Chapter 2 - Chemical Foundations

Glycosidic bonds

Glycosidic bonds

________ are usually formed between a covalently modified sugar and the growing polymer chain.

Biomembranes

________ have a hydrophobic core that separates two aqueous solutions and acts as a permeability barrier.

D Glucose

________ (C6H12O6) is the principal external source of energy for most cells in higher organisms and can exist in three different forms: a linear structure and two different.

Asparagine

________ and glutamine are uncharged but have polar side chains containing amide groups with extensive hydrogen- bonding capacities.

fatty acyl chains

The ________ in each leaflet minimize contact with water by aligning themselves.

Hydrocarbons

________**- molecules made up only of carbon and hydrogen- are virtually insoluble in water.

Sulphur

________ forms two covalent bonds in hydrogen sulphide (H2S), but also can accommodate six covalent bonds, as in sulfuric acid (H2SO4) and its sulphate derivatives.

Nucleotides

________ are nucleosides that have one, two, or three** phosphate groups** esterified at the 5 hydroxyl.

carbon atom

In nucleotides, the 1 ________ of the sugar (ribose or deoxyribose) is attached to the nitrogen at position 9 of a purine (N9) or at position 1 of a pyrimidine (N1)

similar electronegativities

A bond between atoms with identical or ________ is said to be nonpolar.

Nitrogen

________ and phosphorus each have five electrons to share.

CH2O

Monosaccharides are carbohydrates, which are literally covalently bonded combinations of carbon and water in a one- to- one ratio (________) n, where n equals 3, 4, 5, 6, or 7.

tryptophan

Cysteine, ________, and methionine are rare amino acids; together they constitute approximately 5 % of the amino acids in a protein.

Ionic

________ and hydrogen bonds stabilize the interaction of the phospholipid polar head groups with one another and with water.

Arginine

________ and lysine are positively charged; aspartic acid and glutamic acid are negatively charged (their charged forms are called** aspartate** and** glutamate**)

plants

Many species of ________, bacteria, and molds produce cellulose- degrading enzymes.

X ray crystallography

________ combined with computational analysis permits an accurate depiction of the distribution of electrons in covalent bonds and the outermost unbonded electrons of atoms.

Mannose

________ is identical with glucose except that the orientation of the groups bonded to carbon 2 is reversed.

inorganic ions

7 % of the weight is living matter composed of ________ and small molecules (amino acids, nucleotides, and sugars)

Fatty acids

________ with no carbon- carbon double bonds are said to be saturated; those with at least one double bond are unsaturated.

Cells

________ and extracellular fluids in organisms contain small concentrations of** nucleosides**, combinations of a base and sugar without a phosphate.

glycogen

Both ________ and starch are composed of the anomer of glucose.

spherical micelles

When a suspension of phospholipids is mechanically dispersed in an aqueous solution, the phospholipids aggregate into one of three forms: ________ and liposomes and sheetlike, two- molecule- thick phospholipid bilayers.

Polysaccharides

________ are linear or branched polymers of monosaccharides (sugars) such as glucose linked by** glycosidic bonds**

steady state

The system of linked reactions for producing and consuming that substance is said to be in a(n) ________.

Hexoses

________ (n= 6) and pentoses (n= 5) are the most common monosaccharides.

guanine

The bases adenine, ________, and cytosine are found in both DNA and RNA; thymine is found only in DNA, and uracil is found only in RNA.

hydrogen bonds

Rather than constituting an attractive force such as in ________, the hydrophobic effect results from avoidance of an unstable state (extensive water cages around individual nonpolar molecules)

DNA

The monomers from which ________ and RNA are built, called** nucleotides**, all have a common structure: a phosphate group linked by a phosphodiester bond to a pentose (a five- carbon sugar molecule) that in turn is linked to nitrogen- and carbon- containing ring structure commonly referred to as a "base.

rigid planarity

The ________ imposed by double bonds has enormous significance for the shapes and flexibility of large biological molecules such as proteins and nucleic acids.

Adenine

________ and guanine are purines, which contain a pair of fused rings; cytosine, thymine, and uracil are pyrimidines, which contain a single ring.

Disulphide bonds

________ are commonly found in extracellular proteins, where they help stabilize the folded structure.

OOH bonds

Because of its two ________, water molecules (H2O) are dipoles that form electrostatic, noncovalent interactions with one another and with other molecules.

Human digestive enzymes

________ can hydrolyze the glycosidic bonds in starch, but not the glycosidic bonds in cellulose.

epimerase

The ________ enzymes that interconvert different monosaccharides often do so using the nucleotide sugars rather than the unsubstituted sugars.

Nucleic acids

________ are linear polymers containing hundreds to millions of nucleotides linked by phosphodiester bonds.

Larger polysaccharides

________, containing dozens to hundreds of monosaccharide units, can function as reservoirs for glucose, as structural components, or as adhesives that help hold cells together in tissues.

Amino acids

________ with polar side chains are hydrophilic and tend to be on the surfaces of proteins; by interacting with water, they make proteins soluble in aqueous solutions and can form noncovalent interactions with other water- soluble molecules.

exert different attractions for

Many molecules, the bonded atoms ________ the electrons of the covalent bond, resulting in unequal sharing of the electrons.

equilibrium constant Keq

The ________ depends on the nature of the reactants and products, the temperature, and the pressure (particularly in reactions involving gases)

Proteins

________ are linear polymers containing ten to several thousand amino acids linked by peptide bonds.

Van der Waals interactions

________**, involving either transiently induced or permanent electric dipoles, occur in all types of molecules, both polar and nonpolar.

aldehyde group

If the ________ on carbon 1 reacts with the hydroxyl group on carbon 5, the resulting hemiacetal, D- glucopyranose, contains a six- member ring.

hydrogen atom

A(n) ________ forms only one bond.

functions of biomolecules

The weak attractive forces of noncovalent interactions are equally important in determining the properties and ________ such as proteins, nucleic acids, carbohydrates, and lipids.

side chain

The monomeric building blocks of proteins are 20 amino acids, all of which have a characteristic structure consisting of a central carbon atom (C) bonded to four different chemical groups: an amino (NH2) group, a carboxyl (COOH) group, hydrogen (H) atom, and one variable group, called a** ________, or R group**

Covalent bonds

________ are very stable because the energies required to break them are much greater than the thermal energy available at room temperature (25oC) or body temperature (37oC)

RNA

In ________, the pentose is ribose; in DNA, it is** deoxyribose**

Membranes

________ literally define what is a cell (the outer ________ and the contents within the ________) and what is not (the extracellular space outside the ________)

Nucleoside monophosphates

________ have a single esterified phosphate, diphosphates contain a pyrophosphate group, triphosphates have the third phosphate.