amino_acid.html: 05_UN78AminoAcidFormula_L.jpg
Amino acids possess both carboxyl and amino groups and
an asymmetric carbon atom called the alpha (α) carbon,
and can form enantiomers.
Each amino acid has a different
side chain (R group).
Only L isomers are found in proteins.
amino_acids-polar.html: 05_17bPolarAminoAcids.jpg
amino_acids.html: 05_17aNonpolarAminoAcids.jpg
The amino acids can be grouped according to the properties of their side chains (R groups).
These 9 are considered nonpolar; the other 11 are polar.
carbohydrates.html: 05_03Monosaccharides.jpg
Carbohydrates are polymers of monosaccharides (sugar) and include:
cellulose.html: 05_07bCellulose-L.jpg
Parallel cellulose molecules
are held together by hydrogen bonds between hydroxyl groups.
Cellulose is a major component of the tough cell walls
in plants, and is difficult to digest.
cellulose_digest.html: 05_09CelluloseDigesting_UP.jpg
Cows have microbes in their stomachs to facilitate digesting cellulose.
cellulose_struct.html: 05_07CelluloseStruc.jpg
Since its β glucose monomers have the hydroxyl groups
oriented on opposite sides in every other monomer, a cellulose molecule is straight.
The hydroxyl groups are free to hydrogen–bond with parallel cellulose chains,
forming strong microfibrils.
chitin.html: 05_10ChitinStructure_L.jpg
Chitin, like cellulose, is composed of the beta (β) form of glucose,
but the 2 carbon has a nitrogen group.
The polymer is a strong but flexible structural component of arthropod
exoskeletons.
chitin_use.html: 05_10Chitin-L.jpg
| Chitin is an important structural polysaccharide found in the exoskeleton of arthropods. | Chitin is used to make a strong, flexible, and biodegradable surgical thread. |
cholesterol.html: 05_15Cholesterol_L.jpg
The steroid lipid cholesterol
is found in cell membranes and is also a precursor for some hormones.
collagen.html: 05_21gProteinCollagen-L.jpg
Collagen is a fibrous structural protein that has left-handed helical subunits intertwined into a larger
triple helix.
This structure provides flexible strength to connective tissue in skin, tendons, and ligaments in animals.
dehydration.html: 05_02aPolymers-L.jpg
Polymers are formed by connecting monomers
with covalent bonds through loss of a water molecule.
This is called a dehydration, or condensation, reaction,
dna.html: 05_27DNADoubleHelix.jpg
The DNA double helix and its replication.
A DNA molecule is usually double–stranded, with the sugar–phosphate backbone of the polynucleotide strands on the outside of the helix.
Holding the two strands together are pairs of nitrogenous bases attached to each other by hydrogen bonds.
Adenine (A) can pair only with Thymine (T), and Guanine (G) can pair only with Cytosine (C).
enzyme.html: 05_16EnzymeCatalyticCycle.jpg
The catalytic cycle of an enzyme.
The enzyme sucrase accelerates hydrolysis of its substrate (sucrose)
into glucose and fructose by binding the substrate to its active site.
As a catalyst, the protein is not consumed during the cycle, but is available for further catalysis.
fat-saturated.html: 05_12aSaturatedUnsatFat-L.jpg
A saturated fat such as stearic acid found in animal fats
has no double bonds: they are "saturated"
with the maximum number of hydrogen atoms possible.
The straight geometry of these macromolecules allow them to pack tightly and they are usually solids
at room temperature.
fat-trans-linoleic.html: 05_fatty-acids2.gif
Hydrogenation of unsaturated fats removes double bonds by adding hydrogen.
This process often result in trans double bonds.
The trans fats as well as saturated fats are associated with elevated
cholesterol, especially LDL ("bad" cholesterol).
fat-trans.html: 05_fatty-acids2.gif
Trans unsaturated fats such as elaidic acid
have large components on opposite sides relative to the double bond,
and are geometrically similar to saturated fats.
Cis unsaturated fats
have large components on the same side.
fat-unsaturated.html: 05_12bSaturatedUnsatFat-L.jpg
Unsaturated fat such as oleic acid found in olive oil have one or more double bonds.
The mostly cis double bonds cause bending in their geometry; they pack loosely and are usually liquid (oils)
at room temperature.
Unsaturated fats can be converted to solids by hydrogenation.
fat.html: ../ch04/04_06FatMolecule_CL.jpg
The synthesis and structure of a fat, or triacylglycerol.
The molecular building blocks of a fat are one molecule of glycerol and three molecules of fatty acids.
(a) One water molecule is removed for
Each fatty acid is joined to the glycerol by dehydration.
The removal of a hydroxyl (-OH) from the carboxyl group at the end of the fatty acid results in a form of catbobyl
called an acyl group, and the fat molecule is called triacylglycerol, or more commonly triglyceride.
fats.html: 05_11FatStructure.jpg
Lipids (also called fats)
are constructed from a single glycerol molecule and usually 3
fatty
acids, and may also be called "triglycerides".
The fatty acid tails are nonpolar hydrocarbon chains that are hydrophobic.
glucose.html: 05_04GlucoseLinearRing.jpg
glycogen.html: 05_06Polysacchar_Glycogen.jpg
Glycogen is a glucose polymer with highly branched structures.
Animals stockpile glycogen in clusters of granules within mitochondria
of liver and muscle cells.
hemoglobin-sickle.html: 05_22-SickleCellDisease-L.jpg
A single amino acid change (primary structure)
in the β-globin subunit of hemoglobin leads to abnormal folding and assembly in its
secondary, tertiary, and quaternary structure.
This results in reduced capacity to carry oxygen, and sickle-cell disease.
hemoglobin.html: 05_21gProteinHemoglobin-L.jpg
Two α (alpha) globin and
two β (beta) globin chains make up the quaternary structure for one molecule of
hemoglobin, the oxygen-carrying molecule in red blood cells.
Sickle cell anemia is caused by
a mutation in the primary structure of the β globin chain,
which leads to altered conformations in the higher level structures.
hexoses.html: 05_03Hexoses.jpg
The aldoses glucose
and galactose are optical isomers.
Fructose is a ketose.
hydrolysis.html: 05_02bPolymers-L.jpg
Polymers are disassembled to monomers by hydrolysis:
covalent bonds are broken by the addition of water molecules.
lysozyme.html: 05_19Lysozyme_L.jpg
Conformation of a protein, the enzyme lysozyme.
Present in our sweat, tears, and saliva, lysozyme
is an enzyme that helps prevent infection by destroying molecules on the surface of bacteria.
The groove in the protein recognizes and binds to target molecules on bacterial walls.
To be active, the enzyme must be in a specific 3-dimensional shape, or conformation.
maltose.html: 05_05Maltose.jpg
Dehydration reaction in the synthesis of maltose.
Maltose is a disaccharide formed from 2 glucose molecules.
monosaccharides.html: 05_03Monosaccharides.jpg
Monosaccharides
Aldoses have a carbonyl
at the end of the carbon skeleton.
Ketoses have the carbonyl within the skeleton.
Aldoses and ketoses are structural isomers.
Glucose and galactose have an
asymmetric carbon
and are
optical
isomers.
nucleoside.html: 05_27-NucleicAcidCompon-L.jpg
The components of a nucleoside include a nitrogenous base
and a pentose sugar
(either deoxyribose in DNA or ribose in RNA).
The carbon atoms on the sugar are given prime numbers: 1' through 5'.
The nitrogenous base is either a
pyrimidine - Cytosine (C), Thymine (T), and Uracil (U) -
or a
purine - Adenine (A) and Guanine (G).
Thymine is found in DNA (Deoxyribonucleic Acid), while Uracil is found in RNA (Ribonucleic Acid).
nucleotide.html: 05_26Nucleotide.gif
The nitrogenous base is attached to the 1' carbon
of the sugar; together these form a nucleoside.
The phosphate group
is attached to the 5' carbon, forming a nucleotide.
peptide.html: 05_18Peptide.jpg
Making a polypeptide chain.
Peptide bonds formed by dehydration reactions link the
carboxyl group of one amino acid to the amino group of the next.
The polypeptide has a repetitive backbone
to which the side chains are attached.
phospholipid.html: 05_13PhospholipidStructur.jpg
Phospholipids are diglycerides and have two fatty acid chains and a phosphate group.
They contain hydrophilic "heads" and hydrophobic "tails" that form a bilayer in
cell
membranes.
polynucleotide.html: 05_26NucleicAcidComponent.jpg
protein_alpha.html: 05_20cKeratin.jpg
α keratin, the structural protein of hair, has the alpha helix
formation over most of their length.
protein_beta.html: 05_20cSilkFibroin.jpg
The core of a spider's
silk
(fibroin) is made of beta pleated sheets;
the combined strengths of the hydrogen bonds make a spider silk fiver stronger than a steel strand of the same weight.
protein_primary.html: 05_21aProteinStructure-L.jpg
The sequence of amino acids of a polypeptide, linked by covalent bonds, determines its primary structure.
protein_quaternary.html: 05_21eProteinStructure-L.jpg
Some proteins such as collagen
and hemoglobin
possess quaternary structure that results from the aggregation of two or more
polypeptide
subunits.
protein_secondary.html: 05_21cProteinStructure-L.jpg
Secondary structure is the folding of the polypeptide, due to hydrogen bonds,
into repeating patterns
of an
α helix
or a
β pleated sheet.
protein_tertiary.html: 05_20dTertiaryStructure.jpg
Tertiary structure determines the final three-dimensional shape of a polypeptide,
and results from various interactions
between amino acids and R groups.
ribonuclease.html: 05_24XRayCrystallogrphy_CL.jpg
Atoms in a crystallized protein (ribonuclease) deflect X-rays into a diffraction pattern, which can be exposed on a
photographic film. The pattern can be used to reconstruct the 3-dimensional structure of the protein,
bound to a short strand of nucleic acid.
Another technique is nuclear magnetic resonance (NMR)
spectroscopy,
which does not require protein crystallization.
sickle.html: 05_22cSickleCellDisease-L.jpg
Sickle Cell Anemia.
A mutation in the β-globin subunit of hemoglobin results in reduced capacity to carry oxygen.
The red blood cells can become sickle-shaped, which can clog blood vessels and cause organ damage.
starch.html: 05_07bStarch-L.jpg
Starch is a polysaccharide
consisting entirely of glucose monomers and is stored in chloroplasts of plants.
Two forms of starch
are amylose (unbranched) and amylopectin (branched).
starch_struc.html: 05_07StarchStruc.jpg
Due to the linkage of α glucose monomers where all the hydroxyl
grpups are in the same orientation, a starch molecule is helical in shape.
steroid_hormones.html: Steroid_hormones.gif
sucrose.html: 05_05Sucrose.jpg
Dehydration reaction in the synthesis of sucrose.
Sucrose is a disaccharide formed from glucose and fructose.
Notice that fructose, though a hexose like glucose, forms a five-sided ring.