Questions and Answers
What is the primary function of red blood cells?
What is the average lifespan of red blood cells in the blood circulation?
What is the composition of the red cell membrane?
What is the function of the glycocalyx in the red cell membrane?
Signup and view all the answers
Why is the red cell membrane required to be tough but flexible and show deformability?
Signup and view all the answers
What is the role of haemoglobin in red blood cells?
Signup and view all the answers
What is the result of a reduced lifespan of red blood cells?
Signup and view all the answers
Where do red blood cells develop?
Signup and view all the answers
What is the percentage of protein in the red cell membrane?
Signup and view all the answers
What is the main function of the Band 3 protein in the red cell membrane?
Signup and view all the answers
What is the primary function of glycophorins in the red cell membrane?
Signup and view all the answers
What is the percentage of carbohydrate in the red cell membrane?
Signup and view all the answers
What is the primary function of the glucose transport protein in the red cell membrane?
Signup and view all the answers
What is the primary function of spectrin in the red cell membrane?
Signup and view all the answers
What is the primary function of ankyrin in the red cell membrane?
Signup and view all the answers
What is the arrangement of subunits in spectrin?
Signup and view all the answers
What is the function of Band 4.1 in the cytoskeleton?
Signup and view all the answers
What is the function of Ankyrin in the cytoskeleton?
Signup and view all the answers
What is the function of Actin in the cytoskeleton?
Signup and view all the answers
What is the function of Spectrin in the cytoskeleton?
Signup and view all the answers
What is the function of the Glucose Transport Protein (GLUT 1)?
Signup and view all the answers
What is the function of Glycophorin A?
Signup and view all the answers
What is the function of the Red Cell Na+/K+ ATPase?
Signup and view all the answers
What is the result of each ATP hydrolysis by the Red Cell Na+/K+ ATPase?
Signup and view all the answers
What is transported out of the cell during the release of the pump?
Signup and view all the answers
What is the function of Ankyrin in the peripheral proteins of the cytoskeleton?
Signup and view all the answers
What is the shape of the cells in Hereditary Elliptocytosis?
Signup and view all the answers
Which protein binds to spectrin close to the actin binding site?
Signup and view all the answers
What is the result of defective/deficiency of skeletal proteins in Hereditary Spherocytosis?
Signup and view all the answers
What is the characteristic of cells in Rh Null Syndrome?
Signup and view all the answers
Which of the following is NOT a characteristic of Primary Membrane Disorders?
Signup and view all the answers
Which protein is mainly affected in Hereditary Spherocytosis?
Signup and view all the answers
Study Notes
Red Blood Cells
- Also known as erythrocytes, they have a bi-concave disc shape
- Their role is to transport respiratory gases to and from tissues, specifically delivering oxygen to tissues and removing waste products of metabolism
- On average, a healthy adult male has 5,000,000,000,000 red blood cells per liter of blood
Red Cell Facts
- Red blood cells develop in the bone marrow but lose their nucleus by the time they reach the bloodstream
- They contain hemoglobin, which enables oxygen delivery to tissues
- Red blood cells have an average lifespan of 120 days in the blood circulation, and a reduced lifespan can lead to hemolytic anemia
Function of Red Cell Membrane
- The membrane must be tough but flexible and show deformability to function in microcirculation
- This is achieved by the interaction of a protein cytoskeleton with the membrane lipid bilayer
- The main functions of the red cell membrane are:
- Separating the cell contents from the plasma
- Maintaining the characteristic shape of the cell
- Regulating intracellular cat ion concentrations
- Serving as a site for membrane surface receptors
The Red Cell Membrane
- Composed of an outer glycocalyx carbohydrate 'coat', a lipid bilayer, and a framework of peripheral proteins that comprise the red cell cytoskeleton
- The glycocalyx is made up of both extracellular proteins and glycosylated proteins and lipids from the lipid bilayer
- The lipid bilayer is made up of 44% lipid, which acts as a permeability barrier and comprises a basic phospholipid bilayer
- The protein component is 49% of the membrane, comprising integral and peripheral proteins that provide skeletal structure and selective transport across the membrane
- The carbohydrate component is 7% of the membrane, associated with proteins or lipids, and presented on the outside of the membrane
Composition of the Red Cell Membrane
- Membrane lipids:
- 30% cholesterol
- 60% phospholipid (phosphatidyl choline, sphingomyelin, phosphatidyl ethanolamine, phosphatidyl serine)
- 10% glycerides/FFA
- Integral proteins:
- Band 3: facilitates anion transport across the membrane, binding site for skeletal and other red cell proteins
- Glycophorins (A, B, C, D, E): sialoglycoproteins providing negative charge, acting as binding sites for viruses, bacteria, and parasites, and required for structural integrity of the red cell
- Glucose Transport Protein: 12 trans-membrane domains, surface concentration varies
- Rh Proteins: associated into a macrocomplex, transport function, and interact with the cytoskeleton
Peripheral Proteins of the Cytoskeleton
- Spectrin: subunits bind in an anti-parallel arrangement, associates with ankyrin, band 4.1, actin, and anionic phospholipids
- Ankyrin: found in 2 forms, anchors spectrin molecules to the lipid bilayer
- Actin: globular protein that polymerizes readily to form filaments, binds weakly to the tail end of spectrin and holds together in a 2D lattice
- Band 4.1: globular protein that binds to spectrin close to the actin binding site, binds directly to glycophorins A & C, Band 3, phosphatidyl serine, and ankyrin
Red Cell Na+/K+ ATPase 'Cation Pump'
- Enzyme composed of 3 protein subunits, catalyzes the conversion of ATP to ADP to release energy
- ADP formed is reconverted to ATP by the EM Pathway
- Each ATP hydrolyzed removes 3 Na+ molecules and subsequently transports 2 K+ into the cell
Mechanism of Na+/K+ ATPase 'Pump'
- Phosphorylation (energy release) of the pump transports out 3 Na+ molecules
- Dephosphorylation transports 2 K+ into the cell
Primary Membrane Disorders
- Inherited disorders of the red cell membrane
- Affects cell shape, reduced life-span can lead to compensated anemia
- Examples:
- Hereditary Spherocytosis: autosomal inheritance, results in defective/deficiency of skeletal proteins (mainly spectrin), causes spherocytosis and hemolytic anemia
- Hereditary Elliptocytosis: presence of a large proportion of oval or elliptical cells, defective spectrin, Band 4.1, or Band 3
- Rh Null Syndrome: absence of Rh Polypeptides and RhAG in the membrane, stomatocytosis and spherocytosis observed in peripheral blood, patient experiences compensated hemolytic anemia
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Learn about the constituents of the red cell membrane, its function, and how its structure enables it to perform its function. Understand how the membrane works to maximize red cell lifespan.