top right) also contain one or more actin-like MreB homologues (red), which exhibit helix-like localization patterns and are essential for cell width control. At the onset of cell division, the FtsZ ring forms and defines the division plane. C. crescentus, a vibrioid bacterium (bottom), contains a third cytoskeletal element, the intermediate filament-like crescentin (blue), which is required for cell curvature and localizes at the inner curvature of cells.

Cabeen, M. & Jacobs-Wagner, C. 2007. Skin and bones: the bacterial cytoskeleton, cell wall, and cell morphogenesis. The Journal of cell biology, 179(3): 381-387.

Flagella

Bacteria

Eukaryotes

Cells outline

• What is a cell?• Types of cells• Cytoplasm– Cytosol – Organelles– Cytoskeleton

• Cell wall and ECM– Cell junctions

Bacterial ↑

Plant →

Fungal Cell walls:not a wall—a mesh

Extracellular matrix: animals

↑ Human connective tissue with fibroblasts (darker)

Cell junctions: animals

Plasmodesmata: plants

http://www.mhhe.com/biosci/pae/botany/crang/vtphloem/sieve1/mg0700.html

Interactive question #5Plasmodesmata are most like which cell junction in animals?

A.Tight junction

B.Desmosome

C.Gap junction

Cells outline

• What is a cell?• Types of cells• Cytoplasm• Cell wall and ECM

Next:• Membranes