Passive Transport Across the Cell Membrane

Question 1

Passive Transport

Answer 1

Processes that allow substances to move across membrane without energy, along the concentration gradient

Question 2

Diffusion

Answer 2

Movement of particles from area of high concentration to area of low concentration

Question 3

Rate of Diffusion Factors

Answer 3

1. Molecule Size: increased size = slower
2. Molecule Polarity: polar = slower (interior of membrane is non-polar and repels polar molecules)
3. Molecule/Ion Charge: charged molecules cannot diffuse across membrane
4. Temperature & Pressure: increased = faster

Question 4

Osmosis

Answer 4

Special type of diffusion that is the movement of water across a semi-permeable membrane from an area of high concentration to an area of low concentration

Question 5

Osmosis: Hypertonic Solutions

Answer 5

Cell’s environment has greater concentration of solute (lower water concentration) –> since solute cannot pass membrane with ease, water molecules move out of cell - cell shrinks

Question 6

Osmosis: Hypotonic Solutions

Answer 6

Cell’s environment has lower concentration of solute (higher water concentration) –> water molecules move into cell - cell expands (animal cells may burst as membrane isn’t very strong)

Question 7

Osmosis: Isotonic Solutions

Answer 7

Concentration of solute to water is same inside and outside of cell (ideal situation) –> water moves in and out of cell at exact same rate - cell size does not change

Question 8

Facilitated Diffusion

Answer 8

Movement of particles from high to low concentration through protein channels in the cell membrane –> for molecules too polar or too charged (ex. Na+ and glucose)

Question 9

Facilitated Diffusion: Channels

Answer 9

Protein channels’ interior composed of polar amino acids and has specific shape & size that determines which particles can pass through, exterior is non-polar to “anchor” protein

Question 10

Facilitated Diffusion: Carriers

Answer 10

Carrier proteins can bind to specific molecules to help transport across the channel –> often for too large molecules