Membrane Components

Question 1

What is the function of the enzyme flippase in plasma membranes?

Answer 1

“Flips” phospholipids from one side of the membrane to the other.

Question 2

What are the two major types of proteins located in the plasma membrane?

Answer 2

1. integral proteins
   
   1. ​transmembrane
   2. embedded
2. peripheral proteins

Question 3

What are integral (or intrinsic) proteins?

Answer 3

Proteins integrated throughout the entire membrane.

1. transmembrane
2. embedded

These proteins are hydrophobic!

Question 4

What are peripheral (or extrinsic) proteins?

Answer 4

Proteins located on the periphery of membranes.

These proteins are hydrophilic!

Question 5

What are the three types of intercellular junctions that connect animal cells?

Answer 5

1. gap junctions (small tunnels between adjacent cells)
2. desmosomes
3. tight junctions

Question 6

What is the function of tight junctions?

Answer 6

Form a watertight seal which prevents the movement of molecules.

Question 7

What is the function of desmosomes?

Answer 7

Connect adjacent cells (cell to cell adhesion).

(They are found in tissues that undergo stress such as the skin and intestine.)

Question 8

Which intercellular junction is the strongest? Why?

Answer 8

Desmosomes because they are directly attached to the cytoskeleton.

Question 9

[Mnemonic]

Tight junctions form a watertight seal.

(how to remember the function of tight junctions)

Answer 9

Tight junctions form a watertight seal, preventing paracellular transport of water and solutes.

Question 10

**Think HYDROPHOBIC when you see transmembrane”.

Answer 10

Transmembrane helixes or domains are mostly composed of hydrophobic amino acids/proteins.