Transcript Cell Structure and Function

Cell Structure
and Function
Chapter 7
Microscopes : windows to the
world of the cell
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Cells are the basic unit of
life.
The invention and
improvement of microscopes
in the 17th century led to
the discovery and early
study of cells
Robert Hooke observed
“cells” in a slice of cork
History of Cells
1800’s
Schwann –Animal tissues are composed
of cells
Schleiden – Plant materials are
composed of cells
Virchow - All tissues from living
organisms are composed of cells
The Cell Theory
 All
living things are composed of
cells
 Cells are basic units of structure
and function
 All cells come from pre-existing
cells
How Cells are Studied
A.
B.
Microscopy
Cell Fractionation
Microscopes
 An
instrument used
observe minute objects
 Enlarges images of small
objects
Types of Microscope
 Light:
uses light and lenses to
magnify image
 Electron: uses magnets and
electrons to magnify image
Parts of a Microscope
(Eyepiece)
Magnification
 To
calculate:
Power of objective lens x Power
of Eyepiece
 Do these calculations:
Eyepiece = 10x
Objective = 10x; 40x; 100x
Electron Microscope
 Uses
magnets and
electrons to magnify
images
 Magnifies 1000x
better than a light
microscope
 Specimen cannot be
living
Types of Electron
Microscopes
 Transmission
Electron
Microscope: internal
structures
 Scanning Electron
Microscope: surface
structures
The Eukaryotic Animal Cell
The Eukaryotic Plant Cell
Major Type of Cells
 There
are two basic types of
cells
 Prokaryotic & Eukaryotic
 A major difference between
prokaryotic and eukaryotic
cells is the location of
chromosomes.
Prokaryotic Cells
Lacks a nucleus and
most other
organelles
 DNA concentrated
in nucleoid region
 Bacteria and Archae
 1-10 micrometers
 Appear earliest in
earth’s fossil record
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 Nucleus
Eukaryotic Cells
surrounded
by its membrane
 Internal organelles
bounded by
membranes
 10 – 100
micrometers
 Protists, Fungi,
Plants, Animals
Cell Structure
Section 7.2
Cell Organization
 Cytoplasm
Cytoplasmic
 Nucleus
inclusions
/ Nuclear region
 Cell Membrane/Wall
Cytoplasm
 Fluid
portion of the cell
 All cellular organelles are
suspended in it
 Organelles specialized
structures that perform various
functions
Nucleus & it’s Contents
Nucleus & it’s Contents
 Chromosomes
carry the cell’s
genetic information
Always remain in the nucleus
 RNA carries this message
from the nucleus to the
ribosomes moves through the
nuclear pores
Storage, Cleanup and
Support
 Vacuolesstore
water, salts,
carbohydrates & proteins
 Lysosomes filled with
enzymes breakdown of
macromolecules
 Cytoskeleton  maintains shape
& helps in movement
Microfilaments
Threadlike structures made of actin
 Forms an extensive network
 Helps cells move
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Microtubule
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Centriole
Hollow structures made of 
tubulin
Maintain shape in many cells
Centrioles in animals cells 
made of tubulin help organize
cell division not present in
plant cells
Project from the surface cilia
& flagella movement
Cilia
Building Protein
 Ribosomes
 Endoplasmic
Reticulum
 Golgi Apparatus
Ribosome
Endoplasmic Reticulum
(rough & smooth)
Protein Synthesis
Golgi Body
Capture and Release Energy
 The
cellular machinery
constantly needs energy to
function.
 Supplied by two organelles the
Chloroplasts & Mitochondria
Chloroplasts Sunlight to
Chemical energy
Mitochondria
Convert chemical
energy in food to
a form that the
cell can useATP
 All mitochondria
come from the
cytoplasm of the
egg cell
inherited from
the mother
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Endosymbiosis
Chloroplasts and mitochondria are
similar to prokaryotes
 Lynn Margulis in 1960 evidence that
chloroplasts and Mitochondria evolved
as endosymbionts
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 Both
have DNA, RNA and Ribosomes that
prokaryotic
 They replicate their own DNA
 Divide by binary fission
RNA World
Miller & Urey 1953, organic molecules
necessary for life have arisen from
simpler compounds
 Origin of life RNA evolved before
DNA
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Cellular Boundaries
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Cell Walls
 Provides
support
 Confers shape
 Protects the cell
 Present in plants and prokaryotes
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Cell Membranes
 Regulates
what enters and leaves the cell
 Selectively Permiable
Cell/Plasma Membrane
 Boundary
that separates the
interior of a living cell from it’s
surroundings and regulates the
traffic of chemicals into and out of
the cell
 Phospholipid
 Protein
Bilayer
“icebergs” float in a
“sea” of phospholipids
Phospholipid Molecule
 Composed
of
proteins and a type
of lipid called
phosopholipid
(glycerol+2 fatty
acids)
Protein “icebergs” in a “sea” of
phospholipids
Plasma Membrane
Cell Transport
Section 7.3
Function of Cell Membranes
 Materials need to move in and
out of the cell
 Function like gatekeepers,
letting some molecules
through, but not others 
“Selectively Permeable”
Types of Transport
Passive
Transport
Diffusion
Facilitated
Active
Transport
Transport
Diffusion
The spread of molecules
from areas of high
concentration, to areas of
low concentration.
 Equilibrium when the
molecules are even
throughout a space
 Concentration Gradient 
difference between
concentrations in a space.
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Passive Transport
 Diffusion Some
substances are
allowed to move
freely
Facilitated diffusion
transport proteins
Osmosis
 The
diffusion of
water (across a
membrane)
 Water will move in
the direction where
there is a high
concentration of
solute and low
water concentration
Osmosis
 Dissolved molecules ( ions, organic
molecules, etc) are called solutes
 Most solutes cannot cross
membranes
 As solute conc increases “free”
H2O decreases
 Hypertonic high [solute]
 Hypotonic  low [solute]
Isotonic- means the same
Hypotonic- less solute
Hypertonic- high solute
Water Balance in Animal Cells
•Water flow
equal in both
directions
•Net water flow
into the cell
which can burst
(Hemolysis)
Net water flow
out of cell
which shrinks
(Crenation)
Water Balance in Plant Cells
Turgid
Flaccid
Plasmolysis
 Shrinking
of cytoplasm in both
plant and animal cells
Active Transport
 Cell
expends energy to move molecules
or ions across the membrane
 A specific transport protein pumps
solute across a membrane
 The chemical energy is supplied by the
mitochondria
 Example Na+(Sodium) K+(Potassium)
pump.
Active Transport
Transport of Large Molecules
 Large
molecules have to be
packaged to be transported in
and out of the cell
 Vesicles (membranes sacs) are
formed to move the substances
Exocytosis
Endocytosis
Exocytosis & Ednocytosis
More Exo & Endo