Bio Ch 2: Properties of Water and Functional Groups

BSC2010

Water is a universal ____

solvent

Hydrophilic

substances that dissolve easily in water

Hydrophobic

Substances that do not dissolve easily in water

Examples of hydrophilic substances

charged, polar molecules

Examples of hydrophobic substances

nonpolar molecules

Why do ionic compounds dissolve in water?

The ions become surrounded by water molecules in a hydrogen shell; this does not involve the formation or breaking of covalent bonds

A hydrogen shell surrounding cations and anions:

What is heat capacity/specific heat?

the amount of heat it takes to raise the temperature by one degree Celsius

Why does water have a high specific heat?

Water molecules form multiple hydrogen bonds with each other

What is heat of vaporization?

The amount of heat required to change a substance from a liquid to a gaseous state

Why does water have a high heat of vaporization?

The many hydrogen bonds are broken

What is evaporative cooling?

As water evaporates, heat is removed from the surface of living things

Water in living tissues does what?

reduces temperature fluctuations experienced because of changes in environmental temperature

What is cohesion?

The attraction of water molecules to one another; creates surface tension

What is adhesion?

The attraction of water molecules to different molecules, especially polar molecules

What are functional groups?

small groups of atoms with specific chemical properties

When attached to larger molecules, what do functional groups do?

functional groups give their properties to the larger molecule

Exergonic Rxn

Endergonic Rxn

What helps plants raise water from the roots to the leaves?

cohesion and adhesion

Methyl

• Functional group: Methyl

• class of compounds and example: Alkyl —> Alanine

• Nonpolar, an important modification of proteins and cytosine nucleotide

• CH₃

Hydroxyl

• Functional group: Hydroxyl

• class of compounds and example: alcohols —> ethanol

• polar, involved in hydrogen bonding. often participates in condensation rxns. required in the side chain for phosphorylation of proteins

• OH

Sulfhydryl

• Functional group: sulfhydryl

• class of compounds and example: thiols —> mercaptothion

• polar, can form disulfide bridges to stabilize protein structure

• SH

Aldehyde

• Functional group: aldehyde

• class of compounds and example: aldehydes —> acetaldehyde

• polar, very reactive. important in energy-releasing reactions

• O=C—H

• Polar, very reactive. important in energy-releasing reactions

Keto

• Functional group: keto

• class of compounds and example: Ketones —> Acetone

• polar, important in carbohydrates and in energy reactions

• O=C

Carboxyl

• functional group: carboxyl

• class of compounds and example: carboxylic acids —> acetic acid

• charged, acidic, ionizes in living tissues to form —COO^- (and H⁺). reacts with amino group to form peptide bond

• O=C—O

Which functional groups are phosphate groups?

Carboxyl, amino, and phosphate

Amino

• functional group: amino

• class of compounds and example: amines —> methylamine

• charged, basic, accepts H⁺ in living systems to form —NH₃⁺. Reacts with carboxyl group to form peptide bond

• H—N—H

phosphate

• functional group: phosphate

• class of compounds and example: organic phosphates —> 3-phosphoglycerate

• charged, acidic, ionizes in living tissues to form —O—P—O₃^2- (and 2 H⁺). enters into condensation rxns, often with inorganic phosphate, PO₄^3-. when bonded to another phosphate, hydrolysis is strongly exergonic

What is free energy?

the difference in bond energy and the change in entropy that determines whether the total energy change is exergonic or endergonic

Amphipathic

molecules that have both hydrophilic and hydrophobic regions

Most molecules of living things fall into four categories:

1. carbohydrates

2. lipids

3. proteins

4. nucleic acids

These categories all have carbon backbones (organic chemistry)

Molecular diversity is caused by..

The addition of functional groups —> determine how a molecule interacts with other molecules in the cell, resulting in molecular diversity

All functional groups besides what may be found on the outside of biological molecules?

Methyl

It is nonpolar and would not interact well with the aqueous environment encountered on the outside of biological molecules

What are structural isomers?

compounds that differ in how the atoms and functional groups are joined to one another

They differ because they have the same chemical formula but differ with respect to how the atoms are connected to each other