The Cell

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Chapter 7

• The Cell

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• Cells Were discovered by Robert Hooke. He
  observed the slices of cork from the bark of an
  oak tree-dead plant cells. Van Leewenhoek
  observed pond water saw it was full of living
  things.
• Observations and conclusions of scientists from
  the late 17th century to the time of scientists,
  Schwann, Schleiden, and Virchow are summarized
  into the Cell Theory.

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• Three parts of the cell theory1. All living
  things are made of one or more cells.2. The
  cell is the basic unit of structure and function
  in organisms.3. All cells come from
  pre-existing cells.

Life

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• 1. There are two cell types
• 1.) Prokaryote-the simplest cells
• Small, simple and lack membrane-bound
  organelles.
• They have no nucleus.
• DNA is found floating in the cytoplasm.
• Prokaryotic cells contain
• cell wall
• cell or plasma membrane
• cytoplasm
• ribosomes
• Examples BACTERIA
• Flagella-Many bacteria have flagella, which
  are long, threadlike structures that protrude
  from the cells surface and enable movement.
• Bacteria flagella rotate, propelling a
  bacterium through its environment.

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• 2.)Eukaryote
• Large, complex and contain membrane bound
  organelles such as a nucleus.
• Example Plants, Fungi, and Animals
• Eukaryotic cells have a nucleus which is an
  internal compartment that houses the cells DNA.
  Other internal compartments, called organelles,
  enable eukaryotic cells to function in ways
  different from bacteria.
• An organelle is a structure that carries out
  specific activities in the cell.
• Many single-celled eukaryotes use flagella for
  movement. Short hair like structures packed in
  tight rows, called cilia protrude from the
  surface of some eukaryotic cells. Flagella or
  cilia propel some cells through their
  environment.
• In other cells, cilia and flagella move
  substances across the cells surface. Example
  Cilia on cells of the human respiratory system
  sweep mucus and other debris out of the lungs.

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Flagella
Cilia
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• 2. Cell Size
• The symbol µ stands for the prefix micro. A
  micrometer (µm) is a unit of linear measurement
  equal to one-millionth of a meter, or
  one-thousandth of a millimeter. Cell size and
  organelle size is measured in micrometers (µm).
  This means that they are microscopic.

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Both Animal and Plant Cells Contain These
Organelles

• 1. Cell Membrane
• The cell membrane is primarily composed of
  phospholipids. Various proteins are located in
  the lipid bilayer of a cell membrane. A
  phospholipid is a lipid made of a phosphate group
  (head) and two fatty acids (tails).
• A phospholipid head is polar and its two
  fatty acid tails are nonpolar. Transport
  proteins aid in the movement of substances into
  and out of the cell.
• It surrounds and protects the cell and allows
  only certain substances to pass in and out of the
  cell. The cell membrane allows the cell to
  remain separate from the environment.

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Both Animal and Plant Cells Contain These
Organelles

• Cell Membrane Cont.
• It is a Selectively permeable membrane, which
  means it keeps out some molecules but allows
  others to pass through.
• Small molecules like H2O, CO2,O2 and soluble
  end products of digestion pass through easily.
• Large molecules like glucose and ions do not
  pass through easily.
• The cell membrane regulates or controls what
  comes into and out of the cell. Like gases,
  nutrients and wastes. This control keeps the
  cell alive and well. If it wasnt selectively
  permeable everything on the outside would come
  into the inside.

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Both Animal and Plant Cells Contain These
Organelles

• 2. Cytoplasm
• A fluid-like material that fills the space
  between the cell membrane and the nucleus.
• Contains the organelles
• The cytoskeleton (in the cytoplasm) is a web of
  protein fibers that holds the cell together and
  keeps the cell membrane from collapsing or
  folding.

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Both Animal and Plant Cells Contain These
Organelles

• 3. Nucleus
• The control center of brain of the cell (Most
  functions of a eukaryotic cell are controlled by
  the cells nucleus).
• The nucleus directs cell activities and stores
  DNA.
• Stores DNA which forms long strands called
  chromatin. (Chromatin is made of DNA and
  proteins that become chromosomes during cell
  division. Chromosomes carry the genes (DNA
  and are in the nucleus of eukaryotic cells
• The nucelus is surrounded by a double membrane
  called the nuclear envelope or membrane. The
  nuclear envelope is made of two bilayers that
  separate the nucleus form the cytoplasm.
• Substances that are made in the nucleus include
  ribosomal proteins and RNA, which move into the
  cytoplasm through nuclear pores.

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Both Animal and Plant Cells Contain These
Organelles

• 4. Nucleolus
• Dense struc-
• tures inside the
• nucleus.
• Stores RNA
• that forms
• ribosomes.

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Both Animal and Plant Cells Contain These
Organelles

• 5. Ribosomes
• Tiny dot organelles located on the rough ER and
  throughout the cytoplasm.
• They are the site of protein synthesis.
• A cell makes proteins on ribosomes. The building
  of proteins from amino acids occurs on the cells
  ribosomes.
• Some ribosomes float freely in the cytoplasm,
  while others are attached to the endoplasmic
  reticulum.

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Both Animal And Plant Cells Have These Organelles

• 6. Endoplasmic Reticulum
• Materials can be moved around within a cell by
  using the endoplasmic reticulum. The rough ER
  helps transport the proteins that are made by its
  attached ribosomes. As each protein is made, it
  crosses the ER membrane and enters the ER. The
  portion of the ER that contains the completed
  protein then pinches off to form a vesicle. A
  vesicle is a small, membrane-bound sac that
  transports substances in cells. By enclosing
  certain proteins inside vesicles, the eukaryotic
  cell keeps these proteins separate from proteins
  that are produced by free ribosomes in the
  cytoplasm. Proteins must enter the endoplasmic
  reticulum to be transported to other parts of the
  cell.

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Both Animal And Plant Cells Have These Organelles

• 6 Endoplasmic Reticulum Cont.
• A network of tunnels, channels or canals that
  transports proteins and other substances
  throughout the cell. The canals of the ER
  connect the cell membrane with the nuclear
  membrane.
• Two Types of ER
• 1. Rough ER
• Has ribosomes on the membrane and helps transport
  the proteins that are made by its attached
  ribosomes.
• A vesicle is a small, membrane-bound sac that
  transports substances in cells. By enclosing
  certain proteins inside the vesicles, the
  eukaryotic cell keeps these proteins separate
  from proteins that are produced by free ribosomes
  in the cytoplasm.
• 2. Smooth ER
• It lacks ribosomes (appearing smooth) and
  produces certain lipids.

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Both Animal And Plant Cells Have These Organelles

• 7. Golgi Apparatus
• Vesicles that contain newly made proteins move
  through the cytoplasm from the ER to an organelle
  called the golgi apparatus.
• It is stacks of flattened membranes with vesicles
  that packages and assembles many cell products.
  The Golgi Apparatus serves as the packaging and
  distribution center. It receives, chemically
  modifies, and repackages proteins into forms the
  cell can use, expel, or keep stored. The
  modified proteins are then enclosed in new
  vesicles that bud from the surface of the golgi
  apparatus. Some of these vesicles include
  lysosomes.

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Both Animal And Plant Cells Have These Organelles

• 8. Lysosomes
• Small spherical or-
• ganelles that contain
• digestive enzymes.
• They take care of
• foreign particles
• entering the cell and
• digest worn out cell
• parts.

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Both Animal And Plant Cells Have These Organelles

• 9. Mitochondria
• They are called the powerhouse of the cell
  because it produces energy (ATP).
• They are the site of aerobic cellular
  respiration.
• A cell that requires a lot of energy, like a
  muscle cell, would contain large numbers of
  mitochondria.

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Mitochondria
Power
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Both Animal And Plant Cells Have These Organelles

• 10. Vacuole
• Small, fluid-filled structures that store
  materials like food, enzymes, and other materials
  needed by the cell.
• Plant Cell have a single large vacuole.

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Found In Animal cells Only

• Centrioles
• Tiny, cylindrical structures that are found in
  pairs near the nucleus.
• They are involved in cell division.

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Found In Plant Cells Only

• 1. Chloroplasts
• Small green pigmented structures that contain
  chlorophyll.
• It is the site of photosynthesis.

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Found in Plant Cells Only

• 2. Cell Wall
• The cell wall consists of a mixture of proteins
  and carbohydrates, including the polysaccharide
  cellulose. A polysaccharide is also known as a
  sugar.
• Structure found outside of the cell membrane in
  plants that provides strength and rigidity, but
  does not affect passages of materials in and out
  of the cell
• Plant cells have a LARGE vacuole that stores
  water which can occupy most of the space in a
  plant cell.

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