Chapter 7 Cellular Structure and Function

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Chapter 7 Cellular Structure and Function

• 7.1 Cell Discovery and Theory

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The History of the Cell Theory

• Cells are the basic units of living things
• Before microscopes people believed diseases were
  caused by curses and supernatural spirits (wrath
  of God)
• The idea that a living thing like a bacteria
  could cause disease or infection never occurred.
  Why?

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Development of the Light Microscope

• Today's microscope is a compound microscope with
  two lenses
• Eyepiece lens
• Objective lens
• Can magnify 1500 times

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Simple Light Microscope

• Developed by Anton van Leeuwenhoek in the mid
  1600
• One lens
• Much like a magnifying glass

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The Cell Theory

• Robert Hook
• First to use the term cell
• Looked a cork under a microscope, saw the cell
  walls

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Robert Hook

• Contemporary of Anton van Leeuwenhoek
• English
• Published and encouraged others to use microscopes

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Matthias Schleiden

• 1838
• German botanists
• Examined plants of all types
• All plants are made of cells

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Theodore Schwann

• 1839
• German zoologist
• Contemporary of Schleidens
• Examined animal tissues of many types
• All animals are made of cells

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Rudolph Virchow

• 1855
• German physician
• All cells come from preexisting cells

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The Cell Theory

• All organisms are composed of one or more cells
• Unicellular or multicellular
• The cell is the basic unit of organization of all
  organisms
• Structure
• Function
• All cells come from preexisting cells

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Technology Since the 1800s

• Compound light microscopes continued to improve
  so that bacteria were able to be classified
• Most magnification possible with light
  microscopes cannot see inner cell parts

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Electron Microscopes

• Developed in the 1940s
• Uses magnets to focus a beam of electrons (in
  place of light)
• Can magnify 500,000X
• Several types
• Scanning looks at surface get 3-D
• Transmission looks at interior
• Scanning-Tunneling atoms on surface

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Microscope Aids

• Both light and electron microscopes use dyes and
  stains which helps to contrast cell and parts
• Most dyes and stains kill the cells
• Most specimens of electron microscopes need to be
  in a vacuum and/or coated with gold

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Two Basic Cell Types

• Eukaryote
• Have plasma membrane
• Internal membrane bound structures
• Unicellular and multicellular
• Larger size
• Much specialization
• Example animal

• Prokaryote
• Have plasma membrane
• No internal membrane bound structures
• Unicellular
• Smaller in size
• No specialization
• Example bacteria

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Two Basic Cell Types
Prokaryote
Eukaryote
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Two Basic Cell Types
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Chapter 7 Cellular Structure and Function

• 7.2 The Plasma Membrane

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Plasma Membrane Diagram
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Plasma Membrane Micrograph
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Plasma Membrane Structure

• Made of phospholipid bilayer
• Polar ends are hydrophilic
• Nonpolar ends are hydrophobic

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Plasma Membrane Function

• Job of plasma membrane is homeostasis- maintain
  balance
• For cells to survive they must keep the inside in
  and the outside out, yet allow some materials to
  move into and out of the cell

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Structure Fits Function

• The structure of the plasma membrane (how it is
  put together) allows the plasma membrane its
  function or job, selective permeability
• Selective permeability the ability to allow some
  materials into or out of the cell but not other
  materials

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Selective Permeability
Out side of cell is different from inside of cell
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Structure Fits Function

• Both the inside of the cell and the outside are
  water environment so the hydrophilic ends face in
  and out
• The hydrophobic fatty tails are in the middle so
  that materials cant pass through easily

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Structure Fits Function

• Role of proteins in plasma membrane
• Channels or tunnels for substances to pass
  through with specific fit
• Identification of organism and tissue type
• Signal sending proteins
• Provide support for the phospholipids

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Plasma Membrane Proteins
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Plasma Membrane

• Cholesterol stabilizes the plasma membrane in
  animal cells
• Animal cells have no cell wall as do plant cell
• High blood cholesterol is a risk factor for heart
  disease and stroke
• Animals (including us) produce cholesterol for
  the stabilization of the cell membrane

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Fluid Mosaic Model
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Fluid Mosaic Model

• FLUID Plasma membrane in constant motion with
  the phospholipids of one layer moving one
  direction and the phospholipids of the other
  layer moving in the opposite direction
• MOSAIC something consisting of a number of
  different things of different types

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Chapter 7 Cellular Structure and Function

• 7.3 Structures and Organelles

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Cellular Boundaries

• Plant Cell outer most part is the cell wall
  plasma membrane is inside of the cell wall
• Also fungi, algae and other Kingdom Protista
  organisms

• Animal Cell outer most part is the plasma
  membrane
• Also protozoans (Kingdom Protista)

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Cell Wall

• Functions to protect and support
• NOT selectively permeable
• Porous let anything in
• Plant cell wall made of cellulose (wood)

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Plant Cell Wall
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Nucleus

• Controls all cell activities
• Contains information to make proteins all parts
  of the cell depend on proteins to do its job

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Nucleus

• Contains DNA in strands known as chromatin
  (chromosomes are chromatin that is condensed and
  visible during cell reproduction)

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Nucleolus

• Found in the nucleus
• Organelle that makes ribosomes
• Ribosomes are sites where proteins are
  manufactured

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Ribosomes

• Ribosomes are unique because they do not have a
  membrane around them
• Found in prokaryotes and eukaryotes
• Look like pepper on the ER (spaghetti)

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Nuclear Membrane

• Also called Nuclear Envelope
• Surrounds the nucleus
• Same composition as the plasma membrane
• Contains pores to allow large materials to pass
  out (ribosomes and RNA)

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Cytoplasm

• All the gelatinous material with the organelles
  inside the cell between the nucleus and the cell
  membrane
• Cytosol is that part of the cytoplasm that is
  liquid

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Organelles for Assembly, Transport and Storage

• Endoplasmic Reticulum (ER)
• Golgi Apparatus
• Vacuoles
• Lysosomes
• All have phospholipid bilayer membrane structure

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Endoplasmic Reticulum (ER)

• Folded membrane like an accordion for workspace
• Rough ER contains ribosomes for protein
  production
• Smooth ER (No ribosomes) for lipid production
• Tube-like for transport of materials

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Golgi Apparatus

• Takes protein from the ER and makes it ready to
  be transported
• Like UPS, packages it and gives it a destination
  address

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Vacuoles

• Large central vacuole in plant cells to store
  water
• Smaller vacuoles for storage of food, waste,
  water, enzymes and other substances in both plant
  and animal cells

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Lysosomes

• Double membrane bound sac containing digestive
  enzymes
• Digests food particles, engulfed viruses and
  bacteria, and worn out cell parts
• Can fuse with vacuole to digest contents of
  vacuole

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Energy Transformers

• Chloroplasts
• Mitochondria
• Both have phospholipid bilayer membrane structure

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Chloroplasts

• Capture light energy and produce food to be used
  later
• Pigment chlorophyll give plants their green color
• Other plastids store starch, lipids and other
  pigments

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Chloroplasts

• Double membrane
• Clear outer
• Folded inner thylakoid
• Stacks of membranes sacs grana and liquid stroma
• Site of photosynthesis

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Mitochondria

• Break down food to release energy
• Found in eukaryotes

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Mitochondria

• Double membrane
• Outer
• Folded Inner to increase membrane space
• Some cells need much energy and have hundreds of
  mitochondria other cell have few mitochondria
  because these cells use little energy
• Site of cellular respiration

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Structures for Support and Locomotion

• Cytoskeleton
• Cilia
• Flagella

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Cytoskeleton

• Internal framework in the cell to keep the
  organelles in place
• Maintains the cells shape
• Made of microtubules (hollow) and microfilaments
  (solid) protein fibers
• Shown in green

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Centrioles

• Made of groups of microtubules
• Function in cell division (Ch. 9)

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Cilia and Flagella

• Enclosed by plasma membrane
• Used for locomotion and feeding
• Made of pair of microtubules surrounded by 9
  additional pairs

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Cilia

• Short numerous hair like projections
• Beat like oars on a boat
• Line our respiratory system

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Flagella

• Tail like structure that is whip like
• May have one flagella or several
• Mostly used for locomotion

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Chapter 7 Cellular Structure and Function

• 7.4 Cellular Transport

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Passive Transport

• NO energy expended by cell
• Diffusion
• Facilitated diffusion
• Osmosis

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Diffusion

• All molecules are in constant motion called
  Brownian Motion
• The high the temperature the faster the motion
  because they have more energy
• Diffusion is the net movement of particles from
  higher concentration to lower concentration
  because of this movement of particles
• Diffusion is slow because it is a random process

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Rates of Diffusion

• Concentration of substances involved
• More concentrated substances speed up rate of
  diffusion
• Energy by temperature or agitation
• Increased temperature speeds up rate of diffusion
• Agitation or stirring speeds up rate of diffusion
• Pressure
• Increased pressure speeds up diffusion because
  pressure increases molecular movement

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Dynamic Equilibrium

• Equilibrium is reached when there is no net
  concentration change
• Dynamic because Brownian motion continues

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Diffusion in Living Systems

• In living things materials must diffuse into and
  out of cells all the time
• Concentration gradient exists so that substances
  will move into the cell until there is the same
  number on each side
• Liquids, solids and gasses can diffuse into and
  out of a cell

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Facilitated Diffusion

• Diffusion of materials through proteins in cell
  membranes
• NO energy required
• Common for sugars and amino acids

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Osmosis

• Diffusion of water through a cell membrane
• Cell membranes are selectively permeable
• NO energy expended by the cell
• Moves water from high concentration to low
  concentration
• Must occur for homeostasis to occur

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Control of Osmosis

• Unequal distribution of particles on either side
  of a selectively permeable membrane
• Water moves through the membrane until
  equilibrium is reached (no net change)

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Cells in Solutions

• Isotonic Solution same solutes
• Hypotonic Solution lower solutes
• Hypertonic Solution higher solutes

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Cells in Isotonic Solutions

• Isotonic solutions have the same solute
  concentration as the cell, so water moves in and
  out at the same rate no osmosis no net change
• Dissolved substances outside the cell equals
  dissolved substances inside the cell
• Examples Normal saline IV solution (0.9 salt)
  and tap water in most areas

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Cells in Hypotonic Solutions

• Dissolve substances lower outside the cell than
  inside the cell
• Water moves into the cell cell swells
• Animal cell bursts
• Plant cell becomes more firm (higher turgor
  pressure) reason why plants are sprayed at
  grocery store
• Example Distilled water

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Cells in Hypotonic Solutions
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Cells in Hypertonic Solutions

• Dissolved substances higher outside the cell than
  inside the cell
• Water leaves the cell cell shrinks
• Animal cell wrinkled (reason why meat is salted
  after cooking)
• Plant cell plasmolyzed cell membrane moves away
  from cell wall
• Example salt water, syrup

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Cells in Hypertonic Solutions
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Cells in Solutions
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Comparing Plant and Animal Cells
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Active Transport

• ENERGY used by the cell
• Carrier proteins with a SPECIFIC FIT with a
  specific molecule
• Bringing substances into the cell against the
  concentration gradient

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Active Transport

• When molecule fits with carrier protein the
  carrier protein molecule changes shape to allow
  the molecule to move into or out of the cell
• When movement complete, the carrier protein
  changes back to original shape for another
  molecule

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Active Transport

• Also used to rid the cell of materials against
  the concentration gradient
• Takes energy to use a pump
• Much of your cells energy is expended in the
  sodium-potassium pump
• (2 K in 3 Na out)

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Large Materials Into Cells

• Endocytosis, getting large materials INTO the
  cell
• Cell expends energy
• Engulfs and forms a vacuole
• Example white blood cells engulfing a bacteria

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Large Materials Out of Cells

• Exocytosis large materials out of a cell
• Cell expends energy
• Example secretions or hormones
• Example waste products

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