Midterm Review

Fall 2007

Identify the following monomers:

Amino Acids and Proteins

What are the main components of an amino acid?

Amino Acids are monomers that make up ______________

How do amino acids determine the shape of a protein?

How does the shape of a protein determine its function?

Two Amino Acids join to form a peptide bond—a chain of amino acids makes up a peptide or protein

The Main Components of Amino Acids

Contain nitrogen, hydrogen, carbon and oxygen & sometimes Sulpher

(CHON or CHONS) Amino group: NH2 Carboxyl

group: COOH R Group (variable)

There are 20 different amino acids—each with a different R group

The specific amino acids determine the shape of the Protein or Peptides

4 levels of protein structure

PrimarySecondary TertiaryQuaternary

Primary Structure

The unique sequence of amino acids attached by peptide linkages

What could happen if one amino acid is missing or in a different position?

Secondary

Develops when the protein chain takes a particular shape immediately after formation at the ribosome Parts of the chain become folded and/or twisted

The most common shapes: Coiling alpha helix (ά) Folding beta helix (β)

These shapes are permanent and held in place by hydrogen bonds

Tertiary Structure

Precise, compact structure, unique to that protein, which arises when the molecule is further folded

Types of bonds Hydrogen: hydrogen

shared by 2 atoms (weak) Van der Waals: two or

more atoms are very close

Disulphide: strong covalent bond (SH groups)

Ionic: oppositely charged ions

Quaternary Structure

When two or more proteins become held together, forming a complex, biologically active molecule Example hemoglobin, consisting of 4

polypeptide chains held around a non-protein group

Levels of Protein Structure

What is an enzyme

An Enzyme IS a Protein

It is a biological catalyst

Why is shape important to proteins, specifically Enzymes?

Due to its precise shape and distinctive chemical properties, each enzyme is specific for a certain substrate or a VERY small group of substrate molecules.

Shape can be used positively and negatively

Positive If a protein’s active site

and a substrate match, they will bond and react

Negative If a protein’s active site

and an “imposterer” match the intended reaction will not occur

If another site on the protein is filled, the intended reaction will not occur

Illustrate each type of inhibition—Why is protein shape important?

Competitive InhibitionNon-Competitive InhibitionAllosteric Inhibition

End-Product inhibition (negative feedback)

How can a protein lose its shape?

Denaturation is a structural change in a protein that alters its 3-D shape and causes the loss of its biological properties

Cell Theory

1. All organisms are composed of cells(this does not mean that we have some cells--it

means that we are made of cells)

2. All cells come from pre-existing cells(there is no such thing as a cell that comes from

something other than a cell)

3. Cells are the basic unit of structure and function (cells are the smallest unit of life that fulfill all the requirements of life)

Two major types of cells

Prokaryotes Simple Small No nucleus No membrane-bound

organelles Bacteria (archea and

eubacteria Reproduce by binary

fission All unicellular NOT VIRUSES

Eukaryotes More complex Larger Nucleus Membrane-bound

organelles Plants,Animals,

& Fungi,Protists Reproduce by mitosis Unicellular or

multicellular