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7.3 – Cell Transport- Guided Reading

Instructions: Read pages 208-213 in your textbook. As you read, answer each of the questions below or complete the sentence.

Passive Transport

  1. What is one of the most important functions of the cell membrane? To keep the cell’s internal conditions relatively constant.

Diffusion

  1. In any solution, solute particles move constantly . They collide with one another and tend to spread out randomly
  1. Particles tend to move from an area where they are more concentrated to an area where they are less concentrated
  1. What is diffusion? The process in which particles move from an area of high concentration to an area of lower concentration
  1. If a substance can cross the cell membrane, its particles will tend to move toward the area where it is less concentrated until it is evenly distribute.
  1. Equilibrium is reached when once the concentration of the substance on both sides of the cell membrane is the same
  1. Even at equilibrium, particles of a solution continue to move across the membrane in both directions
  1. What is passive transport? The movement of materials across the cell membrane without using cellular energy
  1. Read through Figure 7-15.

Facilitated Diffusion

  1. Proteins in the cell membrane act as carriers, or channels, making it easy for certain molcules to cross
  1. What is facilitated diffusion? Process in which molecules that cannot cross directly diffuse across the membrane through special protein channels

Osmosis

  1. What is osmosis? The diffusion of water through a selectively permeable membrane.
  1. In osmosis, molecules move from an area of higher concentration to an area of lower concentration
  1. Carefully read the paragraph starting ‘How osmosis works.’
  1. Water will tend to move across membranes until equilibrium is reached
  1. Define the terms Isotonic, hypertonic, and hypotonic:

-Isotonic – equal concentration on both sides (same strength)

- Hypertonic – one solution is more concentrated than the other (above strength

- Hypotonic – one solution is less concentrated than the other (below strength)

  1. Read through figure 7-18.
  1. What happens to an animal cell when it is place in an isotonic solution? Water moves in and out equally in both direction – cell stays the same size
  2. What happens to a plant cell when it is place in an isotonic solution? Water moves equally in both directions – cell stays the same size
  3. What happens to an animal cell when it is place in an hypertonic solution? Water will move out of the cell, causing the cell to shrink
  4. What happens to a plant cell when it is place in an hypertonic solution? Water will move out of the cell, causing the cell to shrink, but cell wall stays in place
  5. What happens to an animal cell when it is place in an hypotonic solution? Water will move into the cell, causing it to swell
  6. What happens to a plant cell when it is place in an hypotonic solution? Water will move into the cell, causing it to swell
  1. What is osmotic pressure? Pressure against the cell membrane cause by the force of water pushing against it.

Active Transport

  1. What is active transport? The movement of materials against a concentration difference, which requires energy from the cell

Molecular Transport

  1. Small molecules and ions are carried across membranes by proteins in the membrane that act like pumps

Bulk Transport

  1. Large molecules can be transported by movement of the cell membrane known as bulk transport
  1. Endocytosis is the the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane
  2. What is phagocytosis? A type of endocytosis in which extensions of cytoplasm surround a particle and package it within a food vacuole
  1. What is pinocytosis? Process of taking up liquid, by froming tiny pockets in the cell membrane, filled with liquid, and pinching them off into vacuoles.
  1. What is Exocytosis? The membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell