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Proteins Continued Denaturation Denaturation Unraveling/unfolding of protein Why would this be a problem? When protein loses its 3-D shape and thus its specific function Caused by: Unfavorable changes in pH, temperature or other environmental condition Disrupts the interactions between side chains and causes loss of shape Examples: Frying an egg Straightening your hair Denaturation involves the disruption and possible destruction of both the secondary and tertiary structures not strong enough to break the peptide bonds primary structure (sequence of amino acids) remains the same after a denaturation Denaturation disrupts the normal alpha-helix and beta sheets in a protein Uncoils protein into a random shape= LOSS of FUNCTION Denaturation Occurs b/c the bonding interactions responsible for the secondary structure (hydrogen bonds to amides) and tertiary structure are disrupted tertiary structure: four types of bonding interactions between "side chains" that can be disrupted hydrogen bonding, salt bridges, disulfide bonds, and non-polar hydrophobic interactions Variety of reagents and conditions can cause denaturation The most common observation in the denaturation process is the precipitation or coagulation of the protein Causes of Denaturation: HEAT Heat can be used to disrupt hydrogen bonds and non-polar hydrophobic interactions occurs because heat increases the kinetic energy and causes the molecules to vibrate so rapidly and violently that the bonds are disrupted proteins in eggs denature and coagulate during cooking Other foods are cooked to denature the proteins to make it easier for enzymes to digest them Medical supplies and instruments are sterilized by heating to denature proteins in bacteria and thus destroy the bacteria Causes of Denaturation: ALCOHOL Alcohol Disrupts Hydrogen Bonding Hydrogen bonding occurs between amide groups in the secondary protein structure Hydrogen bonding between "side chains" occurs in tertiary protein structure in a variety of amino acid combinations All disrupted by the addition of another alcohol A 70% alcohol solution is used as a disinfectant on the skin penetrates the bacterial cell wall and denature the proteins and enzymes inside of the cell Why not 95%? 95% alcohol solution merely coagulates the protein on the outside of the cell wall and prevents any alcohol from entering the cell Alcohol denatures proteins by disrupting the side chain intramolecular hydrogen bonding New hydrogen bonds are formed instead between the new alcohol molecule and the protein side chains. Causes of Denaturation: ACIDS/BASES (changing pH) Salt bridges result from the neutralization of an acid and amine on side chains Final interaction= ionic bond b/t the + ammonium group and the acid group Acids and bases disrupt salt bridges held together by ionic charges Double replacement reaction occurs where the positive and negative ions in the salt changes partners with the positive and negative ions in the new acid or base added Occurs in the digestive system, when the acidic gastric juices cause the curdling (coagulating) of milk Causes of Denaturation: Heavy Metals Heavy metal salts act to denature proteins in much the same manner as acids and bases Heavy metal salts usually contain: Hg+2, Pb+2, Ag+1 Tl+1, Cd+2 (and other metals with high atomic weights) Since salts are ionic they disrupt salt Heavy metal + protein insoluble metal protein salt Used for its disinfectant properties in external applications Silver nitrate, AgNO3 used to prevent gonorrhea infections in the eyes of new born infants to treat nose and throat infections, cauterize wounds Mercury salts administered as Mercurochrome or Merthiolate have similar properties in preventing infections in wounds Used in reverse in cases of acute heavy metal poisoning a person may have swallowed a significant quantity of a heavy metal salt As an antidote, a protein such as milk or egg whites may be administered to precipitate the poisonous salt followed by an emetic is given to induce vomiting so that the precipitated metal protein is discharged from the body Causes of Denaturation: Heavy Metals Heavy metals disrupt disulfide bonds They have high affinity/attraction for sulfur denaturation of proteins Have a positive charge (really want e-) Reducing Agents Disrupt Disulfide Bonds (things that can accept electrons) Oxidation - involves the loss of electrons or hydrogen OR gain of oxygen Oxidizing agent is the one thing that LOSES electrons Reduction - involves the gain of electrons or hydrogen OR loss of oxygen Reducing agent is the one thing that GAINS electrons Disulfide bonds are formed by oxidation of the sulfhydryl (-SH) groups on cysteine Hold together chains or loops within a single protein chain Reducing agents would do the opposite...break DISUPLHIDE BRIDGES (denaturation) Classification of Proteins According to biological function. Type: Example: Enzymes- Catalyze biological reactions ß-galactosidase Transport and Storage Hemoglobin Movement Actin And Myosin in muscles Immune Protection Immunoglobulins (antibodies) Regulatory Function within cells Transeription Factors Hormones Insulin Estrogen Structural Collagen Path of a Protein in the Body Check out this story! Inorganic Ions Many important functions in living systems Include: Nerve impulse transmission Excretion from the kidneys Enzyme function transport Calcium Ion Ca2++ Ions important in: transmission of electrical impulses across synapses Muscle contraction Calcium phosphate Structural component of bones and teeth Sodium Na+ Transmission or nerve impulses along neurons Contribute to high concentration built up by loop of Henle in medulla of kidney Enable concentrated urine to be excreted so water is conserved Sodium-potassium pump in cells • Filtering machines of the body • As blood travels through the kidneys, they remove waste products and excess water • Process about 200 liters of blood to sift out about 2 liters of waste products and extra water, everyday. • The waste, along with the water is turned into urine which travels through the remaining components of the urinary system and is excreted • Food consumed provides energy and helps repair cells • Whatever the cells do not use in this process must be eliminated from the body • It is combined with waste from the breakdown of normal tissues in the blood • The kidneys help rid the body of these materials to prevent accumulation that can damage the body Potassium Ions K+ Work with sodium ions Involved in transmission of nerve impulses along neurons Contribute to control of turgidity of cells This controls opening and closing of the stomata STOMOTA: Tiny openings on the underside of cells Surrounded by guard cells Close up to conserve water Three sodium ions enter the pump and attach to binding sites. ATP binds to the pump. One phosphate bond in the ATP molecule breaks, releasing its energy to the pump protein. The pump protein changes shape, releasing the sodium ions to the outside.The new shape reduces its ability to bind to sodium ions and it increases its ability to bind potassium ions. The two potassium binding sites are exposed to the outside, allowing two potassium ions to enter the pump. When the phosphate group detaches from the pump, the pump returns to its original shape. Its ability to bind potassium ions is decreased and its ability to bind sodium ions is increased. The two potassium ions leave, three sodium ions enter, and the cycle repeats itself. Magnesium Ion, Mg2++ Chlorophyll molecules contain magnesium Active sites of ATP synthases contain Magnesium ions ATP sythase ASE = enzyme Enzyme that helps add a phosphate group (PO43-) to an adenosine diphosphate (ADP) molecule to make adenosine triphosphate (ATP) Chloride ion Cl Works with sodium ions Contributes to the high concentration built up by the loop of Henle in the medulla of the kidney Enables concentrated urine to be excreted so water is conserved Help balance the positive charge of cations (Na+ and K+) within and around cells Nitrate ions, NO3 Plants use nitrogen from nitrate ions to make amino acids and nucleotides Ion is able to be surrounded by water molecules and pulled up into root hairs into xylem of plant and carried around the plant This is why polarity of water is important…allows plants to pull up important ions Phosphate Ions, (PO43-) Used in making phospholipids (cell membrane) Used in the making of nucleotides (phosphate group) DNA RNA Combine with calcium to make calcium phosphate, that gives strength to bone Component of ATP, energy currency of cells Iron, Fe2+ Hemoglobin contains this ion to attract oxygen molecule and carry it to cells One hemoglobin contains 4 iron ions