Plasma Proteins Composition and Function

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Questions and Answers

What is the approximate concentration of total protein in human plasma?

8.0-10.0 g/L

6.0-8.0 g/L (correct)

4.0-5.0 g/L

10.0-12.0 g/L

Where are most plasma proteins synthesized?

Heart

Liver (correct)

Kidneys

Lungs

What is the major part of the solids of the plasma?

Proteins (correct)

Metabolites

Nutrients

Electrolytes

What is the percentage of α1-Globulin in plasma proteins?

5.3% Signup and view all the answers

What is the name of the most abundant plasma protein?

Albumin Signup and view all the answers

What is the half-life of albumin in plasma?

20 days Signup and view all the answers

What percentage of albumin is present in the extracellular space?

60% Signup and view all the answers

What happens to albumin levels in cases of injury, infection, and surgery?

Decrease rapidly Signup and view all the answers

What happens to AFP levels during intra-uterine life?

They decrease gradually Signup and view all the answers

What is the function of Ceruloplasmin in copper transport?

It binds copper tightly and prevents exchange Signup and view all the answers

What is the association of elevated maternal AFP levels with?

Neural tube defect Signup and view all the answers

What is the function of Haptoglobin?

It binds to free hemoglobin Signup and view all the answers

What is the consequence of low plasma levels of Ceruloplasmin?

Copper is accumulated in the liver and brain Signup and view all the answers

What is the association of decreased maternal AFP levels with?

Down's syndrome and Trisomy 18 Signup and view all the answers

What is the function of AFP in fetal development?

It protects the fetus from immunologic attack Signup and view all the answers

What is Ceruloplasmin synthesized by?

The liver Signup and view all the answers

What is the main function of albumin in the body?

To maintain oncotic pressure Signup and view all the answers

What is the approximate percentage of plasma oncotic pressure maintained by albumin?

80% Signup and view all the answers

What is the cause of hyperalbuminemia?

Dehydration Signup and view all the answers

What is the function of α1-antitrypsin?

To control proteolytic action of lysosomal enzymes Signup and view all the answers

What is synthesized by the parenchymal cells of the liver in the developing embryo and fetus?

α-fetoprotein Signup and view all the answers

What is one of the effects of hypoalbuminemia?

Decreased blood volume Signup and view all the answers

What is one of the causes of hypoalbuminemia?

Hypothyroidism Signup and view all the answers

What is the function of albumin as a transport protein?

To transport hormones and calcium Signup and view all the answers

Study Notes

Plasma Proteins

Plasma contains over 300 different proteins, with a concentration of approximately 6.0-8.0 g/L.
Most plasma proteins are synthesized in the liver, while some are produced in other sites.

Types of Plasma Proteins

There are three major fractions of plasma proteins: Albumin, Globulin, and Fibrinogen.
These fractions can be further separated into:
- Albumin (55.2%)
- α1-Globulin (5.3%)
- α2-Globulin (8.6%)
- β-Globulin (13.4%)
- γ-Globulin (11.0%)
- Fibrinogen (6.5%)

Albumin

Albumin is the most abundant plasma protein (~40 g/L) in normal adults.
It is synthesized in the liver as prealbumin and secreted as albumin.
About 40% of albumin is present in the plasma, and the other 60% is present in the extracellular space.

Functions of Albumin

Maintains oncotic pressure, which pulls water into the circulatory system.
Maintains fluid distribution in and outside cells and plasma volume.
80% of plasma oncotic pressure is maintained by albumin.
It plays a predominant role in maintaining blood volume and body fluid distribution.
Albumin also buffers pH and is a negative acute-phase reactant protein.
It serves as a non-specific transport protein for various biomolecules.
Albumin serves as a source of amino acids for tissue protein synthesis to a limited extent.

Abnormal Levels of Albumin and their Effects

Hypoalbuminemia

Causes:
- Inadequate source of amino acids (malnutrition and malabsorption)
- Liver disease
- Protein-losing enteropathy or gastrointestinal loss
- Kidney loss to the urine in renal disease
- Skin loss in the absence of the skin barrier
- Hypothyroidism
- Dilution by excess fluids
- Acute disease states

Hyperalbuminemia

Caused by dehydration
No clinical conditions are known that cause the liver to produce large amounts of albumin.

Globulins

Types of Globulins

α1-Globulins
α2-Globulins
β-Globulins
γ-Globulins

α1-Globulins

α1-Antitrypsin:
- Synthesized by the liver and macrophages
- Controls the proteolytic action of lysosomal enzymes from phagocytes
α-Fetoprotein (AFP):
- Synthesized in the developing embryo and fetus by the parenchymal cells of the liver
- Function unknown, but may protect the fetus from immunologic attack by the mother
- Elevated maternal AFP levels are associated with neural tube defects, anencephaly, spina bifida, and abdominal wall defects
- Decreased maternal AFP levels are associated with an increased risk of Down's syndrome and trisomy 18

α2-Globulins

Ceruloplasmin:
- Synthesized by the liver
- Carries >90% of serum copper
- Binds copper very tightly, making it unavailable for exchange
Haptoglobin (Hp):
- Synthesized by the liver
- Binds to free hemoglobin to form complexes that are metabolized in the RES
- Prevents loss of free hemoglobin into the kidney, conserving valuable iron present in hemoglobin
- Plasma level decreases during hemolysis and rises in inflammation

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Description

This quiz covers the composition of plasma, including proteins, and their functions in the human body. It also discusses the concentration of total protein in human plasma and the types of proteins present.