Membrane Transports Study Guide

What is diffusion?

Diffusion is the movement of molecules across the cell membrane from an area of higher concentration to an area of lower concentration.

What is the difference between endocytosis and exocytosis?

Endocytosis is how the molecules from outside of the cell are engulfed by the cell membrane and brought into the cell. Exocytosis is how molecules or particles from the inside of the cell are released to the outside of the cell. Both require energy. (active transport)

What is osmosis?

It is the movement of water across the cell membrane from an area of high concentration of water to an area of low concentration.

Define concentration.

It is the number of molecules of a substance in a mixture in relation to another substance in the same mixture.

What will happen to the blood cell placed in distilled water?

Lysis- swell up and burst, hypotonic

What is the difference between passive and active transport?

Molecules move down their concentration gradient in passive transport: from higher concentration to lower concentration. Passive transport does not require energy. In active transport, molecules move up their concentration gradient. Active transport requires energy.

What will happen to the blood cell placed in pond water?

Nothing - water will move both in and out at the same rate (normal cell), isotonic

What macromolecules are cell membranes mostly made of?

Phospholipids

Why do we say the cell membrane is "selectively permeable"?

Selectively permeable means that only certain types of molecules can go through the cell membrane to enter and exit the cell. (like nutrients and wastes)

What will happen to the blood cell placed in salt water?

Shrink/shrivel up-(crenation), hypertonic

What type of molecules can freely pass through a plasma membrane?

Small and uncharged molecules freely pass through the plasma membrane. Examples: H2O, CO2 , and O2

Provide at least 2 specific examples of diffusion occurring in a real life.

Spraying air freshener Tea bag in hot water Food coloring in water

How do large or charged molecules enter or leave the cell?

Through facilitated diffusion- they use the help of carrier proteins that are embedded in the cell membrane's phospholipid bilayer.