Chapter 7: Cell Structure and Function

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Chapter 7 Cell Structure and Function

• 7.1 Life is Cellular
• 7.2 Eukaryotic Cell Structure
• 7.3 Cell Boundaries
• 7.4 The Diversity of Cellular Life

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Chapter 7 Concept Map
The History of the Cell Theory
Scientists
Leeuwenhoek
Schleiden
Virchow
Robert Hooke
Schwann
Compound Microscope
Cell
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Chapter 7 Concept Map
Structures for Locomotion
Flagella
Cilia
Cellular Organization
Multicellular
Unicellular
Tissue
Organs
Types of Microscopes
Organ System
SEM
TEM
Electron
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Chapter 7 Concept Map
Diffusion
Osmosis
Types of Solutions
Equilibrium
Concentration Gradient
Isotonic Solution
Passive Transport
Hypotonic Solution
Hypertonic Solution
Facilitated Diffusion
Active Transport
Exocytosis
Endocytosis
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The Discovery of Cells

• Cell The basic unit of living organisms.
• Anton van Leeuwenhoek Described living cells by
  looking through a simple microscope.
• Compound Microscope has a series of lenses that
  magnify an object in steps. Used by Robert Hooke
  to study cork.

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Cell Theory

• Schleiden and Schwann concluded that all plants
  and animals were made up completely of cells.
• Virchow said new cells new could be produced
  only from the division of existing cells
• The Cell Theory states that
• All organisms are composed of one or more cells.
• The cell is the basic unit of organization in all
  organisms.
• All cells come from pre-existing cells

• http//www.zoology.ubc.ca/courses/bio204/lab1_phot
  os.htm

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The Electron Microscope

• Capable of magnifying a specimen 500,000X their
  actual size. Does this by sending electrons
  through a magnetic field to focus them on the
  specimen and then through another magnetic field
  to focus them and produce an image on a
  flourescent screen.
• Allows us to see structures
• within a cell!
• Several different kinds of
• electron microscopes
• now exist.

Weevil, mag. by electro microscope

• http//www.mos.org/sln/sem/weevil.html

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Two Cell Types

• There are two basic cell types that you need to
  be aware of
• Prokaryotes Cells that lack internal
• membrane-bound structures
• Ex. Bacteria, see Fig. 7.2 on p. 180
• Eukaryotes Contain membrane-bound
• structures.
• Many chemical rxns. can occur simultaneously
  because of compartmentalization.
• These membrane-bound structures are called
  organelles
• Ex. Animal cells, plant cells, see Fig. 7.2 on p.
  180

• http//micro.magnet.fsu.edu/cells/animalcell.html

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The Plasma Membrane
Found in both prokaryotes and eukaryotes.

• Extremely important in maintaining the
  concentrations of solutes inside and outside of
  the cell.
• It is selecvtively permeable only certain
  molecules are let in or out at any given time.
• Cell must maintain homeostasis the process of
  maintaining the cells chemical environment,
  internally and externally.

http//micro.magnet.fsu.edu/cells/animals/plasmame
mbrane.html
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The Plasma Membrane Structure

• Lipid Bilayer Lipids with a phosphate group
  attached to them and arranged in rows facing each
  other.
• Ex. See p. 182, Fig. 7.12
• These rows of phospholipids form the main
  structural component of the plasma membrane.

Phospholipid Bilayer
http//micro.magnet.fsu.edu/cells/animals/plasmame
mbrane.html
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The Plasma Membrane Structure

• Transport and Membrane-bound proteins Proteins
  found embedded in phospholipid bilayer, they also
  help give structural support.
• They let only certain molecules through
• Often span from the outside to the inside of the
  cell. See Fig. 7.4.
• They help connect the phospholipid bilayer to the
  interior framework of the cell.

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The Plasma Membrane Structure
Membrane-Bound Protein
http//micro.magnet.fsu.edu/cells/animals/plasmame
mbrane.html
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The Plasma Membrane Structure

• The model of the plasma membrane is called the
  fluid mosaic model because the phospholipid
  bilayer and its associated proteins can move like
  fluid and yet still create an impressive barrier
  against the outside environment.

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Cellular Boundries

• We have already discussed the plasma membrane
• Plant, fungi, most bacteria, and other cells have
  a cell wall. It is a rigid structure located
  right outside of the plasma membrane providing
  added protection and support.
• Made of cellulose, not selectively permeable
• See p. 186 Fig. 7.7

http//micro.magnet.fsu.edu/cells/plantcell.html
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The Nucleus

• Controls the activity of the organelles.
• Controls protein production (DNA)
• Contains chromatin In the form of DNA
• Chromatin is simply strands of DNA
• When the cell divides, chromatin condenses, or
  becomes packed into a small area. When this
  happens, the chromatin is then called a
  chromosome.

http//micro.magnet.fsu.edu/search/index.asp
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The Nucleus
http//micro.magnet.fsu.edu/search/index.asp
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The Nucleus

• Nuclear Envelope Creates enclosure for nucleus.
  Has a double membrane and has large pores for
  rapid transport of materials.
• Nucleolus An organelle within the nucleus that
  produces ribosomes.
• Ribosomes are the sites where proteins
• and enzymes are assembled
• according to the instructions
• given by the DNA.
• Not found only in the nucleus.

http//micro.magnet.fsu.edu/cells/animals/ribosome
s.html
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The Nucleus
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The Nucleus
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Cytoplasm

• Defined as the clear gelatinous fluid inside of a
  cell.
• Holds all of the organelles of the cell.
• Kept out of nucleus by nuclear envelope.

http//micro.magnet.fsu.edu/cells/animals/endoplas
micreticulum.html
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Diffusion

• Diffusion is the movement of particles through a
  medium from an area of high concentration to an
  area of low concentration. Diffusion continues
  until there is no more concentration gradient.
• Diffusion occurs because of Brownian motion, or
  the random movement of molecules caused by their
  kinetic energy.

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Cellular Transport

• Osmosis The diffusion of water across a
  selectively permeable membrane.
• Review
• Plasma Membrane- Phospholipid Bilayer
• Concentration Gradient
• Homeostasis
• Fig. 8.1 p. 202

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Types of Solutions

• Isotonic Solution Concentration of solutes is
  the same inside and outside the cell.
• No osmosis occurs
• A dynamic equilibrium is occurring molecules are
  moving back and forth across membrane but there
  is no concentration gradient created.
• Dynamic Movement or change
• Equilibrium An equality or balance

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Types of Solutions

• Hypotonic Solution The concentration of solutes
  is less outside the cell than inside the cell.
  See p. 203, Fig. 8.3
• Remember we call the cells environment the
  solution that it is in.
• Water moves by osmosis into the cell!
• The cell tends to swell.

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Types of Solutions

• Hypertonic Solution The concentration of solutes
  is more outside the cell than inside the cell.
  See p. 203 Fig. 8.4
• Osmosis causes water to flow out of the cell.
• Cells will shrink or shrivel for this reason.

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Comparison of Hypo, Iso, and Hypertonic Solutions
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Not in Book!!

• Turgor Pressure The pressure in a plant cell
  that results from water flowing into the cell.
• Associated with a hypotonic soltuion.
• Gives plants their shape and ability to stand up.
  Without it they wilt!

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Not in Book!!

• Contractile Vacuole A vacuole that contacts and
  removes water from the inside of the cell.
• Only found in certain organisms (common in
  one-celled).

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Not in Book!!

• Plasmolysis Loss of pressure within a cell
  causing the cell to shrivel
• Associated with a hypertonic solution
• In plants turgor pressure is lost (wilting
  occurs), animal cells just shrivel

http//www.apsnet.org/online/feature/xmasflower/im
ages/figure22sm.jpg
http//www.biology.arizona.edu/cell_bio/problem_se
ts/membranes/graphics/hypertonic_plt.gif
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Cell Membrane Proteins

• Carrier Proteins Span through plasma membrane
  (transport proteins) and change shape to help
  molecules get from one side to the other.
• Their exposed ends open and close like a gate.
• Channel Proteins Span through plasma membrane
  (transport proteins) and create an opening where
  molecules can pass through.
• They do not change shape.

Carrier
Channel
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/io.uwinnipeg.ca/simmons/cm1503/membranefunction.
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Passive Transport

• Passive Transport the process of particles
  moving through a membrane with no assistance or
  energy from the cell or its parts.
• Water, lipids, and some lipid soluble substances
  can move by passive transport.
• Also O, N, and CO2
• Molecules can move through channel proteins or
  through membrane itself.

http//www.bmb.psu.edu/courses/bisci004a/cells/fac
iltat.jpg
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Facilitated Diffusion

• Facilitated Diffusion The process of proteins
  helping large molecules across the plasma
  membrane.
• No energy is used by the cell or its parts!
  (passive)
• Movement is powered by the concentration
  gradient.
• See p. 204 Fig. 8.5

http//www.mhhe.com/biosci/genbio/enger/student/ol
c/art_quizzes/genbiomedia/0086.jpg
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Active Transport

• Active Transport The process of the cell using
  its own energy to move molecules across the
  plasma membrane against the concentration
  gradient.
• These molecules are moving the opposite way they
  would naturally move due to diffusion.
• Carrier proteins receive the energy and then do
  the work.
• Energy comes from the mitochondria

http//www.bmb.psu.edu/courses/bisci004a/cells/act
ive.jpg
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Active Transport

• Endo- and Exocytosis
• Both forms of active transport
• See p. 206 Fig. 8.7
• Learn these on your own!
• Note Phagocytosis and Pinocytosis is a form of
  endocytosis
• Phagocytosis one cell engulfing another.
• Pinocytosis tiny pockets form along the cell
  membrane fill with liquid and pinch off to form
  vacuoles within the cell.