Lesson 7c: Proteins Proteins: 15:56: B C1B1A3F8E&blnFromSearch=1&productcode=US

Proteins: Multipurpose molecules

collagen (skin) Proteins Examples  muscle  skin, hair, fingernails, claws  collagen, keratin  pepsin  digestive enzyme in stomach  insulin  hormone that controls blood sugar levels insulin pepsin

Proteins  Function:  many, many functions  hormones  signals from one body system to another  insulin  movement  muscle  immune system  protect against germs  enzymes  help chemical reactions

Proteins  Building block = amino acid amino acid – amino acid – amino acid – amino acid – —N——N— H H H | —C— | C—OH || O variable group amino acids  20 different amino acids There’s 20 of us… like 20 different letters in an alphabet! Can make lots of different words

Amino acid chains  Proteins  amino acids chained into a polymer  Each amino acid is different  some “like” water & dissolve in it  some “fear” water & separate from it amino acid

Water-fearing amino acids  Hydrophobic (phobia – fear)  “water fearing” amino acids  try to get away from water in cell – but HOW?  the protein folds

Water-loving amino acids  Hydrophillic (phil – love)  “water loving” amino acids  try to stay in water in cell  the protein folds

pepsin 3-D protein structure  Proteins fold & twist into 3-D shape  that’s what happens in the cell!  Different shapes = different jobs collagen hemoglobin growth hormone

Its shape that matters!  Proteins do their jobs, because of their shape  Unfolding a protein destroys its shape  wrong shape = can’t do its job  unfolding proteins = “denature”  temperature  pH (acidity) folded unfolded “denatured” In Biology, it’s not the size, it’s the SHAPE that matters!