Chapter 3 Notes, part 1

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Chapter 3 Notes, part 1

• Looking at Cells
• Cells were discovered in the 17th century, when
  microscopes were invented.

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Cells were discovered by..

• Robert Hooke, in 1665 he looked at a thin piece
  of cork and saw a lot of little boxes which
  reminded him of the small rooms where monks live,
  so he called them cells
• Anton von Leeuwenhoek used a microscope ten years
  later to view water from a pond, and he called
  the tiny organisms he saw animalcules

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Measurement

• See table 1, p. 50
• Cells are measured in units of micrometers,
  abbreviated µm. The symbol µ stands for the
  prefix micro
• See figure 2, page 51, which shows the sizes of
  different objects

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Know these words..

• Magnification the amount of times a specimen
  being viewed is enlarged in order to be seen,
  varies with power of microscope
• Resolution the ability that the microscope has
  to distinguish between two different objects, ie.
  The nucleus vs. the endoplasmic reticulum
• Contrast ability to see detail within the
  specimen clearly

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Types of microscopes

• Light microscope
• Transmission and scanning electron microscopes
• Scanning tunneling microscope

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Compound light microscopes

• What we work with in class
• Light rays pass through specimen and come into
  focus through two glass lenses.
• The eyepiece lens gives a total of 10x
  magnification. The objective lens varies with
  microscopes but can be up to 100x magnification.
  Total magnification is found by multiplying
  eyepiece lens by objective lens.

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Transmission Electron Microscopes

• Use electrons to pass through specimens to view
  detail image projected onto screen or
  photographic film

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Scanning electron microscopes

• The specimen is first coated with a thin layer of
  metal and an image is produced by the electrons
  which bounce off of the image

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Scanning tunneling microscopes

• New video and computer techniques are increasing
  microscope resolution and magnification
• This type of microscope uses a needle-like probe
  to measure voltages of electrons. It can track
  the movement of electrons and can see atoms!

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Compare the images produced by different
microscopes..

• See p. 52 for a light microscope image of sperm
• See p. 53 for a T.E.M. image of sperm
• See p. 54 for an S.E.M. image of sperm

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Section 3.2 Cell Features

• The cell theory was bulit on the ideas of Hooke
  and Leeuwenhooek by the following
• Schleiden who said that cells make up every part
  of a plant
• Schwann who claimed that animals are also made of
  cells
• Virchow who determined that cells come from other
  cells.

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The cell theory summarized

• All living things are made of one or more cells
• Cells are the basic unit of structure and
  function in organisms
• All cells arise from existing cells

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Cell size and sufrace areavolume ratio

• Small cells function more efficiently than larger
  cells
• If the surface area of a cell is larger than its
  volume, then the cell can gather essential
  nutrients and water and they can get in fast.
• If the surface area to volume ratio is close in
  number to the volume, it takes too long for
  materials to reach the interior of the cell
• See table 2 p. 55

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Common features of cells

• Most cells have
• A cell membrane encloses cell, separates
  interior
• Cytoplasm the fluid in which interior cell
  structures are suspended, also called cytosol
• Cytoskeleton for cellular structure
• Ribosomes make proteins
• DNA all cells have DNA which contains
  instructions for making proteins, regulating the
  activities of the cell, and allowing the cell to
  reproduce. Red blood cells lose their DNA at a
  certain point in their life.

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Prokaryotes

• A single-celled organism that lacks a nucleus and
  other internal compartments
• Common prokaryotes which cause infection and
  spoil food Bacteria

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Characteristics of Prokaryotes

• Have little internal structure
• Many have a capsule and flagella
• DNA is located near the center of the cell and is
  not contained in a nucleus
• A cell wall surrounds the membrane and provides
  structure and support
• Many have flagella which propel them along

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Typical prokaryote
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Eukaryotic Cells

• Cells with a nucleus and other organelles
• An organelle is a structure within a cell that
  carries out specific activities for that cell
• Some eukaryotic cells have cilia which are short
  hairlike structures that protrude from the
  surface of the cells

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cytoskeleton

• Provides the internal framework of an animal
  cell, much as our skeleton provides the internal
  framework of our bodies
• Three types of cytoskeleton fibers
• Actin fibers found just inside of the cell
  membrane helps cell membrane move
• Microtubules transport information from nucleus
  to different parts of the cell
• Intermediate fibers keep ribosomes and enzymes
  in place within cell

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The cell membrane

• to separate the internal from external
  environment of the cell
• Regulates materials entering and leaving the
  cell.
• Helps the cell, in turn the organism, maintain
  homeostasis

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cell membrane structure

• Made up of a phospholipid bilayer
• Phospholipid a molecule with a hydrophilic
  (water-loving) head and a hydrophobic
  (water-fearing) tail

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Cell membrane proteins

• Proteins embedded in the membrane have polar and
  nonpolar ends just like the membrane this keeps
  them embedded inside of the membrane
• These proteins have different functions
• Receptor proteins recognize and bind to
  substances outside the cell
• Enzymes assist chemical reactions in the cell
• Transport proteins help substances move across
  the membrane

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Upcoming Biology Schedule

• This weekends homework worksheet packet
• Monday chapter 3 lab (read)
• Wednesday go over lab/test review
• Friday (Happy Halloween!) TEST!!!