Chapter 3 Cells The Basis of Life

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Chapter 3 Cells The Basis of Life

• Environment of the cell
• A. Extracellular environment
• Fluid filled area outside the cell
• B. Intracellular environment
• Fluid filled area inside cell
• Drawings on p.49 fig. 3-1 a and b

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A. Extracellular Environment

• Area outside the cell.
• Contains gases, salts, food particles, and
  cellular products which are materials synthesized
  by cell and released by secretion.
• These cellular
• products are proteins, hormones and vitamins.
• Matrix
• Solid
• Provides structural support

• Intercellular environment
• Compartment of Extracellular environment
  between adjacent cells
• In the extracellular environment, you have
  extracellular fluid (ECF)
• This is a syrup like mixture of water
  products and other substances

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2 Types of ECF

• 1. Plasma
• Located within vessels
• Provides liquid medium for transport of
  substances in blood
• 2. Interstitial fluid
• Located between cells of body
• Provides pathway for substances going to and
  from the cells

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B. Intracellular Environment

• Protoplasm
• Substance of a cell. Composed of water,
  proteins, carbohydrates, fats, nucleic acids and
  electrolytes.
• It is alive when all materials carry out
  activities.
• Characteristics of living things.
• Organization, growth, metabolism,
  reproduction, excitability.

•  This is where most internal cell functions
  occur.
• Energy production.
•  Energy storage.
• Synthesis of new products.

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3 Parts of Protoplasm

• 1.Plasma Membrane (cell membrane)
• Separates inside of cell (intracellular
  environment) from its outside environment
  (extracellular environment). Contains
  intracellular fluid (ICF) which is a mixture of
  water, proteins and other chemicals.

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3 Parts of Protoplasm

• 2.Cytoplasm
• Thickened gel like material which occupies
  most of the ICF. This is where the organelles
  are.

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3 Parts of Protoplasm

• 3. Nucleus
• Regulates activities of cell. Lies within
  intracellular environment.

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Packet questions pp.35-37 1-29

• ?

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Cell Structure and Function

• Common features of cells are plasma membrane,
  cytoplasm and nucleus which all work together to
  provide cellular functions.
• Size is small and measured in micrometers which
  is 1 millionth of a meter. 25,400 micrometers
  equals 1 inch.
• Size varies according to function of cell.

• Model of a cell. Drawing p.50 fig.3-3 Also do
  2-3 observing a human cell.

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Plasma Membrane

• Separates intracellular environment from
  extracellular environment.
• Regulates movement of materials between these
  areas.
• Envelopes cell completely.
• Maintains homeostasis because plasma.
• Membrane regulates materials.

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A. Structure

• Lipid bilayer and protein molecules and a little
  carbohydrates
• Is less than one millionth of an inch thick
• Selectively permeable only allows certain
  substances to pass through.

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Plasma Membrane
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Structure

• Glycoproteins
• Union of proteins and carbohydrates.
  Receptors for substances that must distinguish
  between different types of cells like hormones,
  growth factors and antibodies.

• Proteins
• Peripheral proteins attach to outside and
  inside of cell surface.
• Integral proteins are embedded in the lipid
  bilayer and extend out. These proteins form
  channels and give the cell its status of
  selectively permeable.

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 Modifications of Plasma Membrane

• 1.Microvilli
• Tiny plasma membrane extensions
• Increase surface area
• More materials cross over
• In cells which absorb
• cells lining small intestines
• excretory cells in kidneys

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 Modifications

• 2.Cilia
• Longer
• Contain protein microtubules for structure and
  support
• Do not absorb but keep things moving
• Cells lining respiratory tract, to keep mucous
  moving
• ciliary action

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 Modifications

• 3.Flagella
• 1 and long
• Contains protein microtubules
• Provide propulsion
• sperm cells

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 B. Functions

• Ways in which materials cross the plasma membrane
• Based on the energy that is required
• 1. passive transport
• 2. active transport

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1. Passive Transport

• Powered by kinetic energy, force which causes
  molecules to move about randomly.
• Requires no energy from the cell.

• 3 types
• i. Diffusion
• ii. Osmosis
• iii. Filtration

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I.Diffusion

• Kinetic energy only
• Molecules move from a region of higher
  concentration to a region of lower concentration.
• Movement continues until equilibrium is reached
• Diffusion moves with a concentration gradient
• A diffusion in concentration from one region
  to another

• EX. Spray a freshener in air.
• EX. In body, movement of oxygen molecules from
  air sacs in lungs to blood vessels that surround
  air sacs.

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Diffusion

• Diffusion through plasma membrane.
• lipid-soluble solutes diffuse right in.
• lipid-insoluble solutes like glucose use
• facilitated diffusion with the integral
  protein to
• get in

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Passive Transport
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 II. Osmosis

• The movement of water molecules across a
  selectively permeable membrane from a region of
  higher water molecule concentration to a region
  of lower water molecule concentration (lower
  water molecule concentration means higher solute
  concentration).

• Just like diffusion, osmosis moves with a
  concentration gradient until equilibrium is
  reached.

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Osmosis

• Osmotic pressure is the force exerted by the
  water molecule. It depends on magnitude of
  concentration gradient.
• In cells, osmosis is important to cell survival.
  The water molecules move quickly through channels
  formed by the integral proteins.

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• 3 examples of osmosis with respect to the
  solution.
• 1. Isotonic
• 2. Hypertonic
• 3. Hypotonic

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ISOTONIC

• Put a red blood cell (RBC) into a solution
  which contains equal amounts of solute. The water
  will flow from inside cell to outside cell at
  equal rate and visa versa. This happens because
  concentration is equal on both sides. The state
  of equilibrium of extracellular fluid is ISOTONIC
  to intracellular fluid. (iso means equal).

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HYPERTONIC

• Put a RBC into a solution that contains a
  greater concentration of solutes. This
  means that there is less water in the solution
  then in the RBC, so water will tend to flow out
  of the cell. This causes the cell to shrink.
  This is known as crenation. The extracellular
  fluid is HYPERTONIC to the intracellular fluid.
• (hyper means above normal).

• http//www.tvdsb.on.ca/westmin/science/sbi3a1/Cell
  s/Osmosis.htm

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HYPOTONIC

• Put a RBC into a solution that contains a
  lesser concentration of solutes. This means that
  there is more water in the solution then in the
  RBC, so water will tend to move into the cell.
  This causes the cell to swell. This is known as
  hypertrophy. The Extracellular fluid is
  HYPOTONIC to the intracellular fluid. (hypo means
  below normal)

• http//www.tvdsb.on.ca/westmin/science/sbi3a1/Cell
  s/Osmosis.htm

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 III. Filtration

• Movement of molecules across a selectively
  permeable membrane from a region of high pressure
  to a region of low pressure.
• Occurs in kidneys when waste product urea is
  forced by pressure of blood to cross membrane.

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2. Active Transport

• Needs energy from cell (ATP)
• Recall ATP ?? ADP PO4-2 E

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Active Transport

• Requires use of energy (ATP)
• Transport of substances
• against a concentration
• gradient across a
• selectively permeable
• Membrane.
• Requires carrier proteins for assistance.
• Needed to maintain levels of ions inside cell in
  spite of concentration gradient.

• Also used for amino acids to be carried into
  cell
• where their numbers are larger.
• CYTOSIS is the transport of large volume of
• materials and large particles across the
  membrane.
• There are 2 types endocytosis and exocytosis.

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1. Endocytosis

• Import material into the cell
• A. Phagocytosis (fig. 3-10)
• Portion of membrane forms pseudopod, engulfs
  substance. Substance is digested by enzymes from
  lysosome.
• Notable in WBC.

• B. Pinocytosis cell drinking
• Bulk movement of fluid into cell.
• Only slight folding of plasma.
• Cells lining blood vessels and kidneys.

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Endocytosis
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2. Exocytosis

• Export material out of cell.
• Releases either waste products or molecules
  manufactured in cytoplasm.
• The membranes of the organelles fuse with plasma
  membrane and release materials into extra
  cellular environment.

• A. Excretion
• Removal of waste materials
• B. Secretion
• Releasing molecules produced by
  organelles into Extracellular environment. i.e.
  Digestive enzymes, mucous, hormones, antibodies.

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Exocytosis
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Packets pp. 39-43

• Quiz on pp.48-59 and all notes from ch. 3
• Followed by webquest on cell