Types and Functions of Proteins

• Proteins are large molecules essential for structure, catalyzing reactions, and various biological functions.
• Protein roles are diverse and are classified based on their specific biological functions.

Types and Functions of Proteins

• Enzymes are the most varied and specialized proteins, known for their catalytic activity in cells.
• Amylase breaks down starch into smaller sugars.
• Pepsin aids in breaking down proteins into smaller peptides.
• Trypsin is a protease that breaks down proteins into smaller peptides and amino acids.
• Lactase breaks down the sugar lactose found in milk.
• Catalase breaks down hydrogen peroxide (H2O2) into water and hydrogen.
• Lysozyme destroys cell walls and is used to kill bacteria.
• Carbonic anhydrase catalyzes the hydration of carbon dioxide (CO2).
• Transport proteins bind and carry molecules or ions through the blood to various organs.
• Hemoglobin transports oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs.
• Glucose transporter transports glucose across the plasma membrane via facilitated diffusion.
• Sodium-Potassium pump transports Na and K ions across the cell membrane.
• Channel protein creates pores in the membrane.
• Albumin carries fatty acids, hormones, and drugs.
• Transferrin transports iron.
• Ceruloplasmin transports copper.
• Nutrient and storage proteins store nutrients needed for growth, especially in seedlings.
• Ferritin stores iron.
• Casein, found in milk, provides amino acids for growth and development.
• Zein is a storage protein in maize.
• Gluten serves as a storage protein in wheat.
• Contractile or motile proteins facilitate contraction, shape changes, or movement in cells and organisms.
• Actin is involved in muscle contraction and cell movements.
• Myosin is a key muscle fiber component that generates force during muscle contraction.
• Tropomyosin is a regulatory protein that controls muscle contraction.
• Troponin regulates muscle contraction through actin binding.
• Structural proteins provide strength or protection through supporting filaments, cables, or sheets.
• Collagen is present in connective tissues like skin, tendons, and ligaments.
• Keratin forms hair, nails, horns, and feathers and is known for its protective qualities.
• Elastin is found alongside collagen.
• Silk Fibroin is produced by silkworms and spiders.
• Resilin is found in insect exoskeletons and offers resilience.
• Defense proteins protect organisms from invasion by other species.
• Immunoglobulins are antibodies that neutralize specific substances.
• Complement System proteins circulate in the blood and boost immune responses.
• Defensins are antimicrobial peptides that kill bacteria and fungi.
• Regulatory proteins regulate cellular or physiological activities.
• Insulin regulates blood sugar levels.
• Lac Repressor regulates the expression of the lac operon in bacteria.
• Leptin regulates energy balance and appetite.
• Glucagon raises blood glucose levels by stimulating the liver.
• Calcitonin lowers blood calcium levels by inhibiting bone resorption.

Amino Acids

• Every amino acid has a central carbon bonded to an amino group, a carboxyl group, and a hydrogen atom.
• There are 20 types of amino acids, each differing by their side group.
• Peptide bonds are covalent bonds between amino acids to form polypeptides.
• Peptide bonds form through dehydration synthesis.

Levels of Protein Organization

• Primary structure is the sequence of amino acids and disulfide bonds.
• Secondary structure involves recurring arrangements like α-helix and β-conformation.
• Tertiary structure is the complete 3D structure of a polypeptide.
• Quaternary structure refers to the spatial arrangement of multiple polypeptide subunits.