Homeostasis

1
Homeostasis Transport

• Chapter 5

2
Passive Transport

• Section 5.1

3
Homeostasis?

• How do cell membranes help maintain homeostasis
  within a cell?
• By controlling what goes into and out of the cell.

4
Passive Transport

• The movement of materials across a cell membrane
  WITHOUT the use of energy (ATP).
• Four Types
• Diffusion
• Osmosis
• Facilitated Diffusion
• Ion Channels

5
Diffusion

• Movement of molecules from an area of high
  concentration to an area of low concentration.

6
Diffusion through a Membrane

Cell membrane
Solute moves DOWN concentration gradient (HIGH
to LOW)
7
Concentration Gradient

• Difference in concentration of molecules across a
  space (or cell membrane).
• Down the gradient
• Movement from high to low concentration

8
Equilibrium

• When the concentration is EQUAL throughout the
  space (or on each side of the cell membrane)
• End of diffusion
• No NET movement, RANDOM movement still occurs

9
Diffusion of Liquids
10
Diffusion across a membrane

• Depends upon size, shape, and chemical makeup
• Easy to diffuse
• Small
• Nonpolar

11
Osmosis

• WATER diffusion across a membrane
• Down the gradient
• Hypotonic solution to hypertonic solution
• Osmosis
• animation

12
Osmosis
13
Hypotonic Solution

• The solute concentration is higher inside the
  cell, the water concentration is higher outside
  the cell.
• Net movement Water into the cell
• May cause Cytolysis

14
Hypertonic Solution

• The solute concentration is higher outside the
  cell, the water concentration is higher inside
  the cell.
• Net movement Water out of the cell
• May cause Plasmolysis

15
Isotonic Solution

• The solute and water concentrations are EQUAL on
  both sides of the membrane.
• Equilibrium

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17
Osmosis in Red Blood Cells
Isotonic
Hypotonic
Hypertonic
18
hypotonic
hypertonic
isotonic
hypertonic
isotonic
hypotonic
19
Facilitated Diffusion

• Use of carrier proteins the assist diffusion
  across a membrane.
• Specific carrier proteins for specific molecules
  (like glucose or amino acids)
• Down the gradient

20
Diffusion via ion channels

• Use of membrane proteins to assist diffusion of
  ions across a membrane
• Channel is usually specific to 1 type of ion
• Common ions
• Sodium
• Potassium
• Chlorine
• Calcium

21
Notebook Quiz

1. Osmosis is the diffusion of _____________.
2. During diffusion, molecules tend to move in what
   direction?
3. Does the movement of molecules stop once
   equilibrium is reached? Explain.
4. What is the function of carrier proteins?
5. If the external solution is hypotonic compared to
   the cell, which direction will water move?

22
Active Transport

• Section 5.2

23
Active Transport

• Uses energy (ATP) to move materials against the
  gradient
• Up the gradient
• Low to high concentration

24
1. Sodium Potassium Pump

• Transports sodium and potassium ions across the
  membrane up their gradients
• Low to high concentration
• Uses ATP

25
2. Endocytosis

• Movement of large amounts of material into the
  cell
• Formation of a vesicle from the cell membrane
  that will go to the lysosome for digestion
• Uses ATP

26
2 types of endocytosis

• 1. pinocytosis cell drinking
• Transport of a large quantity of liquid into the
  cell
• 2. phagocytosis cell eating
• Transport of a large quantity of solids into the
  cell
• Uses ATP

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Moving the Big Stuff
Large molecules move materials into the cell by
one of three forms of endocytosis.
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3. Exocytosis

• The movement of a large amount of materials out
  of the cell
• Vesicle fuses to the cell membrane to release
  contents out of the cell
• Uses ATP

29
Exocytosis
30
Passive Active Transport

• Animation

31
Lab Time!

• Starch Molecule

32

• Iodine Molecule