Secondary Structure• non-linear• 3 dimensional• localized to regions of an

amino acid chain• formed and stabilized by

hydrogen bonding, electrostatic and van der Waals interactions

• Non-linear• 3 dimensional• Global, and across distinct

amino acid polymers• Formed by hydrogen

bonding, covalent bonding, hydrophobic packing and hydrophilic exposure

• Favorable, functional structures occur frequently and have been categorized

HISTORYHISTORYQuaternary Structure KOENIGSBERGCHARACTERISTICS

Polarity

• Polarity of water molecules allows them to form hydrogen bonds with each other– Contributes to four properties of water critical to

life processes

Hydrogenbonds

+

+

H

H+

+

–

–

– –

Figure 3.2

Cohesion

– The bonding of a high percentage of molecules to neighboring molecules

– Helps pull water up through the microscopic vessels of plants

Water conducting cells

100 µmFigure 3.3

Cohesion

Surface tension (related to cohesion) is measure of how hard it is to break the surface of a liquid

Figure 3.4

A universal solvent

• Is polar– Can dissolves salts

Water as a solvent

• The different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them Negative

oxygen regions

of polar water molecules

are attracted to sodium

cations (Na+).

+

+

+

+Cl ––

–

–

–

Na+Positive

hydrogen regions of water molecules

cling to chloride anions (Cl–).

++

+

+

–

––

–

–

–Na+

Cl–

Figure 3.6