Movement of Substances Across the Membrane

The fluid mosaic model proposes that plasma membranes consist of:

• a protein bilayer with phospholipids interspersed between the protein molecules

• two layers of lipid with protein between them

• two layers of protein with lipid between them

• a phospholipid bilayer with protein molecules interspersed between the phospholipid molecules

Proteins in the plasma membrane may be involved in:

• transport of ions in and out of cells through ion pores

• cell recognition

• Receptors

• all of the above

Proteins in the plasma membrane may be involved in:

• transport of ions in and out of cells through ion pores

• cell recognition

• Receptors

• all of the above

Ions cannot pass across a plasma membrane by simple diffusion because the particles are:

• too large

• non-polar

• hydrophobic

• charged

Facilitated diffusion always involves:

• movement of ions

• movement against a concentration gradient

• ATP

• transport proteins

As the concentration gradient is increased:

• the rate of both simple diffusion and facilitated diffusion will increase continually

• the rate of simple diffusion will rise and then level off but the level of facilitated diffusion will increase

  continually

• the rate of simple diffusion will increase continually but the rate of facilitated diffusion will rise and

  then level off

• the rate of both simple diffusion and facilitated diffusion will rise and then level off

What is Osmosis?

• equal concentration
• diffusion of water through a selectively-permeable membrane
• high to low concentration
• non-polar tail

Which is true about active transport?

• It requires energy
• it does not require energy
• It moves substances down the concentration gradient
• it moves material from high to low concentration

Passive transport requires no

• concentration gradients
• osmosis
• motion
• energy

Which of the following substances passes through the plasma membrane   through the process of osmosis?

• glucose
• water
• protein
• sodium