Cell Structure and Function

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Cell Structure and Function

• Chapter 7

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Microscopes windows to the world of the cell

• 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

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History of Cells
1800s Schwann Animal tissues are composed of
cells Schleiden Plant materials are composed
of cells Virchow - All tissues from living
organisms are composed of cells
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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

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How Cells are Studied

1. Microscopy
2. Cell Fractionation

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Microscopes

• An instrument used observe minute objects
• Enlarges images of small objects

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Types of Microscope

• Light uses light and lenses to magnify image
• Electron uses magnets and electrons to magnify
  image

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Parts of a Microscope
(Eyepiece)
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Magnification

• To calculate
• Power of objective lens x Power of Eyepiece
• Do these calculations
• Eyepiece 10x
• Objective 10x 40x 100x

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Electron Microscope

• Uses magnets and electrons to magnify images
• Magnifies 1000x better than a light microscope
• Specimen cannot be living

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Types of Electron Microscopes

• Transmission Electron Microscope internal
  structures
• Scanning Electron Microscope surface structures

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The Eukaryotic Animal Cell
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The Eukaryotic Plant Cell
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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.

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Prokaryotic Cells

• Lacks a nucleus and most other organelles
• DNA concentrated in nucleoid region
• Bacteria and Archae
• 1-10 micrometers
• Appear earliest in earths fossil record

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Eukaryotic Cells

• Nucleus surrounded by its membrane
• Internal organelles bounded by membranes
• 10 100 micrometers
• Protists, Fungi, Plants, Animals

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Cell Structure

• Section 7.2

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Cell Organization

• Cytoplasm
• Cytoplasmic inclusions
• Nucleus / Nuclear region
• Cell Membrane/Wall

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Cytoplasm

• Fluid portion of the cell
• All cellular organelles are suspended in it
• Organelles? specialized structures that perform
  various functions

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Nucleus its Contents
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Nucleus its Contents

• Chromosomes? carry the cells genetic information
• Always remain in the nucleus
• RNA? carries this message from the nucleus to the
  ribosomes? moves through the nuclear pores

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Storage, Cleanup and Support

• Vacuoles?store water, salts, carbohydrates
  proteins
• Lysosomes? filled with enzymes? breakdown of
  macromolecules
• Cytoskeleton ? maintains shape helps in
  movement

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Microfilaments

• Threadlike structures made of ?actin
• Forms an extensive network
• Helps cells move

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Microtubule
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
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Building Protein

• Ribosomes
• Endoplasmic Reticulum
• Golgi Apparatus

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Ribosome
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Endoplasmic Reticulum (rough smooth)
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Protein Synthesis
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Golgi Body
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Capture and Release Energy

• The cellular machinery constantly needs energy to
  function.
• Supplied by two organelles the Chloroplasts
  Mitochondria

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Chloroplasts? Sunlight to Chemical energy
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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
• Both have DNA, RNA and Ribosomes that prokaryotic
• They replicate their own DNA
• Divide by binary fission

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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

• Cell Walls
• Provides support
• Confers shape
• Protects the cell
• Present in plants and prokaryotes
• Cell Membranes
• Regulates what enters and leaves the cell
• Selectively Permiable

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Cell/Plasma Membrane

• Boundary that separates the interior of a living
  cell from its surroundings and regulates the
  traffic of chemicals into and out of the cell
• Phospholipid Bilayer
• Protein icebergs float in a sea of
  phospholipids

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Phospholipid Molecule

• Composed of proteins and a type of lipid called
  phosopholipid (glycerol2 fatty acids)

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Protein icebergs in a sea of phospholipids
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Plasma Membrane
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Cell Transport

• Section 7.3

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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

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Types of Transport

• Passive Transport
• Diffusion
• Facilitated Transport
• Active Transport

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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

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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

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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

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Isotonic- means the same
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Hypotonic- less solute
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Hypertonic- high solute
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Water Balance in Animal Cells

• Net water flow into the cell which can burst
  (Hemolysis)

• Water flow equal in both directions

Net water flow out of cell which
shrinks (Crenation)
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Water Balance in Plant Cells

• Turgid Flaccid

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Plasmolysis

• Shrinking of cytoplasm in both plant and animal
  cells

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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.

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Active Transport
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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

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Exocytosis Ednocytosis
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More Exo Endo