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How Cells Are Put Together

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In animal cells, continuous with nuclear membrane. Extends throughout cytoplasm ... Present only in animal cells of certain tissues. Most stable cytoskeletal elements ... – PowerPoint PPT presentation

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Title: How Cells Are Put Together


1
How Cells Are Put Together
  • Chapter 4

2
The 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

3
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

4
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

5
Structure of Cells
  • All start out life with
  • Plasma membrane
  • Region where DNA is stored
  • Cytoplasm
  • Two types
  • Prokaryotic
  • Eukaryotic

Eukaryotes
Prokaryotes
6
Lipid Bilayer
  • Main component of cell membranes
  • Gives the membrane its fluid properties
  • Two layers of phospholipids

7
Fluid Mosaic Model
  • Membrane is a mosaic of
  • Phospholipids
  • Glycolipids
  • Sterols
  • Proteins
  • Most phospholipids and some proteins can drift
    through membrane

8
Membrane Proteins
  • Adhesion proteins
  • Communication proteins
  • Receptor proteins
  • Recognition proteins

9
Prokaryotic Cells
  • Archaea and Bacteria
  • DNA is not enclosed in nucleus
  • Generally have one circular genome
  • Generally the smallest, simplest cells
  • No organelles

10
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11
Prokaryotic Structure
bacterial flagellum
pilus
plasma membrane
bacterial flagellum
Most prokaryotic cells have a cell wall outside
the plasma membrane, and many have a thick,
jellylike capsule around the wall.
cytoplasm, with ribosomes
DNA in nucleoid region
12
Eukaryotic Cells
  • Have a nucleus and other organelles
  • Eukaryotic organisms
  • Plants
  • Animals
  • Protistans
  • Fungi

Eukaryotes
Prokaryotes
13
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

14
Components of Nucleus
Nuclear envelope Nucleoplasm Nucleolus Chromatin
15
Chromatin
  • Cells collection of DNA and associated proteins
  • Chromosome is one DNA molecule and its associated
    proteins
  • Generally multiple linear chromosomes
  • per genome
  • Appearance changes as cell divides

16
Nuclear Envelope
  • Two outer membranes (lipid bilayers)
  • Innermost surface has DNA attachment sites
  • Pores span bilayer

one of two lipid bilayers (facing nucleoplasm)
NUCLEAR ENVELOPE
one of two lipid bilayers (facing nucleoplasm)
nuclear pore (protein complex that spans both
lipid bilayers)
17
Nucleolus
  • Dense mass of material in nucleus
  • May be one or more
  • Cluster of DNA and proteins
  • Materials from which ribosomal subunits are built
  • Subunits must pass through nuclear pores to reach
    cytoplasm

18
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19
Endomembrane System
  • Group of related organelles in which lipids are
    assembled and new polypeptide chains are modified
  • Products are sorted and shipped to various
    destinations

20
Components of Endomembrane System
  • Endoplasmic reticulum
  • Golgi bodies
  • Vesicles

21
Endoplasmic Reticulum
  • In animal cells, continuous with nuclear membrane
  • Extends throughout cytoplasm
  • Two regions rough and smooth

22
Rough ER
  • Arranged into flattened sacs
  • Ribosomes on surface give it a rough appearance
  • Some polypeptide chains enter rough ER and are
    modified
  • Cells that specialize in secreting proteins have
    lots of rough ER

23
Smooth ER
  • A series of interconnected tubules
  • No ribosomes on surface
  • Lipids assembled inside tubules
  • Smooth ER of liver inactivates wastes, drugs

24
Golgi Bodies
  • Put finishing touches on proteins and lipids that
    arrive from ER
  • Package finished material for shipment to final
    destinations
  • Material arrives and leaves in vesicles

25
Vesicles
  • Membranous sacs that move through the cytoplasm
  • Lysosomes
  • Peroxisomes

26
Central Vacuole
  • Fluid-filled organelle
  • Stores amino acids, sugars, wastes
  • As cell grows, expansion of vacuole as a result
    of fluid pressure forces cell wall to expand
  • In mature cell, central vacuole takes up 50-90
    percent of cell interior

27
Mitochondria
  • Produce energy for eukaryotic cells
  • ATP-producing powerhouses
  • Double-membrane system
  • Carry out the most efficient energy-releasing
    reactions
  • These reactions require oxygen

28
Mitochondrial Structure
  • Outer membrane faces cytoplasm
  • Inner membrane folds back on itself
  • Membranes form two distinct compartments
  • ATP-making machinery is embedded in the inner
    mitochondrial membrane

29
Chloroplasts
  • Convert sunlight energy to ATP through
    photosynthesis

30
Structure of a Chloroplast
  • Two outer membranes around semifluid interior
    (stroma) bathes inner membrane
  • Often, this single membrane is folded back on
    itself as a series of stacked, flattened disks
  • Each stack is called a thylakoid, which contains
    chlorophylls and other substances involved in
    photosynthesis

31
Endosymbiotic Theory
  • Both mitochondria and chloroplasts resemble
    bacteria
  • Have own DNA, RNA, and ribosomes
  • Once free-living bacteria

32
Plant Cell Features
33
Animal Cell Features
34
Cytoskeleton
  • Present in all eukaryotic cells
  • Basis for cell shape and internal organization
  • Allows organelle movement within cells and, in
    some cases, cell motility

35
Cytoskeletal Elements
intermediate filament
microtubule
microfilament
36
Microtubules
  • Largest elements
  • Composed of the protein tubulin
  • Arise from microtubule organizing centers (MTOCs)
  • Polar and dynamic
  • Involved in shape, motility, cell division

37
Microfilaments
  • Thinnest cytoskeletal elements
  • Composed of the protein actin
  • Polar and dynamic
  • Take part in movement, formation and maintenance
    of cell shape

38
Accessory Proteins
  • Attach to tubulin and actin
  • Motor proteins
  • Crosslinking proteins

39
Intermediate Filaments
  • Present only in animal cells of certain tissues
  • Most stable cytoskeletal elements
  • Six known groups
  • Desmins, vimentins, lamins, etc.
  • Different cell types usually have 1-2 different
    kinds

40
Mechanisms of Movement
  • Length of microtubules or microfilaments can
    change
  • Parallel rows of microtubules or microfilaments
    actively slide in a specific direction
  • Microtubules or microfilaments can shunt
    organelles to different parts of cell

41
Flagella and Cilia
  • Structures for cell motility
  • 9 2 internal structure

42
False Feet
  • Some free-living cells, such as amoebas, form
    pseudopods (false feet)
  • These temporary, irregular lobes project from the
    cell and function in locomotion and prey capture
  • Pseudopods move as microfilaments elongate inside
    them motor proteins attached to the
    microfilaments drag the plasma membrane with them

43
Cell Wall
Plasma membrane
  • Structural component that wraps around the plasma
    membrane
  • Occurs in plants, some fungi, some protistans

Primary cell wall of a young plant
44
Plant Cell Walls
Secondary cell wall (3 layers)
Primary cell wall
45
Plant Cuticle
  • Cell secretions and waxes accumulate at plant
    cell surface
  • Semi-transparent
  • Restricts water loss

46
Matrixes between Animal Cells
  • Animal cells have no cell walls
  • Some are surrounded by a matrix of cell
    secretions and other material

47
Cell Junctions
  • Plants
  • Plasmodesmata
  • Animals
  • Tight junctions
  • Adhering junctions
  • Gap junctions

plasmodesma
48
Animal Cell Junctions
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