5.1 - Structure and functions of plasma membranes

Question 1

why is one of the models known as the fluid mosaic model?

Answer 1

fluid - components are able to move freely across the membrane
mosaic - components of different shapes and sizes fit all together

Question 2

what fluid is on the external part of membrane?

Answer 2

• tissue fluid

Question 3

what fluid is on the internal part of a membrane?

Answer 3

• cytoplasm

Question 4

what does a plasma membrane have?

Answer 4

• a phospholipid bilayer

Question 5

what is the structure of a phospholipid in a membrane?

Answer 5

• a hydrophilic phosphate head
• two hydrophobic fatty acid tails

Question 6

what is compartmentalisation?

Answer 6

• provides specific conditions for certain reactions to occur

Question 7

what is the site of chemical reactions?

Answer 7

• holds proteins/enzymes that are involved in certain chemical reactions

Question 8

why does the phospholipid bilayer act like a barrier?

Answer 8

• partially permeable
• only allows small, lipid-soluble, non polar molecules to pass through

Question 9

what are the specific types of intrinsic proteins in a plasma membrane?

Answer 9

• carrier proteins

Question 10

what is a carrier protein?

Answer 10

• able to change its shape using energy to face different directions in the membrane
• used to transport molecules across the membrane
  -can be via. facilitated diffusion OR active transport

Question 11

what is a channel protein?

Answer 11

• allows certain molecules to go down the concentration gradient across the membrane
• for example can allow polar molecules to enter the membrane without the hydrophobic core interfering
• can be via. facilitated diffusion

Question 12

specific type of channel proteins:

Answer 12

• aquaporins
• Na+/K+ channel proteins

Question 13

what are the branches that may be on a phospholipid or a protein?

Answer 13

• a carbohydrate chain

Question 14

what is a phospholipid with a carbohydrate chain attached to it called?

Answer 14

• a glycolipid

Question 15

what is a protein with a carbohydrate chain attached to it called?

Answer 15

• a glycoprotein

Question 16

what do the carbohydrate chains do?

Answer 16

• act like an antigen for cell recognition
• act like receptors for cell signalling