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  1. Cells! • Cell Scientists & Cell Theory• Structure & Function

  2. Early Study of Cells Anton van Leeuwenhoek mid 1600’s • ______________________: used early ‘scope to look at living “animalcules” in pond water • _____________: looked at cork & named “cells” Robert Hooke

  3. more Early Study of Cells Matthias Schleiden early 1800’s • _________________: all plants are made of cells • ________________: all animals are made of cells mid 1800’s • _______________: animal & plant cells are produced only by division of pre-existing cells Theodor Schwann Rudolf Virchow Theodor Schwann Matthias Schleiden

  4. Cell Theory(commonly accepted assertions in cell biology) • All living things are made of cells • Cells are the basic units of structure & function in living things • All cells come from pre-existing cells • Cells contain genes that serve as the instructions for cell functioning and growth

  5. Categories of cells

  6. Prokaryotic Cells • No nucleus • “naked” DNA found free in cytoplasm. • Has cell membrane, bacterial cell wall, and ribosomes. • Some also have protective sticky capsule, grasping pili, and/or propelling prokaryotic flagella. In prokaryotic cells, all metabolic processes occur in same main “compartment,” unlike more complex eukaryotic cells which have several compartments.

  7. Composite Animal Cell Eukaryotic Cells • Havenuclei • Have membrane-bound organelles • All these organelles are separate compartments in the cell • Having all these compartments allows each organelle to have its own specialized “job” or role -- a unique characteristic of eukaryotic cells Small vacuoles Composite Plant Cell

  8. Eukaryotic Cell: Animal Small vacuoles

  9. Eukaryotic Cell: Plant

  10. Cell Structures & their Functions

  11. The Nucleus

  12. Ribosomes & the ER Ribosomes - found in the cytoplasm (free) or attached to ER (bound) • “protein factories”; site of protein synthesis • made up of RNA & protein Endoplasmic Reticulum (ER) - found in cytoplasm, near nucleus • network of compartments that store & transport materials around/out of cell (via transport vesicles) Smooth ER (sER) - w/o ribosomes • also synthesizes (makes) lipids, can store enzymes Rough ER (rER) - w/ ribosomes • also modifies proteins made by ribosomes, creates new membranes

  13. The ER is continuous with the Nuclear Membrane (aka “nuclear envelope”)

  14. Proteins made by bound Ribosomes are modified by the Rough ER, (usually for eventual export from the cell…)

  15. The Smooth ER is often connected to the Rough ER

  16. Golgi Body (or Golgi Complex) Stack of flattened sacs that modify, package & distribute substances made by the ER; looks like a stack of pita pockets

  17. Lysosomes (found mostly in animal cells) • ”Suicide sacs" filled with digestive enzymes • break down food, foreign particles, & old organelles in cytoplasm • produced by rER and Golgi • also called "recycling centers" of the cell

  18. Steps of Protein Production

  19. Vacuoles • Can store water, nutrients, wastes, enzymes • Plants often have one large central vacuole that regulates turgor (water pressure) and that serves as a large lysosome • Amoebas have food vacuoles • Paramecia have contractile vacuoles that pump out water

  20. Peroxisomes Sacs containing a variety of enzymes; sites of various metabolic reactions (such as detox. of alcohol); also break down hydrogen peroxide (H2O2), a toxic byproduct of these metabolic rxns Can you name a specific enzyme you’d expect to find in a peroxisome? What is the advantage to a working eukaryotic cell of having these types of reactions occur in a specialized compartment? CATALASE!!

  21. Mitochondrion (pl. mitochondria) • "Powerhouse" of cell, site of cell respiration(uses organic compounds like glucoseto produce chemical energy (ATP) for cell) • has outer & inner membrane • has own DNA, replicates self

  22. Chloroplast (plants & some protists only)(found in leaf cells & sometimes cells of stem) • site of photosynthesis (uses energy of sun to make organic compounds); • has one outer and two inner membranes • also has own DNA, replicates self

  23. more Plastids (plants only) Store food or pigments; Examples: • Chloroplasts (contain chlorophyll) • Leukoplasts (store starch) • Chromoplasts (store pigments for flowers, fruit, leaves)

  24. Centrosome(aka Micro-tubule Organizing Center) • The area in the cell where microtubules are made • Helps carry out cell division in eukaryotic cells, by forming spindle fibers that separate duplicated chromosomes/DNA • In animal cells also contains a pair of centrioles– structures made of microtubules (9 bunches of 3 tubules arranged in circular pattern)

  25. Centrioles (animal cells only) • Help carry out/direct cell divisionin animal cells • Occur in pairs in cell • Part of Centrosome in animal cells • Made of microtubules

  26. Centrioles (animal only) Help carry out/direct cell division; made of microtubules

  27. Cytoskeleton • Supports cell & gives it shape; supports organelles; allows for organelle and cell movement

  28. Cytoskeleton: Microfilaments Long thin actin protein fibers; aid in cytoplasmic streaming (movement of cytoplasm); specialized for contraction (muscle cells)

  29. Cytoskeleton: Intermediate filaments Fibrous ropelike proteins; reinforce cytoskeleton; anchor some organelles to cytoskeleton

  30. Cytoskeleton: Microtubules Hollow tubulin protein tubes that make up cytoskeleton; support and shape cell; aid in movement of organelles; aid in movement of cell --> form centrioles, cilia, flagella

  31. Cytoskeleton (another view) Red = Microfilaments Green = Microtubules Blue = nucleus

  32. Flagella & Cilia(attached to cell surface) Flagella: Locomotion in single-celled org. Ex) Cilia: 1: Push materials over cell surface Ex) 2: Allow cell to sense what is in it’s environment Ex) Sperm, some protists & some bacteria Cells lining respiratory tract (trachea, bronchi) Paramecium

  33. Flagella & Cilia: How they move

  34. Flagellum Structure

  35. Euk. Organelles & their Functions

  36. Differences between Prokaryotic & Eukaryotic Cells

  37. Differences betweenPlant and Animal Cells

  38. Differences between Prokaryotic & Eukaryotic Cells: • Nuclei: • Membrane-bound organelles: • Size: • Other:

  39. Differences betweenPlant and Animal Cells: • Shape: • Location of nucleus: • Organelles/structures: • Vacuole: • Cell wall: • Chloroplasts: • Centrioles: • Lysosomes: • Flagella:

  40. Why are cells so gosh darn SMALL anyway? • It’s a question of geometry… • Cells are like little factories, taking in raw materials, processing them, and often releasing the products. • How well a cell can function depends on two things, structurally: how well a cell can get stuff in & out across its surface area AND how much space it has inside to “process” materials. • If a cell has lots of volume inside to process, but cannot get stuff in & out fast enough (due to too little surface area), the extra space inside is not going to be useful… • Question: What is a good way to guarantee a cell has enough surface area? (on to next slide)

  41. Answer: Stay Small Why? Because of the relationship between cell volume & surface area. Let’s compare one large cell to several small cells of equal volume to see which is better: Volume of 27 small cells: 27 (10µm x 10µm x 10µm) = 27000 µm3 Volume of one large cell: 30µm x 30µm x 30µm = 27000 µm3 Winner!