General Biochemistry I - Proteins Quiz

General Biochemistry I - BCH 201

• Course taught by Dr. Adedeji Nelson Ademakinwa in Deanry, Room 46 (Floor One)
• Course held in PFA 9-11 on Tuesdays
• Course outline includes topics like introduction, proteins, amino acids, enzymes, carbohydrates, nucleic acids, buffers, and metabolism studied across weeks 1-11.
• Specific lecturers for each topic are mentioned in the outline.

Proteins

• Proteins are naturally occurring biopolymers composed of amino acids.
• The function of a protein is determined by its three-dimensional structure.
• The primary sequence (order of amino acids) contains all information required for correct folding into a functional protein.
• Amino acid properties influence protein folding and function.
• Average adult contains ~10kg of protein; ~300g is replaced daily by recycling and intake.
• Daily protein intake varies with age, size, and energy demand (infants: 1.8g/kg/day; children: 1.0g/kg/day; adults: 0.8g/kg/day) and dietary needs. Daily intake is also associated with a ~15% of daily caloric intake.
• Proteins are not stored in significant amounts in the body and are constantly broken down and rebuilt to get major N-source.
• Proteins lost include urine, fecal material, sweat, hair/nails, and skin.
• Protein functions include catalysis (e.g., enolase, DNA polymerase), transport (e.g., hemoglobin, lactose permease), structure (e.g., collagen, keratin), and motion (e.g., myosin, actin).
• Proteins can be classified as simple (fibrous, insoluble, structural, like hair and horn, and globular, soluble, reactive, like enzymes) or conjugated (lipo-, glyco-, hemo-).
• Examples of fiborous proteins include collagens (bones, tendons, cartilage), elastins (lungs, ligaments), keratins (hair, nails, feathers, horns) and myosins (muscles).
• Examples of globular proteins include albumins (egg whites) and globulins (antibodies, enzymes).

Amino Acids

• Amino acids are the building blocks of proteins.

• They are linear heteropolymers of α-amino acids.

• Key properties include: capacity to polymerize, useful acid-base properties, and varied physical/chemical properties including functionality.

• Essential amino acids (10) are needed in our diet: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine (and arginine in infants).

• Non-essential amino acids (10) can be synthesized in the body.

• Amino acids are organized into groups by R substituents (nonpolar, aliphatic, aromatic, polar, uncharged, positively charged, negatively charged).

• A list of 20 major amino acids, their one and three-letter codes, and their categories is provided alongside their respective chemical structures and examples.

• Each amino acid has a carboxyl group (-COOH) and an amino group (-NH2), which are attached to a central carbon atom (α-carbon).

• All naturally-occurring amino acids (except glycine) are chiral and are L-stereoisomers.

• Amino acids vary in size, structure, electric charge, and solubility in water

• Amino acids can act as buffers due to multiple pKa values (e.g. the a-carboxyl group with pKa ~2.3 and the a-amino group with pKa ~9.6) allowing variations in the peptide's net charge at various pH levels.

• Ionizable side chains in amino acids, such as histidine, influence the pI of the protein and these side chains can be titrated.

• Acid/base properties and ionization/titration processes are described including the different forms an amino acid may exist (cation, anion, or zwitterion) and their respective pKa values.

Peptides

• Peptides are short chains of amino acids.
• Formed via condensation reactions.
• Broken by hydrolysis.
• Can perform various functions (hormones, pheromones, neuropeptides, antibiotics, toxins, etc.).
• Peptides are named from N-terminal to C-terminal, using abbreviated names/full amino acid names.
• Techniques for amino acid analysis and peptide chemistry are described such as acid hydrolysis of peptides (6M HCl, 24hrs), separation by ion-exchange chromatography, detection by ninhydrin, and automated methods.