Cell Structure and Function

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Cell Structure and Function

• Chapter 3

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AKS STANDARDS 8a - state the cell theory
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The size range of cells.
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The History of the Microscope
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Early studies led to the development of the cell
theory.
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Cells The Basic Unit of Life

• The accumulated research of Schleiden, Schwann,
  and Virchow can be summarized in the cell theory,
  one of the first unifying concepts in the field
  of biology
• All organisms are made of cells.
• All existing cells are produced by other living
  cells.
• The cell is the most basic unit of life.

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Prokaryotic cells lack a nucleus and most
internal structures of eukaryotic cells.

• Prokaryotes
• NO NUCLEUS, but do have nucleoid region with DNA
  present
• Small and Simple do not contain membrane-bound
  organelles
• Have cell membranes and cytoplasm
• All are single-celled
• Ex. Bacteria Archaea
• Eukaryotes
• Contain nucleus that house genetic information
• Contains organelles that perform specialized
  functions
• Can be unicellular or multicellular
• Ex. Protists, fungi, plants, and animals

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Prokaryotic Cell v. Eukaryotic Cell
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Diversity of Cellular Life

• Unicellular organisms are made of a single cell.
• This grouping includes all prokaryotes (i.e.
  bacteria archaea) and some eukaryotes (such as
  algae and yeasts).
• Multicellular organisms are made of many cells.
• These organisms are always Eukaryotic (i.e. many
  protistans, most fungi, all plants and animals).

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Cell Specialization

• Cell specialization describes an event where a
  cell becomes specialized to perform a specific
  function for an organism.
• Muscle cells
• Skin cells
• Leaf cells
• Nerve Cells
• Etc.

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Levels of Cellular Organization

• In multicellular organisms
• Individual cells basic unit of life
• Tissues groups of similar cells working
  together for a similar function
• Organs groups of tissues working together
• Organ systems groups of organs working together

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A Comparison of Cells
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Prokaryotic Cell (Bacterium)
Not in Prokaryotic Cells -nucleus -membrane
bound organelles
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Practice, Application Critical Thinking

• The following virtual textbook activities are
  highly recommended
• Section 3.1 Assessment Questions (Textbook pp.
  72)
• Classzone.com Animated Biology Cell Structures
• Interactive Review Concepts Maps Section 1

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AKS STANDARDS 8c - identify common cell
organelles and describe the function of each
(e.g. diagrams and microscopic examinations), 8d
- explain the role of cell organelles (including
the cell membrane) in maintaining homeostasis and
cell reproduction for both prokaryotic and
eukaryotic cells (GPS),
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Cells have an internal structure.

• On a small scale, your cells carry out a
  necessary division of labor.
• They contain specialized structures that work
  together to respond to stimuli and efficiently
  carry out other necessary processes.
• Cell organelles and molecules are anchored to
  specific sites, which vary by cell type.
• The division of labor provided by membrane-bound
  organelles works to increase the overall
  efficiency of cellular processes.

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Animal Cell
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Plant Cell
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Cytoskeleton

• Each eukaryotic cell has a cytoskeleton, a
  network of proteins that is constantly changing
  to meet the needs of the cell.
• The cytoskeleton provides structural support, and
  aids in cell motility and cell regulation.

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Organelleshttp//bcs.whfreeman.com/thelifewire/co
ntent/chp04/0402001.html

• Organelles that function in control
• Nucleus (plant and animal)
• Centrosome (plant and animal)
• Organelles that function in assembly, transport,
  and storage
• Endoplasmic reticulum (plant and animal)
• Ribosomes (plant and animal)
• Golgi apparatus (plant and animal)
• Vacuoles (plant has 1 large and animals
  have many)
• Lysosomes (animal)
• Organelles that function in energy
  transformations
• Chloroplasts (plant only)
• Mitochondria (plant and animal)

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The Nucleus, Nucleolus, and Nuclear Envelop 
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Ribosomes
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Endomembrane System

• Many of the different membranes of the eukaryotic
  cell are part of an ENDOMEMBRANE SYSTEM.
• Membranes within cell are not identical in
  structure or function (modifications are present
  according to job).
• Includes
• nuclear envelope
• endoplasmic riticulum (smooth and rough)
• Golgi apparatus,
• lysosomes
• vacuoles
• plasma membrane

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Relationships Among Organelles of the
Endomembrane System 
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Endoplasmic Reticulum

• The ER is a membranous system of channels and
  flattened sacs that traverse the cytoplasm.
• Exists in 2 varieties
• Rough ER the site of protein synthesis resulting
  from the attached ribosomes
• Smooth ER assists in the synthesis of steroid
  hormones and other lipids
• Also connects rough ER to the Golgi apparatus and
  carries out various detoxification processes in
  liver
• Smooth and rough E.R. are actually connected, not
  distinct, separate sections

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The Golgi Apparatus
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Vesicles

• Cells need to separate reactants for various
  chemical reactions until it is time to be used.
• Vesicles are a general name used to describe
  small membrane-bound sacs that divide some
  materials from the rest of the cytoplasm.
• They transport these materials from place to
  place within the cell.
• Vesicles are generally short-lived and are formed
  and recycled when needed.

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Vacuoles

• A vacuole is a fluid-filled sac used for the
  storage of materials needed by the cell.
• Most animal cells contain many small vacuoles.
• A large central vacuole, as shown in the diagram
  to the right, is a prominent structure unique to
  plant cells.
• It is filled mostly with a watery fluid that
  strengthens the cell and helps to support the
  entire plant.
• When a plant wilts, its leaves shrivel because
  there is not enough water in each cells central
  vacuole to support the leafs normal structure.

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Lysosomes

• Lysosomes are membrane-bound sacs of hydrolytic
  enzymesthey are the principle site of
  intracellular digestion.
• Different lysosomes break down each of the major
  classes of macromolecules proteins,
  polysaccharides, fats, and nucleic acids.
• Lysosomes defend a cell from invading bacteria
  and viruses and are also used in autophagy the
  recycling of the cells own organic material for
  use.

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The Formation and Functions of Lysosomes (Layer 1)
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The Formation and Functions of Lysosomes (Layer 2)
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The Formation and Functions of Lysosomes (Layer 3)
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Centrosomes Centrioles

• The centrosome is a small region of the cytoplasm
  that produces microtubules.
• In animal cells, it contains two small structures
  called centrioles.
• Centrioles are cylinder-shaped organelles
  arranged in a circle.
• Before an animal cell divides, the centrosome,
  including the centrioles, doubles and the two new
  centrosomes move to opposite ends of the cell.
• Microtubules grow from each centrosome forming
  spindle fibers that attach to the chromosomes and
  aid during cell division.

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Peroxisomes
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Mitochondria
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Chloroplasts
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Endosymbiosis and the First Eukaryoteshttp//high
ered.mcgraw-hill.com/sites/9834092339/student_view
0/chapter4/animation_-_endosymbiosis.html

• The hypothesis of endosymbiosis proposes that
  mitochondria and chloroplasts were formerly small
  prokaryotes living within larger host cells.
• An endosymbiont is a cell that lives within a
  host cell.

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Theory of Endosymbiosis
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Evidence Supporting the Endosymbiotic Theory

• Evidence for this hypothesis includes
• Both organelles have enzymes and transport
  systems homologous to those found in the plasma
  membranes of living prokaryotes.
• Both replicate by a splitting process similar to
  prokaryotes.
• Both contain a single, circular DNA molecule, not
  associated with histone proteins.
• Both have their own ribosomes which translate
  their DNA into proteins.

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Cilia and Flagella
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Cell Walls

• In plants, algae, fungi, and most bacteria, the
  cell membrane is surrounded by a strong cell
  wall.
• This rigid layer provides protection, support,
  and shape to the cell.
• The cell walls of multiple cells can adhere to
  each other and help support the entire organism.
• Cell wall composition varies and is related to
  the different needs of each type of organism
• Plants Algae cellulose
• Fungi chitin
• Bacteria peptidoglycan

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Practice, Application Critical Thinking

• The following virtual textbook activities are
  highly recommended
• Section 3.2 Assessment Questions (Textbook pp.
  79)
• Classzone.com Animated Biology Cell Structures
• Interactive Review Concepts Maps Section 2
• Classzone.com WebQuests Organelle Dysfunction
• Data Analysis (Textbook pp. 80) Defining
  Variables

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AKS STANDARDS 8d - explain the role of cell
organelles (including the cell membrane) in
maintaining homeostasis and cell reproduction for
both prokaryotic and eukaryotic cells
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Cell Membrane

• The cell membrane, or plasma membrane, forms a
  boundary between a cell and the outside
  environment and controls the passage of materials
  into and out of a cell.
• The cell membrane consists of a double layer of
  phospholipids interspersed with a variety of
  other molecules.
• The phospholipid heads are polar and are
  directed toward the outside of the membrane.
• The phospholipid tails are nonpolar and are
  directed toward the inside of the membrane.

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Structure Function of Cell Membrane
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Some Functions of Membrane Proteins
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Fluid Mosaic Model of the Cell Membrane
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Selective Permeability

• The cell membrane has the property of selective
  permeability, which means it allows some, but not
  all, materials to cross.
• Selective permeability enables a cell to maintain
  homeostasis in spite of unpredictable, changing
  conditions outside the cell.
• How a particular molecule crosses the membrane
  depends on the molecules size, polarity, and
  concentration inside versus outside the cell.

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Selective Permeability
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Practice, Application Critical Thinking

• The following virtual textbook activities are
  highly recommended
• Section 3.3 Assessment Questions (Textbook pp.
  84)
• Interactive Review Concepts Maps Section 3

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AKS STANDARDS 8g - describe processes whereby
substances enter and leave the cell (passive and
active transport mechanisms), 8h - investigate
factors that affect the rate of cellular
transport (e.g., molecule size, charge,
concentration, temperature), 8i - compare the
reaction of plant and animal cells in solutions
of different solute concentrations (e.g.,
isotonic, hypotonic, hypertonic solutions),
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Passive Transport

• Cells almost continuously import and export
  substances. Passive transport is the movement of
  molecules across a membrane without energy input
  from the cell.
• Diffusion is the movement of molecules in a fluid
  or gas from a region of higher concentration to a
  region of lower concentration.
• A concentration gradient is the difference in the
  concentration of a substance from one location to
  another.
• Molecules generally diffuse down their gradient,
  from a region of high concentration to a region
  of low concentration.
• Diffusion exists in TWO forms
• Dialysis the PASSIVE movement of particles
  across a semi-permeable membrane from an area of
  high particle concentration to an area of low
  particle concentration (no energy).
• Osmosis the PASSIVE movement of water molecules
  across a semi-permeable membrane from an area of
  high water concentration to an area of low water
  concentration (no energy).

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Molecules of dye
Membrane (cross section)
WATER
Equilibrium
Net diffusion
Net diffusion
(a) Diffusion of one solute
Equilibrium
Net diffusion
Net diffusion
Net diffusion
Net diffusion
Equilibrium
(b) Diffusion of two solutes
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Types of Solutions

• All of the components of a solution are evenly
  distributed throughout the solution
• The substance that is dissolved is the solute.
• The substance in which the solute is dissolved is
  the solvent.
• Example salt/water mixture salt is the solute
  and water is the solvent.
• A solution may be
• Hypertonic more solutes than liquid.
• Hypotonic less solutes than liquid.
• Isotonic equal amount of solute and liquid.

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Water Balance of Cells WITHOUT Walls
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Water Balance of Cells WITH Walls
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Hypotonic solution
Isotonic solution
Hypertonic solution
H2O
H2O
H2O
H2O
(a) Animal cell
Lysed
Normal
Shriveled
H2O
H2O
H2O
H2O
(b) Plant cell
Turgid (normal)
Flaccid
Plasmolyzed
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Facilitated Diffusion

• In facilitated diffusion, transport proteins
  speed the passive movement of molecules across
  the plasma membrane from high to low
  concentration NO ENERGY REQUIRED!
• Channel proteins provide corridors that allow a
  specific molecule or ion to cross the membrane
• Channel proteins include
• Aquaporins, for facilitated diffusion of water.
• Ion channels that open or close in response to a
  stimulus (gated channels).
• USEFUL ANIMATION
• http//highered.mcgraw-hill.com/sites/0072507470/s
  tudent_view0/chapter3/animation__how_facilitated_d
  iffusion_works.html

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EXTRACELLULAR FLUID
Channel protein
Solute
CYTOPLASM
(a) A channel protein
Solute
Carrier protein
(b) A carrier protein
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Practice, Application Critical Thinking

• The following virtual textbook activities are
  highly recommended
• Section 3.4 Assessment Questions (Textbook pp.
  87)
• Classzone.com Animated Biology Getting Through
  a Cell Membrane
• Interactive Review Concepts Maps Section 4

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AKS STANDARDS 8g - describe processes whereby
substances enter and leave the cell (passive and
active transport mechanisms),
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Active Transport

• Active Transport uses energy to move molecules
  AGAINST their concentration gradients or in large
  quantity (bulk).
• Active transport is performed by specific
  proteins embedded in the cell membranes.
• Active transport allows cells to maintain
  concentration gradients that differ from their
  surroundings.

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http//www.wiley.com/college/pratt/0471393878/stud
ent/animations/membrane_transport/index.html
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Bulk Transport Across the Cell Membrane

• Small molecules and water enter or leave the cell
  through the lipid bilayer or by transport
  proteins.
• Large molecules, such as polysaccharides and
  proteins, cross the membrane in bulk via
  vesicles.
• Bulk transport requires energy (ACTIVE).
• There are two types of bulk transport in cells
• Endocytosis
• Exocytosis

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Endocytosishttp//highered.mcgraw-hill.com/olc/dl
/120068/bio02.swf

• In endocytosis, the cell takes in liquids or
  fairly large molecules by engulfing them in a
  membrane.

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Exocytosishttp//highered.mcgraw-hill.com/olc/dl/
120068/bio02.swf

• Exocytosis is the opposite of endocytosis, it
  releases substances out of the cell by the fusion
  of vesicles with the membrane.

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Practice, Application Critical Thinking

• The following virtual textbook activities are
  highly recommended
• Section 3.4 Assessment Questions (Textbook pp.
  91)
• Classzone.com Animated Biology Getting Through
  a Cell Membrane
• Interactive Review Concepts Maps Section 5
• Reviewing Vocabulary (Textbook p. 95)
• Reviewing Main Ideas (Textbook pp. 95)
• Critical Thinking (Textbook pp. 96)
• Analyzing Data (Textbook pp. 96)
• Connecting Concepts (Textbook pp. 96)