Chemistry Ch 6: Amino Acids & Proteins (Proteins & Heme Derivatives)

What enzyme is missing in patients with Phenylketonuria (PKU)?

Phenylalanine hydroxylase

Function:

• Converts phenylalanine → tyrosine

Results of deficiency:

• Increased phenylalanine

• Intellectual disability if untreated

• "Mousy" odor

Lack of what enzyme leads to a buildup of homogentisic acid?

Homogentisate oxidase

Disease:

• Alkaptonuria

Signs:

• Urine turns black upon standing

• Arthritis later in life

List 5 functions of proteins.

✅ Transport substances

✅ Maintain oncotic (osmotic) pressure

✅ Immune defense (immunoglobulins)

✅ Blood coagulation

✅ Buffering acid-base balance

Additional functions:

• Enzymes

• Hormones

• Structural support

• Storage

What protein is the largest fraction of plasma proteins? How much?

✅ Albumin

Makes up approximately:

✅ 60% of total plasma proteins

Major function:

• Maintains oncotic pressure

What is Prealbumin?

✅ Prealbumin = Transthyretin

Functions:

• Transports thyroxine (T4)

• Transports retinol-binding protein (Vitamin A)

Clinical significance:

✅ Sensitive indicator of nutritional status

What is the reference range for albumin?

✅ 3.5 - 5.5 g/dL

(35-55 g/L)

Exam memory trick:

Albumin = 3.5-5.5 g/dL

Where are almost all proteins made?

✅ The liver

Exception:

✅ Immunoglobulins are produced by plasma cells

Important exam question:

Protein	Produced By
Albumin	Liver
Transferrin	Liver
Ceruloplasmin	Liver
Immunoglobulins	Plasma Cells

Name an Alpha-1 band protein.

✅ Alpha-1 Antitrypsin

Other acceptable answer:

• Alpha-fetoprotein

Most commonly tested:

✅ Alpha-1 Antitrypsin

Name a globulin in the Alpha-2 band.

✅ Haptoglobin

✅ Ceruloplasmin

✅ Alpha-2 Macroglobulin

Most frequently tested:

✅ Haptoglobin

✅ Alpha-2 Macroglobulin

Name a protein in the Beta globulin fraction.

✅ Transferrin

Other possibilities:

• Hemopexin

• Complement

Most commonly tested:

✅ Transferrin

Remember:

Transferrin transports iron

Name three acute phase reactants.

✅ C-Reactive Protein (CRP)

✅ Haptoglobin

✅ Ceruloplasmin

Other acceptable answers:

• Fibrinogen

• Complement proteins

When do acute phase reactants increase in the body?

✅ Infection

✅ Inflammation

✅ Trauma

✅ Tissue injury

✅ Surgery

Important:

Positive Acute Phase Reactants

Increase

• C-Reactive Protein

• Haptoglobin

• Ceruloplasmin

• Fibrinogen

Negative Acute Phase Reactant

Decreases

• Albumin

13. Draw a normal protein electrophoresis curve and label it.

Order from Anode → Cathode

✅ Albumin

✅ Alpha-1

✅ Alpha-2

✅ Beta

✅ Gamma

Oligoclonal bands are classically associated with what disease?

Multiple Sclerosis

What are oligoclonal bands

Immunoglobulin bands in the gamma region of CSF electrophoresis indicating intrathecal immunoglobulin production.

CSF protein reference range

15–45 mg/dL.

What test identifies the specific monoclonal immunoglobulin?

Immunofixation electrophoresis (IFE)

What does a monoclonal spike in the gamma region suggest?

Monoclonal gammopathy (Multiple Myeloma, Waldenström Macroglobulinemia, MGUS)

Which fraction migrates the least?

Gamma globulins

Which fraction migrates farthest toward the anode?

Albumin

How does dehydration affect serum proteins?

Protein concentration increases due to loss of plasma water.

How does nephrotic syndrome affect serum proteins?

Protein is lost in urine causing decreased albumin and hypoproteinemia.

Give four causes of hypoproteinemia.

• Malnutrition

• Liver disease

• Renal disease

• Burns

Give two causes of hyperproteinemia.

• Dehydration

• Excess gamma globulin production (Multiple Myeloma, Waldenström Macroglobulinemia)

Principle of the Biuret reaction?

Copper ions react with peptide bonds in alkaline solution to form a violet-colored complex.

Routine method for total protein?

Biuret method

Reference method for total protein?

Kjeldahl method

Reference range for total protein?

6.4 – 8.3 g/dL.

Which immunoglobulin is associated with allergies?

IgE

Which immunoglobulin is found mainly in secretions?

IgA

Which immunoglobulin is the major antibody in secondary immune response?

IgG

49. Which immunoglobulin appears first after antigen stimulation?

IgM

Which protein predominates in the Gamma fraction?

Immunoglobulins

Which Beta globulin binds free heme?

Hemopexin

Which Beta globulin transports iron?

Transferrin

Name a Beta globulin.

Transferrin

Largest Alpha-2 globulin often increased in nephrotic syndrome?

Alpha-2 macroglobulin

Name a protein in the Alpha-2 fraction.

Haptoglobin

Ceruloplasmin

Name a protein in the Alpha-1 fraction.

Alpha-1 antitrypsin.

Alpha-fetoprotein

Which major plasma protein is a negative acute phase reactant?

Albumin

When do acute phase reactants increase?

Inflammation, infection, tissue injury, trauma

Name three acute phase reactants.

• C-reactive protein

• Haptoglobin

• Ceruloplasmin

Also fibrinogen and complement

What are acute phase reactants?

Proteins whose concentrations change during inflammation.

35. What is the most common cause of increased albumin?

Dehydration

Give three causes of decreased albumin.

• Liver disease

• Malnutrition

• Renal disease

Also gastrointestinal loss and dilution

What is the albumin reference range?

35–55 g/L.

What does prealbumin transport?

• Thyroid hormones

• Retinol (Vitamin A)

What is the major clinical use of prealbumin?

Assessment of nutritional status.

What is prealbumin also called?

Transthyretin

Which plasma cells produce immunoglobulins?

Plasma cells (B-cell derivatives)

Where are most plasma proteins synthesized?

Liver

What percentage of plasma protein is albumin?

Approximately 60%

Which plasma protein transports copper?

Ceruloplasmin

Which plasma protein maintains oncotic pressure?

Albumin

List five functions of proteins.

• Enzymes

• Hormones

• Transport

• Immunity

• Structural support

Additional:

• Storage

• Energy source

• Osmotic regulation

Name four types of conjugated proteins.

• Metalloproteins

• Lipoproteins

• Glycoproteins

• Nucleoproteins

(Also phosphoproteins and mucoproteins.)

What are conjugated proteins?

Proteins with a nonprotein group attached

Name the two major classes of proteins.

• Simple proteins

• Conjugated proteins

What is denaturation?

Loss of protein structure and function due to heat, pH, chemicals, ultraviolet light, or mechanical force

Which structure consists of multiple protein chains?

Quaternary structure

Which structures are affected by pH changes?

• Secondary

• Tertiary

• Quaternary

Primary structure is generally unaffected

Which protein structure is simply the amino acid sequence?