Protein

• Proteins are essential for the functioning of living cells and are the physical basis of life.
• Motion and locomotion rely on contractile proteins.
• Biochemical reactions are facilitated by enzymes, which are predominantly composed of proteins.
• Cells' structural integrity and the extracellular matrix that surrounds them are primarily made up of collagens, which are the most abundant proteins in the human body.
• The transport of materials in body fluids depends on various proteins, including transferrin and transmembrane receptors for hormones.
• Amyloid stains with Congo red and is associated with amyloidosis.
• Amyloidosis involves the abnormal deposition of amyloid proteins in organs and tissues.
• Amyloid β42 (Aβ42) and Tau protein tests can help differentiate Alzheimer's disease from other forms of dementia in research settings.
• Amyloid deposits can lead to organ failure and are linked to various conditions, including chronic infections, malignancies, and rheumatologic disorders.
• Amyloid is an insoluble fibrous protein aggregate formed due to a change in secondary structure.
• Transcription factors, necessary for gene transcription, are also proteins.
• Proteins play a crucial role in the immune system as they form antibodies, a major component of immune responses.
• Proteins are large macromolecules composed of one or more unbranched chains of amino acids.
• Most plasma proteins are synthesized in the liver and secreted by hepatocytes, except for immunoglobulins produced in plasma cells.
• Genes encode the unique amino acid sequence of proteins through the DNA's nucleotide sequence, which is translated into mRNA in the nucleus.
• Translation, the process of protein synthesis, occurs in the cytoplasm on ribosomes.
• Total Protein Test is a rough measure of all proteins in plasma, reflecting nutritional status, kidney disease, liver disease, and various conditions.
• Amino acids are joined together to form a polypeptide chain during translation, continuing until the termination codon is reached.
• Abnormal total protein requires further tests to identify specific abnormal protein fractions for a diagnosis.
• Myelin basic proteins in CSF are assessed for active demyelination and are elevated in multiple sclerosis, meningoencephalitis, CNS lupus, diabetes mellitus, and chronic renal failure.
• Hormones such as thyroxine, growth hormone, insulin, and testosterone regulate protein synthesis, while glucagon and cortisol affect protein catabolism.
• Hypoproteinemia is a condition where total protein is below the reference interval, caused by negative nitrogen balance, excessive loss, decreased intake, or decreased synthesis.
• Hyperproteinemia is an increase in total plasma proteins, resulting from dehydration, excessive production, or both.
• Protein synthesis can take place on free ribosomes in the cytoplasm or on ribosomes attached to the rough endoplasmic reticulum, with a rate of about two to six peptide bonds formed per second.
• Proteins are composed of carbon, oxygen, hydrogen, nitrogen, and sulfur.
• Total Nitrogen measures all chemically bound nitrogen and is applicable to various biologic samples, including plasma and urine, used in assessing nitrogen balance, crucial for patients on total parenteral nutrition.
• The average nitrogen content in serum proteins is around 16%, and this nitrogen measurement is utilized in one method for determining total protein content.
• Total Proteins are often determined in serum, no fasting specimen required, with a reference interval for serum total protein of 6.5–8.3 g/dL for ambulatory adults.
• Unlike fats and carbohydrates, the body lacks designated storage for nitrogen.
• Methods of analysis for total proteins include Kjeldahl, refractometry, biuret, and dye-binding.
• An insufficiency of even a single amino acid in the diet can rapidly restrict the synthesis and decrease essential protein levels in the body.
• Most proteins undergo constant synthesis and degradation.
• The balance between protein anabolism (synthesis) and catabolism (breakdown) is generally maintained.
• Kjeldahl Method is a classic but not used in clinical labs due to being time-consuming, assuming 16% nitrogen mass in protein for calculations, involving protein precipitation, digestion, and measurement of released nitrogen.
• Different proteins have varying lifespans; some like plasma proteins have short half-lives, while structural proteins like collagen are more stable, with half-lives lasting for years.
• Refractometry is a rapid, easy method using the refractive index, measuring the velocity of light passing through serum, needing calibration for nonprotein solids and being affected by icteric, lipemic, or hemolyzed samples.
• Healthy adults are typically in nitrogen balance, with intake and excretion of nitrogen being equal.
• Pregnant women, growing children, and recovering adults may be in positive nitrogen balance, where nitrogen intake exceeds loss.
• Biuret Method is recommended by the International Federation of Clinical Chemistry, involving cupric ions complexing with peptide bond groups in an alkaline medium, forming a colored chelate, with absorbance measured at 540 nm, proportional to total protein level.
• The isoelectric point (pI) is the pH at which a protein or amino acid carries no net charge.