(M) Lec 5: Amino Acids (P2: Proteins) Flashcards
Most plasma proteins are synthesized in what organ?
Liver
The liver is responsible for producing numerous plasma proteins except for what?
Immunoglobulins (aka antibodies which are produced by lymphocytes)
This panel is used to test the synthetic function of the liver (if it normally produces the proteins needed by the body)
Protein Panel
The process of degrading proteins to become free amino acids
Protein Catabolism
Protein Catabolism Pathways
Degrades extracellular and some intracellular proteins
Lysosomal pathway
Protein Catabolism Pathways
Important in degrading intracellular proteins
Cytosolic pathway
- Refers to the removal of amino acid nitrogen from the body
- Removal of an α-amino group (N alone is toxic to the body) from an amino acid by transaminases to a ketocarbon which produces ketoacids
Transamination
These 2 products of transamination:
1. Are converted to urea by the liver (via the urea cycle)
2. Are converted to glucose/fat (via the Krebs cycle)
(2 answers)
- Ammonia
- Ketoacids
Protein Structures
- Overall shape and confirmation; there is folding and a 3D configuration (determines the function and phsyiochemical properties)
- Alpha-helix and Beta-pleated sheet (adds strength and flexibility)
- The basic amino acid sequence
- The shape/structure from the interaction of one or more protein molecules/sub-units held by noncovalent bonds
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
- C
- B
- A
- D
Protein Properties
TOF: Proteins are always negatively charged
False (can be BOTH)
Protein Properties
Refers to the pH at which amino acids and protein have no net charge
Isoelectric Point
Protein Properties
- If pH > pI, a protein has a net (+ or -) charge
- If pH < pI, a protein has a net (+ or -) charge
- pH > pI = negative
- pH < pI = positive
Protein Properties
Basic or Acidic Group?
Lysine, Arginine, and Histidine
Basic
Protein Properties
Basic or Acidic Group?
Glutamate, Aspartate, Cysteine, and Tyrosine
Acidic
Protein Properties
If there is a charge at the protein surface, the protein is (hydrophilic or hydrophobic)?
Hydrophilic
Note: The charge makes it more soluble
Protein Properties
A protein’s lowest solubility is at what point?
Its isoelectric point (there is no net charge)
Protein Classifications (by function)
- These catalyze chemical reactions
- Most are composed of proteins EXCEPT ribozyme (composed of nucleic acids)
Enzymes
Protein Classifications (by function)
Chemical signals that are important for the endocrine system
Hormones
Can be made up of proteins or steroids
Protein Classifications (by function)
These are responsible for carrying certain ions/molecules
Transport Proteins
Protein Classifications (by function)
- Are antibodies important for the defense mechanism and immunity
- Binds to foreign antigens
- Not produced by the liver but rather the plasma cells
Immunoglobulins
Protein Classifications (by function)
Examples are fibers, collagen, and keratin
Structural Proteins
Protein Classifications (by function)
An example is ferritin (iron-storage)
Storage Proteins
Protein Classifications (by function)
A source of this comes from gluconeogenesis
Energy Source
Protein Classifications (by function)
- Pressure that holds the fluid inside the blood vessels
- Is greatly affected by albumin therefore this functions to distribute water throughout the different compartments of the body
Osmotic Force
Protein Classifications (by structure)
Composed purely of proteins and amino acids
- Globular (enzymes, messengers, transporters, hemoglobin, plasma proteins, and peptide hormones)
- Fibrous/Structural (fibrinogen, troponin, and collagen)
Simple
Protein Classifications (by structure)
Attached to non-protein molecules
- An apoprotein + prosthetic group
- Metalloproteins - ferritin, hemoglobin, and ceruloplasmin (carries copper)
- Lipoproteins - HDL, LDL, VLDL, and chylomicrons
- Glycoproteins - anti-trypsin and haptoglobin
- Nucleoproteins - chromatin
- Mucoproteins/Proteoglycans - mucin
Conjugated
Nitrogen Balance
- Protein catabolism exceeds anabolism
- Burns, wasting disease, high fever, and starvation
Negative Nitrogen Balance
Nitrogen Balance
- Protein anabolism is greater than catabolism
- Growth, pregnancy, and repair processes
Positive Nitrogen Balance
Plasma Proteins
What are the 2 major groups?
Albumin and Globulin
Majority is albumin (50-60%)
Plasma Proteins
Plasma Protein Panel Normal Values:
1. Total Protein
2. Albumin
3. Globulin
4. A/G Ratio
A. 1.1-1.8
B. 6.5-8.3 g/dL
C. A computed value only
D. 3.5-5.5 g/dL
- B
- D
- C
- A
Globulin = TP - Albumin
Plasma Proteins
What is the SI unit conversion factor for proteins?
g/dL x 10 = g/L
Serum Protein Electrophoresis
- pH = ?
- Charge of proteins = (+ or -)
- Protein separation and migration move from what point of origin to what end point?
(3 answers)
- pH = 8.6
- Proteins are (-) charged
- From cathode (-) to anode (+)
Serum Protein Electrophoresis
Order the proteins from most to least abundant and their migratory distance:
- Y-globulins
- Albumin
- B-globulins
- A1-globulins
- A2-globulins
Note: Their concentrations and migratory distances are ordered the same
- Albumin
- A1-globulin
- A2-globulin
- B-globulin
- Y-globulin
Study the percentages in the recorded lecture
High Resolution Electrophoresis
Separated into as many as how many bands?
12
Note: Study the additional zones in the lecture
Additional modifications include: Higher voltage, cooling system, and a more concentrated buffer
Serum Proteins
- Aka transthyretin; it migrates ahead of albumin
- Transport protein for thyroxine (T4) and triiodothyronine (T3)
- Binds with retinol binding protein to form a complex that transports retinol
- Half life:** 2 days**
- Rich in tryptophan
- A sensitive marker of poor nutritional status
Pre-Albumin
Serum Proteins
- Highest protein concentration in the plasma (50-65%)
- Synthesized by the liver at 9-12 g/day
- Half life: 20 days
- Glycated Albumin - Fructosamine (alternative to HbA1c)
- Functions:
1. Maintains 80% of colloid osmotic pressure (a decrease leads to edema)
2. Negative acute phase reactant (decreases when there is infection/inflammation)
3. Buffers pH
4. Transportation (Iron, Fatty Acids, Bilirubin (B1), Electrolytes, Steroids, Drugs, Hormones)
Albumin
Albumin
Increased (hyperalbuminemia) or Decreased (hypoalbuminemia)?
1. Inadequate source of amino acids in malnutrition and malabsorption
2. Liver disease
3. Protein losing enteropathy or gastrointestinal loss (diarrhea)
4. Kidney loss to urine in renal disease
5. Skin loss in burns or exfoliative dermatitis
6. Hypothyroidism
7. Dilution by excess intake of water or administration of intravenous fluids
8. Genetic mutation resulting from an autosomal recessive trait
9. Redistribution by hemodilution (e.g. sepsis)
10. Increased catabolism - massive burns and malignancy
Decreased (hypoalbuminemia)
Albumin
TOF: Hyperalbuminemia has a higher clinical significance than hypoalbuminemia
False (hyperalbuminemia has no significance)
Albumin
Increased (hyperalbuminemia) or Decreased (hypoalbuminemia)?
- Severe dehydration and prolonged torniquet application
Increased (hyperalbuminemia)
Albumin
- An inherited error of albumin synthesis
- Albumin level is decreased because the patient is not capable of synthesizing it
Analbuminemia
Albumin
- Can be inherited or acquired
- 2 albumin bands are present in electrophoresis
Bisalbuminemia
Serum Proteins
- Consists of α1, α2, β and γ fractions (through electrophoresis)
- Each consists of a number of different proteins with
different functions
Globulins