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CHAPTER 7 A TOUR OF THE CELL

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CHAPTER 7. A TOUR OF THE CELL. Cytology: science/study of cells ... Autophagy: recycle cell's. own organic material. Tay-Sachs disease~ lipid digestions disorder ... – PowerPoint PPT presentation

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Title: CHAPTER 7 A TOUR OF THE CELL


1
CHAPTER 7A TOUR OF THE CELL
2
Cytology science/study of cells
  • Light microscopy resolving power measure of
    clarity
  • Electron microscopy
  • TEM electron beam to study cell
    ultrastructure
  • SEM electron beam to study cell
    surfaces
  • Cell fractionation cell separation organelle
    study
  • Ultracentrifuge cell fractionation 130,000rpm

3
A cell is a living unit greater than the sum of
its parts
  • While the cell has many structures that have
    specific functions, they must work together.

4
Cell Types Prokaryotic
  • Nucleoid DNA
  • concentration
  • No organelles with
  • membranes
  • Ribosomesprotein synthesis
  • Plasma membrane (all
  • cells) semi-permeable
  • Cytoplasm/cytosol(all cells)

5
Cell types Eukaryotic
  • Nucleusmembrane enclosed organelle containing
    chromosomes
  • Membrane bound organelles of specialized form and
    function
  • Generally larger than prokaryotic cells

6
Cell Size
  • As cell size increases, the surface area to
    volume ratio decreases
  • Rates of chemical exchange may then be inadequate
    for cell size
  • Cell size, therefore, remains small

7
Nucleus
  • Genetic material
  • chromatin
  • Chromosomes
  • Nucleolus rRNA
  • ribosome synthesis
  • Double membrane
  • with pores
  • mRNA protein synthesis

8
Ribosomes
  • Protein manufacture
  • Types a) free cytosolprotein function in cell
  • b) bound endoplasmic reticulum
    membranes, organelles and export

9
The Endomembrane System
  • Endoplasmic reticulum(ER)
  • Continuous with nuclear envelope
  • Smooth ER
  • no ribosomes
  • Synthesis of lipids
  • Metabolism of carbohydrates
  • Detoxification of drugs poisons
  • Rough ER
  • With ribosomes
  • Synthesis of secretory proteins
  • (glycoproteins)
  • Membrane production

10
The Golgi apparatus
  • ER products are modified, stored, and then
    shipped
  • Cisternae flattened membranous sacs
  • Trans face(shipping) cis face (receiving)
  • Transport vesicles

11
Lysosomes
  • Sac of hydrolytic
  • enzymes digestion of
  • macromolecules
  • Phagocytosis
  • Autophagy recycle cells
  • own organic material
  • Tay-Sachs disease
  • lipid digestions disorder

12
Vacuoles
  • Membrane-bound
  • sacs(larger than vesicles)
  • Food (phagocytosis)
  • Contractile (pump excess
  • water)
  • Central (storage in plants)
  • Tonoplast membrane

13
Other Membranous Organelles
  • Mitochondria and chloroplasts are the main energy
    transformers of cells
  • Both organelles have small quantities
    of DNA that direct the synthesis of the
    polypeptides produced by these internal
    ribosomes.
  • Mitochondria and chloroplasts grow and reproduce
    as semiautonomous organelles.
  • 2. Peroxisomes generate and degrade H2O2 in
    performing various metabolic functions

14
Mitochondria
  • Site of cellular respiration
  • have a smooth outer membrane
  • and a highly folded inner membrane, the cristae
  • inner membrane encloses the mitochondrial matrix,
  • a fluid-filled space with DNA, ribosomes, and
    enzymes.

15
chloroplasts
  • found in plants and eukaryotic algae
  • site of photosynthesis.
  • Inside the innermost membrane is a fluid-filled
    space, the stroma, in which float membranous
    sacs, the thylakoids.

16
Peroxisomes
  • generate and degrade H2O2 in performing various
    metabolic functions
  • bounded by a single membrane.
  • They form not from the endomembrane system, but
    by incorporation of proteins and lipids from the
    cytosol.

17
The Cytoskeleton
  • Providing structural support to the cell, the
    cytoskeleton also functions in cell motility and
    regulation

18
There are three main types of fibers in the
cytoskeleton microtubules, microfilaments, and
intermediate filaments.
19
Microtubules
  • the thickest fibers, are hollow rods about 25
    microns in diameter.
  • They move chromosomes during cell division.
  • Another function is as tracks that guide motor
    proteins carrying organelles to their
    destination.

20
cilia and flagella.
  • Microtubules are the central structural support
  • Cilia usually occur in large numbers on the cell
    surface.
  • There are usually just one or a few flagella per
    cell

21
cilia and flagella.
  • A flagellum has an undulatory movement

22
cilia and flagella.
  • Cilia move more like oars with alternating power
    and recovery strokes.

23
cilia and flagella
  • have the same ultrastructure.

24
Microfilaments
  • the thinnest class of the
  • cytoskeletal fibers,
  • are solid rods of the globular protein
  • actin.
  • designed to resist tension
  • form a three-dimensional
  • network just inside
  • the plasma membrane.

25
Microfilaments
  • In muscle cells, thousands of actin filaments are
    arranged parallel to one another.
  • Thicker filaments, composed of a motor protein,
    myosin, interdigitate with the thinner actin
    fibers

26
Microfilaments
  • In other cells, these actin-myosin aggregates are
    less organized but still cause localized
    contraction
  • Pseudopodia, cellular extensions, extend and
    contract through the reversible assembly and
    contraction of actin subunits into microfilaments.

27
Microfilaments
  • In plant cells (and others), actin-myosin
    interactions and sol-gel transformations drive
    cytoplasmic streaming.

28
Intermediate filaments,
  • more permanent fixtures
  • of the cytoskeleton than
  • are the other two classes
  • reinforce cell shape
  • and fix organelle location.

29
Cell Surfaces and Junctions
  • 1. Plant cells are encased by cell walls
  • 2. The extracellular matrix (ECM) of animal
    cells functions in support, adhesion, movement,
    and regulation
  • 3. Intercellular junctions help integrate cells
    into higher levels of structure and function
  • 4. The cell is a living unit greater than the
    sum of its parts

30
Plant cells are encased by cell walls
  • The cell wall, found in prokaryotes, fungi, and
    some protists, has multiple functions.
  • In plants, the cell wall protects the cell,
    maintains its shape, and prevents excessive
    uptake of water.
  • It also supports the plant against the force of
    gravity.

31
A mature cell wall consists of a primary cell
wall, a middle lamella with sticky
polysaccharides that holds cell together, and
layers of secondary cell wall.
32
The extracellular matrix (ECM) of animal cells
functions in support, adhesion, movement, and
regulation
  • In many cells, fibronectins in the ECM connect to
    integrins, intrinsic membrane proteins.

33
. Intracellular junctions help integrate cells
into higher levels of structure and function
  • Plant cells are perforated with plasmodesmata,
    channels allowing cysotol to pass between cells.

34
Animal have 3 main types of intercellular links
tight junctions, desmosomes, and gap junctions
  • In tight junctions, membranes of adjacent cells
    are fused, forming continuous belts around cells.
  • This prevents leakage of extracellular fluid.

35
Desmosomes (or anchoring junctions) fasten cells
together into strong sheets, much like rivets.
  • Gap junctions (or communicating junctions)
    provide cytoplasmic channels between adjacent
    cells.

36
Microtubules
  • In many cells, microtubules grow out from a
    centrosome near the nucleus.
  • In animal cells, the centrosome has a pair of
    centrioles, each with nine triplets of
    microtubules arranged in a ring.
  • During cell division the centrioles replicate.
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