Proteins Flashcards
Objective 1: Differentiate among the primary, secondary, tertiary, and quaternary structure of proteins.
• Primary: specific sequence of amino acids
• Secondary: Recurring spatial arrangement in a 3-D space
• Tertiary: Folding into a 3-D conformation – confers specific biological properties
• Quaternary: Uniting of several proteins/protein + another structure
Objective 2, Part B: Four examples of globular proteins
• Albumin (water-soluble – hydrogen bonding takes place outside the molecule)
• Globulins (water-insoluble – hydrogen bonding takes place on the interior of the molecule)
• Histones
• Protamines
Objective 2, Part C. Three examples of fibrous proteins
• Collagen
• Elastin
• Keratin
Objective 2, Part D. Six examples of conjugated proteins
• Nucleoproteins
• Mucoproteins
• Glycoproteins
• Lipoproteins focus for clinical chemistry
• Metalloproteins
• Phosphorproteins
Objective 3. List eight biological functions of proteins, according to the lecturer. [DO NOT need to know all eight (8) – potential short answer exam question]
• Transport
• Receptors
• Catalysis
• Structure
• Nutrition
• Maintenance of oncotic pressure
• Host defense
• Hormonal
Objective 4. Define “acute phase reactant” (APR), and list three negative acute phase reactants.
Proteins that increase/decrease in response to an acute phase infection/injury
• Prealbumin (Transthyretin)
• Albumin
• Transferrin
Objective 5. Discuss the following aspects of nitrogen balance:
a. Definition
b. Differentiation between positive and negative balance and its impact on patient health
c. Two names for the plasma protein commonly analyzed for its assessment
• An equilibrium between intake and output of nitrogen
• Positive Nitrogen Balance: Intake exceeds use or output
• Negative Nitrogen Balance: Use or output exceeds intake
Good balance improves healing, etc. in patient and can aid in recovery from illness
Prealbumin (transthyretin)
Objective 6. Explain “denaturation” according to the structures in Objective #1 above that it disrupts and processes that may denature proteins.
Disrupts the bonds that hold together the protein (secondary, tertiary, quaternary) – when this occurs it loses its biological function
• Extreme temperature (> 60 Celsius or freezing)
• pH change (strong acid or alkali)
• Detergents, metals, organic solvents
• Mechanical mixing
Objective 7. List the two GENERAL processes which may cause total protein abnormalities according to the lecturer.
• Relative (apparent) change: due to changes in water volume (i.e. dehydration)
• True (absolute) change: protein level is directly affected
Objective 8. List causes of hyperproteinemia due to BOTH relative and absolute change in protein concentration.
Relative:
• Inadequate water intake
• Excessive water loss (i.e. severe vomiting, diarrhea)
Absolute: • Increased production (i.e. malignancy)
Objective 9. List causes of hypoproteinemia due to BOTH relative and absolute changes in protein concentration.
Relative:
• Increased plasma water volume
Absolute:
• Increased loss (i.e. trauma, severe blood loss, severe burns)
• Low protein intake or starvation
• Decreased production
Objective 10: Define the terms “hemodilution” and “hemoconcentration.”
• Hemodilution: increase in body water, causing an apparent decrease in plasma protein concentration
• Hemoconcentration: decrease in body water, causing an apparent increase in plasma protein concentration
Define “isoelectric point” (pl).
Is the pH at which an amino acid has a net charge of zero
Discuss the importance of pH in determining the charge demonstrated by an amino acid, including the net charge on the amino acid at, above, or below a pH of 7.40.
Amino acids are amphoteric, meaning they contain two (2) ions within their structure. When pH > pl, NH3+ has an H+ removed resulting in a negative charge for the molecule. When pH < pi, COO- picks up a H+ resulting in a positive charge for the molecule
Transthyretin (Prealbumin)
a. Function?
b. Acute phase reactant (APR) properties?
a. Indicator of nutritional status – transports thyroid hormones, retinol
b. Negative acute phase reactant – decreases during acute stress on body
Albumin
a. Function?
b. Acute phase reactant (APR) properties?
a. Transport of water-insoluble compounds and maintenance of colloid osmotic pressure
b. Negative acute phase reactant
List three general causes of hypoalbuminemia and conditions associated with each cause
Decreased production
a. Liver disease
b. Heredity analbuminemia
Decreased intake
a. GI disease
b. Starvation
Increase loss
a. Renal disease
b. Severe burns
Alpha-1 Antitrypsin
a. function
b. clinical significance of increase and decreased levels
a. Inactivates protease enzymes (so that we are unable to break down our own body tissues)
b. Increased in “stress” states (Positive APR)
Decreased in juvenile-onset cirrhosis and emphysema
Alpha-1 Glycoprotein
a. function
b. clinical significance of increase and decreased levels
a. Inactivate progesterone
b. Increased in “stress”, rheumatoid arthritis, lupus, and Crohn’s disease
Decreased in malnutrition, liver damage, protein loss
Alpha-1 Fetoprotein
a. source
b. clinical significance
a. Fetal liver
b. Prenatal marker for neural tube defects; increased in spina bifida and decreased in Down’s syndrome
Tumor marker
List the names of the alpha-1 globulins
• Alpha-1 Antitrypsin
• Alpha-1 Acid Glycoprotein
• Alpha-1 Fetoprotein
List the names of the alpha-2 globulins
• Haptoglobin
• Alpha-2 Macroglobulin
• Ceruloplasmin
Haptoglobin
a. function
b. clinical significance of increase and decreased levels
a. binds free hemoglobin and transports it to the RES to be degraded
b. increased in “stress” states (Positive APR)
decreased in hemolytic anemia
Alpha-2 Macroglobulin (NOT AN APR)
a. function
b. clinical significance of increase levels
a. functions as a protease inhibitor – helps break down of clot formed in coagulation
b. increased in nephrotic syndrome
