Proteins

Primary

FOUR LEVELS OF PROTEIN STRUCTURE

Determined by amino acid sequence

Secondary

FOUR LEVELS OF PROTEIN STRUCTURE

Folding of short segments of polypeptide into geometrically ordered units

Tertiary

FOUR LEVELS OF PROTEIN STRUCTURE

Overall 3D shape of the protein

Quaternary

FOUR LEVELS OF PROTEIN STRUCTURE

Number and types of polypeptide units of oligomeric proteins and their spatial arrangement

Prealbumin

Type of protein that is an indicator of malnutrition

• Binds thyroid hormones and retinol-binding protein

Albumin

Type of protein that is a major contributor to oncotic pressure

• Binds bilirubin, steroids, and fatty acids

• Present in the highest concentration in serum

Alpha-1-antitrypsin

Type of protein that serves as a protease inhibitor

Alpha-1-fetoprotein

It is the principal fetal protein

Alpha-2-macroglobulin

Type of protein that inhibits thrombin, trypsin, and pepsin

Transthyretin

Prealbumin is also known as:

Poor nutritional status

A low prealbumin level is a sensitive marker of:

• Transports protein for thyroid hormones

• Transports vitamin A by forming a complex with retinol-binding protein

What are the functions of prealbumin?

• Provides nearly 80% of colloid osmotic pressure (COP) of intravascular fluid

• Buffers pH

• Binds to various substances in blood

What are the functions of albumin?

Dehydration

Albumin is increased in:

• Patients receiving steroids

• Alcoholism

• Chronic renal failure

Prealbumin is increased in:

Inhibition of the protease neutrophil elastase

What is the most important function of Alpha-1-antitrypsin?

Smoking

What is the most common cause of Emphysema?

Pink Puffers or Barrel-Chest

Patients suffering from Emphysema are characterized by a complexion called:

• Neural tube defects

• Presence of twins

Elevated levels of AFP causes:

Increased risk for Down syndrome

Decreased levels of AFP causes:

Wilson’s disease

Ceruloplasmin is used in the diagnosis of:

Kayser-Fleischer rings

These are diagnostic eye abnormalities seen in Wilson's disease

Nephrotic syndrome

Alpha-2-macroglobulin is increased in:

Nephrotic syndrome

A glomerular disorder characterized by proteinuria

Haptoglobin

Used primarily to help detect and evaluate hemolytic anemia

Transferrin

It is tested to determine the cause of anemia

Hemolytic anemia

Low hemopexin levels are diagnostic of:

Fibronectin

A glycoprotein produced by fetal membranes responsible for the cellular adhesiveness of placenta and membranes to the decidua.

Cross-linked C-telopeptides

Proteolytic fragments of collagen I formed during bone resorption

CTX

It is a biochemical marker of bone resorption that can be detected in serum or urine

Troponin

It governs excitation-contracting coupling in muscles

• Troponin T

• Troponin I

It is used as an AMI indicator because of specificity and early rise in serum concentration following AMI

• Gold standard for diagnosing MI

Myoglobin

It is used as a negative predictor in the first 2-4 hours following chest pain

Natriuretic peptides

Neurohormones that affect body fluid homeostasis and blood pressure

Heart failure

Brain natriuretic peptide (BNP) has been a popular marker for:

0.5 mg/dL

Normal concentration levels of CRP

200-400 mg/dL

Normal concentration levels of Alpha-1-antitrypsin

110-400 mg/dL

Normal concentration levels of fibrinogen

40-200 mg/dL

Normal concentration levels of haptoglobin

20-40 mg/dL

Normal concentration levels of ceruloplasmin

60-140 mg/dL

Normal concentration levels of C3

A negative nitrogen balance exists

Hypoproteinemia occurs in any condition where:

Digestion of protein; measurement of nitrogen content

What is the principle of the Kjeldahl method?

Measurement of refractive index due to solutes in serum

What is the principle of Refractometry?

Formation of violet-colored chelate between Cu2+ ions and peptide bonds

What is the principle of the Biuret method?

Protein electrophoresis

It is performed when an abnormality in total protein or albumin is found

• Coomassie blue

• Amido black

• Ponceau S

Stains used in protein electrophoresis

Monoclonal immunoglobulin disease

The most significant finding from an electrophoretic pattern is:

Cirrhosis

On serum protein electrophoresis, the β and γ regions appear fused together without a clear separation, a finding known as β–γ bridging. This electrophoretic pattern is most commonly associated with which of the following conditions?

Multiple myeloma

A patient’s serum protein electrophoresis shows a sharp, narrow spike in the γ region (monoclonal spike). This finding is most commonly associated with which of the following conditions?

Nephrotic syndrome

A serum protein electrophoresis (SPEP) pattern shows the following abnormalities:

• Decreased albumin

• Markedly increased α2-globulin

• Increased β-globulin

This pattern is most consistent with which condition?