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Functions of Proteins

Functions of Proteins. By: Alec Hoover, Katie Klick, and Cory Yerger (14.1-14.4). Functions of Proteins. Structural support Animals have structural proteins. These are chief constituents in skin, bones, hair, and nails. Two important proteins are: Collagen and keratin Catalysis

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Functions of Proteins

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  1. Functions of Proteins By: Alec Hoover, Katie Klick, and Cory Yerger (14.1-14.4)

  2. Functions of Proteins • Structural support • Animals have structural proteins. These are chief constituents in skin, bones, hair, and nails. • Two important proteins are: • Collagen and keratin • Catalysis • All reactions that take place in living organisms are catalyzed by proteins called enzymes • Without enzymes reactions would be slow and useless

  3. Continued… • Movement • Muscle are made up of protein molecules • Myosin and actin • Transport • Hemoglobin in the blood carries oxygen from the lungs to the cells and carbon dioxide from the cells to the lungs • Move molecules across the cell brain

  4. Continued… • Hormones • Many hormones are protein • insulin, erythropoietin, human growth hormone • Protection • The body makes proteins called antibodies to counteract foreign proteins • This is one of the major mechanisms used by the body to fight off diseases • Fibrinogen is the protein used in blood clotting

  5. Continued… • Storage • Proteins store material • Example: casein in milk and ovalbumin in eggs store nutrients for newborn mammals and birds. • Ferritin: protein in the liver that stores iron. • Regulation • Control the expression of genes • Regulate the kind of proteins synthesized in a particular cell • Dictate when it is controlled

  6. Continued… • A typical cell contains about 9000 different proteins; the entire human body has 100,000 different proteins • Classified by two major types: • Fibrous proteins • Insoluble in water and used mainly for structural purposes • Globular proteins • More or less soluble in water and used mainly for nonstructural purposes • Click Link:

  7. Side Chains • Side chains are responsible for the characteristics and functions of amino acids • Some amino acids have charged side chains • EX: Glutamic Acid & Aspartic Acid

  8. Cysteine • Two identical cystine monomers make up cysteine • Unique because its side chain ( -SH) can form disulfide bridges with another cysteine

  9. Charged Amino Acids • When an amino acid has an additional carboxyl group it loses a proton and forms a corresponding carboxylate anion • EX: Glutamic Acid  Glutamate • Side chain is negatively charges at neutral pH • Histidine, Lysine, & Arginine have basic side chains • Lysine & Arginine have side chains that are positively charges at or near neutral pH

  10. Aromatic Rings • Phenylalanine, Tryptophan, & Tyrosine have aromatic rings in their side chains • Allow us to locate and measure proteins because the aromatic rings absorb strongly • Can be detected using a spectrophotometer • Key precursors to neurotransmitters (substances involved in the transmission of nerve impulses)

  11. Serotonin • Tryptophan is converted to serotonin, calming agent • Low levels of serotonin are associated with depression • High levels produce a hyper condition • Bipolar disorder can be managed by controlling levels of serotonin

  12. L-dopa • L-Dihydroxyphenylalanine = L-dopa • Low levels of L-dopa are involved in Parkinson’s disease • Tyrosine or phenylalanine supplements increase levels of dopamine because it passes into the brain quickly through brain-blood barrier

  13. Hormones • Tyrosine and Phenylalanine are transformed into norepinephrine and epinephrine, stimulants • Epinephrine is the “Flight or Fight” hormone • Causes the release of glucose and other nutrients into the blood • Stimulates brain function

  14. Side Effects • Tyrosine & Phenylalanine may have unexpected effects in some people • Some people get headaches from the phenylalanine in aspartame, artificial sweetener in diet soft drinks • Tyrosine gives some people a morning lift • Tryptophan helps you sleep at night • Milk proteins are an aid in inducing sleep

  15. What Are Amino Acids? • Contains amino and carboxyl groups. • Structure: (side chain)

  16. What Are Amino Acids? • Form chains that make up proteins • 20 common amino acids found in nature • Called alpha amino acids • Listed on page 303 in figure 14.1

  17. How do we categorize them? • Classified into four groups based off of their polarity. • Non-polar • Polar But Neutral • Acidic • Basic • Non-polar side chains are hydrophobic and the side chains of the rest are hydrophilic. • Side chains are responsible for determining both the structure and function of each protein molecules.

  18. What are Zwitterions? • Compounds with a positive charge on one atom and a negative charge on another are known as zwitterions.

  19. Zwitterions • Zwitter is a German word meaning “hybrid” • Amino acids are zwitterions in a water solution and in the solid state • As the pH is changed in the solution, the amount of positive and negative charges in the molecules change. • When the pH is at the level where the positive and negative charges are balanced, it is known as the isoelectric point.

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