Regents Biology

Proteins

Regents Biology 2006-2007

Proteins:Multipurpose molecules

Regents Biology

Proteins

Building block =

aminoacid

aminoacid– amino

acid– aminoacid– amino

acid–

—N—H

H

H|

—C—| C—OH

||O

variable group

amino acids

20 different amino acids used in the bodyThere’s

20 of us…like 20 different

letters in analphabet!

Can make lots of different

words

Regents Biology

Proteins Function:

many, many functions hormones

signals from one body system to anotherinsulin

movementmuscle

immune systemprotect against germs

enzymescatalysts in chemical reactions

Regents Biology

collagen (skin)

Proteins

insulin

Examples Muscle

Repair and rebuild cells Skin, hair, fingernails, claws

collagen, keratin Pepsin

digestive enzyme in stomach

Insulin hormone that controls blood

sugar levels

pepsin

Regents Biology

Amino acid chains Proteins

amino acids chained into a polymer called a polypeptide

Each amino acid is different some “like” water & dissolve in it some “hate” water & separate from it

amino acid amino acid amino acid amino acid amino acid

Regents Biology

Water-hating amino acids Hydrophobic

“water hating” amino acids try to get away from water in cell

the protein folds

Regents Biology

Water-loving amino acids Hydrophillic

“water loving” amino acids try to stay in water in cell

the protein folds

Regents Biology

Sickle cell anemia

I’mhydrophilic!

But I’mhydrophobic!

Just 1out of 146

amino acids!

Regents Biology

Protein Formation:1. Amino acids link up to form long

chains called polypeptides

2. Polypeptide chains twist or spiral

3. The spiraled chain then folds into subunits

4. The protein forms its final shape by linking together multiple subunits

Regents Biology

A. Primary Structure (1°)

Amino acids bonded together by peptide bonds.

aa1 aa2 aa3 aa4 aa5 aa6

Peptide Bonds

Amino Acids (aa)

Regents Biology

B. Secondary Structure (2°)

3-dimensional folding arrangement of a primary structure into coils and pleats held together by hydrogen bonds.

Regents Biology

B. Secondary Structure (2°)

Two examples:

Alpha Helix

Beta Pleated Sheet

Hydrogen Bonds

Regents Biology

Alpha Helix

Beta Pleated Sheets

Regents Biology

C. Tertiary Structure (3°)

Secondary structures bend and fold into a more complex 3-D arrangement.

Called a “subunit”.

Regents Biology

C. Tertiary Structure (3°)

Alpha Helix

Beta Pleated Sheet

Regents Biology

D. Quaternary Structure (4°)

Composed of 2 or more “subunits”. Example: enzymes (hemoglobin)

3° subunits

Regents Biology

Subunits

Regents Biology pepsin

For proteins: SHAPE matters!

collagen

Proteins fold & twist into 3-D shape that’s what happens in the cell!

Different shapes = different jobs

hemoglobingrowth

hormone

Regents Biology

It’s 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 of proteins = “denature”

temperature pH (acidity) salinity

folded

unfolded“denatured”

With protein,it’s not the size,but the SHAPEthat matters!

Regents Biology

Quick review: With a partner1. What is denaturing? What causes it?

2. What is the role of hydrophobic and hydrophilic amino acids in protein formation?

3. List at least 4 protein functions.