Cellular life
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This document summarizes cellular life by describing the key differences between prokaryotic and eukaryotic cells. It explains that prokaryotes like bacteria were the earliest forms of life on Earth and lack internal structures, while eukaryotic cells in plants, animals and protists have complex organelles within the cell including a nucleus. It describes how mitochondria and chloroplasts likely originated from endosymbiotic prokaryotes that took up permanent residence within cells. The document outlines the distinguishing features of plant and animal cells and provides details on important cellular structures and their functions.
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Cellular life
- 1. Cellular Life • Two cell types: prokaryotes & eukaryotes • Cell structure • Cell organelles & their functions
- 2. Origin of living cells: Prokaryotes fossilized bacteria living bacteria • prokaryotic cells (bacteria & archaea) • found as fossils: 3.5 billion years old • heterotrophic (not photosynthetic)
- 6. Origin of eukaryotic cells Endomembrane system • includes nuclear membrane, endoplasmic reticulum, etc. • derived from plasma membrane Mitochondria & chloroplasts • endosymbiosis hypothesis • remnants of once free-living prokaryotes took up residence inside transitional prokaryotic-eukaryotic cell
- 7. Evidence for the endosymbiotic hypothesis Mitochondria & chloroplasts: • have own DNA • protein synthesis similar to bacteria • divide / replicate independently
- 8. Earliest eukaryotes similar to present-day unicellular members of Kingdom Protista
- 11. Multicellular forms of life probably arose from colony-forming protists
- 12. 2 general categories of cellular life Prokaryotic cells: bacteria, blue-green algae • simple design - lack internal organelles • primitive - first forms of life, mostly unicellular • small - 1/10th size of eukaryotic cells Eukaryotic cells: plants, fungi, animals, protistans • complex internal design - intracellular organelles • more derived than prokaryotic cells • larger than prokaryotic cells (10 – 100x their size)
- 13. Prokaryotic cell
- 14. Internal organelles & nucleus Present in eukaryotic cell, lacking in prokaryotic
- 15. Red blood cells Bacteria on pin tip
- 16. The plasma membrane • A semi-permeable barrier: some substances move easily across, others do not • Membrane is permeable to water, not larger or ionized molecules
- 17. The plasma membrane: composed of phospholipid molecules and protein
- 18. Important ideas: • The concentration of water on either side of a cell membrane is related to solute concentration • If membrane is not permeable to solute, water will move (osmosis) from region of low solute concentration to higher solute concentration •region of higher solute concentration termed: hypertonic •region of lower solute concentration termed: hypotonic •if both regions the same: isotonic
- 19. Water will move (diffuse=osmosis) from hypotonic region to hypertonic region, until water concentration is the same
- 20. Normal blood plasma Distilled water Very salty water Cell is in: isotonic solution hypotonic solution hypertonic solution
- 21. Plant vs. animal eukaryotic cells Plant cells have, in addition to preceding features: 1. Cell wall • exterior to plasma membrane, cellulose 2. Central vacuole • fluid-filled organelle • occupies most of cell interior • organic nutrient storage 3. Chloroplasts • organelles of photosynthesis
- 22. Eukaryotic cell - Plant
- 23. Eukaryotic cell - Animal
- 24. Endomembrane system Endoplasmic reticulum (ER) Rough - new membrane proteins & secretory proteins Smooth - many functions including • Synthesizes lipids, • Detoxes poisons in bloodstream Golgi apparatus • products from ER transported here • enzymes modify the products • distributes final molecules to appropriate organelles
- 25. C6H12O6 + 6O2 6CO2 + 6H2O + ATP Glucose & oxygen react to yield carbon dioxide, water & ATP Mitochondria: site of cellular respiration
- 26. Chloroplasts: site of photosynthesis •Plants and algae only •Convert solar energy to chemical energy (carbohydrates)
- 29. Cytoskeleton: • maintenance of cell shape & organelle position • cell motility • movement of substances within cell
- 30. Cilia & flagella: • cell motility • movement of substances external to cell ciliaflagellum
- 31. The nucleus • membrane bound region containing DNA • segments of DNA (genes) have information for construction of other molecules
- 32. Nitrogenous Bases of DNA The building blocks (monomers) of nucleic acids
- 34. portion of a DNA double-helix
Editor's Notes
- Cells are the basic “unit” of life All living things are made of cells Cells are smallest unit capable of life, Living things may be unicellular or multicellular
- Prokaryotes Arose ~3.5 billion years ago Lived and evolved alone on Earth for 2 billion years! Today found where ever there is life, outnumber all the eukaryotes combined Found in hostile habitats – e.g. thermophiles of hotsprings, walls of a gold mine 2 miles below Earth’s surface Some cause serious illness (Black death (aka bubonic plague), TB, cholera, food poisoning) But also are beneficial (bacteria in our intestines give us vitamins, some in our mouths prevent growth of harmful fungi) Also largely responsible for break-down of dead organic materials *without prokaryotes, live on earth would end (but could do just fine without eukaryotes)
- Shape is important identifier of prokaryotes 3 shapes are: Top left – spirochetes (spirals, e.g. syphilis, Lyme disease) Bottom left – cocci (spheres, from Greek word for berries, e.g. staph – staph infection, streptococcus – strep throat) Bottom right – bacilli (rods) Most prokaryotes are unicellular and very small (but some form colonies, some have simple multicellular arrangement with specialized cells)
- Left – yellow rods are bacteria (Haemophilus influenzae) on skin cells of human nose interior -pathogens transmitted through air, cause pneumonia and other lung infections that kill ~4million people per yr around world Right – tick that carries the Lyme disease and Bull’s eye rash Lymes is currently the most widespread pest carried disease in the US Caused by a spirochaete bacterium carried by ticks that live on deer and field mice Usually starts as a red rash shaped like a bull’s eye around the bite Antibiotics cure if given within a month of the bite Without treatment = arthritis, heart disease, nervous disorders Use insect repellant, wear light colored clothing & check for ticks!
- After photosynthetic prokaryotes evolved, oxygen accumulated in Earth’s atmosphere (~2.5 mya) Eukaryotes arrived about 1.7 million years ago -explosion in forms of eukaryotes (these were the protists) -then (~1 billion ya) multicellular forms of eukaryotes (again, protists; from colonial single cell forms)
- Eukaryotes differ from Prokaryotes in a number of ways we’ll discuss in detail today. One major difference is Euks have membrane bound organelles that proks lack Thought they got these through a two step process Plasma membrane folds in and creates all organelles but mt and cp including... prok cell engulfs other prok cells that serve as mt and cp
- Evidence to support this theory includes...
- Earliest Euk were similar to present day unicellular members of the Kingdom Protista
- Flagellate algae (Chlamydomonas) – unicellular green algae with a pair of flagella Amoeba – with it’s psuedopodia Paramecium
- You can imagine that as single cell org divide, they might stay stuck together sometimes! If they stay together and cells differentiate to have different jobs leads to colonial forms, then multi-cellular forms! Like this Volvox!
- Upper left is a bacterium (prokaryote) Lower right is a euk. Nucleoid region of prok is a concentrated region of DNA within cell (but no nucleus) Euk cells are ~10 times the size of prok cells!
- Again, diff in size. Left = euk red blood cells Right = prok – bacteria on tip of a pin
- whether prokaryotic or eukaryotic: cells characterized by a delimiting membrane absolutely required for cell existence
- Phospholipid bilayer = heads are hydrophilic, tails are hydrophobic Phosolipids and proteins float around in plan of membrane = a “fluid mosaic”
- If conc of solutes differs on opposite sides of membrane, either solutes or water moves to compensate When water moves = osmosis
- Water will move (diffuse=osmosis) from hypotonic region to hypertonic region, until water/solute concentration is the same
- For a single cell, looks like this Isotonic – same amt of water in & out of cell If in hypotonic solution (solute conc higher in cell than out) – water moves into cell and it bursts If in hypertonic solution (solute conc. Lower in cell) – water moves out of cell and it shrivels up
- Extra features found only in plant cells....
- Also some feature found in animal but not plant cells... Centrioles – can shaped structures made of microtubules, help in nuclear division Lysosomes – membrane enclosed sac of digestive enzymes, a compartment where cells can digest macromolecules safely and keep digestive enzymes away from their own tissues Cilia & Flagella – for locomotion, more on that in a bit
- Endoplasmic reticulum (ER) Labyrinth of tubes and sacs in cytoplasm Two types of ER – rough & smooth (rough is covered with ribosomes, smooth is not) Look at cell
- Other organelles – mitochondria is site of cellular respiration (we’ll talk more about this next week) Harvest energy from sugars and converts it to ATP Lots of these in almost all euk cells including yours
- Chloroplasts – site of photosynthesis (talk more about this next week) Conversion of light energy from the sun to chemical energy of sugars and other organic molecules
- This is what chloroplasts look like..... The reaction takes place in the grana – these green stacks are like the cp power packs
- Here are plant cells with thick cell walls and cp
- Euk cells have cytoskeleton – network of fibers throughout cytoplasm that aid in... Three kinds (see above)
- Cytoskeletal structures for.... are cilia and flagella Some prokaryotes have flagella as well! Flagella (like human sperm on lower left) propel by a whip-like motion Cilia – like lining of human respiratory tract (center) and paramecium (right), propel by moving in waves together like many oars on a ship
- Major diff is Euk have nucleus and prok don’t Nucleus is...
- monomer building blocks of DNA, RNA Pictured here are four nitrogenous bases of DNA
- Nucleotide = a phosphate group, bound to a sugar, bound to a nitrogenous base Nucleotides bond together to create a polymer (polynucleotide) that is a single strand of DNA or RNA
- DNA: 2 nucleotide polymers wrapped around each other in a “double-helix” RNA: a single strand of nucleotides These strands, of course, contain the information for protein production = GENES! And are packed up into chromosomes within the eukaryotic nucleus