Proteins

Proteins DoEverything!

!

Proteins• All proteins are polymers of

amino acids.• There are only 20 amino acids

and they are used by organisms to make every known protein.

• There are approximately two million known proteins.

The Amino Acids

20 different R groups form 20 different amino acids

Amino Acids have 3 Groups– Amino group

(NH2)– Carboxyl Group

(COOH)– Side group (“R”

group)

Amino Acid structure

Amino acids join together to form peptides, polypeptides, and polypeptide chains.

Linking Amino Acids• Condensation reaction links amino group of one

amino acid with carboxyl group of next • Forms a peptide bond

Water forms as a by-product

Forming A Protein• Peptide bonds – bond

between 2 amino acids. (Dehydration Synthesis= water lost in process)

• A bunch of amino acids together = protein or polypeptide.

Bonding in Proteins• 2 amino acids dipeptide• More than 2 amino acids polypeptide• DNA determines the sequence of amino acids

in a protein or polypeptide chain.• Sequence of amino acids is unique to each

protein

Functions of proteins

• Movement–Actin & myosin in

muscles• Structure

–Collagen in skin (or lip injections Example: Angelina Jolie)

Antibodies - are specialized proteins involved in defending the body from antigens (foreign invaders). One way antibodies destroy antigens is by immobilizing them so that they can be destroyed by white blood cells.

Storage Proteins - store amino acids. Examples include ovalbumin and casein. Ovalbumin is found in egg whites and casein is a milk-based protein.

Functions of proteins

Hormonal Proteins - are messenger proteins which help to coordinate certain bodily activities. Examples include insulin, oxytocin, and somatotropin.

Insulin regulates glucose metabolism by controlling the blood-sugar concentration.

Oxytocin stimulates contractions in females during childbirth.

Somatotropin is a growth hormone that stimulates protein production in muscle cells.

Functions of proteins

ProteinsFunction Example

Structure/support collagenFight infection antibodies (immune

system)Transport hemoglobin carries O2

Catalyst enzyme

Movement actin & myosin in muscle

Enzymes The controller of all CHEMICAL reactions

in your body

Functions of proteins

Chemical Control (Enzymes)-at all times there are billions of chemical reactions taking place in any organism

-all organisms therefore need to control these chemical reactions that make up metabolism

- Enzymes control chemical reactions and therefore control Metabolism

There are over 2000 known enzymes, each of which is

involved with one specific chemical reaction

Enzymes• Enzymes

– enzymes are proteins– enzymes are referred to as organic catalysts

• catalysts - inorganic or organic substance which speeds up the rate of a chemical reaction – Chemical reaction = Dehydration Synthesis and Hydrolysis

• activation energy - the energy that must be overcome in order for a chemical reaction to occur. – enzymes lower the energy needed to start a chemical reaction.

(lower activation energy)

Activation Energy

Structure• Structures of Enzymes

- enzymes are large, complex proteins- all enzymes are either all protein or are protein with non-protein parts called coenzymes- coenzymes are often vitamins

- ASE• Usually enzymes end in – ase

• Enzymes are named according to the substrate they are specific to– substrates are the chemicals that each enzyme acts upon

Example of Naming: • The enzyme maltase (enzyme) breaks down (acts upon) the

dissaccharide maltose (substrate) into 2 monosacchardies

• The enzyme peptidase breaks the peptide bonds in proteins

Active Site or Binding Site

• Active Site or Binding Site -enzymes are usually much bigger than their substrates

-enzymes have a specific pocket or site where the substrate can fit and interact

-the specificity of the enzyme is dependent upon its active site

“Lock and Key Theory”

"Lock and Key Theory” – each enzyme is specific

for one and ONLY one substrate

(one lock - one key)

Enzyme Substrate Complex

1. Enzyme forms a temporary association with the substrate or substrates

2. The Enzyme and Substrate form a close physical association between the molecules called an enzyme substrate complex.

Enzyme – Substrate Complex

Enzyme Substrate Complex

3. While the enzyme substrate complex is formed, the enzyme action takes place and the substrate is broken down into its smaller, simpler parts

4. After completion, the enzyme and the products separate. The enzyme is then ready to react with another substrate.

New Enzymes • Although enzymes may be reused in cells, they

eventually are destroyed and new ones must be synthesized.

• Enzymes begin to be destroyed above 45 C. (above this temperature all proteins begin to be destroyed)

Factors Influencing Rate of Enzyme Action

• pH - the optimum (best) in most living things is close to 7 (neutral) -- high or low pH levels usually slow enzyme activity

• Temperature - strongly influences enzyme

activity – optimum temperature for maximum enzyme

function is usually about 35-40 C. – reactions proceed slowly below optimal

temperatures – above 45 C. most enzymes are destroyed

Denaturation• An enzyme may change shape as a result of

high temperatures or extreme pH values. This process is called denaturing

– Denaturing will cause an enzyme to become useless