Cellular Structure and Function

1. Cellular Structure and Function Cell theory Cell size – why are cells so small? Cell Shape Basic Internal Organization Prokaryotic cells Eukaryotic cells

2. Cell Theory Cell Theory consists of three principles: • All living things are composed of one or more cells. • Cells are the basic units of structure and function in an organism. • Cells come only from the replication of existing cells.

3. Observing Cells • Light microscope • Can observe living cells in true color • Magnification of up to ~1000x • Resolution ~ 0.2 microns – 0.5 microns

4. Observing Cells TEM • Electron Microscopes • Preparation kills the cells • Images are black and white – may be colorized • Magnifcation up to ~100,000 • Transmission electron microscope (TEM) • Scanning electron microscope (SEM) 2-D Image SEM 3-D Image

5. CELL DIVERSITY Enormous diversity in size, shape, and internal organization.

6. CELL SIZE Cells are small for two main reasons: 1. The cell’s nucleus can only control a certain volume of active cytoplasm. 2. Cells are limited in size by their surface area to volume ratio.

7. Cell Size

8. Cell Size and Scale http://learn.genetics.utah.edu/content/begin/cells/scale/

9. CELL SHAPE • Cells come in a variety of shapes – depending on their function: E.g. The neurons from your toes to your head are long and thin; E.g. Blood cells are rounded disks, so that they can flow smoothly.

10. Internal Organization All cells contain 4 basic structures: 1. an external plasma membrane; 2.ribosomes; 3. Cytoplasm; and 4. nucleic acids.

11. 1. Plasma Membrane Structure • All membranes are phospholipidbilayers with embedded proteins, glycolipids, glycoproteins, and cholesterol

12. Plasma Membrane * Fluid Mosaic Model

13. Plasma Membrane Function Outer plasma membranes • isolate cell contents • control what gets in and out of the cell • receive signals Inner plasma membranes • play a role in energy transformation e.g. thylakoid membranes mitochondrial cristae.

14. 2. Ribosomes STRUCTURE: • parts made in the nucleolus and assembled in cytoplasm • consist of large and small subunits • made up of rRNA surrounded by protein molecules • 3 types of ribosomes exist: Free-floating, attached to RER, and those associated with mitochondria/chloroplasts

15. Ribosomes FUNCTION: Provide a surface for the assembly of protein molecules

16. 3. Cytoplasm STRUCTURE: • material between nucleic acids (nucleoid regionor nucleus) and plasma membranes FUNCTION: • site of some chemical reactions, surrounds and supports organelles

17. 4. Nucleic Acids • DNA = found in nucleus or nucleoid region. • RNA = all three types for protein synthesis. • See Macromolecule Notes for Structure and Function!

18. Prokaryotic Vs. Eukaryotic • No nuclear compartments • No membrane-bound internal compartments • Archaebacteria and Eubacteria are prokaryotic organisms • Membrane-bound nuclear material • Do have membrane-bound internal compartments • Protists, Plants, Fungi, and Animals are eukaryotic organisms

19. Prokaryotic Vs. Eukaryotic

20. Prokaryotic Cells Cell wall (S) composed primarily of peptidoglycan (F) maintains the overall shape of a bacterial cell Gram Positive Gram Negative

21. Prokaryotic Cells Capsule (S) slime layer made up of polysaccharides (F) Protects (versus drying, immune attack, being engulfed by predatory protozoa, or antimicrobial agents), helps bacteria adhere to external surfaces, and may act as a nutrient reserve.

22. Prokaryotic Cells Flagella (S) corkscrew like structure made of protein (F) spins about its axis like a propeller pushes bacterium along

23. Prokaryotic Cells Pili (S) Hollow hair-like structures made of protein (F) Help bacteria adhere to surfaces, substrates, other cells or tissues, and one another during mating

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25. Eukaryotic Cells Nucleus (S) largest organelle surrounded by a porous double membrane called the nuclear envelope (F) which separates the nuclear material within from the cytoplasm without and allows RNA, proteins, and water to move in and out (F) directs cellular activity through protein coding

27. Eukaryotic Cells Nucleolus (S) dense area within nucleus (F) ribosomal subunits constructed here

28. Eukaryotic Cells Mitochondria (S) sausage shaped organelle surrounded by a double membrane - smooth outer membrane - highly folded inner membrane ( SA for energy transformations) - folds = cristae

29. Eukaryotic Cells

30. Eukaryotic Cells (F) Glucose is Transformed Into useable Energy (ATP)

31. Eukaryotic Cells Endoplasmic Reticulum (S) network of tubes (SER) and flattened sacs (RER) which are continuous with outer nuclear membrane

32. Eukaryotic Cells Endoplasmic Reticulum (F) Proteins are folded, modified, and distributed to other subcellular compartments. Lipid biosynthesis and Ca handling also occur here.

33. Eukaryotic Cells Golgi Apparatus (S) series of stacked flattened sacs

34. Eukaryotic Cells Golgi Apparatus (F) the main function of the Golgi body is to store, modify, and package proteins for delivery.

35. Eukaryotic Cells Lysosomes (S) slightly acidic, fluid filled sacs surrounded by a single membrane produced by the Golgi apparatus

36. Eukaryotic Cells Lysosomes (F) contain and transport digestive enzymes that accelerate the breakdown of proteins, carbohydrates, nucleic acids, and lipids.

37. Eukaryotic Cells Peroxisomes (S) small sacs surrounded by a single membrane that pinch off from the endoplasmic reticulum

38. Eukaryotic Cells Peroxisomes (F) contain enzymes, such as catalase, to breakdown harmful chemicals, such as hydrogen peroxide

39. Eukaryotic Cells Vacuoles (S) large fluid-filled vesicles surrounded by a single membrane store various materials for a variety of purposes: • water to provide turgor pressure (plants), or regulate water levels (protists) • food • toxins (defence mechanism in plants)

40. Eukaryotic Cells Plant vacuole Contractile vacuole in a Paramecium

41. Eukaryotic Cells Cytoskeleton (F) overall, helps cell maintain its shape, anchors organelles, and causes cell movement (S) dynamic set of fibres within the cytosol, consisting of three components: 1. Microfilaments(Actin) 2. Microtubules (Tubulin) 3. Intermediate filaments

42. Eukaryotic Cells

43. Cytoskeleton • http://sciencelife.uchospitals.edu/2011/09/08/machine-gunning-the-cells-legos/

44. Eukaryotic Cells Plastids (F) storage molecules in plants (S) two major types exist: 1. Leucoplasts which are colourless and 2. Chromoplastswhich contain colourful pigments MORE DETAIL • Amyloplasts are a type of leucoplast that store starch granules. They stain a purple colour using iodine or Lugol's solution • Chloroplasts are a type of chromoplast that contain chlorophyll which plays a role in photosynthesis • Other chromoplasts - which contain red, yellow, and orange pigments - can be found in the petals and fruits of angiosperms to aid in pollination and seed dispersal

45. Eukaryotic Cells Chloroplast Structure

46. Eukaryotic Cells Chloroplast Function

47. Eukaryotic Cells Cell Wall (S) composed of polysaccharides (chitin in fungi, cellulose in plants & protists) (F) provides support for cell, limits cell volume, passively restricts water flow into/out of cell

48. Eukaryotic Cells Cell Wall Structure

50. MOLECULES AND MEMBRANES • Cells within an organism must exchange compounds with their environment • These must pass across their biological membranes. • In eukaryotic cells, there is also transport across membrane-bound organelles such as the nucleus, endoplasmic reticulum, and mitochondria. • Examples of compounds commonly exchanged across membranes include metabolites such as glucose and pyruvate; ions such as sodium, potassium, calcium, and chloride; as well as amino acids and nucleotides.