The red blood cell structure and function

Question 1

Shape of RBC

Answer 1

Biconcave disc-shaped

Question 2

Membrane of RBC

Answer 2

Flexible membrane but tough

Question 3

RBC(surface area to volume ratio)

Answer 3

High surface area to volume ratio

Question 4

Diameter of RBC

Answer 4

8 microns

Question 5

What does RBC lack?

Answer 5

Lacks:
Nucleus
Mitochondria
ER

Question 6

What is the cytoplasm of a RBC rich in?

Answer 6

Rich in haemoglobin

Question 7

Primary function of RBC

Answer 7

• Primary function is transport of respiratory gases to and from tissue

RBC should be capable of traversing microvascular system without mechanical damage

Question 8

In a red blood cell, what determines strength and flexibility?

Answer 8

Interactions between membrane and cytoskeletal proteins determines strength and flexibility

Question 9

What is the outer hydrophilic region portion of an RBC composed of?

Answer 9

Outer hydrophilic portion composed of glycolipids, glycoproteins and proteins

Question 10

What is the central hydrophobic layer of an RBC composed of?

Answer 10

Central hydrophobic layer containing proteins, cholesterol and phospholipids

Question 11

What is the inner hydrophilic layer of an RBC composed of?

Answer 11

Inner hydrophilic layer of mesh like cytoskeletal proteins to support lipid bilayer

Question 12

Distribution of membrane lipids

Answer 12

Asymmetric phospholipid distribution

Question 13

What is between membrane lipids?

Answer 13

Unesterified free cholesterol between them

Question 14

What lipids are on the outer layer of the membrane?

Answer 14

○ Uncharged phospholipids on outer layer:
§ Phosphatidyl choline
Sphingomyelin

Question 15

What lipids are on the inner layer of the membrane?

Answer 15

○ Charged phospholipids on inner layer:
§ Phosphatidyl ethanolamine
Phosphatidyl serine

Question 16

What does increased cholesterol cause in RBC?

Answer 16

RBC with increased cholesterol appear distorted resulting In acanthocytosis

Question 17

What is a cause of target cells(RBC)?

Answer 17

Increase in cholesterol and phospholipid is a cause of target cells

Question 18

Integral membrane proteins in RBC

Answer 18

Extend from outer surface and traverse entire membrane to inner surface

Question 19

2 major integral membrane proteins

Answer 19

Glycophorins

Band 3:anion transporter

Question 20

Other integral proteins

Answer 20

Na+/K+ ATPase, surface receptors

Question 21

Peripheral proteins in RBC

Answer 21

Limited to cytoplasmic surface

Question 22

What do peripheral proteins in RBC form?

Answer 22

Forms the RBC cytoskeleton

Question 23

Peripheral protein (Spectrin)

Answer 23

§ Most abundant
§ Composed of alpha and beta chains
§ V.important in integrity of RBC membrane
□ Binds with other peripheral proteins to form cytoskeletal network of microfilaments
Controls biconcave shape and deformability of cell

Question 24

Peripheral protein (Ankyrin)

Answer 24

Anchors lipid bilayer to membrane skeleton by interactions with spectrin and band 3

Question 25

Peripheral protein (Protein 4.1)

Answer 25

§ Link with cytoskeleton to the membrane by means of its associations with glycophorin

Stabilises interaction of spectrin with actin

Question 26

Peripheral protein (Actin)

Answer 26

Responsible for contraction and relaxation of membrane

Question 27

What maintains surface area in RBC?

Answer 27

Strong cohesion between bilayer and membrane skeleton maintains surface area

Question 28

Function of RBC(SHAPE)

Answer 28

Provides optimum surface area to volume ratio for respiratory exchange and essential to deformability

Question 29

Function of RBC(Elasticity)

Answer 29

○ Provides elasticity:

Allows for passage through micro vessels

Question 30

What do RBC regulate?

Answer 30

Regulate intracellular cation concentration

Question 31

What do RBC act as?

Answer 31

Act as interface between the cell and its environment via membrane surface receptors

Question 32

Membrane abnormalities with RBC

Answer 32

○ Hereditary elliptocytosis
§ Shape becomes eliptical
○ Hereditary spherocytosis:
Shape becomes spherical

Question 33

Haemoglobin structure

Answer 33

• 4 polypeptides

2 alpha and 2 beta chains

Question 34

RBC metabolism provide energy for:

Answer 34

○ Maintenance of cation pumps
○ Maintenance of Hb in reduced state
○ Maintenance of reduced sulfhydryl group in Hb and other proteins

Maintenance of RBC integrity and deformability

Question 35

RBC metabolism in glycolytic pathway

Answer 35

○ Generates 90-95% of energy needed by RBC’s
○ Glucose is metabolized and generates 2 molecules of ATP

Functions in the maintenance of RBC shape, flexibility and the cation pumps

Question 36

RBC metabolism in pentose phosphate pathway

Answer 36

○ RBC needs GSH to protect from oxidative damage
○ Pentose phosphate shunt provides the reducing power, NADPH

NADPH maintains glutathione in reduced form

Question 37

RBC metabolism in methaemoglobin reductase pathway

Answer 37

○ Maintains Fe2+ state

In absence of this enzyme, methaemoglobin accumulates and cannot carry oxygen

Question 38

RBC metabolism in Luebering Rapoport shunt

Answer 38

Permits the accumulation of 2,3-DPG which is essential for maintaining normal oxygen tension, regulating haemoglobin affinity

Question 39

What is cytoplasmic viscosity of a RBC determined by?

Answer 39

Cytoplasmic viscosity determined by MCHC

• As MCHC rises, viscosity rises exponentially