Download Transport Across Plasma Membrane

Membrane Transport Across the Plasma Membrane
Directions:
Insert and install your Interactions: Foundations CD.
a. Click the "Contents" button.
b. Open the Cellular Level of Organization file.
c. Click on Animations.
d. Work through Transport Across the Plasma Membrane.
Introduction
1. Briefly describe each of the following plasma membrane functions.
a. importing –needed for maintenance of the metabolic processes of the cell. It is also
needed for normal cell function. (ex taking in organic molecules and salts)
b. exporting – sends molecules out of the cell after they are produced (ex: cell secretions)
c. communicating – when a substance from one cell induces the transport of chemicals across the plasma
membrane of another cell. This may make action potential possible.
Types of Transport
2. Describe two general types of passage through the plasma membrane.
Some chemicals pass through the membrane’s phospholipid bilayer boundary
while others can only pass threw with the aid of membrane transport
proteins.
3. Contrast the two types of transport processes.
a. passive transport – travels down concentration gradient. Molecules move from high levels of
concentration to low levels of concentration, does not require energy
b. active transport – travels against the concentration gradient. Molecules go from low to high levels of
concentration. Requires the use of ATP.
Diffusion
3. Describe gas transport across the plasma membrane. Passes through bilayer by
diffusion and moves along the concentration gradient. Uses gradient energy
4. Describe ion movement across the plasma membrane. Ions Diffuse
through membrane pores and gated channels. Pores are always open.
While gates channels can be opened or closed. The number of pores determine how many ions can
diffuse threw the membrane.
Facilitated Diffusion
5. a. Describe the function of transporter proteins in the plasma membrane. Molecules( ex glucose) bind with
the transporter protein that changes shape to facilitate the transport of the molecule.
b. Describe how insulin affects the plasma membrane. Insulin promotes the production of transporter proteins.
More transporters allow more facilitated transport of the nutrient.
Osmosis
5. Describe the role of aquaporins with regard to water movement. They are pores
That allow water across the plasma membrane.
7. a. Explain how solute concentrations determine water concentration.
More ions result in a lower water concentration; less ions result in higher
Water concentration.
b. Contrast the following types of solutions:
isotonic – has the same amount of ions in both solutions, so the water moves
in equal directions
hypertonic –ionic solution is high allowing water into the cell . the water concentration is low so the
direction of osmosis will be toward the cell.
hypotonic – Ionic concentration will be low pushing water out of the cell. The water concentration
will be high so osmosis will be moving away from the cell.
Primary Active Transport
8. Describe primary active transport mechanisms using the sodium-potassium pump as an example. A
membrane pump used to maintain electrochemical gradients in neurons. Requires ATP.
Secondary Active Transport
9. a. Define secondary active transport. Uses previously established gradient of
NA or hydrogen ions to move other chemicals
b. How does secondary active transport maintain low calcium concentrations
in the cytosol and/or absorption of nutrients into cell?
In many cells antiporters move calcium out of the cell while sodium flows in.
This maintains the low calcium concentration in the cytosol.
Endocytosis
10. Contrast each of the following types of endocytosis and describe how each is
used by cells.
Phagocytosis – The “ eating cell” is a common form of endocytosis. It helps protest the body against
disease. Once the pseudopod containing an organism like bacteria it pinches off into a vesicle it will
bind with a lysosome where the bacteria will be digested.
Pinocytosis – The “drinking cell” the process in which the cell drinks extracellular fluids and solutes,
then is form vessels, pinches off and binds with a lysosome where the solutes are then digested.
Receptor Mediated – imports needed material into the cell.
Exocytosis
11. What is the function of exocytosis? Is another method of vesicular transport that moves large volumes of
fluid or chemicals out of the cell. The cells remove waste products ending in endocytosis, secretions of
neurotransmitters, hormones and digestive enzymes are an important function of exocytosis.