Cells
This presentation is the property of its rightful owner.
Sponsored Links
1 / 22

Cells PowerPoint PPT Presentation


  • 66 Views
  • Uploaded on
  • Presentation posted in: General

Cells. What is a cell? A cell is a membrane bound unit containing hereditary material and other compounds that make metabolism, growth and reproduction possible. Hereditary material. Plasma membrane. Cytoplasm. Cells. Overview of cell structure Cells are surrounded by a plasma membrane.

Download Presentation

Cells

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Cells

Cells

  • What is a cell?

    A cell is a membrane bound unit containing hereditary material and other compounds that make metabolism, growth and reproduction possible.

Hereditary

material

Plasma

membrane

Cytoplasm


Cells1

Cells

  • Overview of cell structure

    • Cells are surrounded by a plasma membrane.

    • DNA the hereditary material is packaged in one or more chromosomes located in a nuclear region or nucleus.

    • The cytoplasm contains molecules and organelles needed for cellular activities.

    • Ribosomes are the factories in which proteins are manufactured.


Cells2

Cells

  • How were cells discovered?

    • 1665 Robert Hooke

      Examined cork in simple microscope.

      Saw empty compartments and

      called them ‘cellulae’ (small rooms).

    • 1650 - 1700 Anton Van Leeuwenhoek

      Made his own microscope that could magnify 200 X.

      Observed living things.

      Called them ‘Animacules’ (little animals).


Cells3

Cells

  • Formation of the cell theory

    • 1838 Matthias Schleiden

      Concludes that all plants are made of cells or their derivatives.

      He called this theory phytogenesis

    • 1839 Theodore Schwann

      All animal tissue is made of cells and within an organism these cells are identical.

    • The theory they presented from these observations is often called the Schleiden and Schwann Cell Theory


Cells4

Cells

  • 1855 Rudolph Virchow

    Studied pathenogens and concluded

    ‘omnis cellula e cellua’ which means that all cells arise from pre-existing cells.

  • Principles of the Cell Theory

    • All organisms are composed of one or more cells.

    • Cells are the basic unit of life.

    • Cells arise only by division of a previously existing cell.


  • Cells5

    Cells

    • Cell size

      • Does small cell sizes have advantages?

      • The surface area increases as the square (10 )of the diameter of a sphere, but the volume increases as the cube (10 ).

        small cube - surface area

        small cube - volume

    2

    3

    10 m

    2

    6 x (10 m x

    10 m) = 600 m

    3

    10 m x 10 m x 10 m = 1000 m


    Cells6

    Cells

    2

    6 x (30 m x 30 m) = 5400 m

    • big cell - surface area

    • big cell - volume

    3

    30 m x 30 m x 30 m = 27000 m


    Cells7

    Cells

    2

    • Comparing different sizes

      • Surface area

        1 small = 600 m

        27 small = 16.200 m

        1 big = 5400 m

      • Volume is the same for 1 big and 27 small

      • The ratio of surface to volume

        • 27 small 16200/27000 = 0,6

        • 1 big 5400/27000 = 0,2

        • surface area of small is 3X greater

    2

    2


    Cell size

    Cell size

    • Why aren´t cells larger?

      • limitations of molecular diffusion

        • faster passage through small cells

        • more efficient communication

      • limitations of surface/volume ratio

        • with in size greater in volume

        • interaction occurs only at surface

        • insufficient exchange of materials at plasma membrane


    Structure of prokaryotes

    Structure of prokaryotes

    • Strong cell wall made of carbohydrate matrix and peptide units.

      • Slime capsule (some times with pili), not always present.


    Structure of prokaryotes1

    Structure of prokaryotes

    • Simple interior organization

      • lack internal compartmentalization

      • reactions not separated, one metabolic unit

      • lack membrane-bound organelles

      • infolding of plasma membrane

    • Rotating flagella

      • cell movement - screw like motion


    Structure of prokaryotes2

    Structure of prokaryotes

    • Ribosomes in the cytoplasm

      • protein synthesis

    • Circular nuclear matter (DNA)

      • located in the nucleoid region

    • Plasmids

      • small independent circular DNA

    • Mesosome

      • infolding of plasma membrane often associated with photosynthesis


    Structure of eukaryotes

    Structure of eukaryotes

    • More complex than prokaryotes

    • They are compartmentalized

      • possess internal membrane bound organelles

        • ribosomes

        • rough endoplasmic reticulum (rER)

        • lysosomes

        • Golgi apparatus (complex)

        • mitochondria

        • nucleus

        • chloroplasts


    Structure of eukaryotes1

    Structure of eukaryotes

    • Nucleus the largest organelle

      • the nuclear envelope

        • double layer of membranes,

        • outer continuous with ER

        • nuclear pores

        • restrict passage of molecules to proteins and RNA

      • chromosomes - chromatid

        • contain hereditary material

        • divided into linear chromosomes, associated with histone protein


    Structure of eukaryotes2

    Structure of eukaryotes

    • the nucleolus

      • an assembly plant for ribosomal subunits

        • ribosomal proteins are made in the cytoplasm

        • ribosomal RNA made in the nucleus


    Organelles

    Organelles

    • Endoplasmic reticulum

      • Thin membrane not visible in the light microscope.

      • Divides interior into compartments.

      • Cytoskeleton, holds the cell shape.

    • Rough ER

      • covered with ribosomes

      • manufactures proteins for export

    • Smooth ER

      • lacks ribosomes

      • carbohydrate and lipid synthesis


    Organelles1

    Organelles

    • Ribosomes

      • Made of two parts.

      • Made in the nucleus.

      • Assist in the manufacture of proteins.

    • Golgi apparatus


    Organelles2

    Organelles

    • Mitochondrion

    • Lysosome


    Organelles3

    Organelles

    • Chloroplast


    Cells8

    Cells

    • State two similarities between prokaryotic and eukaryotic cells.

    • State two differences between the eukaryotic nucleus and the prokaryotic nuclear material.


    Endosymbiosis

    Endosymbiosis

    • Symbiosis is two organisms living in close association.

  • Mitochondria and chloroplasts are thought to be ancient bacteria that became incorporated into eukaryotic cells.

    • Evidence supporting Theory:

      • both are surrounded by double membranes

      • mitochondria and bacteria hvae similar size

      • mitochondrial ribosomes resemble bacterial ribosomes

      • both have circular DNA like bacteria

      • mitochondria divide by simple fission


  • The plant cell wall

    The Plant Cell Wall


  • Login