Proteins & Nucleic Acids Also Known As… The Workers & Directors

Proteins Also Known As… The “Rock Star” Worker Molecules

Protein – Basic Info  Proteins are the “working” molecules of the body. They can act as enzymes, aiding in chemical reactions, or be structural components such as fingernails.  Proteins have a very specific 3-D shape which relates directly with their function – if this shape is not exact in every way, the protein may not function at all.  On top of this, if the conditions in which the proteins must function are not just right – the protein may function at a lower capacity or not at all – even if it had the right shape to start.  Think of proteins as the spoiled rock stars of the body – if they are not feeling right or the stage or dressing room they have to perform in is a little off – the show may be cancelled altogether.

Protein Building Blocks  The monomer for the proteins is the amino acid.  There are 20 different amino acids. They have the same “body” with a different “head”.  The “body” of an amino acid, that is common to all 20 of them, has the following parts: An alpha (α)carbon – the central carbon that holds it all together. There is always a hydrogen bonded to this alpha carbon. An alpha (α)carbon – the central carbon that holds it all together. There is always a hydrogen bonded to this alpha carbon. An amino group – NH 2. An amino group – NH 2. A carboxyl group – COOH. A carboxyl group – COOH.  There is also an R-Group – this is the head of the amino acid that is used to identify which of the 20 amino acids it happens to be.

Making Proteins  Amino acids are bonded together using a dehydration synthesis reaction – remove the water and connect the leftovers.  The water comes from a “H” on the amino group and the “OH” of the carboxyl group.  The bond that is made between the amino acids is called a peptide bond.  This means, of course, that proteins are taken apart by hydrolysis – stick the water back in and break it up. This is what you do when you eat a hamburger and break down the protein of the beef.

Protein Making

Protein Structure (Shape)  Structural proteins tend to be linear.  The proteins that act as enzymes have a more pronounced 3-D that is absolutely necessary for the proper function of the enzyme – damn rock stars!  There are 4 levels of protein structure… Primary – straight line. Primary – straight line. Secondary – α-helix or β-pleated sheet. Secondary – α-helix or β-pleated sheet. Tertiary – “Kinky slinky” with folds. Tertiary – “Kinky slinky” with folds. Quaternary – A bunch of tertiary proteins acting as one. Quaternary – A bunch of tertiary proteins acting as one.

Primary & Secondary Structure  Primary structure is the straight chain of amino acids that has just been built. This structure can be called a polypeptide – many peptide bonds. aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-etc… aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-aa-etc…  Secondary structure sees this chain assume the α-helix (corkscrew) shape or a β-pleated sheet (fan) shape.  The secondary structure is held together by hydrogen bonding between nearby carboxyl and amino groups within the polypeptide chain.

Tertiary & Quaternary Structure  Tertiary structure occurs when the helix and sheet interact and twist around each other – it’s like a slinky and a fan getting mangled together.  Tertiary shape is held together by R-group bonding within the chain and R-group interactions with the environment.  Tertiary structure is also aided by prosthetic groups that are inorganic compounds that act as a central point for bonding within the protein.  Quaternary structure occurs when a few tertiary structures fit together to act as one functional unit.

Go Exact Or Go Home!!!  Proteins are the rock stars of the body but they are very specific in their construction – if they are not built exactly right – they may not work.  This need for the exact 3-D shape is known as specificity and it is based on two things: The number of amino acids. The number of amino acids. The order of the amino acids. The order of the amino acids.  If the protein is built exactly right it will function properly unless environmental conditions get to tough.

I Fall To Pieces…  If the environment is too tough – the protein may denature – fall apart and lose that special 3-D shape.  Denaturing may occur is response to: Temperature changes – especially heat. Temperature changes – especially heat. Changes in pH. Changes in pH. Changes in salt/ion concentration. Changes in salt/ion concentration.  In your body, a protein may denature but chaperone proteins will help reassume the proper shape.  In a lab, there are no chaperone proteins so once the protein denatures – it is gone for good!

Nucleic Acids Also Known As… The Directions on How to Make Proteins Just Right.

Nucleic Acids – Basic Info  They carry genetic information. This information determines all of your structural and functional characteristics.  DNA – Deoxyribonucleic Acid - houses the genetic code within the nucleus of the cell.  RNA – Ribonucleic Acid - carries a copy of the code to the protein-making areas of the cell in the cytoplasm.  ATP – the cell’s energy – is also made from a nucleic acid building block.

Building DNA & RNA  The monomer for the nucleic acids is the nucleotide.  The nucleotide has three parts: 5-carbon Sugar 5-carbon Sugar Phosphate group Phosphate group Nitrogen-containing Base Nitrogen-containing Base  It‘s the sequence of the nitrogenous bases that provides the code/instructions for making the proteins.

DNA  Double helix composed of two strands of nucleotides held together by hydrogen bonds. The two strands are antiparallel to each other and are made of millions of nucleotides.  Ladder shape – Rails - A series of alternating phosphates and sugars linked by covalent bonds known as phosphodiester bonds. Rungs of the ladder are made of the nitrogenous bases and their hydrogen bonds.  The nitrogenous bases involved with DNA are adenine, cytosine, guanine and thymine.  The adenine and thymine pair up using two hydrogen bonds and cytosine and guanine pair up using three hydrogen bonds (Chargaff’s Base-Pair Rule).  The nitrogenous bases can be either purines (A & G) or pyrimidines (C & T or U in RNA).

DNA Structure

RNA  RNA is a code-carrying, single-stranded molecule made of many nucleotides.  There are several differences between RNA and DNA.

RNA vs. DNA DNA  Double-stranded.  A, C, G & T.  Deoxyribose - sugar.  H-bonds present.  Works in nucleus. RNA  Single-stranded.  A, C, G, & U.  Ribose - sugar.  No H-bonds  Works in cytoplasm – built in nucleus.

RNA vs. DNA (Diagram)

ATP  ATP (Adenosine Triphosphate) is the cellular form of energy.  It is composed of three phosphates, a ribose sugar and an adenine base.  The energy of the molecule is found in the bonds between the phosphate groups.

ATP Structure

FIN!