Biochemistry Chapter: Proteins and Their Functions
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Questions and Answers

What is the molecular weight of Prealbumin?

62 kDa

Prealbumin is an immature form of albumin.

False (B)

Prealbumin has a longer half-life compared to albumin.

False (B)

What is the primary function of Alpha1-Antitrypsin?

<p>Neutralizing trypsin and trypsin-like enzymes.</p> Signup and view all the answers

What is another name for Alpha1-Antitrypsin?

<p>Alpha1-Antiproteinase</p> Signup and view all the answers

What is the molecular weight of Alpha1-Antitrypsin?

<p>53 kDa</p> Signup and view all the answers

What is the most common phenotype of Alpha1-Antitrypsin?

<p>MM phenotype</p> Signup and view all the answers

The SZ genotype is associated with a higher risk of emphysema.

<p>True (A)</p> Signup and view all the answers

What is the main role of Alpha1-Antitrypsin in elastase regulation?

<p>To inhibit elastase activity.</p> Signup and view all the answers

What is the most common cause of lung inflammation?

<p>Smoking</p> Signup and view all the answers

What amino acid residue is oxidized by smoking in Alpha1-Antitrypsin?

<p>Methionine-358 (Met-358)</p> Signup and view all the answers

Reduced elastase activity leads to the formation of larger air spaces in the lungs.

<p>False (B)</p> Signup and view all the answers

The PiZZ genotype is particularly severe in emphysema patients due to a significant deficiency in functional alpha1-antitrypsin.

<p>True (A)</p> Signup and view all the answers

Mutations in the alpha1-antitrypsin gene can alter the protein's shape, leading to aggregation.

<p>True (A)</p> Signup and view all the answers

Where is Alpha1-fetoprotein synthesized?

<p>In the yolk sac of the fetus and later by liver parenchyma cells.</p> Signup and view all the answers

Low levels of Alpha1-fetoprotein are associated with Down's syndrome.

<p>True (A)</p> Signup and view all the answers

What is the molecular weight of Haptoglobin?

<p>90 kDa</p> Signup and view all the answers

Haptoglobin's half-life is shortened when it binds to hemoglobin.

<p>True (A)</p> Signup and view all the answers

What is the molecular weight of Ceruloplasmin?

<p>160 kDa</p> Signup and view all the answers

Most of the copper in the blood is bound to Ceruloplasmin.

<p>True (A)</p> Signup and view all the answers

What is the genetic liver disorder associated with low Ceruloplasmin levels?

<p>Wilson's disease</p> Signup and view all the answers

What type of enzyme is ferroxidase?

<p>A ferroxidase</p> Signup and view all the answers

What does CRP stand for?

<p>C-reactive protein</p> Signup and view all the answers

What is the normal range for CRP levels?

<p>Less than 5</p> Signup and view all the answers

Most plasma proteins are synthesized in the liver.

<p>True (A)</p> Signup and view all the answers

Elevated levels of gamma globulins can indicate cancer.

<p>True (A)</p> Signup and view all the answers

Renal failure can lead to a decrease in all protein bands in circulation.

<p>True (A)</p> Signup and view all the answers

Flashcards

Prealbumin (Transthyretin)

A protein that transports thyroid hormones (T4 and T3). It gets its name from migrating ahead of albumin in gel electrophoresis.

Prealbumin Properties

A small glycoprotein with a molecular weight of 62 kDa. It is rich in tryptophan and contains 0.5% carbohydrates.

Prealbumin Half-Life

Prealbumin has a short half-life of 2 days, making it useful for diagnosing diseases or poor protein nutrition.

Globulins

A group of proteins classified based on their migration speed in electrophoresis.

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Alpha1-Antitrypsin (A1AT)

An alpha-1 globulin that inhibits the activity of trypsin and other proteolytic enzymes.

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Alpha1-Antiproteinase

Alpha1-Antitrypsin also inhibits a wide range of proteases, hence the name Alpha1-Antiproteinase.

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A1AT Molecular Weight

Alpha1-Antitrypsin has a molecular weight of 53 kDa.

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A1AT in Serum

Alpha1-Antitrypsin constitutes about 90% of the alpha-1 globulin fraction in serum protein electrophoresis.

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Alpha1-Antitrypsin Polymorphism

Alpha1-Antitrypsin exhibits polymorphism with over 75 known forms. The most common form is the MM phenotype.

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A1AT Alleles

The PiM PiS, PiZ, and PiF alleles are responsible for the different forms of alpha1-antitrypsin.

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ZZ Genotype and Deficiency

The ZZ genotype is associated with the most severe deficiency of A1AT, leading to a high risk of emphysema.

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SZ Genotype and Deficiency

Individuals with the SZ genotype can also experience A1AT deficiency, especially when no M copy is present.

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MS and MZ Genotypes

MS and MZ genotypes are usually not affected by A1AT deficiency.

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A1AT and Elastase Regulation

Alpha1-Antitrypsin inhibits elastase, an enzyme released by macrophages during inflammation. This prevents excessive tissue damage.

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A1AT as an Acute Phase Protein

Alpha1-Antitrypsin is an acute-phase protein. Its concentration increases during inflammation, cancer, or trauma.

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Smoking and Inflammation

Smoking can induce chronic inflammation and increase elastase production.

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Smoking and A1AT Oxidation

Smoking can oxidize methionine-358 (Met-358) in Alpha1-Antitrypsin, preventing it from binding to elastase.

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Elastase and Emphysema

Elastase breaks down the walls of the alveoli, reducing the surface area for gas exchange. This leads to emphysema.

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PiZZ Genotype and Emphysema

Individuals with the PiZZ genotype are particularly vulnerable to emphysema due to A1AT deficiency and smoking.

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A1AT Aggregation and Liver Damage

Alpha1-Antitrypsin is produced in the liver, but mutations can cause it to aggregate and damage the liver.

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ZZ Genotype and Cirrhosis

About 10% of individuals with the ZZ genotype develop cirrhosis due to A1AT aggregation in the liver.

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Alpha1-Fetoprotein (AFP)

A protein synthesized in the yolk sac of the fetus and later by liver cells. Its levels increase during pregnancy or in cases of liver cancer or hepatitis.

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Functions of AFP

Alpha1-Fetoprotein protects the fetus from immune attacks, modulates fetal growth, and transports compounds like steroids.

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AFP and Down Syndrome

Low AFP levels in newborns can be associated with Down syndrome.

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Haptoglobin (HP)

An acute-phase protein that binds to free hemoglobin to prevent its loss and facilitate iron recycling.

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Haptoglobin Phenotypes

Haptoglobin exists in three phenotypes: Hp1-1, Hp2-1, and Hp2-2.

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Ceruloplasmin

Ceruloplasmin is a copper-containing protein that regulates copper levels in circulation.

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Ceruloplasmin and Wilson's Disease

Ceruloplasmin levels can be low or defective in Wilson's disease, leading to copper accumulation and toxicity.

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C-Reactive Protein (CRP)

C-reactive protein (CRP) helps in the defense against bacteria and foreign substances by recognizing foreign cell wall components.

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C-reactive Protein (CRP)

The protein that works against the C fraction of cell walls of microorganisms, particularly pneumococci.

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CRP Clinical Significance

CRP is a major acute-phase inflammatory protein and a widely used clinical monitoring marker.

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CRP Reference Range and Significance

CRP levels should be less than 5. Higher levels indicate acute rheumatic fever, bacterial infection, gout, or tissue damage.

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CRP Peak and Monitoring

CRP levels reach a peak after 48 hours of an incident, making it a valuable monitoring marker.

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Study Notes

Biochemistry Study Notes

  • Prealbumin (transthyretin): Not an immature form of albumin, but a protein (transthyretin) transporting thyroid hormones (T4 and T3). It migrates ahead of albumin in electrophoresis. A small glycoprotein with a molecular weight of 62 kDa. Rich in tryptophan and contains 0.5% carbohydrates. Low blood levels are around 0.25g/L. Has a short half-life (2 days), making it useful in diagnosing diseases or poor protein nutrition, but is less reliable for liver function tests due to low concentration in blood.

  • Globulins: A group of proteins, including alpha-1 globulins, alpha-2 globulins, beta globulins, and gamma globulins. Each type has specific functions and components.

  • Alpha-1-Antitrypsin (A1AT): A protease inhibitor, also called alpha-1-antiproteinase. It neutralizes trypsin and trypsin-like enzymes, which break down proteins in the body. Molecular weight of 53 kDa. Constitutes roughly 90% of alpha-1 globulin. Polymorphic form (MM, PiZ, PiF) with different allele options. A gene deficiency is associated with a 10% reduction in A1AT activity, a high risk of emphysema, and severe deficiency in individuals with the ZZ genotype.

  • Role in Elastase Regulation: A1AT inhibits elastase, an enzyme produced by macrophages during inflammation. This plays a crucial role in regulating the inflammation process, controlling inflammation-related tissue damage by ensuring elastic fiber maintenance.

  • Oxidation of Alpha1-Antitrypsin: Smoking can oxidize methionine-358 on the surface of alpha-1-antitrypsin. This prevents binding to elastase, rendering the protein unable to inhibit elastase activity effectively.

  • Acute Phase Protein (Alpha1-antitrypsin): Elevated in response to inflammation, cancer, or trauma. It is part of the body's response to these conditions.

  • Pathophysiology of Emphysema: Elastase continuously breaks down the walls of alveoli (the sites of gas exchange in the lungs), reducing surface area. This leads to larger air spaces in the lungs, and the characteristic barrel chest seen in emphysema patients.

  • Impact on PiZZ Individuals: Individuals with the PiZZ genotype have a significant deficiency in functional alpha-1-antitrypsin. Smoking further worsens this by both increasing elastase activity and oxidizing remaining functional A1AT, resulting in rapid disease progression and severe complications.

  • Alpha1-antitrypsin protein shape alteration and aggregation A gene mutation can cause protein shape alteration and leads to aggregation in the ZZ phenotype, due to interactions in beta loops, resulting in liver damage and cirrhosis in some patients.

  • Alpha-1-fetoprotein: Synthesized in the fetus' yolk sac and liver. Not typically elevated in adults unless there is liver cancer (like hepatoma) or acute hepatitis. It helps protect the fetus, and plays roles in regulating some growth aspects. Lower levels have been linked to Down syndrome.

  • Haptoglobin: An acute phase protein. Its molecular weight is 90 kDa binds to free hemoglobin to prevent loss of hemoglobin and iron in the urine, aiding in iron recycling. Its half-life is shortened to 90 minutes when bound to hemoglobin, facilitating the uptake and recycling process in the liver

  • Ceruloplasmin: Ceruloplasmin is a 160 kDa copper-containing glycoprotein. It stores and regulates copper levels. Roughly 90% of blood copper is transported by ceruloplasmin, with the remaining 10% by albumin. Copper tissue regulation happens through metallothioneins. Low or defective ceruloplasmin can cause Wilson's Disease or excess of copper in the body leading to tissue damage.

  • C-reactive protein (CRP): A protein that helps defend against microorganisms (like pneumococci). Elevated levels are associated with inflammation, infections, acute rheumatic fever, bacterial infections, gout, and tissue damage. High CRP means there's an inflammatory process. It is a monitoring marker, reaching peak after 48 hours post-infection.

  • Plasma Protein Diseases: Kidney diseases and renal failures cause protein to leave circulation. This leads to reduced protein levels. Gamma globulins can be high in some liver diseases, as they are produced elsewhere. A sharp increase in gamma globulin suggests cancer (myeloma) involving these cells.

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Biochemistry Sheet 27, 2024- PDF

Description

Dive into the intricate world of proteins in this biochemistry quiz. Explore the roles of prealbumin, globulins, and alpha-1-antitrypsin, understanding their importance in transport, function, and diagnosis. Challenge your knowledge of these essential biomolecules.

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