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THE CELL

Cell Theory • All organisms are composed of cells (unicellular/multicellular). • Cells are the structural & functional unit of all organisms. The cell is the smallest unit of life. • All cells arise from preexisting cells. • Cells contain hereditary material, which they pass to offspring.

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Main Categories of Cells Eukaryotes

Prokaryotes Both

Main Categories of Cells Prokaryotes

• No nucleus (circular DNA in nucleoid region) • Lack organelles & complex cytoskeleton • Small, simple unicellular organisms • Smaller ribosomes • Surrounded by cell wall • KINGDOMS • Bacteria – organized based on cell wall • Archaea – organized by environment

Both

• Cell membrane • Cytoplasm/cytosol • DNA • Ribosomes • Cytoskeleton

Eukaryotes

• Nucleus (stores DNA) • Specialized organelles for specific functions • Larger, complex • Extensive cytoskeleton • Larger ribosomes • Some have cell wall – plants, fungi, & some protists • KINGDOMS • • • •

Protists Plants Fungi Animals

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Prokaryotic Cells • “before the nucleus” • Unicellular • Plasmids – small circles of DNA • Some have flagella (movement) or pili (movement or attachment)

Prokaryotic Unicellular Organisms – Kingdom Archaea Genus: Methanococcales Found in extremely hot and oxygendeprived waters around deep ocean geothermal vents; Methanogens are extremely important in environments that are anaerobic (lacking oxygen) because as they convert organic compounds into methane they provide pathways for compounds that exist in anaerobic environments to escape into the atmosphere.

Genus: Halobacteriales Found in water saturated or nearly saturated with salt; unique way of creating energy through photosynthesis that is different from other forms of photosynthesis that use chlorophyll.

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Prokaryotic Unicellular Organisms – Kingdom Bacteria The most abundant and successful organisms on the planet, bacteria are found everywhere—in soil, in water, in the intestines inside your body.

Spirillum volutans

Streptococcus pyogenes Escherichia coli

Biofilms • Community of microorganisms living within a shared layer of slime (polysaccharides & proteins) • Example – dental plaque • Why would multiple species live together like this? - Allows cells to stay in same spot instead of getting swept away by fluid currents - Rigid netlike secretions of some species serve as permanent scaffolding for others - Some species breakdown toxic chemicals allowing more sensitive ones to thrive in polluted habitats - Some consume waste products of others https://youtu.be/twxPyvdc-EE https://youtu.be/be-mjOGiquk

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Theory of Endosymbiosis Endo = within Symbiosis = 2 organisms living together • All organisms are believed to have descended from a common ancestral cell about 3.5 billion years ago • Proposes that eukaryotic cells emerged when mitochondria & chloroplasts (once free-living prokaryotes) took up permanent residence inside other larger cells.

Theory of Endosymbiosis • Mitochondria & Chloroplasts are very similar to prokaryotic bacteria • • • •

DNA Ribosomes Reproduce by binary fission 2 membranes

• http://my.hrw.com/content/hmof/science/high_school_sci/tx/gr912/hmd_bio_9780544073890_/dlo/animatedbiology/b12_04as110/i ndex.html • http://highered.mheducation.com/sites/9834092339/student_view0 /chapter4/animation_-_endosymbiosis.html

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Eukaryotic Unicellular Organisms – Kingdom Protista

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Eukaryotic Unicellular Organisms – Kingdom Protista

Eukaryotic Unicellular Organisms – Kingdom Fungi Microsporidia

Chytridiomycota

Obligate, spore-forming, intracellular parasites that invade vertebrates and invertebrates. A characteristic feature of microsporidia is the polar tube or polar filament found in the spore used to infiltrate host cells. They are widely distributed in nature with over 1200 species characterized.

Yeasts – Ascomycota & Basidiomycota

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Typical Eukaryotic Cell

Function Dictates Form & Form Dictates Function

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How Do We See Cells?

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Why are cells so small?

Why are Cells so Small? • Cell volume determines the amount of metabolic activity in cytoplasm • Cell membrane surface area limits the amount of material that can enter & leave the cell. • As cells grow larger, their metabolism increases but their surface area (membrane) doesn’t keep up. • Cell size is limited by the surface-to-volume ratio. • Cells need a large surface area to volume ratio • Complex organisms consist of millions of tiny cells carrying out different functions instead of 1 giant all-purpose cell. 1µm

2µm

5µm

3µm

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Cell Size Lab

Surface-to-Volume Ratio

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Solving the Problem • Bigger cells have a greater metabolism than smaller cells • BUT bigger cells have a proportionally less surface for exchange • How to increase surface area with increasing size? • DISCUSS

© 2010 Paul Billiet ODWS

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Membrane Extensions increase SA:V - Microvilli Microvilli (singular: microvillus) are microscopic cellular membrane protrusions that increase the surface area of cells and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction.

Microvilli of small intestine epithelium

Image Credit www.cytochemistry.net/

Membrane Extensions increase SA:V – Root Hairs • Flowering plants have an extensive, branched rooting system to absorb water and minerals

Image Credit http://ecomerge.blogspot.com

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Flat & Thin shape increases SA:V

Dividing the cytoplasm into smaller volumes Early human embryos Zygote

Image Credit http://www.advancedfertility.com/

8-cell Embryo

Image Credit http://www.rmfcfertility.com/

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Folding increases SA:V Mammals have a long small intestine with internal folding to absorb digested food

Image Credit C. Candalh, INSERM

HOMEWORK: Cell Structure & Function Packet Textbook Teacher Webpage: notes & lectures

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https://youtu.be/HBvfBB_oSTc

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CELL LAB 1. Observe & diagram eukaryotic cells 1. plant cell 2. animal cell 2. Diagram a prokaryotic cell (page 58) Use map colors for diagrams – must be in color

Cytoskeleton • Function • structural support • maintains shape of cell • provides anchorage for organelles • protein fibers • microfilaments, intermediate filaments, microtubules • motility • cell locomotion • cilia, flagella, etc. • regulation • organizes structures & activities of cell

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Cytoskeleton

https://youtu.be/FzcTgrxMzZk

Cells need workers = PROTEINS! • Making proteins • to run daily life & growth, the cell must… • read genes (DNA) • build proteins • structural proteins (muscle fibers, hair, skin, claws) • enzymes (speed up chemical reactions) • signals (hormones) & receptors • organelles that do this work… • nucleus • ribosomes • endoplasmic reticulum (ER) • Golgi apparatus

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One of the major job of cells is to make proteins, because…

Proteins do all the Work! structural enzymes signals receptors

DNA

proteins

cells

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https://youtu.be/URUJD5NEXC8

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