Cell structure and function
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Cell Structure and Function. Chapter 4. Early Discoveries. Mid 1600s - Robert Hooke observed and described cells in cork Late 1600s - Antony van Leeuwenhoek observed sperm, microorganisms 1820s - Robert Brown observed and named nucleus in plant cells. Developing Cell Theory.

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Early discoveries
Early Discoveries

  • Mid 1600s - Robert Hooke observed and described cells in cork

  • Late 1600s - Antony van Leeuwenhoek observed sperm, microorganisms

  • 1820s - Robert Brown observed and named nucleus in plant cells


Developing cell theory
Developing Cell Theory

  • Matthias Schleiden

  • Theodor Schwann

  • Rudolf Virchow


Cell theory
Cell Theory

1) Every organism is composed of one or more cells

2) Cell is smallest unit having properties of life

3) Continuity of life arises from growth and division of single cells


Cell

  • Smallest unit of life

  • Can survive on its own or has potential to do so

  • Is highly organized for metabolism

  • Senses and responds to environment

  • Has potential to reproduce


Structure of cells
Structure of Cells

All start out life with:

  • Plasma membrane

  • Region where DNA is stored

  • Cytoplasm

Two types:

  • Prokaryotic

  • Eukaryotic


Lipid bilayer

one layer

of lipids

one layer

of lipids

Lipid Bilayer

  • Main component of cell membranes

  • Gives the membrane its fluid properties

  • Two layers of phospholipids

Figure 4.3Page 56


Membrane proteins
Membrane Proteins

Recognition protein

Receptor protein

extracellular environment

lipid bilayer

cytoplasm

Protein pump across bilayer

Protein channel across bilayer

Protein pump

Figure 4.4Page 57


Why are cells so small
Why Are Cells So Small?

  • Surface-to-volume ratio

  • The bigger a cell is, the less surface area there is per unit volume

  • Above a certain size, material cannot be moved in or out of cell fast enough


Microscopes
Microscopes

  • Create detailed images of something that is otherwise too small to see

  • Light microscopes

    • Simple or compound

  • Electron microscopes

    • Transmission EM or Scanning EM


Eukaryotic cells
Eukaryotic Cells

  • Have a nucleus and other organelles

  • Eukaryotic organisms

    • Plants

    • Animals

    • Protistans

    • Fungi


Animal cell features
Animal Cell Features

  • Plasma membrane

  • Nucleus

  • Ribosomes

  • Endoplasmic reticulum

  • Golgi body

  • Vesicles

  • Mitochondria

  • Cytoskeleton

Figure 4.10bPage 61


Plant cell features

Cell wall

Central vacuole

Chloroplast

Plant Cell Features

  • Plasma membrane

  • Nucleus

  • Ribosomes

  • Endoplasmic reticulum

  • Golgi body

  • Vesicles

  • Mitochondria

  • Cytoskeleton

Figure 4.10aPage 61


Functions of nucleus
Functions of Nucleus

  • Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm

  • Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells


Components of nucleus
Components of Nucleus

nuclear envelope

nucleoplasm

nucleolus

chromatin

Figure 4.11bPage 62


Nuclear envelope
Nuclear Envelope

  • Two outer membranes (lipid bilayers)

  • Innermost surface has DNA attachment sites

Nuclear pore

bilayer facing cytoplasm

Nuclear envelope

bilayer facing nucleoplasm

Figure 4.12bPage 63


Cytomembrane system
Cytomembrane System

  • Group of related organelles in which lipids are assembled and new polypeptide chains are modified

  • Products are sorted and shipped to various destinations


Components of cytomembrane system
Components of Cytomembrane System

Endoplasmic reticulum

Golgi bodies

Vesicles


Endoplasmic reticulum
Endoplasmic Reticulum

  • In animal cells, continuous with nuclear membrane

  • Extends throughout cytoplasm

  • Two regions - rough and smooth


Golgi body
Golgi Body

  • Puts finishing touches on proteins and lipids that arrive from ER

  • Packages finished material for shipment to final destinations

  • Material arrives and leaves in vesicles

budding

vesicle

Figure 4.15Page 65


Vesicles
Vesicles

  • Membranous sacs that move through cytoplasm

  • Lysosomes

  • Peroxisomes


Mitochondria
Mitochondria

  • ATP-producing powerhouses

  • Membranes form two distinct compartments

  • ATP-making machinery embedded in inner mitochondrial membrane


Mitochondrial origins
Mitochondrial Origins

  • Mitochondria resemble bacteria

    • Have own DNA, ribosomes

    • Divide on their own

  • May have evolved from ancient bacteria that were engulfed but not digested


Specialized plant organelles
Specialized Plant Organelles

  • Plastids

  • Central Vacuole


Chloroplasts
Chloroplasts

Convert sunlight energy to ATP through photosynthesis


Other plastids
Other Plastids

  • Chromoplasts

    • No chlorophyll

    • Abundance of carotenoids

    • Color fruits and flowers red to yellow

  • Amyloplasts

    • No pigments

    • Store starch


Cytoskeleton
Cytoskeleton

  • Present in all eukaryotic cells

  • Basis for cell shape and internal organization

  • Allows organelle movement within cells and, in some cases, cell motility


Flagella and cilia
Flagella and Cilia

microtubule

  • Structures for cell motility

  • 9 + 2 internal structure

dynein

Figure 4.25Page 73


Plant cell walls
Plant Cell Walls

Secondary cell wall

(3 layers)

Primary cell wall


Plant cuticle
Plant Cuticle

  • Cell secretions and waxes accumulate at plant cell surface

  • Semitransparent

  • Restricts water loss


Matrixes between animal cells
Matrixes between Animal Cells

  • Animal cells have no cell walls

  • Some are surrounded by a matrix of cell secretions and other material


Prokaryotic structure
Prokaryotic Structure

pilus

cytoplasm

with ribosomes

DNA

flagellum

capsule

cell wall

plasma membrane


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