Homeostasis and Transport

What is the fluid mosaic model?

A mosaic is a piece of art comprised of many small tiles pieced together. A cell membrane is comprided of many smaller parts pieced together. It is fluid in that the pieces are not fixed, and can move around within the membrane.

How do passive and active transport differ?

Active requires energy, passive does not

Why do some molecules require the use of protein channels, as in faciliated diffusion?

Charged of large molecules do not dissolve well in the lipid interior of the phospholipid membrane. They therefore require the use of protein channels.

During diffusion, when the concentration of molecules on both sides of the membrane is equal, molecules will do what?

Continue to move across the membrane in both directions

What is the function of the plasma membrane?

Controls the flow of substances into and out of the cell

List and describe the types of passive transport

Diffusion- substances move from high to low concentration, but cannot pass directly through the membrane, instead passing through protein channels Osmosis- faciliated diffusion of water

Compare and contrast hypertonic, hypotonic, and isontonic solutions.

Hypertonic solutions have a lower concentration of solution than the cell, causing water to move in to the cell Isontonic solutions have an equal concentration of solute inside and outside the cell, causing no net gain or loss of water

Explain equilibrium

In equilibrium, the concentration of solute: solvent is equal on both sides of the membrane. Molecules continue to move back and forth across the membrane in equal quantities

Why did diffusion occur?

Molecules constantly move and collide into one another

What are the basic parts of the fluid mosaic model of the plasma membrane? Describe each in terms of structure and function.

Phospholipid bilayer-forms a barrier around the cells, controls movement into the cell Carbohydrate markers- serve as chemical identifiers Channels and pumps- function in transport of materials into and out of the cell

The cell membrane contains channels and pumps which help in transport. What are these materials made of?

Protein

Explain the relationship between the endoplasmic reticulum and Golgi apparatus in terms of cell transport.

The ER makes the proteins and lipids, the Golgi modifies and stores them

What is the phospholipid bilayer? How does the structure of a phospholipid relate to its function in plasma membranes?

The phospholipid bilayer is a double layer of lipids which form into membranes. phospholipids have a polar head and a nonpolar tail. The watery environment outside of cells causes the tails to turn in towards each other, forming a double layer.

What is the relationship between diffusion and osmosis?

Osmosis is a type of diffusion, specifically the facilitated diffusion of water

Explain, in terms of osmosis, why a raisin placed in a cup of pure water overnight will puff up.

The water is hypotonic to the raisin, causing water to move into the raisin.

Explain how each of the following organelles is involved in cell transport:

Vacuoles and vesicles- store materials for transport Golgi apparatus- modifies, stores, and packages molecules for storage or transport Endoplasmic reticulum- assembles proteins and lipids Cytoskeleton- transport