Cell Structure and its Environment.ppt
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Cell Structure and
its Environment
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Early Discoveries
During 1665, Robert Hooke observed and
described cells in cork
Tiny compartments = cellulae
Small rooms
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Early Discoveries
Antonie Van Leeuwenhoek
- improves microscope
- first to observe and describe the single-
celled organisms
(animalculesmicroorganisms)
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Early Discoveries
Robert Brown (1831)published observationsreporting the discovery and widespreadoccurrence of nuclei in the cells
Matthias Schleiden (1838)Discovered thatplant parts are made of cells
Theodore Schwann (1839)Discovered that
animal parts are made of cells Rudolph Virchow (1855)Stated that all living
cells come only from other living cells
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Cell Theory
1) Every organism is composed of one or
more cells2) Cell is smallest unit having properties of
life
3) Continuity of life arises from growth and
division of single cells
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Cell
Smallest unit that lives on its own
Each cell is structurally organized for
metabolism
Potential to reproduce
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Types of Cell
Prokaryotic cell
Eukaryotic cell
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Prokaryotic cell
Smallest known cell
Tiny volume of cytoplasm
Membranes dont enclosed DNA
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Parts
Or capsule
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Eukaryotic cell
Present in plants, animals and fungi
Has organelles and nucleus
Animal cell Plant cell
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Structural Organization of Cells
Plasma membrane
Nucleus
Cytoplasm
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Plasma Membrane
Selectively isolates the cells contents from
the external environment
Regulates the exchange of essentialsubstances between the cells contents
and the external environment
Communicates with other cells
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Plasma MembraneLipid Bilayer
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Membrane Proteins
Proteinpump across
bilayer
Proteinchannel
across bilayer
Protein pump
Recognitionprotein
Receptorprotein
extracellularenvironment
cytoplasm
lipid bilayer
Figure 4.4Pa e 57
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Membrane Proteins
proteins
double layer of lipids
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Why arent all cells big?
The smaller or narrower the cell, the more
efficiently materials cross its surface and
become distributed through the interior.
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Common Features of Eukaryotic
Cells Nucleuslocalizing the cells DNA
Endoplasmic reticulumprotein and lipid
synthesis Golgi bodysorting and shipping proteins
Lysosomes/Peroxisomestransporting or
storing a variety of substance
Mitochondriaproducing many ATP molecules
in highly efficient fashion
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The Nucleus
Control center of
eukaryotic cells
The organelle thatphysically separates
DNA from cytoplasmic
machinery
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Components of Nucleus
nuclear envelope
nucleoplasm
nucleolus
chromatin
Figure 4.11b
Page 62
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Components of the Nucleus
Nuclear Envelopepore riddled double
membrane system that selectively controls
the passage of various substances intoand out of the nucleus
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Nuclear Envelope
Two outer membranes (lipid bilayers)
Innermost surface has DNA attachment sites
Nuclear pore bilayer facing cytoplasm Nuclear envelope
bilayer facingnucleoplasm
Figure 4.12bPa e 63
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Components of the Nucleus
Nucleoplasmfluid interior portion of the
nucleus
NucleolusConstruction site wherecertain RNAs and proteins are combined
to make ribosomal subunits
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ChromatinTotal collection of all DNA
molecules and their associated proteins in
the nucleus ChromosomeOne DNA molecule and
many proteins that are intimately
associated with it
Components of the Nucleus
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Series of functionally connected
organelles in which lipids are assembled
and new polypeptide chains are modified. Products are sorted and shipped to
different destination
Endomembrane System
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Components of Endomembrane
System
Endoplasmic Reticulum
Golgi Bodies
Vesicles
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Endoplasmic Reticulum
In animal cells, continuous with nuclear
membrane
Extends throughout cytoplasm
Two regions - rough and smooth
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Endoplasmic Reticulum and the Ribosomes: protein
production machine
Endoplasmic Reticulum (ER)
source: http://cellbio.utmb.edu/cellbio/ribosome.htm
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Golgi Body
Puts finishing touches on proteins and
lipids that arrive from ER
Packages finished material for shipment tofinal destinations
Material arrives and leaves in vesicles
buddingvesicle
Figure 4.15Pa e 65
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Vesicles
Membranous sacs that move through
cytoplasm
Lysosomes
Organelle of intracellular digestion
Peroxisomes
Breaks down fatty acids and amino acids
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Lysosomes Rich in digestive enzymes (that work at low
pH)
Digest bacteria that invade a cell
Recycling of membrane components
Repair damage to plasma membrane
Get rid of toxic substances Many in the liver
Peroxisomes
lysosome
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Mitochondrial Origins
Mitochondria resemble bacteria
Have own DNA, ribosomes
Divide on their own
May have evolved from ancient bacteriathat were engulfed but not digested
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Mitochondria
Contain their own genome
(distinct from nuclear
genome)
Self-replicating
Critical role in generation of
energy (called ATP):
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Glycolysis (without oxygenuse)
- Krebs cycle (in presence of
oxygen)
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Non-membranous Structures and
their Functions RibosomesAssembling polypeptide
chains
CytoskeletonImparting overall shapeand internal organization to the cell;
locomotion
MicrotubulesMicrofilaments
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Cytoskeleton
Reinforce, organize, and move internal cell
parts
MicrofilamentsTwo polypeptide chains of actin monomers
Structural support
MicrotubulesProteins cylinders (tubulin monomers)
move cell interior
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Cytoskeleton
Intermediate filaments
Help strengthen and maintain the shape of
cells and cell parts
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The cytoskeleton: a cell's
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The cytoskeleton: a cell sscaffold
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Specialized Plant Organelles
Chloroplasts
Chromoplasts
Amyloplasts Central Vacuole
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Chloroplast
Use sunlight energy to drive the formation
of ATP and NADPH.
Used to assemble sugars and some otherorganic compounds
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Chloroplast
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Thylakoid membrane
The first stage of photosynthesis starts
where many light-trapping pigments,
enzymes and other proteins areembedded
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Plastids
Chromoplast
- Lacks chlorophyll, but they have an
abundance in carotenoids
Amyloplast
- Lacks pigments, often they store starch
grains and are abundant in cells of stems,potato tubers, and seeds
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Central Vacuole
Fluid-filled organelle surrounded by singlemembrane
Stores amino acids, sugars, ions and toxic
wastes Helps the cell grow
It expands during growth
Blue or purple pigments stored in the central
vacuoles are responsible for the colors of theflower
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How Do Cells Move?
Cilia
Flagella
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Cell Surface Specializations
Cell wall
- structural component that wraps
continuously around the plasmamembrane
- it is porous
Cell Junction- where a cell sends and receives signalsand materials, and where it recognizesitself to cells of the same type
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Plant Cell Walls
Primary cell wall
Secondary cell wall
(3 layers)
Thin and pliable
Permits the cell to continue to
enlarge under the pressure of
incoming water
reinforces cell shape
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Animal Cell Junctions
tight
junctionsadhering
junctiongap
junction
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Cell Communication
- one cell signals another to change its
activities
Cell Surface Specializations