1 / 64

PROTEINS

PROTEINS. Proteins. Proteins do the nitty-gritty jobs of every living cell. Proteins are made of long strings of individual building blocks known as amino acids. Amino acids contain an amino group, a carboxyl group, a carbon and a unique R group.

Télécharger la présentation

PROTEINS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. PROTEINS

  2. Proteins • Proteins do the nitty-gritty jobs of every living cell. • Proteins are made of long strings of individual building blocks known as amino acids.

  3. Amino acids contain an amino group, a carboxyl group, a carbon and a unique R group

  4. Polar R groups make the amino acid hydrophilic Non-polar R groups make the amino acid hydrophobic

  5. Ionic R groups make the amino acid hydrophilic

  6. How do our cells know what order to put amino acids into to make the right protein?

  7. There are 20 commonly occurring amino acids that are found in proteins • leucine - leu - L • lysine - lys - K • methionine - met - M • phenylalanine - phe - F • proline - pro - P • serine - ser - S • threonine - thr - T • tryptophan - trp - W • tyrosine - tyr - Y • valine - val - V • alanine - ala - A • arginine - arg - R *** • asparagine - asn - N • aspartic acid - asp - D • cysteine - cys - C • glutamine - gln - Q • glutamic acid - glu - E • glycine - gly - G • histidine - his - H *** • isoleucine - ile - I “Essential Amino Acids” are those that must be ingested in the diet (our body can’t make them)

  8. Peptide Bonds join amino acids • It’s a condensation reaction • (meaning that H20 is released • when the bond is formed). • Two amino acids form a • DI-PEPTIDE • POLYPEPTIDES • are formed from more • than two amino acids • bonded together

  9. Proteins have four levels of organization

  10. Primary structure is the amino acid sequence

  11. The amino acid sequence is coded for by DNA and is unique for each kind of protein

  12. The amino acid sequence determines how the polypeptide will fold into its 3D shape

  13. Even a slight change in the amino acid sequence can cause the protein to malfunction For example, mis-formed hemoglobin causes sickle cell disease

  14. Proteins have four levels of organization

  15. Secondary structure results from hydrogen bonding between the oxygen of one amino acid and the hydrogen of another

  16. The alpha helix is a coiled secondary structure due to a hydrogen bond every fourth amino acid

  17. The beta pleated sheet is formed by hydrogen bonds between parallel parts of the protein

  18. A single polypeptide may have portions with both types of secondary structure Link to video

  19. Proteins have four levels of organization

  20. Tertiary structure depends on the interactions among the R group side chains

  21. = charged = hydrophobic Types of interactions • Hydrophobic interactions: amino acids with nonpolar side chains cluster in the core of the protein, out of contact with water

  22. Types of interactions • Hydrogen bonds between polar side chains

  23. Types of interactions • Ionic bonds between positively and negatively charged side chains

  24. Types of interactions • Disulfide bridge (strong covalent bonds) between sulfur atoms in the amino acid cysteine Link to video

  25. Proteins have four levels of organization

  26. Quaternary structure results from interactions among separate polypeptide chains.

  27. For example, hemoglobin is composed of 4 polypeptide chains Link to video

  28. Proteins have four levels of organization

  29. The folding of proteins is aided by other proteins, called chaperones • Act as temporary braces as proteins fold into their final conformation • Research into chaperones is a area of research in biology

  30. Denaturation results in disruption of the secondary, tertiary, or quaternary structure of the protein

  31. Denaturation may be due to changes in pH, temperature or various chemicals

  32. Protein function is lost during denaturation, which is often irreversible

  33. Folded proteins are placed into two general categories

  34. Fibrous proteins have polypeptide chains organized in long fibers or sheets • Water insoluble • Very tough physically, may be stretchy

  35. Functions of fibrous proteins • Structural proteins function in support • Insects and spiders use silk fibers to make cocoons and webs • Collagen and elastin are used in animal tendons and ligaments • Keratin is the protein in hairs, horns and feathers

More Related