Unit 1 KA 1.3 ✓

Question 1

What is the Fluid mosaic model?

Answer 1

The fluid mosaic model is the plasma membrane, as they isn’t static and includes a variety of proteins

Question 2

What is the Phospholipid bilayer?

Answer 2

The phospholipid bilayer is what the plasma membrane is mostly comprised of. It is made up of two layers of phospholipids

NOTE: Phospholipids have a hydrophilic head and a hydrophobic tail

Question 3

What are Integral membrane proteins?

Answer 3

Integral membrane proteins are found within the phospholipid bilayer

e.g. Receptors, transporters and channels

Question 4

What are Transmembrane proteins?

Answer 4

Transmembrane proteins are integral proteins that span the entire width of the membrane

Question 5

What are Peripheral membrane proteins?

Answer 5

Peripheral membrane proteins are found on the surface of the membrane (intra or extracellular).
They can interact with integral membrane proteins

Question 6

What is Facilitated diffusion?

Answer 6

Facilitated diffusion is the passive transport of substances across the membrane through specific transmembrane proteins. It doesn’t require energy as substances are moved down their concentration gradient

e.g. Transmembrane proteins - channels, transporters

Question 7

In terms of transmembrane proteins:

What are Channels?

Answer 7

Channels are multi-subunit proteins. The subunits are arranged to form water filled pores which extend across the membrane. Most channel proteins are highly selective. Some channels must undergo a conformational change to allow/prevent diffusion

e.g. Ligand and Voltage gated channels

Question 8

In terms of transmembrane proteins:

What are Transporters?

Answer 8

Transporter proteins bind to the specific substance that must be transported across the membrane. They undergo a conformational change to transfer the solute across the membrane

NOTE: Transporters alternate between two conformations

Question 9

What are ATPases?

Answer 9

ATPases are protein pumps which are coupled with an energy source that hydrolyses ATP, converting it into ADP + Pi and releasing energy which causes the conformational change required to move the substance across the membrane

Question 10

What is the Concentration gradient?

Answer 10

The concentration gradient is the difference in concentration of a solute across the plasma membrane

Question 11

What is the Membrane potential?

NOTE: Also known as the Electrical potential difference

Answer 11

The membrane potential/electrical potential difference is created when there is a difference in electrical charge on the two sides of the plasma membrane

Question 12

What is the Electrochemical gradient?

Answer 12

The electrochemical gradient is the combination of concentration gradient and membrane potential. It determines how a charged molecule is transported/in which direction

Question 13

What is the Sodium-potassium pump?

Na/K- ATPase

Answer 13

The sodium-potassium pump is a protein pump which transports 3 Na ions out of the cell and 2 K ions into the cell against their concentration gradient using energy directly taken from ATP hydrolysis. This establishes a concentration gradient across the membrane and results in an overall negative charge in the cell

Question 14

What is the Glucose symport?

Answer 14

The glucose symport is proteins that move glucose into the small intestines at the same time as Na (from the sodium-potassium pump). This is active transport as it is dependant on the gradient established by the Na/K-ATPase

NOTE: Symports cotransport two substances at the same time + direction