4. Transport Across The Cell Membrane Pt1

Question 1

State 7 methods of cell transport

Answer 1

• Diffusion
• Osmosis
• Active transport
• Endocytosis
• Exocytosis
• Phagocytosis / Pinocytosis

Question 2

Why do lipid tails have no charge?

Answer 2

As they are nonpolar.

Question 3

Why do phosphate heads have a charge?

Answer 3

As they are polar.

Question 4

Explain what types of molecules can pass through the cell membrane. Provide 2 examples

Answer 4

Only small hydrophobic molecules can squeeze throgh spaces in the bilayer and can be described as lipid soluble.
E.g. CO2, O2

Question 5

How do small nonpolar molecules pass through the membrane? Provide 3 examples

Answer 5

Small nonpolar (uncharged) molecules are mostly permeable to the cell membrane and they do this through diffusion and osmosis. E.g. H2O, urea and glycerol

Question 6

How do large nonpolar molecules pass through the membrane?

Answer 6

Large nonpolar (uncharged) molecules are mostly permeable to the cell membrane, but requires transport via proteins. Like Facillitated diffusion which uses protein channels and carriers.

Question 7

Define ATP

Answer 7

ATP stands for andonin tri phosphate and it is what provides energy for the cell.

Question 8

Define selectively permeable

Answer 8

A selectively permeable membrane is something that only allows certain molecules or substances to enter and leave the cell.

Question 9

Define passive transport

Answer 9

Passive transport is the movement of substances from an area of high concentration to an area of low concentration without ATP.

Question 10

Define Active transport

Answer 10

Active transport is the movement of substances from an area of low concentration to an area of high concentration with ATP.

Question 11

Define Diffusion

Answer 11

Difussion is the passive movement of substances in a gas or liquid moving from an area of high concentration to an area of lower concentration until they are evenly spread out.

Question 12

Define Concentration Gradient

Answer 12

The steeper the concentation gradient, the faster diffusion takes place.

• Steeper concentration gradient = Fast rate of diffusion
• Less steep concentration gradient = Slow rate of diffusion

Question 13

Define Passive Transport

Answer 13

Passive require no energy as a molecule is travelling down the concentration gradient from an area of high to low concentration.

Question 14

Define Simple Diffusion and list particle that past through the membrane through simple diffusion

Answer 14

Simple diffusion is a type of passive transport where molecules travel from an area of high concentration to an area of low concentration with no energy required. The particle that can diffuse through the phosopholipids are O2, CO2, alcohol and steroids. The ions that are to large to pas through the membrane have to go through channels and the are Na+/K+ and water.

Question 15

Define Osmosis

Answer 15

Osmosis is a special type of diffusion - the diffusion of water. Osmosis is the diffusion of water molecules through a selectively permeable membrane from an area of high water concentration to an are of lower water concentration.

Question 16

Define Osmotic Pressure

Answer 16

If a membrane is present, water will flow to the area with the highest concentration of solute (HWC -> LWC). Osmotic pressure is the pressure created by water moving across a membrane due to osmosis. The moe water moving across the membrane, the higher the osmotic pressure.

Question 17

Define tonicity in cells

Answer 17

This refers to the ability of an extracellular solution to make water move into or out of a cell by osmosis.

Question 18

Define Isotonic. Provide an example.

Answer 18

Equal water concentraion inside a cell as to the surrounding fluid. E.g. blood plasma and red blood cells have equal water concentration, therefore there is no net gain or loss of water in either direction.

Question 19

Define Hypotonic Solutions. Provide an example.

Answer 19

Hypo = low solute concentration
If blood plasma had low solute levels e.g. glucose, salts etc, then it would have a HWC. Water would move by osmosis into the red blood cell, causing it to burst.

Question 20

Define Hypertonic Solutions. Provide an example.

Answer 20

Hyper = high solute concentration.
If blood plasma had high solute levels e.g. glucose, salt etc, then it would have a LWC. Water would move by osmosis out of the red.

Question 21

Define Facilitated Transport

Answer 21

Uses proteins to transport substances across the cell membrane: Channel Proteins and carrier proteins. Help hydrophilic particles to travel across the membrane without coming into contact with the hydrophobic tails.

Question 22

Explain facilitated transport of glucose

Answer 22

Glucose molecules bind to a carrier protein, causing it to go change shape. Glucose is transported across the membrane from one side to the other in this process. Still passive and HC —>LC

Question 23

Define Facilitaded diffusion

Answer 23

High to Low
Cariers: glucose and amino acids
Bind -> Shape change -> Release