Review from Biology A

Transcription

1 Chapter 4

2 Review from Biology A The Cell Theory All organisms are made of cells Cells come from pre-existing cells The cell is the simplest collection of matter that can live Scientists whose work you should know: Leeuwenhoek Hooke Schleiden Schwann Virchow (Margulis)

3 Ways to investigate cells Microscopes (LM, SEM, TEM) Light: dynamic SEM: hi-res Cell fractionation Freeze-fracture» Transmission electron microscope (TEM); macrophage (rat)

4 SEM

5 Calculating Magnification Magnification = Image Size / Actual Size of Specimen I M x A

6 You need three things:

7 A) Use a ruler to measure the length of the scale bar in mm = 32mm B) Convert measurement to same units as scale bar = 32000µm C) M = I / A M = 32000µm / 100µm M = 320

8 Practice M = I / A M = 13cm / 50µm M = µm / 50µm M = µm

9 Calculating actual specimen size What if we know xmag but don t know specimen size? A = I / M e.g. What is the actual size of this tarsus? A = 27cm / 2600 A = µm / 2600 A = 104µm

10 Cells Two types Prokaryotic Eukaryotic Evolutionary relationship

11 Endosymbiotic Theory First proposed by Margulis in 1966

12 Prokaryotes Pili: attachment structures on the surface of some prokaryotes Nucleoid: region w/ DNA is located (no membrane) Bacterial chromosome Ribosomes: organelles that synthesize proteins Plasma membrane: membrane enclosing the cytoplasm Cell wall: rigid structure outside the plasma membrane Capsule: jelly-like outer coating of many prokaryotes 0.5 µm (a) A typical rod-shaped bacterium Flagella: locomotion organelles of some bacteria (b) A thin section through the bacterium Bacillus coagulans (TEM)

13 Eukaryotes Characteristics? true nucleus nuclear envelope bigger (10:1) membrane-bound organelles

14 More Review from Biology 1 Surface area increases while total volume remains constant limits on cell size logistics of cellular metabolism 5 A smaller cell higher surface to volume 1 1 ratio Total surface area (height width number of sides number of boxes) Total volume (height width length number of boxes) Surface-to-volume ratio (surface area volume)

15 CELL PARTS

16 Cell membrane Outside of cell The plasma membrane selective barrier Hydrophilic Carbohydrate side chain region Allows passage of nutrients and waste Inside of cell (a) 0.1 µm TEM of a plasma membrane. The plasma membrane, here in a red blood cell, appears as a pair of dark bands separated by a light band. Hydrophobic region Hydrophilic region Phospholipid Proteins (b) Structure of the plasma membrane

17 Cell Membrane ECM shown too

18 Fluid Mosaic Model Integral Membrane Proteins

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20 A View of the Eukaryotic Cell ENDOPLASMIC RETICULUM (ER) Nuclear envelope Flagelium Rough ER Smooth ER Nucleolus Chromatin NUCLEUS Centrosome Plasma membrane CYTOSKELETON Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Figure 6.9 Peroxisome Mitochondrion Lysosome In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm)

21 A View of the Eukaryotic Cell Nuclear envelope Nucleolus NUCLEUS Chromatin Centrosome Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes (small brwon dots) Central vacuole Golgi apparatus Tonoplast Microfilaments Intermediate filaments Microtubules CYTOSKELETON Mitochondrion Peroxisome Plasma membrane Cell wall Chloroplast Figure 6.9 Wall of adjacent cell Plasmodesmata In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata

22 ANIMATION Over the top cell movie

23 Genetic Library of the Cell Nucleus Why 1 µm Nucleolus Nucleus Chromatin would the nuc. Nuclear envelope: Inner membrane Outer membrane have Nuclear pore complex pore Pore complex Rough ER system? Surface of nuclear envelope. Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Figure 6.10 Pore complexes (TEM). Nuclear lamina (TEM).

24 Nuclear Pore

25 Functions of Rough ER Produces proteins and membranes

26 Functions of Smooth ER Synthesizes lipids Metabolizes carbohydrates Stores calcium Detoxifies poison

27 Golgi Apparatus

28 The Golgi: Shipping & Receiving Ctr Puts integral memb proteins into memb. makes lysosomes adds carbs to glycoproteins (glycosylation) makes mucus in plants: cell plate/wall

29 Lysosomes: Digestive Compartments A lysosome hydrolytic enzymes acidic ph digests endosome = acidic membrane organelle, transports molecules to lysosome

30 Organelles for energy changes have their own DNA, proteins Mitochondria cellular respiration Chloroplasts photosynthesis

31 Peroxisomes: Oxidation made by ER in all euks breakdown H2O2 into water synthesize cholesterol, myelin Chloroplast Peroxisome Mitochondrion Figure µm

32 Cytoskeleton network of (easily reconfigured!) fibers Gives mechanical support & intracellular transport Microtubule Figure µm Microfilaments

33 Roles of the Cytoskeleton, cont d Cytoskeleton & motor proteins ATP Motor protein (ATP powered) Vesicle Receptor for motor protein Microtubule of cytoskeleton (a) Motor proteins that attach to receptors on organelles can walk the organelles along microtubules or, in some cases, microfilaments. Vesicles Microtubule Figure 6.21 A, B 0.25 µm (b) Vesicles containing neurotransmitters migrate to the tips of nerve cell axons via the mechanism in (a). In this SEM of a squid giant axon, two vesicles can be seen moving along a microtubule. (A separate part of the experiment provided the evidence that they were in fact moving.)

34 Cilia and Flagella Cilia and flagella Contain specialized arrangements of microtubules Are locomotor appendages of some cells (a) Motion of flagella. A flagellum usually undulates, its snakelike motion driving a cell in the same Direction of swimming direction as the axis of the flagellum. Propulsion of a human sperm cell is an example of flagellatelocomotion (LM). 1!m

35 Cilia & Flagella Structure 0.1 µm Outer microtubule doublet Dynein arms Plasma membrane Central microtubule Microtubules Plasma membrane Outer doublets cross-linking proteins inside Radial spoke Basal body (b) (a) 0.5 µm 0.1 µm Triplet (c) Figure 6.24 A-C Cross section of basal body

36 Dynein Is responsible for the bending movement of cilia and flagella Microtubule doublets ATP Figure 6.25 A (a) Dynein arm Powered by ATP, the dynein arms of one microtubule doublet grip the adjacent doublet, push it up, release, and then grip again. If the two microtubule doublets were not attached, they would slide relative to each other.

37 Outer doublets cross-linking proteins ATP Anchorage in cell (b) Figure 6.25 B In a cilium or flagellum, two adjacent doublets cannot slide far because they are physically restrained by proteins, so they bend. (Only two of the nine outer doublets in Figure 6.24b are shown here.)

38 Microfilaments (Actin Filaments) cleavage furrow cellular motility: also w/ myosin: Muscle cell Actin filament Myosin filament Myosin arm

39 Intracellular movement contraction of actin and myosin filaments cytoplasmic streaming/cyclosis Cortex (outer cytoplasm): gel with actin network Extending pseudopodium Inner cytoplasm:cytosol with actin subunits Figure 6.27 B (b) Amoeboid movement