University:
Sam Houston State University
Course:
BIOL 2413 | General Zoology
Academic year:

2019
Views:

476

Pages:

12
Author:

Clint W.

AMINO ACID HYDROPHOBICITY  Hydrophobicity is a long word that simply means whether or not a molecule is attracted to or repelled by water For example, oil is hydrophobic – it does not mix with water  Salt is hydrophilic – it easily dissolves in water  Hydrophobic – water hating (it has a ‘phobia’ of water)  Hydrophilic – loves water (Philadelphia is the city of Brotherly Love)  Hydrophobic amino acids will move to the inside to get away from water  Hydrophilic amino acids will move to the outside to move towards water  CYSTEINE BONDS Cysteines are one of the 20 amino acids  Cysteines are like the obnoxious couples that are always together – they can’t stand to be apart  Two cysteines will always move closer to each other  When they move close, they will form what is called a “disulfide bond” or “disulfide bridge”  1 Hydrogen bond СН 2 1 о н. . о 1 С-ОН 1 СН2 Hydrophoblc interactions (clustering of hydrophoblc / groups away from water) 1 and van der Waals сн interactions / "С С ---Polypeptide Нз Нз с С backbone Н з , / Нз сн 1 -CH 2 -S-S�CH 2Disulfide bridge о 1 -CH 2 -CH 2 -CH2 -CH 2 -NH 3+ -o-C-CH2lonic bond SUMMARY  So, three major factors affect how amino acids change from a straight line to a 3D protein Charge – like charges repel, opposite charges attract  Hydrophobicity – some amino acids are attracted to water and move to the outside; others are repelled by water and move to the inside  Cysteine bonds – two cysteine amino acids will form a disulfide bond together  cys - - - + Hydrophilic Amino Acids on the Outside Hydrophobic Amino Acids on the Inside Disulfide Bond between Cys - + Neg & Pos attraction cys SHAPES OF PROTEINS  There are two kinds of shapes that can result because of the factors that affect protein shapes α helix (pronounced “alpha helix”)  β sheet (pronounced “beta sheet”)  LEVELS OF PROTEIN ORGANIZATION The primary level of protein organization is the order of amino acids as determined by mRNA and DNA  The secondary level of protein organization is the shape created by these amino acids     Only two shapes occur - α helix or β sheet  This will be a mix of α helixes and β sheets The tertiary level is the overall shape created by the entire string of amino acids The final level, the quaternary level, is the mixture of proteins (subunits) to create a functional protein - С,· J>-G""-,�o4i.,C�,. i::,. .· ..· , .... ..._ � • G � Pleatedl ;sheet .... ..... ..... ..... '' .... ._ .._ ..,, '' ' ....,, \ ....,, \ \ \ \ \ \ '\__..._=....... ,(е) Primary structu1r·e (Ь) Sec,ondary slructure (с) Terti.ary slructure ✓ �-P•oly1pep,tidle chai1n (3 Chai1n (а) Collagen (Ь) IHem,oglllobln OBJECTIVES Review central dogma of molecular biology.  Discuss type of protein.  Assess amino acids.  Demonstrate folding proteins. 