1. What type of bond and chemical reaction link adjacent amino acids together to form a polypeptide chain? ?

Linking of Amino Acids - Dehydration of an Hydrogen on the Nitrogen and an hydroxide on the second carbon (i assume you know the structure of an amino acid)

4 Levels of Protein Structure - Primary-Amino Acid Chain
Secondary- Hydrogen bonds between backbone of amino acids, way it folds
Tertiary-Linking of R groups of amino acids, can be hydrogen bonds, disulfide bridges or van der Waals interactions, 3D shape of protein
Quaternary - Shape of multiple bonds bonding

3D Shape Important - Yes, it affects the function (ex. Enzymes can only catalyze reactions if they are the right shape)

Amino acids bond together by means of dehydration synthesis (chemical reaction), forming peptide bonds.

1. Primary: Determined by linear sequence of amino acids.
2. Secondary: Determined by hydrogen bonds of the amino acid backbone.
3. Tertiary: Determined by the interaction of the R groups in the amino acid back bone.
4. Quartenary: Determined by aggregation of polypeptide subunits.

3-D shape is important because shape correlates with the protein's function.