3.3 and 3.4 Chapter 3

Proteins are

polymers of amino acids

How many different amino acids are there

20

Amino acids

contain an amino group (-Nh2) and an acidic carboxyl group (-COOH)

The specific order of amino acids

determine the proteins structure and function

How are the unique properties of each amino acid determined?

By the side chain R group

The 20 amino acids are grouped into 5 chemical classes

Non polar

polar uncharged

charged

aromatic

special functions/unique properties

The amino and carboxyl groups of a pair of amino acids can undergo

A dehydration reaction to form a covalent bond

Bond linking two amino acids together is called a

Peptide Bond

One of the unique features of
a peptide bond, is that bonded
amino acids are not free to
rotate around the N-C linkage

True

Who is Frederick Sanger

A British biochemist known for his work on the structure of proteins, particularly insulin, and developing the Sanger sequencing method for DNA.

Polypeptide

One or multiple chains can make up a protein

Protein structure determines its function

true

What are the 4 levels of proteins

Primary, secondary, tertiary, quaternary

The levels of the proteins can also be classified as

ordered complexity and emergent properties

Primary structure

the proteins amino acid sequence
* any changes can have drastic effects on function

Secondary Structure

the polypeptide backbone can
hydrogen bond with water or other amino acids

What kind of helixes does the secondary structure have

α-helix: peptide coiled into a spiral
β-pleated sheet: interactions between peptides
next to each other to form a planar structure

Tertiary Structure

the overall three-dimensional shape of a protein formed by interactions among various side chains (R groups) of the amino acids

Changing a single amino acid can

Drastically alter tertiary structure

Quaternary Structure

final structure for the protein
Arrangement of multiple polypeptide subunits

When 2 or more polypeptide chains associate to form a protein the individual chains are called

subunits

Example of Hemoglobin

composed
of two α–chain subunits and two β–
chain subunits

Motifs

similar structural elements (secondary structures) found in
dissimilar proteins

Domains

functional units within a larger protein structure, most proteins are made up of multiple domains that make up
different parts of the proteins function

Chaperone Proteins

Proteins that help other proteins fold correctly

Improper folding can cause

Disease

Heat shock proteins (HSP)

high temperatures, can cause
proteins to unfold, HSP help protein to re-fold after heat shock

Chaperone protein deficiencies may be implicated in diseases
such as

Cystic Fibrosis

Denaturation inactivates proteins

pH, temperature, or changes in ion
concentration

Enzymes

proteins that catalyze chemical
reactions usually have a very narrow
of environmental conditions

Subunits of proteins with quaternary structure

may dissociate

Lipids are

loosely defined as molecules that are insoluble in water

Lipids are insoluble in water because they have

a high proportion of nonpolar C-H bonds

Lipids can be

Storage fats (i.e. animal fat)
Oils
Waxes
Steroids & Hormones
Some vitamins

Storage fats

Triglyceride

A glycerol molecule with three fatty acid chains attached

Fatty Acids

long chain hydrocarbons, with a carboxyl group (COOH)

Triglyceride

A glycerol molecule with three fatty acid chains attached

Saturated

if all the internal carbon atoms in the fatty acid are
bonded to two hydrogen atoms
maximum # of hydrogen

Unsaturated

if double bonds occur between one or more of the
carbon atoms

= fewer H atoms

Fatty acids with one double bonds

= Monounsaturated

Multiple double bonds

= Polyunsaturated

Having double bonds changes the behavior to the molecules

True

free rotation cannot occur around

C=C

Polyunsaturated fats have low

melting points, liquid at room temperature

Most saturated fats are

solid at room temperature

Fats are excellent energy storage molecules

True

Most fats contain

40+ carbons, the ratio of C-H bonds in more than 2X
carbohydrates

Excess carbohydrates are converted to

Fat for storage

Most fats contain 40+ carbons will

Release more energy upon oxidation

On average fats yield

9 kilocalories of energy per gram relative
to ~4kcal/g for carbohydrates

Complex lipid molecules are called

phospholipids

Glycerol

Forms the backbone of the phospholipid
molecule

Fatty Acids

Have two fatty acid chains

Phosphate Group

attached to one end of the glycerol
*Phosphate group is charged, and usually has a charged
organic molecule linked to it (i.e. choline)