Transport across the membrane

Question 1

How do lipid soluble molecules move?

Answer 1

They enter through bilayer by dissolving in the phospholipid

Question 2

What are examples of lipid soluble molecules?

Answer 2

Alcohols, steroids and hormones

Question 3

How do small molecules move across a membrane?

Answer 3

They move through gaps between the phospholipids

Question 4

What are examples of small molecules?

Answer 4

Oxygen, carbon dioxide and some water molecules

Question 5

What molecules can be transported without proteins (simple diffusion)?

Answer 5

Lipid soluble molecules and small molecules

Question 6

How doo small charged particles move across a membrane?

Answer 6

They can move through ion channels

Question 7

What is an example of a small charged particle?

Answer 7

Ions

Question 8

How do larger molecules move across membrane?

Answer 8

They move through protein transporters

Question 9

How does water move across a membrane?

Answer 9

Through aquaporins

Question 10

What are aquaporins?

Answer 10

Protein channels with a hydrophilic centre?

Question 11

What can protein channels be?

Answer 11

They may be gated

Question 12

What moves through protein channels or by protein carriers (facilitated diffusion)?

Answer 12

Small, charged particles, larger molecules and water

Question 13

What are examples of larger molecules?

Answer 13

Glucose and lipid insoluble molecules

Question 14

What is diffusion?

Answer 14

The net movement of molecules or ions from a region of their high concentration to a region of their lower concentration until the concentrations are equal

Question 15

What happens when dynamic equilibrium is reached?

Answer 15

The particles are still moving but are in a constant state of random motion due to kinetic energy

Question 16

What direction can particles move in in diffusion?

Answer 16

Any direction

Question 17

What is the movement of diffusion?

Answer 17

There is an overall net movement

Question 18

What kind of process is diffusion?

Answer 18

A passive process as no ATP is used

Question 19

What are factors effecting diffusion?

Answer 19

Surface area of the membrane, difference in concentration on either side of the membrane, the thickness of the membrane, size and type of molecule and temperature

Question 20

How is surface area of a membrane increased?

Answer 20

By membrane folds and microvilli

Question 21

How is surface area of a membrane increased in the digestive system?

Answer 21

Villi with microvilli within the intestine increase the SA of intestine to increase the rate of diffusion

Question 22

How is surface area of the membrane increased in the gas exchange system?

Answer 22

There are many alveoli with many divisions of tissue to increase surface area of the lungs

Question 23

How do substance move when there is a difference in concentration?

Answer 23

They move down a concentration gradient until the 2 concentrations are equal

Question 24

What does a larger difference in concentration mean?

Answer 24

Diffusion will be faster

Question 25

How is difference in concentration used in the gas exchange system?

Answer 25

Blood maintains a high concentration gradient through ventilation

Question 26

How does thickness of a membrane vary?

Answer 26

It is usually the same as it is made of phospholipids

Question 27

How is thickness of the membrane affected in the gas exchange system?

Answer 27

In alveoli, the capillaries are close to the epithelial cells lining in the lung, so the distance is short and they also have thin 2 cell layer

Question 28

How do gases move?

Answer 28

They are small and can slip between phospholipid molecules easily

Question 29

Why cannot water not pass easily?

Answer 29

It is polar

Question 30

What si the effect of temprature on diffusion?

Answer 30

Higher temperature increases kinetic energy

Question 31

What is Ficks law?

Answer 31

Rate of diffusion ∝ (surface area x difference in concentration) / thickness of exchange surface

Question 32

What is facilitated diffusion?

Answer 32

Diffusion requiring a specific transmembrane protein

Question 33

How do carrier proteins work?

Answer 33

They bind to substance, change its shape and move it across

Question 34

How does active transport work>

Answer 34

A specific substrate binds to a carrier on one side and there is a conformational change of carrier, then the substrate is released on the other side

Question 35

What kind of process is active transport?

Answer 35

It is an active process with ATP required

Question 36

What direction does active transport go in?

Answer 36

Against a concentration gradient

Question 37

What is needed for active transport?

Answer 37

Transport proteins which are specific due to their binding site which has a complementary fit with a particular molecule

Question 38

What is cytosis?

Answer 38

It is a bulk transport of large materials through vesicles

Question 39

What is phagocytosis?

Answer 39

Transport of large particles/cells/parts of cells through the membrane

Question 40

What is pinocytosis?

Answer 40

The movement of fluids across the membrane (solutions/suspension of particles)

Question 41

What is an example of a substance that moves by pinocytosis?

Answer 41

Lipids in the small intestine

Question 42

What is an example of phagocytosis?

Answer 42

White blood cells engulfing bacteria