Amino Acids and Proteins Quiz

Amino Acids and Proteins

• Proteins are the building blocks of life, supporting various biological activities like growth, repair, and maintenance.
• Twenty amino acids are essential for these bodily functions.
• Half of the amino acids must be acquired through diet.

Classification of Amino Acids

• Amino acids have both an amino group and a carboxylic acid functional group.
• Alpha amino acids feature an amino group directly bonded to the alpha-carbon.
• Each alpha amino acid has a unique R group attached to the alpha carbon.

Peptide Bonds

• A peptide bond is an amide bond forming between a carboxyl group of one amino acid and an amino group of another amino acid.

Essential and Nonessential Amino Acids

• Essential amino acids are obtained from diet.
• Nonessential amino acids can be produced by the body.
• Essential amino acids include: Valine, Leucine, Isoleucine, Methionine, Tryptophan, Phenylalanine, Threonine, Lysine, and Histidine.
• Many others are categorized as nonessential.

Amino Acid Synthesis

• Proteolytic enzymes like Pepsin and Trypsin break down dietary proteins into amino acids.
• These enzymes remove amino groups from amino acids.
• Deamination breaks down amino acids, and transamination transfers amino acids.

Aminoacidopathies

• Aminoacidopathies are inherited metabolic disorders.
• These disorders are caused by enzyme deficiencies leading to amino acid build-up.

Types of Aminoacidopathies

• Phenylketonuria (PKU): a deficiency in phenylalanine hydroxylase resulting in phenylalanine buildup and mental retardation. Common symptoms include: musty urine odor, phenylalanine in excess can cause mental retardation.
• Tyrosinemia type I is the most severe type of tyrosinemia involving tyrosine, with high excretion of tyrosine and tyrosine catabolites in the urine. Typical symptoms of tyrosinemia include kidney and liver failure and cirrhosis. Treatment includes low protein diet and drug nitisinone.
• Alkaptonuria (lack of homogentisate oxidase) causes excess of homogentistate acid making urine to turn black when left at room temperature.. Symptoms can include arthritic symptoms later in life and development of arthritis; Treatment is with Vitamin C.
• Maple Syrup Urine Disease (MSUD): deficiency in alpha-ketoacid decarboxylase, causing a high level of leucine, isoleucine, and valine in the body in babies, and characteristic maple syrup odor of urine, skin, and breath.
• Homocystinuria: lack of cystathionine beta-synthase, preventing the breakdown of methionine. Symptoms can include muscle weakness, CNS problems, bone abnormalities, and thrombosis.
• Cystinuria: defective amino acid transport system in the renal tubules preventing reabsorption of cysteine. Typical symptoms include kidney stones. Treatment includes high fluid intake to prevent cystine stone formation.

Protein Structures

• Primary Structure: linear sequence of amino acids linked together from the N-terminus to the C-terminus (e.g., hemoglobin).
• Secondary Structure: repeating structures stabilized by hydrogen bonds (e.g., alpha-helix, beta-pleated sheets).
• Tertiary Structure: overall shape of a protein formed by interactions between side chains which can bond and form functional properties.
• Quaternary Structure: interaction of multiple protein molecules to form a larger functional protein (e.g., hemoglobin).

Denaturation of Proteins

• Denaturation is the disruption of protein structure, causing loss of function. This occurs when certain factors interfere with the structure like Heat, Hydrolysis, strong acid (pH), strong alkali (pH), enzymatic action, urea exposure or other substance, ultraviolet exposure, and heavy metals and solvents.

Proteins Characteristics

• Proteins are described by their content like nitrogen content (approximately 16%.), charge (isoelectric point), and solubility (hydrophilic).
• Proteins contain carbon, hydrogen, oxygen, sulfur, and nitrogen unlike carbon/lipids that don't contain nitrogen.

Functions ofProteins

• Enzymes: catalyze biochemical reactions.
• Hormone receptors: bind hormones to trigger cellular responses.
• Transporters: carry molecules across membranes.
• Immunoglobulins: protect against foreign invaders.
• Structural proteins: provide support and shape.
• Storage proteins: store amino acids or other molecules.
• Energy source: provide energy when other sources are depleted.
• Osmotic force: helps maintain fluid balance.
• Tissue nutrition: provide nutrients for tissues.

Two Major Classifications of Proteins

• Simple proteins: composed solely of amino acids.
• Conjugated proteins: contain both an amino acid component and a non-protein component (e.g., glycoproteins, lipoproteins).

Plasma Proteins

• Plasma proteins are proteins in the blood; They include albumin, globulins, and other important proteins like fibrinogen, transferrin, and immunoglobulins.

Plasma Protein Methods

• Electrophoresis is a method to separate proteins based on charges and sizes in the blood.
• Dye-binding is a method for measuring albumin by using dyes that bind only to albumin.

Proteins in Other Body Fluids

• Urinary protein: qualitative (reagent test strips) and quantitative (24-hour urine specimen).
• Cerebrospinal fluid (CSF) protein: measures protein in CSF (to determine if damage to blood barrier; during disease or trauma).

Other Plasma Proteins

• Myoglobin, Cardiac Troponin, BNP, Fibronectin,
• Myoglobin: single-chain globulin (153 amino acids), contains heme group, cardiac biomarker, toxic to kidneys.
• Cardiac Troponin: represents a complex of regulatory proteins; important for diagnosing acute coronary syndrome.
• BNP: released by heart in response to congestive heart failure, indicating heart muscle dysfunction.
• Fibronectin: amniotic sac protein; detects pre-term labor through amniotic fluid, etc.

Total Protein Abnormalities

• Hypoproteinemia (low total protein): causes include excessive protein loss, poor protein absorption, or decreased protein intake.
• Hyperproteinemia (high total protein) causes include dehydration and other conditions.