Unit 1, AOS1, Chapter 3B: Passive Transport

Identify the 3 factors that affect the ability of a substance to diffuse across the plasma membrane

1. Size

2. Polarity/charge

3. Concentration on either side of the membrane

Define Passive Diffusion

The movement of molecules down their concentration gradient through a semipermeable membrane, without an input of energy

Identify the 3 types of Passive Diffusion

1. Simple Diffusion

2. Facilitated Diffusion

3. Osmosis

Identify the features of molecules that can be transported by simple diffuse

Small, non-polar/hydrophobic molecules

Provide 3 examples of molecules that can freely diffuse

- Oxygen

- Hydrogen

- Carbon dioxide

- Lipids

- Gases

- Water (hydrophilic but very small)

Provide 3 examples of molecules that cannot freely diffuse

- Ions

- Amino acids

- Proteins

- Glucose

- Nucleic acids

Define Facilitated Diffusion

The passive movement of molecules down their concentration gradient through a membrane-bound protein (carrier or channel proteins)

Identify which molecules can use facilitated diffusion

Facilitated diffusion allows large and/or polar molecules to diffuse through the membrane, although some small and/or non-polar molecules (like water) have dedicated protein channels for faster transport

Define Osmosis

The diffusion of water from an area of low solute (high solvent) concentration to an area of high solute (low solvent) concentration

Identify the 3 types of tonicity

1. Hypotonic (low solute)

2. Hypertonic (high solute)

3. Isotonic (equal concentrations)

Water moves out of _________ solutions and into __________ solutions. There is no net movement of water between _______ solutions.

hypotonic, hypertonic, isotonic

An animal cell in a hypotonic solution will _____ or ____.

swell, lyse/burst

An animal cell in a hypertonic solution will _______.

shrivel

A plant cell in a hypotonic solution will become ______ but not _____ due to its ________.

turgid, lyse/burst, cell wall

A plant cell in a hypertonic solution will _____ and become ___________.

shrink, plasmolysed