Biochem PS

Question 1

What is PS?

pulmonary surfactant

Answer 1

A complex mixture of lipids (90%)and proteins (10%) produced alveoli in
within the lung and secreted along the alveolar surface

Question 2

Where is PS found?

Answer 2

along the air-liquid interface on the surface the alveolar walls

Question 3

Why is it important?

Answer 3

• Decreases surface tension within the alveoli to prevent

collapse and facilitate respiration

Question 4

defects in PS production&raquo_space;

Answer 4

increase ST & difficultly w/ respiration.

Question 5

Gas exchange between air in alveoli( Large moist surface for gas )is by

Answer 5

diffusion

Question 6

Gas exchange between air in alveoli and erythrocytes in pulmonary capillaries • Via

Answer 6

alveolar type I cell

Question 7

Gas molecules move

through——-covering alveolar wall

Answer 7

thin fluid layer

Question 8

alveolar cells epithelial type

Answer 8

squamous

Question 9

Define surface tension

Answer 9

Film of water along the alveolar wall
tendency
(Force)of liquid surfaces to shrink into the minimum surface area possible.

Question 10

Describe the mechanism of surface tension

Answer 10

• Cohesion between adjacent water molecules
• Lack of forces pulling water molecules away from fluid at air
interphase creates tension along surface

Question 11

• Cohesion between adjacent water molecules

Answer 11

• Hydrogen bonding between molecules
• H 2O molecules prefer to interact with each other rather than air
• Minimize surface area

Question 12

Laplace Law:

Answer 12

P = 2T/r

Question 13

Attraction and alveolar size

Answer 13

Attraction increases and alveolar size decreases

Question 14

Cohesive forces result in

Answer 14

increased thickness of this fluid layer
& decrease in overall surface area.

the fluidity of the aqueous layer increase
the amount of P decrease

Question 15

————-reduce surface tension and prevent collapse of alveoli

Answer 15

Pulmonary surfactants

Question 16

to reinflate:——- ST

Answer 16

decrease

Question 17

How does pulmonary surfactant reduce surface tension in alveoli?

Answer 17

because of amphipathic structure
1)Cohesive forces between water molecules pulling them DOWN and
2)Surfactant film neutralizes this effect by creating a new cohesive force pulling UP
• Increases the fluidity of the aqueous layer and reduces the amount of
pressure required to expand alveoli i.e. makes breathing easier

Question 18

amphipathic structure

Answer 18

Hydrophobic tails interact with gas layer

Hydrophilic polar heads interact with water molecules

Question 19

Absences of surfactant :

Answer 19

• High surface tension: alveoli collapse on expiration

* Fluid flow from blood to alveolar space (pulmonary edema)

Question 20

Lipid composition of PS

Answer 20

1)DPPC (dipalmitoylphosphatidylcholine)mainly

2) Unsaturated phospholipids (PC) and
3) neutral lipids like cholesterol

PC= phosphatidylcholine

Question 21

DPPC

Answer 21

a saturated (single bond) glycerophospholipid with two C16 saturated fatty acyl
chains

Question 22

• Excellent compaction, but pure films ——-at 37℃

Answer 22

lack fluidity

Question 23

Unsaturated phospholipids (PC) and neutral lipids like
cholesterol
Function

Answer 23

Increase fluidity and surfcant films

Question 24

What happens in case of excess cholesterol

Answer 24

prevents full activity of surfactant
bcz it is preventing full compaction necessary,and

is often associated with lung injury

Question 25

How DPPC synthesized?

Answer 25

In cytoplasm
Conversion of Glucose to Dihydroxyacetone phosphate (DHAP)to
Glycerol 3-phosphate and fatty acyl -CoA

Question 26

From Dihydroxyacetone phosphate (DHAP to glycerol 3-phosphate by

Answer 26

Glycerol 3-phosphate dehydrogenase

Question 27

Fa tty acid at—- position replaced by palmitic acid (C16)

Answer 27

2

Question 28

Where does this take place within the cell?

Biosynthesis of pulmonary surfactant

Answer 28

In type 2 alveolar cells
Synthesis of the lipid components,
matures from RER to the golgi then to
MVB,  then 
LB to the extra cellular space.

Question 29

Pu lmonary surfactant proteins

Answer 29

• Hydrophilic/amphipathic proteins

* Hydrophobic proteins

Question 30

Hydrophilic/amphipathic proteins mention them

Answer 30

SP-A,

SP-D

Question 31

Hydrophilic/amphipathic proteins known as

Answer 31

Collectins (Ca 2+ dependent C-type lectins)

Question 32

Function of amphipathic proteins?

Answer 32

1) Immune function and protection from pathogens

2) Regulation of lipid secretion

Question 33

Mention the Hydrophobic proteins

Answer 33

SP-B, SP-C

Question 34

SP-B

Answer 34

lipid associated

Question 35

SP-C

Answer 35

integral membrane protein

Question 36

Function of Hydrophobic proteins?

Answer 36

1) Important for the integrity and maintenance of the PS film organization an
2) ability to compress and extend during respiration

Question 37

SP-A

Characteristics?

Answer 37

1)Large glycoprotein
2)Most abundant surfactant
protein
3)High affinity for DPPC

Question 38

SP-A
Associated with surfactant
lipids on alveolar surface through

Answer 38

CRD = carbohydrate recognition domain

Question 39

Function of SP-D

Answer 39

1) Activation of macrophages
2) Agglutination of bacteria
3) Protection against pathogens
4) part of innate immune system (main role)

Question 40

Hexamers of trimers

Answer 40

SP-A

Question 41

Tetramer of trimers

Answer 41

SP-D

Question 42

PS function in immune response

Answer 42

1) Aggregation
2) Opsonization
3) Inhibition of microbial growth
4) increase cell membrane permeability
5) pro- and anti-inflammatory roles