69. The Membrane

Question 1

what is a plasma membrane

Answer 1

phospholipid bilayer making the outer boundary of each cell

Question 2

key features of plasma membrane

Answer 2

selectively permeable, maintains ion conc., participates in joining of cells to form tissues, enables cells to respond to signals of the environment

Question 3

what is the cell membrane composed of

Answer 3

(phospho)lipid and protein

Question 4

Head and tail- which is polar/non-polar etc

Answer 4

head is polar - hydrophilic
tail is non polar - hydrophobic

Question 5

do phospholipid bilayer move

Answer 5

yes. they twirl and vibrate

Question 6

what does cholesterol do in the membrane

Answer 6

aids in the stiffening of the membrane

Question 7

what are phospholipid bilayer impermeable to

Answer 7

charged molecules

Question 8

what can pass through the phospholipid membrane

Answer 8

O2, CO2, NH3 and H20

Question 9

what are the 3 functions of the bilayer

Answer 9

1. forms basic structure
2. served as a barrier
3. responsibility for fluidity of the membrane

Question 10

what are the 2 types of membrane proteins

Answer 10

peripheral and integral

Question 11

describe peripheral proteins

Answer 11

not embedded within the membrane.
Adhere tightly to the cytoplasmic surfaces of the PM

Question 12

what are the 3 types of integral membrane protein

Answer 12

1. transmembrane - span the bilayer once or several time
2. some are embedded but do not cross the bilayer
3. some are linked to a lipid component

Question 13

what are the 2 functions of integral proteins

Answer 13

ligand binding receptors and adhesion molecules

Question 14

what are ligand binding receptors

Answer 14

bind extracellular signalling molecules eg Hormone receptors

Question 15

what are adhesion molecules

Answer 15

• Form contact with the extracellular matrix or cellular neighbours
• Important in regulating cell shape, growth and differentiation, allowing the cell to adapt to its immediate surroundings

Question 16

what are examples of adhesion molecules

Answer 16

integrins (cell-matrix adhesion molecules)
cadherins (cell adhesion molecules) etc.

Question 17

what are integrins

Answer 17

cell-matrix adhesion molecules

Question 18

what are cadherins

Answer 18

cell adhesion molecules etc.

Question 19

what are the 3 ways Integral membrane proteins can carry out the transmembrane movement of water-soluble substances

Answer 19

Pores and channels
Carriers
Pumps

Question 20

describe integral protein pumps

Answer 20

Use energy that is released through the hydrolysis of ATP to drive the transport of substances into or out of cells against energy gradient

Question 21

describe integral protein carriers

Answer 21

Either facilitate the transport of a specific molecule or couple the transport of a molecule to that of other solutes

Question 22

describe integral protein Pores and Channels

Answer 22

Serve as conduits that allow water or specific ions to flow passively through the lipid bilayer

Question 23

Integral membrane proteins can also be …. can …..

Answer 23

enzymes and participate in intracellular signalling

Question 24

name another type of membrane protein

Answer 24

docking- marker acceptors

Question 25

where can you find docking marker acceptors

Answer 25

inner membrane surface

Question 26

what do docking marker acceptors interact with?? which leads to???

Answer 26

interact with secretory vesicles leading to exocytosis of vesicle contents

Question 27

where are docking marker acceptors important

Answer 27

nervous system

Question 28

when using the term ‘sugar coating’ what do we mean

Answer 28

A small amount of membrane carbohydrate is located on the outer surface of cells

Question 29

Short carbohydrate chains are often bound to membrane proteins and to a lesser extent lipids. What are they called.

Answer 29

Glycoproteins and Glycolipids

Question 30

Glycoproteins and Glycolipids form a layer called…?

Answer 30

Glycocalyx- which coats cells

Question 31

what are Glycoproteins and Glycolipids

Answer 31

Short carbohydrate chains are often bound to membrane proteins and to a lesser extent lipids

Question 32

Glycocalyx is made up of what

Answer 32

Glycoproteins and glycolipids

Question 33

some cells are linked by 3 specialized cell junctions

Answer 33

1. tight junctions
2. desmosomes
3. Gap junctions

Question 34

what is a tight junction

Answer 34

Join the lateral edges of epithelial cells near their luminal (apical) membranes (tight or leaky)

Question 35

what is desmosomes

Answer 35

Adhering junctions that anchor cells together, especially in tissues subject to stretching (e.g. skin, heart, uterus)

Question 36

what is a gap junction

Answer 36

‘Communicating’ junctions that allow the movement of charge carrying ions and small molecules between two adjacent cells.

Question 37

Carbohydrates have a 2 roles

Answer 37

self recognition
cell to cell interactions

Question 38

what is the ‘bigger picture’ diagram where you see everything

Answer 38

fluid mosaic model