transport across cell membrane

Question 1

any model of membrane structure must show the following… ?

Answer 1

• lipids (mostly phospholipids)
• proteins
• carbohydrates

Question 2

what does a successful model must also show ?

Answer 2

how the cell surface membrane acts as a barrier between the cell and its environment

Question 3

features of the fluid mosaic model ?

Answer 3

• makes a repeated pattern of proteins (mosaic)
• is in constant motion (fluid)

Question 4

what kind of membranes have the same structure ?

Answer 4

all cells and organelle membranes have the same structure

Question 5

why is the membrane described as a fluid mosaic model ?

Answer 5

• due to the mixture and movement of the phospholipids, proteins, glycoproteins and glucolipids it is made of

Question 6

what is the key component of the cell surface membrane ?

Answer 6

the phospholipid bilayer
- due to the hydrophilic heads being attracted to water and the hydrophobic tails being repelled by water

Question 7

what is the function of cholesterol in the phospholipid bilayer ?

Answer 7

• it affects how fluid the membrane is by restricting the lateral movement of other molecules in the membrane

Question 8

why is the function of cholesterol useful ?

Answer 8

• it makes the membrane less fluid at high temperatures and prevents water and dissolved ions from leaking out

Question 9

proteins embedded in the cell membrane can be either… ?

Answer 9

• peripheral ( do not extend completely across the membrane)
• integral ( span across from one side of the bilayer to another)

Question 10

what is the function of peripheral proteins ?

Answer 10

• they provide mechanical support
• or they are connected to proteins or lipid to make glycoproteins or glycolipids.

Question 11

what is the function of glycoproteins or glycolipids ?

Answer 11

cell recognition

Question 12

what is the function of integral proteins ?

Answer 12

• they are protein carriers or channel proteins involves in the transport of molecules across the membrane

Question 13

what do protein channels form ?

Answer 13

• they form tubes that fill with water to enable water-soluble ions to diffuse

Question 14

what do the carrier proteins do ?

Answer 14

• they will bind with other and larger molecules such as glucose and amino acids and change shape to transport them to the other side of the membrane

Question 15

what are the molecules that can pass through the membrane ?

Answer 15

• lipid soluble substances
• very small molecules
  that can pass through simple diffusion

Question 16

what are the molecules that cannot pass through the cell membrane ?

Answer 16

• water soluble (polar substances e.g sodium ions)
• and large molecules (glucose)