2.3 - Cell transport

Question 1

Define simple diffusion

Answer 1

Movement of molecules from an area of higher concentration to an area of lower concentration through a partially permeable membrane (phospholipid bilayer)

Question 2

Define facilitated diffusion

Answer 2

Movement of molecules from an area of higher concentration to an area of lower concentration through channel or carrier proteins

Question 3

Define osmosis

Answer 3

Movement of water molecules from an area of higher water potential to an area of lower water potential through a partially permeable membrane

Question 4

Define active transport

Answer 4

Movement of molecules from an area of lower concentration to an area of higher concentration using energy released from hydrolysis of ATP and carrier proteins

Question 5

Define co-transport

Answer 5

Movement of two substances simultaneously from an area of lower concentration to an area of higher concentration using energy released from hydrolysis of ATP and carrier proteins

Question 6

Explain how channel proteins function and the molecules they transport

Answer 6

Channel proteins transport charged molecules (ions) which are dissolved as the channel contains water

Question 7

Explain how carrier proteins function and the molecules they transport

Answer 7

Carrier proteins transport large molecules by the binding of an inorganic phosphate to the molecule which enables the large molecule to bind

Question 8

Describe the absorption of sodium ions and glucose in the ileum in terms of cell transport

Answer 8

A - Sodium ions actively transported out of epithelial cell into blood
This establishes a sodium concentration gradient between the ileum lumen and epithelial cell
F - Sodium ions then diffuse from lumen down their concentration gradient into epithelial cell
C - Glucose/amino acids attach to co-transporter protein with sodium ions and are transported into epithelial cell against their concentration gradient
F - Glucose moves by facilitated diffusion from the epithelial cell into the blood

Question 9

How can cells be adapted for rapid transport across internal or external membranes?

Answer 9

Increase in surface area
Increase in number of protein channels
Increase in number of carrier proteins

Question 10

How do differences in water potential/concentration gradients affect the rate of movement?

Answer 10

The larger the gradient, the fastest the rate of movement across the membrane