Human Biology

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Chapter 3

• Human Biology
• Seventh Edition
• Dr. Linda J. Pepper
• (c) The McGraw-Hill Companies, Inc.

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Cell Size

• All living things are composed of cells.
• The cell is the smallest functional living unit
  of the body.
• New cells arise only from preexisting ones.
• Cells are small to maintain an optimal surface
  area to volume ratio so they can adequately
  exchange materials with their environment.

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Microscopy and Cell Structure

• The compound light microscope passes light rays
  through specimens and uses glass lenses to view
  objects.

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Transmission Electron Microscope

• This type of microscope passes electrons through
  a specimen, focuses with a magnetic lenses, and
  projects images onto a fluorescent screen or
  photographic film.

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Scanning Electron Microscope

• Passes a beam of electrons over the surface of a
  metal-coated specimen, collecting them to produce
  a television-type 3-D picture on a screen.

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Cellular Organization

• A human cell is bounded by a plasma membrane
  which encloses a central nucleus surrounded by
  cytoplasm. The cytoplasm contains organelles,
  small membraneous structures and the cytoskeleton.

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The Plasma Membrane

• Plasma membrane is a bilayer of phospholipids
  with embedded or attached proteins. These
  embedded proteins may serve as hormone receptors,
  transport channels and enzymes in metabolic
  reactions. The plasma membrane is selectively
  permeable allowing molecules into and out of the
  cell.

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Plasma Membrane Functions

• Diffusion Random movement of molecules from an
  area of higher concentration to one of lower
  concentration.
• Osmosis diffusion of water across a plasma
  membrane.
• Transport by Carriers
• Facilitated crosses the membrane with the help
  of a protein carrier using no energy.
• Active uses carrier but requires energy

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The Nucleus

• The nucleus stores the genetic information in the
  cell. The DNA directs protein synthesis in the
  cytoplasm. It contains one or more nucleoli,
  where ribosomal RNA (rRNA) is manufactured. The
  nuclear envelope is a double membrane with
  nuclear pores

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Ribosomes

• Ribosomes are the site of protein synthesis in
  the cytoplasm and are a mix or rRNA and proteins.
  Ribosomes occur in the cytoplasm, both singly
  and in groups. Numerous ribosomes are attached
  to the endoplasmic reticulum.

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Membraneous Canals and Vesicles

• The endomembrane system consists of the nuclear
  envelope, endoplasmic reticulum, the Golgi
  apparatus, and several vesicles like lysosomes
  (tiny membraneous sacs).

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The Endoplasmic Reticulum

• Series of membranes that form tubular channels
  within the cytoplasm. Rough ER with ribosomes
  specializes in protein synthesis. Smooth ER
  produces different compounds in different cells.

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The Golgi Apparatus and Lysosomes

• A stack of flattened vacuoles with vesicles near
  the edges, packages, stores, and distributes the
  proteins the ER produces. Also produces lysosomes
  which contain enzymes that digest unwanted
  materials inside the cell, including worn-out
  cell parts.

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Mitochondria

• Bounded by a double membrane.
• Inner membrane is folded into a cristae.
• Gel-like material between cristae is the matrix.
• Converts energy stored in glucose.
• Carry on cellular respiration and help you
  release carbon dioxide.

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The Cytoskeleton

• Filamentous protein structures, microtubules, and
  actin filaments that serve as the framework for
  the cells interior.
• Centrioles-short cylinders with an arrangement of
  9 microtubules that occur in pairs. Centrioles
  give rise to the formation of cilia and flagella.

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The End.