L6 | PROTEIN

• PROTEIN

  • also called peptide
  • made of long chain of amino acids
  • instrumental in about everything about the organisms
  • most diverse molecule
• FUNCTIONS:

  • STRUCTURAL SUPPORT
  • MOVEMENT
  • STORAGE
  • INTERCELLULAR SIGNALING
  • TRANSPORT OTHER SUBSTANCES
  • DEFENSE AGAINST FOREIGN SUBSTANCES
  • REGULATE METABOLISM
• ENZYMEs

  • special protein
  • acts as a catalyst
  • hasten or make the chemical reaction faster
• 4 PARTS OF AMINO ACIDS

  • AMINO GROUP
  • ALPHA CARBON
  • CARBOXYL GROUP
  • R GROUP (SIDE CHAIN)
• STRUCTURES OF PROTEINS

  1. DIPEPTIDE
  2. TRIPEPTIDE
  3. OLIGOPEPTIDE
  4. POLYPEPTIDE
• DIPEPTIDE

  • 2 amino acids
• TRIPEPTIDE

  • 3 amino acids
• OLIGOPEPTIDE

  • 3-49 amino acids
• POLYPEPTIDE

  • 50+ amino acids
• 20 AMINO ACIDS

  • 9 essential amino acids
  • 11 non essential amino acids
• • n terminus - ends in amino group
  • c terminus - ends in carboxyl group
• LEVELS OF PROTEIN STRUCTURE (HIERARCHY):

  1. PRIMARY STRUCTURE
  2. SECONDARY STRUCTURE
  3. TERTIARY STRUCTURE
  4. QUATERNARY STRUCTURE
• PRIMARY STRUCTURE

  • Assembly
  • Sequence of a.a bonded to form polypeptide
  • occurs at the ribosome
• SECONDARY STRUCTURE

  • Folding/coiling
  • Due to attractions and repulsions between like parts of the a.a
  • occurs in the cytosol
  • Secondary structures, a-helix and B-sheet, have regular hydrogen- bonding patterns
• TERTIARY STRUCTURE

  • Packing (occurs in cytosol)
  • Determined by a variety of interactions of the R groups and between R groups
• TERTIARY STRUCTURE

  • Interactions include: 
  • Hydrogen bonds (polar and/or charged areas)
  • Ionic bonds between charged R groups
  • Hydrophobic interactions
  • Van der Waals interactions among hydrophobic R groups
• QUATERNARY STRUCTURE

  • Interaction
  • Results from the aggregation of two or more polypeptide subunits
  • These subunits fit together to form the functional protein
• LEVELS OF PROTEIN STRUCTURE

  A) PRIMARY

  B) ASSEMBLY

  C) SECONDARY

  D) FOLDING

  E) TERTIARY

  F) PACKING

  G) QUATERNARY

  H) INTERACTION

  
• PEPTIDE BONDS LINK AMINO ACIDS

  • Form when the carboxyl group (COOH) of one amino acid joins with the amine group (NH2) of a second amino acid
  • Formed through condensation
  • Broken through hydrolysis
• DENATURING

  • Alteration of protein’s shape and thus function through the use of
  • Heat
  • Acids
  • Bases
  • Salts
  • Mechanical agitation
  • Primary structure is unchanged by denaturing
• PROTEIN FUNCTION

  • Protein structure determines protein function
• ROLE OF PROTEIN

  1. STRUCTURAL AND MECHANICAL SUPPORT AND MAINTENANCE
  2. ENZYMES AND HORMONE
  3. FLUID BALANCE
  4. ACID BASE BALANCE
  5. TRANSPORT
  6. ANTIBODIES AND THE IMMUNE RESPONSE
  7. ENERGY
• STRUCTURAL AND MECHANICAL SUPPORT AND MAINTENANCE

  • Proteins are the body’s building materials, providing strength and flexibility 
  • Also needed for maintenance of the body
• ENZYMES AND HORMONES

  • Proteins are needed to make most enzymes that speed up reactions in the body and many hormones that direct specific activities
• FLUID BALANCE

  • Ensuring that the body fluids are evenly dispersed in the blood and inside and outside cells
• ACID BASE BALANCE

  • act as a buffer to help keep the pH of body  fluids within a tight range
• TRANSPORT

  • Proteins shuttle substances such as oxygen, waste products, and nutrients through in the blood and into and out of the cells
• ANTIBODIES AND THE IMMUNE RESPONSE

  • Proteins create specialized antibodies that attack pathogens that may cause illness
• ENERGY

  • Because protein provide 4 calories per gram, they can be used as fuel or energy
• FIBROUS PROTEINS

  • Involved in structure: tendons, ligaments, blood clots (e.g. collagen and keratin)
  • Contractile proteins in movement: muscles, microtubules (cytoskeleton, mitotic spindle, cilia, flagella)
• GLOBULAR PROTEINS

  • Most proteins that move around (e.g. albumen and casein in milk)
  • Proteins with binding sites: enzymes, haemoglobin, immunoglobulins, membrane receptor sites
• PROTEINS CLASSIFIED BY FUNCTION

  1. CATALYTIC
  2. STORAGE 
  3. TRANSPORT
  4. COMMUNICATION
  5. CONTRACTILE
  6. PROTECTIVE
  7. TOXINS
  8. STRUCTURAL
• CATALYTIC 

  • enzymes
• STORAGE 

  • ovalbumin (in eggs)
  • casein (in milk),
  • zein (in maize)
• TRANSPORT

  • Hemoglobin 
• COMMUNICATION

  • hormones (eg insulin) 
  • neurotransmitters
• CONTRACTILE

  • actin, myosin, dynein (in microtubules)
• PROTECTIVE

  • Immunoglobulin, fibrinogen, blood clotting factors
• TOXINS

  • snake venom
• STRUCTURAL

  • cell membrane proteins, 
  • keratin (hair)
  • collagen