Topic 3 Chemical Basis of Life

Are made of only a selection of 92 naturally occurring elements, 4 of which (C, H O and N) make up 96.5 % of an organisms weight.

Comparison of covalent and ionic bonds

(in the electrical sense) is one with positive charge concentrated toward one end (the positive pole) and negative charge concentrated toward the other (the negative pole).

Four Types of Noncovalent Attractions Help Bring Molecules Together in Cells:

Covalent bonds in which the electrons are shared unequally in this way are therefore known as

These result from the attractive forces between oppositely charged atoms. They are quite strong in the absence of water. They readily form between permanent dipoles, but are greatest when the two atoms involved are fully charged (ionic bonds).

This bond represents a special form of polar interaction in which an electropositive hydrogen atom is partially shared by two electronegative atoms.

The electron cloud around any nonpolar atom will fluctuate, producing a flickering dipole. Such dipoles will transiently induce an oppositely polarized flickering dipole in a nearby atom. This interaction generates a very weak attraction between atoms. But since many atoms can be simultaneously in contact when two surfaces fit closely, the net result is often significant. Water does not weaken these so- called ____.

is caused by a pushing of nonpolar surfaces out of the hydrogen-bonded water network, where they would otherwise physically interfere with the highly favorable interactions between water molecules.

a weak attractive force which occurs if two molecules with transitory dipoles are very close to one another and oriented in the appropriate manner

Water is a _____. Therefore, it is able to form multiple hydrogen bonds, which account for many of its special properties

any molecule that is capable of accepting a proton

capable of releasing (donating) a hydrogen Ion

The acidity of a solution is measured by the concentration of hydrogen ions and is expressed in terms of __.

compounds that react with free hydrogen or hydroxyl ions, thereby resisting changes in pH

compounds produced by living organisms

simplest group of organic molecules containing only carbon and hydrogen atoms; but do not occur in significant amounts on most living cells

are particular groupings of atoms that often behave as a unit and give organic molecules their physical properties, chemical reactivity, and solubility in aqueous solution.

huge, highly organized molecules that form the structure and carry out the activities of cells.

MACROMOLECULES can be divided into four major categories:

Macromolecules (proteins, nucleic acids, polysaccharides) are polymers built by linking together small subunits called

Proteins

Nucleic acids

Polysaccharides

each series of chemical reactions happening in the cell

compounds formed along the pathways leading to the end products that might have no function per se.

Broadly speaking, cells contain four major families of small organic molecules:

Carbohydrates (or glycans as they are often called) include simple sugars (or monosaccharides) and all larger molecules constructed of sugar building blocks function:

Sugars containing 3, 4, 5, 6, 7 carbons

form by reaction between carbon atom C1 of one sugar and the hydroxyl group of another sugar, generating a —C—O—C— linkage between the two sugars.

composed of only two sugar units.

a polymer of sugar units joined by glycosidic bonds

glucose and fructose

glucose and galactose

glucose and glucose

A major component of plant cell walls

structural material among invertebrates, particularly in the outer covering of insects, spiders, and crustaceans.

ex. Heparin (secreted by cells in the lungs and other tissues in response to tissue injury)

are a diverse group of non-polar biological
molecules (ex. fats, steroids, and phospholipids)

Fats consist of a glycerol molecule linked by ____ to three fatty acids; the composite molecule is termed a triacylglycerol (also called a triglyceride or a neutral fat)

Fatty acids that lack doublebonds, such as stearic acid and those possessing double bonds

very rich in chemical energy; a gram of ___ contains over twice the energy content of a gram of carbohydrate
• It provides energy
• Absorbs certain nutrients
• Maintains your core body temperature

are built around a characteristic four-ringed hydrocarbon skeleton

contain two ends that have very different properties:
• the end containing the phosphate group has a
distinctly hydrophilic character;
• the other end composed of the two fatty acid tails has a distinctly hydrophobic character.

are the macromolecules that carry out virtually all of a cell’s activities; they are the molecular tools and machines that make things happen.
– Enzymes
– Some hormones
– Muscle
– Structural protein – ex. keratin
– Etc.

During the process of protein synthesis, each AA is joined to two other AA’s, forming a long, continuous, unbranched polymer called

aka small protein

joins AA resulting from the linkage of the carboxyl group of one amino acid to the amino group of its neighbor, with the elimination of a molecule of water

AA sequence of a polypeptide

3D structure (conformation)
of sections of the polypeptide backbone

conformation of the entire polypeptide

arrangement of the subunits if the protein consists of more than one polypeptide chain

The entire inventory of proteins that is produced by an organism, whether human or otherwise.

Nucleic acids are macromolecules constructed out of long chains (strands) of monomers called ______.

• Mainly, storage and transmission of genetic Information
• may also have structural or catalytic roles

Two types of nucleic acids: