Chapter 4 Notes Cell Physiology

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Chapter 4 NotesCell Physiology

• Biology
• Hamilton Science Department

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Homeostasis

• Organisms must maintain a balance of materials
  that enter and leave their cells.
• Without this ability, they will die.

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The Cell (Plasma) Membrane

• The property of a membrane to allow only certain
  particles through while keeping others out is
  known as selective permeability.
• One way cells maintain homeostasis is by having a
  selectively permeable cell membrane.

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The Plasma Membrane
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PASSIVE TRANSPORT-no energy required

• 1 DIFFUSION
• THE MOVEMENT OF PARTICLES FROM HIGHER
  CONCENTRATION TO AN AREA OF LOWER CONCENTRATION

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• Diffusion occurs with CONTINUOUS MOVEMENT until
  EQUILIBRIUM is reached
• EQUILIBRIUM equal amounts of substance are on
  both sides of the cell membrane

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• PASSIVE TRANSPORT continued..
• 2 OSMOSIS
• DIFFUSION OF WATER MOLECULES THROUGH A
  SELECTIVELY PERMEABLE MEMBRANE.

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• 3 TYPES OF SOLUTIONS AROUND A CELL (3
  Possibilities for the Direction of Water
  Movement around a Cell)
• 1. ISOTONIC CONCENTRATION OF DISSOLVED
  SUBSTANCES AND WATER SAME ON BOTH SIDES OF
  MEMBRANE
• 2. HYPOTONIC CONCENTRATION OF DISSOLVED
  SUBSTANCES IS LOWER THAN IN THE CELL (high
  concentration inside the cellcell swells)
• 3. HYPERTONIC CONCENTRATION OF DISSOLVED
  SUBSTANCES IS HIGHER THAN IN THE CELL (low
  concentration inside the cellcell shrinks)

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Hypertonic SolutionHypotonicSolution-
If a cell is placed in a.
Water moves out of the cell (Balloon shrivels)
Water moves into the cell!! (Balloon overfull)
ISOTONIC SOLUTIONS ARE BALANCED !!
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• 3 FACILITATED DIFFUSION
• Diffusion of substances from area of high
  concentration to area of low concentration with
  help of carrier proteins.

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4 DIFFUSION THROUGH ION CHANNELS

• Movement of ions ( Na, K, Cl-) through cell
  membrane by means of ion channel
• Ion Channel a transport protein with a polar
  pore through which ions can pass
• Some ion channels have gates that open/close
• Channels are specific to a certain kind of ion

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• ACTIVE TRANSPORT
• REQUIRES ENERGY
• Energy used is from ATP
• MOVEMENT OF SUBSTANCES FROM LOW CONCENTRATION. TO
  ALREADY HIGH CONCENTRATION
• Opposite of Passive Transport
• Substances move
  AGAINST GRADIENT (or opposite of equilibrium)

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Active Transport 1 Ion Channel Pumps

• Uses ion channel (aka carrier proteins)-allows
  sodium, calcium, and potassium ions to enter and
  leave the cell against gradient
• called Membrane Pumps
• Most noteable Ion Pump is the Sodium-Potassium
  Pump

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Active Transport

• 2 Endocytosis and Exocytosis
• For substances that are too big to be moved
  across cell membrance by carrier proteins
• Examples Proteins and Polysaccharides

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• ENDOCYTOSIS
• USE ENERGY TO TAKE IN LARGE PARTICLES. CELL
  SURROUNDS THE PARTICLES Forms vesicle around
  particles.

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• EXOCYTOSIS
• RELEASE OF WASTES FROM CELL VESICLE. VESICLE
  FUSES WITH MEMBRANE AND CONTENTS ARE RELEASED TO
  OUTSIDE.