Cell membrane (L08)

Question 1

What is the properties of biological membrane?

Answer 1

• Semi-permeable membrane
• Made up of phospholipid bilayer

Able to enter/leave the cell membrane:

• Very small molecules
• Lipid-soluble molecules
• Gases

Unable to enter/leave the cell membrane:

• Large molecules
• Water-soluble molecules

Question 2

What is the function of biological membrane?

Answer 2

Maintain different environment inside and outside of the cell/organelles

Question 3

What does it mean when a solution is hypotonic?

Answer 3

• Net flow of water into the cell
• Cell gains volume
• Solute concentration outside of the cell is lower than inside of the cell
• Solute cannot enter the cell

Question 4

What does it mean when a solution is isotonic

Answer 4

• No net flow of water into/out of the cell
• Cell volume remain stable
• Solute concentration outside of the cell is the same as inside of the cell
• Solute cannot leave/enter the cell

Question 5

What does it mean when a solution is hypertonic?

Answer 5

• Net flow of water out of the cell
• Cell loses volume
• Solute concentration outside of the cell is higher than inside of the cell
• Solute cannot leave the cell

Question 6

What is the function of membrane transport system?

Answer 6

Facilitates the movement of charged/polar molecules across the membrane

Question 7

What is a channel protein?

Answer 7

It forms a protein-lined passageway across the membrane

Multiple water molecules/ions are able to move simultaneously at a very rapid rate

Question 8

What is a transporter protein?

Answer 8

Binds to only one/ a few substrate molecules at a time

Undergoes a conformational change so that bound substrate molecules are transported across the membrane

Question 9

What is secondary active transport?

Answer 9

Energy for secondary active transport is obtained from the transportation of the co-transported molecule down its concentration gradient

Question 10

What is primary active transport?

Answer 10

Energy for primary active transport is obtained from the hydrolysis of ATP

Question 11

What is an uniport?

Answer 11

Carrying out passive transport of a single substrate down its concentration gradient

Question 12

What is symport?

Answer 12

Co-transport of 2 substrates by a membrane transport protein
Substrates cross the membrane in the same direction

Question 13

What is an antiport:

Answer 13

Co-transport of 2 substrates by a membrane transport protein
Substrates cross the membrane in opposite directions

Question 14

What is a coupled transporter?

Answer 14

Transmembrane protein that transports one substrate against its concentration gradient, by coupling it to a transport of a second substrate down its concentration gradient

Question 15

What is endocytosis?

Answer 15

Movement of particles into the cell

Vesicles carry essential materials into the cell

Question 16

What is exocytosis?

Answer 16

Movement of particles out of the cell

Vesicles carry materials for secretion out of the cell

Question 17

How does enzyme move in and out of the cell?

Answer 17

IN:
Cell imports enzymes into the cell via endocytosis
Vesicles will carry the enzymes into the cell

OUT:
Cells export enzymes out of the cell via exocytosis
Vesicles will carry the enzymes out of the cell

Question 18

How does water move in and out of the cell?

Answer 18

Free water molecules are able to pass through the plasma membrane by osmosis
Water is also able to enter and leave the cell through pores in aquaporins

Question 19

How does potassium move in and out of the cell?

Answer 19

Potassium ions move in and out of the cell through a specific ion channel
Potassium ion move by diffusion (passive transport)

Question 20

How does sodium move in and out of the cell?

Answer 20

Sodium continuously move through ion channels, to achieve a balance on both sides of the membrane

When there is a need for a low concentration of sodium inside the cell and a low concentration of potassium ion outside of the cell, the cell uses the sodium-potassium pump.
This is to export sodium ions and import potassium ions via primary active transport.

Question 21

How does glucose move in and out of the cell?

Answer 21

Glucose travels into the cell with the help of GLUT2 transporter, via facilitated diffusion (passive transport)

Inside the cell:
An enzyme binds to the glucose molecule, preventing it from passing through the GLUT2 transporter, hence glucose stays in the cell
The concentration of glucose outside of the cell remains higher than inside of the cell, hence glucose molecules are able to enter the cell via diffusion

Question 22

How does carbon dioxide enter/leave the cell?

Answer 22

Carbon dioxide is able to pass through the lipid bilayer
When the cell generates carbon dioxide, there is a higher concentration of carbon dioxide in the cell than outside of the cell.
Carbon dioxide leaves the cell via diffusion

Question 23

How does oxygen leave/enter the cell?

Answer 23

Oxygen is able to pass through the lipid bilayer
Concentration of oxygen within the cell is lower than outside of the cell
Oxygen is able to enter the cell via diffusion