STRUCTURE AND FUNCTION OF THE CELL

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STRUCTURE AND FUNCTION OF THE CELL

• Developed by Adam F. Sprague

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Cells

• Both Living and Nonliving Things are composed of
  molecules made from chemical elements such as
  carbon, hydrogen, oxygen, and nitrogen.  The
  organization of these molecules into Cells is one
  feature that distinguishes Living Things from all
  other matter.  The CELL is the smallest unit of
  matter that CAN Carry on ALL the PROCESSES OF
  LIFE.

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OBJECTIVES

• Outline the discoveries that led to the
  development of the Cell Theory. 
• State the cell theory.  
• Describe the relationship between cell shape and
  cell function. 
• Distinguish between prokaryotes and eukaryotes.

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History

• 1. In 1665, the English Scientist Robert Hooke
  used a microscope to examine a thin slice of cork
  and described it as consisting of "a great many
  little boxes".  It was after his observation that
  Hook called what he saw "Cells". They looked like
  "little boxes" and reminded him of the small
  rooms in which monks lived, so he called the
  "Cells".
• 2 . In 1838, German Botanist Matthias Schleiden
  studied a variety of PLANTS and concluded that
  all PLANTS "ARE COMPOSED OF CELLS".
• 3. The next year, German Zoologist Theodor
  Schwann reported that ANIMALS are also made of
  CELLS and proposed a cellular basis for all life.
  
• 4. In 1855, German Physician Rudolf Virchow
  induced that "THE ANIMAL ARISES ONLY FROM AN
  ANIMAL AND THE PLANT ONLY FROM A PLANT" OR " THAT
  CELLS ONLY COME FROM OTHER CELLS".
• 5.   His statement contradicted the idea that
  life could arise from Nonliving Matter.  "Theory
  of Spontaneous Generation"  The process by which
  life begins when ethers enter nonliving things.

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CELL THEORY

• A. All living things are composed of one or more
  cells.
•     B. Cells are the basic units of structure and
  function in an organism.
•     C. Cells come only from reproduction of
  existing cells.

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CELL SHAPE

• Cells come in a variety of Shapes
• THE SHAPE OF A CELL DEPENDS ON IT'S FUNCTION
• ExampleCells of the Nervous System that carry
  information from your toes to your brain are long
  and threadlike.
• 6.  Blood Cells are shaped like round disk that
  can squeeze through tiny blood vessels.

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INTERNAL ORGANIZATION

• 1. Cells contain a variety of Internal Structures
  called ORGANELLES.
• 2. An organelle is a Cell Component that PERFORMS
  SPECIFIC FUNCTIONS FOR THE CELL.
• 3. The entire cell is Surrounded by A THIN
  MEMBRANE, called the CELL MEMBRANE
• 4. A Large Organelle near the Center of the Cell
  is the NUCLEUS.  IT CONTAINS THE CELL'S GENETIC
  INFORMATION AND CONTROLS THE ACTIVITIES OF THE
  CELL.

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The PRESENCE OR ABSENCE of a NUCLEUS is important
for Classifying Cells.

• 1. ORGANISMS WHOSE CELL CONTAIN A NUCLEUS AND
  OTHER MEMBRANE-BOUND ORGANELLES ARE CALLED
  EUKARYOTES.
• 2. ORGANISMS WHOSE CELLS NEVER CONTAIN (OR LACK)
  A NUCLEUS AND OTHER MEMBRANE-BOUND ORGANELLES ARE
  CALLED PROKARYOTES.

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Differences between

• - UNICELLULAR ORGANISMS such as bacteria and
  their relatives are Prokaryotes.
• -   All other organisms are Eukaryotes plants,
  fish, mammals, insects and humans.
• -  The difference between Prokaryotes and
  Eukaryotes is such an important distinction that
  Prokaryotes are placed in Two Kingdoms, Separate
  from Eukaryotes.

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PARTS OF THE EUKARYOTIC CELL

• OBJECTIVES 
• Describe the structures, composition, and
  function of the cell membrane. 
• Name the major organelles found in a Eukaryotic
  cell, and describe their function. 
• Describe the structure and function of the
  nucleus. 
• Describe three structures characteristic of
  plant cells.

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THE CELL MEMBRANE

• All cells, from all organisms, are surrounded by
  a CELL MEMBRANE
• The Cell Membrane is a thin layer of Lipid and
  Protein that separates the cell's content from
  the world around it
• The Cell Membrane CONTROLS the ease with which
  substances pass into and out of the cell-some
  substances easily cross the membrane, while
  others cannot cross at all.  For this reason, the
  Cell Membrane is said to be SELECTIVELY PERMEABLE

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Cell Membranes are made mostly of PHOSPHOLIPID
MOLECULES

• Phospholipids are a kind of Lipid that consists
  of TWO FATTY ACIDS (TAILS), and PHOSPHATE GROUP
  (HEADS)
• A Phospholipid Molecule has a  POLAR "Head" and
  Two NONPOLAR "Tails
• The Phosphate Head is HYDROPHILIC meaning
  "WATERLOVING".   Because of its hydrophilic
  nature, the head of a Phospholipid will orient
  itself so that it is as close as possible to
  water molecules.
• The Lipid Tails are HYDROPHOBIC meaning
  "WATER-FEARING", the Hydrophobic tails will tend
  to orient themselves away from water
• When dropped in WATER, PHOSPHOLIPIDS line up on
  the surface with their Phosphate Heads Sticking
  into the Water and Lipid Tails pointing up from
  the surface.

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MEMBRANE PROTEINS

• There are many kinds of Proteins in membranes
  they HELP to MOVE Material INTO and OUT of the
  Cell
• Some Integral Proteins form Channels or Pores
  through which certain substances can pass
• Other Proteins bind to a substance on one side of
  the Membrane and carry it to the other side of
  the Membrane

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FLUID MOSAIC MODEL OF CELL MEMBRANES

• 1.Membranes are FLUID and have the consistency of
  vegetable oil.
• 2. The Lipids and Proteins of the Cell Membrane
  are always in motion.
• 3. Phospholipids are able to drift across the
  membrane, changing places with their neighbor.
• 4. Because the Membrane is FLUID with a MOSAIC of
  Proteins, scientists call the modern view of
  Membrane Structure THE FLUID MOSAIC MODEL

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CYTOPLASM

• 1.  EVERYTHING BETWEEN THE CELL MEMBRANE AND THE
  NUCLEUS IS THE CELL'S CYTOPLASM.
• 2.  CYTOPLASM consists of TWO MAIN COMPONENTS 
  CYTOSOL and ORGANELLES.
• 3.  CYTOSOL is a jellylike mixture that consists
  MOSTLY OF WATER, along with PROTEINS,
  CARBOHYDRATES, SALTS, MINERALS and ORGANIC
  MOLECULES.
• 4.  Suspended in the Cytosol are tiny ORGANELLES
  (ORGANS).
• 5.  ORGANELLES ARE STRUCTURES THAT WORK LIKE
  MINIATURE ORGANS, THEY CARRY OUT SPECIFIC
  FUNCTIONS IN THE CELL.

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MITOCHONDRIA

• THE "POWERHOUSE" OF THE CELL
• Mitochondria are the sites of Chemical Reactions
  that transfer Energy from Organic Compounds to
  ATP.  Energy contain in food is released.
  Converted to ATP.  ATP is the molecule that most
  Cells use as their main Energy Currency
• Mitochondria are Usually more numerous in Cells
  that have a High Energy Requirement - Your muscle
  cells contain a large number of mitochondria

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RIBOSOMES

• Ribosomes are the site of PROTEIN SYNTHESIS
• They are Most Numerous Organelles in almost all
  cells
• Some are free in the Cytoplasm others line the
  membranes of ROUGH ENDOPLASMIC RETICULUM

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ENDOPLASMIC RETICULUM

• The ER functions Primarily as an Intracellular
  Highway, a path along which molecules move from
  one part of the cell to another
• Transports materials through the cell
• ROUGH ER is studded with RIBOSOMES and processes
  PROTEINS to be exported from the cell.
•     B. SMOOTH ER IS NOT Covered with RIBOSOMES
  and processes LIPIDS and CARBOHYDRATES. The
  Smooth ER is involved in the synthesis of
  steroids in gland cells, the regulation of
  calcium levels in muscle cells, and the breakdown
  of toxic substances by liver cells

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GOLGI APPARATUS

• The Golgi Apparatus is the Processing, Packaging
  and Secreting Organelle of the Cell.
• 2. The Golgi Apparatus is a system of membranes.
  Made of Flattened SAC like Structures called
  CISTERNAE.
• 3. It works Closely with the ER, the Golgi
  Apparatus modifies proteins for export by the
  cell.

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LYSOSOMES

• Lysosomes are the Site of Food Digestion in the
  Cell.
• 3.  Lysosomes are formed from pieces of the GOLGI
  APPARATUS that break off.
• 4. Lysosomes are common in the Cells of Animals,
  Fungi, and Protists, But Rare in Plant Cells

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CYTOSKELETON

• In Animal Cells, an internal framework called
  CYTOSKELETON maintains the Shape of the Cell
• The CYTOSKELETON consists of TWO Types of
  structures MICROFILAMENTS AND MICROTUBULES

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MICROFILAMENTS AND MICROTUBULES

• MICROFILAMENTS
• 1. MICROFILAMENTS are NOT HALLOW and have a
  structure that resembles ROPE made of TWO
  TWISTED CHAINS OF PROTEIN called ACTIN.
• 2. MICROFILAMENTS can CONTRACT, causing movement.
  
• 3. Muscle Cells have many microfilaments.
• MICROTUBULES
• 1. Microtubules are HALLOW TUBES like plumbing
  pipes. They are the Largest Strands of the
  Cytoskeleton.
• 2. Microtubules are made of a PROTEIN called
  TUBULIN.
• 3.  Microtubules have THREE FUNCTIONS
•     A. To maintain the shape of the cell.
•     B.  To serve as tracks for organelles to move
  along within the cell.
•     C.   When the Cell is about to divide,
  bundles of Microtubules known as SPINDLE FIBERS
  come together and extend across the cell to
  assist in the movement of Chromosomes during Cell
  Division

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CILIA AND FLAGELLA

• CILIA ARE SHORT HAIRLIKE PROJECTIONS.
• FLAGELLA ARE LONG WHIPLIKE PROJECTIONS

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THE NUCLEUS

• The Nucleus contains DNA, the HEREDITARY MATERIAL
  OF CELLS
• It maintains its shape with the help of a Protein
  skeleton known as the NUCLEAR MATRIX
• The nucleus is surrounded by a Double Layer
  Membrane called the NUCLEAR ENVELOPE
• The DNA is in the form of a long Strand called
  CHROMATIN
• During Cell Division, Chromatin strands COIL and
  CONDENSES into thick structures called
  CHROMOSOMES.
• 10. The Chromosomes in the nucleus contain coded
  "BLUEPRINTS" that control all cellular activity
• The NUCLEOLUS MAKES (syntheisizes) RIBOSOMES,
  WHICH IN TURN, BUILD PROTEINS

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PLANT CELLS

• Plant Cells have Three Additional Structures Not
  found in animals cells - CELL WALLS, VACUOLES,
  AND PLASTIDS that are extremely important to
  Plant Function

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CELL WALL

• Fungi such as Mushrooms and Yeast also have Cell
  Walls.  Cell Walls of Fungi are made of CHITIN.
• 3.  A Cell Wall DOES NOT REPLACE the Cell
  Membrane Cells with WALLS also have a CELL
  MEMBRANE.  Plant Cells are covered by a Rigid
  Cell Wall that lies Outside the Cell Membrane
• Cell Walls of Plants contain POLYSACCHARIDE (long
  chains) CELLULOSE a complex carbohydrate

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CELL WALLS ARE OF TWO TYPES

• A. PRIMARY CELL WALL - While a Plant cell is
  being formed, a primary cell wall develops just
  outside the cell membrane.  As the cell expands
  in length, cellulose and other molecules are
  added, enlarging the cell wall.  When the cell
  reaches full size, a Secondary Cell Wall MAY
  Form.
•     B. SECONDARY CELL WALL - The secondary cell
  walls forms Between the Primary Cell Wall and the
  Cell Membrane.  The Secondary Cell Wall is Tough
  and Woody, in fact the Secondary Cell Wall is
  what we call WOOD.  One a Secondary Cell Wall
  forms, a plant cell can Grow NO Further.  The
  Cells are Dead.

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VACUOLES

• The VACUOLE serves as a STORAGE AREA, and may
  contain stored PROTEINS, IONS, WASTE, OR OTHER
  CELL PRODUCTS
• VACUOLES of some plants contain Poison that
  discourages animals from eating the plant's
  leaves
• Cells of Animals and other organisms also MAY
  contain VACUOLES, but they are much smaller and
  are usually involved in FOOD DIGESTION

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PLASTIDS

• A THIRD distinguishing feature of PLANT CELLS is
  the presence of STRUCTURES CALLED PLASTIDSTHAT
  MAKE OR STORE FOOD
• A common kind of PLASTID is the CHLOROPLAST,
  (figure 4-17) an organelle that converts
  SUNLIGHT, CARBON DIOXIDE, AND WATER INTO SUGARS. 
  This process is called PHOTOSYNTHESIS
• Each Chloroplast encloses a system of Flattened,
  Membranous Sacs called THYLAKOIDS.  It is in the
  Thylakoids that Photosynthesis occurs
• Chloroplasts are GREEN because they contain
  CHLOROPHYLL, a PIGMENT that ABSORBS ENERGY IN
  SUNLIGHT.  THEY ARE FOUND ONLY IN ALGAE, SUCH AS
  SEAWEED, AND IN GREEN PLANTS.
• Other PLASTIDS store reddish-orange pigments that
  color fruits, vegetables, flowers, and autumn
  leaves

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MULTICELLULAR ORGANIZATION

• In a Unicellular Organism, one cell carries out
  all of the functions of life.  In contrast, most
  cells in a Multicellular Organism are Specialized
  to perform one or a few functions.  Because of
  cell specialization, the cells of Multicellular
  Organisms depend on other cells in the organism
  for their survival.

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OBJECTIVES 

• Distinguish between
• tissue,
• organs, and
• organ systems. 

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TISSUE, ORGANS, AND ORGAN SYSTEMS

• Cellular Level  The smallest unit of life
  capable of carrying out all the functions of
  living things.
•     Tissue Level  A group of cells that performs
  a specific function in an organism form the
  TISSUE.
•     Organ Level  Several different types of
  tissue that function together for a specific
  purpose form an ORGAN.
•     Organ System Level  Several organs working
  together to perform a function make up an ORGAN
  SYSTEM.  The different organ systems in a
  multicellular organism interact to carry out the
  processes of life

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Plants also have Tissue and Organs, although they
are arranged somewhat differently from those of
Animals

• A. Dermal Tissue System forms the outer layer of
  a plant.
•     B. Ground Tissue System makes up the bulk of
  roots and stems
•     C. Vascular Tissue transports water and food
  throughout the plant.
•     D. The FOUR Plant Organs are ROOTS, STEMS,
  LEAVES AND FLOWERS

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The End