Transport through the membrane

Question 1

Components of the phospholipid bilayer?

Answer 1

• 2 fatty acids
• a glycerol
• a phosphate group

Question 2

What is a hydrophobic tail?

Answer 2

repels water

Question 3

What is a hydrophilic head?

Answer 3

Attracted to water

Question 4

Role of cholesterol in the membrane?

Answer 4

Cholesterol restricts the lateral movement of other molecules in the membrane. This is useful as it makes the membrane less fluid like at high temperatures and prevents water and dissolved ions leaking out of the cell.

Question 5

What is a glycoprotein?

Answer 5

A protein with a carbohydrate attached

Question 6

What is a glycolipid?

Answer 6

A lipid with a carbohydrate attached to it

Question 7

What are peripheral proteins?

Answer 7

The peripheral proteins provide mechanical support, or they are connected to proteins or lipids to make glycoproteins and glycolipids. The function of these is cell recognition.

Question 8

What are integral proteins?

Answer 8

Integral proteins are protein carriers or channel proteins involved in the transport of molecule across the membrane.

Question 9

What are protein channels?

Answer 9

Protein channels form tubes filled with water and this enables water- soluble ions to pass through the membrane. The is still selective, as the channel proteins only open in the presences of certain ions when they bind to the protein.

Question 10

What are carrier proteins

Answer 10

They will bind to a molecules, such as glucose, which causes a change in the shape of the protein. This shape change enables the molecule to be released to the other side of the membrane.

Question 11

Which molecules can pass through the membrane?

Answer 11

Lipid- soluble substances (some hormones) and very small molecules (CO2, oxygen water)

Question 12

Which molecules cannot pass through the membrane?

Answer 12

Water soluble (polar) substances (sodium ions) and large molecules (glucose)

Question 13

4 types of transport

Answer 13

• Simple diffusion
• Facilitated diffusion
• Active transport
• Osmosis

Question 14

What is simple diffusion?

Answer 14

The net movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached. It does not require energy.

Question 15

What is facilitated diffusion?

Answer 15

This is a passive process that uses proteins to transport molecules. The movement of ions and polar molecules, which cannot simply diffuse, can be transported across membranes by facilitated diffusion using protein channels and carrier proteins.

Question 16

What is osmosis?

Answer 16

Osmosis is the movement of water from an area of higher water potential to an area of lower water potential across a partially permeable membrane.

Question 17

What is water potential?

Answer 17

Water potential is the pressure created by water molecules and is measured in kPa and represented with the symbol (). Pure water has a water potential of 0, so when solutes are dissolved in water, the water potential will become negative. The more negative the water potential, the more solute must be dissolved in it.

Question 18

What is an isotonic solution?

Answer 18

The water potential is the same in the solution and the cell within the solution

Question 19

What does hypotonic?

Answer 19

The water potential of a solution is more positive than the cell

Question 20

What does hypertonic mean?

Answer 20

It is when the water potential of a solution is more negative than the cell

Question 21

What is active transport?

Answer 21

The movement of a substance from a low concentration to a high concentration using metabolic energy and a carrier protein

Question 22

How does active transport work?

Answer 22

1. Transport is through carrier proteins spanning the cell membrane.
2. Molecules bind to a receptor complementary in shape on the protein.
3. ATP binds to the carrier protein from the inside of the cell and it is hydrolysed into ADP+Pi.
4. This causes the carrier protein to change shape and release the molecule to the other side.
5. The ion is then released and the protein returns to its original shape.

Question 23

Co- transport of glucose and sodium ions in the ileum

Answer 23

1. Sodium ions are actively transported out of the epithelial cell into the blood.
2. This reduces the sodium ion concentration in the epithelial cell.
3. Sodium ions can then diffuse from the lumen down the concentration gradient into the epithelial cell.
4. The protein the sodium ions diffuse through is a co- transporter protein, so either glucose or amino acids also attach and are transported into the epithelial cell against the concentration gradient.
5. Glucose then moves by facilitated diffusion from the epithelial cell to the blood.

Question 24

Effects of to much/ little water in animal and plant cells

Answer 24

Animal:
To much- burst
To little- shrink
Plant:
To much- turgid
To little- Flacid

Question 25

2 ways to increase the rate of active transport

Answer 25

• Increase surface area
• Increase the number of protein channels and carrier proteins