BIOCHEMISTRY
BIOCHEMISTRY
GLOSSARY
acid group A functional group consisting of –COOH.
adenosine triphosphate A biomolecule with the formula C10H16N5O13P3 that is used as a main vessel for energy transport in living organisms.
alkanes Hydrocarbons with the general formula CnH2n+2.
amine group In an amino acid, the -NH2 group.
amino acids The individual units that, when linked together in a specified order, form proteins. Amino acids have a central carbon atom, an amine group, an acid group and a side chain (that varies in structure from one amino acid to another).
base pair The two parts of nucleic acids that uniquely pair together to form the double helix in DNA and allow precise copying. In DNA, adenine pairs with thymine and guanine pairs with cytosine.
carboxylic acid group The –COOH group in organic and biochemical compounds. The group is polar and acidic.
cellulose A complex carbohydrate composed of repeating glucose units. Cellulose is the main structural material in plants.
DNA Deoxyribonucleic acid, a biomolecule composed of repeating units (called nucleotides) responsible for carrying the genetic information in all known living organisms.
disaccharides A class of sugars composed of two monosaccharides linked together.
esters A class of organic compounds consisting of a –COO– group sandwiched between two or more carbon atoms.
flash photolysis A technique to study light-activated chemical reactions in which a flash of light is used to initiate the chemical event which is then monitored as a function of time.
genome The complete set of genetic material of an organism.
glucose A carbohydrate with the formula C6H12O6 that circulates in the blood of animals and humans.
hormones Biochemical compounds that are transported in the blood to targets where they stimulate and regulate biochemical processes.
modular polymers Polymers that can be built up one unit (or monomer) at a time.
monosaccharides A carbohydrate composed of three to eight carbon atoms and one aldehyde or ketone group.
nonpolar A substance composed of molecules with uniform charge distribution. Nonpolar substances generally do not mix well with water.
nucleotide The individual unit that, when linked with other nucleotides, forms a nucleic acid (such as DNA). Each nucleotide contains a phosphate group, a sugar and a base.
polar A substance composed of molecules with an asymmetric charge distribution.
polynucleotide A chain of nucleotides bonded together found in hereditary molecules such as DNA and RNA.
recombinant DNA Synthetic DNA that contains genetic material from different sources.
ribonucleotide The monomer that, when linked to other ribonucleotides, forms RNA.
sucrose A carbohydrate with the formula C12H22O11.
triglyceride A type of fat that has a three-carbon backbone with three fatty acids attached (one to each carbon atom).
CARBOHYDRATES
the 30-second chemistry
Carbohydrates are so named because their general formula is a multiple of one carbon atom and one water molecule, (CH2O)n. Structurally, the carbon atoms are arranged in a ring (that can interconvert into a straight chain) and have multiple hydroxyl (OH) groups attached, making simple carbohydrates polar and therefore soluble in water. The ability to dissolve in water is important to one of the main functions of carbohydrates: storing and transporting energy for living organisms. The carbohydrate glucose (C6H12O6) is typical. It must be easily transported in the blood to places in the body where energy is being used. Carbohydrates such as glucose (which are also called monosaccharides, meaning one sugar) can link together to form disaccharides, such as sucrose (C12H22O11), which is table sugar. They can also link together to form long, chain-like molecules called complex carbohydrates such as starch, glycogen and cellulose. Starch (think potatoes) is the main energy storage medium for plants, and glycogen is used by animals as a compact way to store glucose in the muscles. Cellulose is the most common organic substance on Earth. It is more rigid than the other complex carbohydrates and is the main structural component in plants.
3-SECOND NUCLEUS
Carbohydrates are multi-carbon aldehydes or ketones with many OH groups attached; they act as short-term energy stores and the main structural components of plants.
3-MINUTE VALENCE
Carbohydrates are common in the foods we eat. Monosaccharides can pass directly through our intestinal wall and enter the bloodstream as ready sources of energy. Disaccharides and complex carbohydrates, however, must be broken down into monosaccharides before they can pass into the bloodstream. Our bodies can break down sugars and starches, but we lack the enzyme to break down cellulose (also known as dietary fibre), which is why cellulose passes through the digestive tract, giving bulk to stools and preventing constipation.
RELATED TOPICS
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3-SECOND BIOGRAPHIES
ANDREAS MARGGRAF
1709–82
German chemist who first isolated glucose from raisins
EMIL HERMANN FISCHER
1852–1919
German chemist and winner of the 1902 Nobel Prize in Chemistry for his pioneering work on sugars
30-SECOND TEXT
Nivaldo Tro
Carbohydrates include simple sugars such as glucose (top) and complex carbohydrates such as cellulose (bottom).
LIPIDS
the 30-second chemistry
Lipids are the only biomolecule defined by what they are not: lipids are not able to dissolve in water. This insolubility enables lipids to form thin, oily membranes and to clump together into oily droplets that serve as high-density stores of metabolic energy. In fact, many lipids contain a large, burnable hydrocarbon group similar to the alkanes in gasoline. In fatty acids (a type of lipid), for instance, a long hydrocarbon chain is attached to a single polar carboxylic acid group. In tryglycerides (another type of lipid) three long hydrocarbon chains are attached to a short three-carbon head. This highly nonpolar structure causes tryglycerides to glob together into oily ‘fat’ droplets. Another type of lipid has only two long hydrocarbon chains attached to a more polar head (a three-carbon unit containing a phosphate group). The result is a rod-like molecule with a charged water-loving ‘head’ and oily tail. These form sheets with the tails lined up in oily sheets on the one side and the ‘heads’ all facing to the other. To keep the oily surface of the tails out of water, two sheets line up to give a bilayer membrane, with the tails on the inside and the heads forming the water-facing surfaces. These bilayer membranes are the fundamental barriers that encapsulate living cells.
3-SECOND NUCLEUS
Lipids’ insolubility in water enables them to form extended membranes that enclose biological solutions and to function as particularly dense stores of metabolic energy.
3-MINUTE VALENCE
Even though they cannot be built up into modular polymers in the same way that other biomolecules can, lipids perform many varied biological functions. Lipid membranes act as barriers between the insides and outsides of cells while triglyceride ‘fats’ function as long-term energy stores in plants and animals. Other lipids called hormones act as biological messengers, being secreted by glands and carried to target cells where they trigger a physiological response.
RELATED TOPICS
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THE FORCES THAT HOLD MATTER TOGETHER
3-SECOND BIOGRAPHIES
MICHEL CHEVREUL
1786–1889
French chemist who was a pioneer in studying the chemistry of soaps, fats and oils
CHARLES ERNEST OVERTON
1865–1933
British biologist who first proposed that lipids might act as a cell membrane
30-SECOND TEXT
Stephen Contakes
One of the many functions of lipids is to encapsulate cells by forming a bilayer.
AMINO ACIDS & PROTEINS
the 30-second chemistry
Proteins are chain-like biomolecules that carry out a bewildering array of functions. Some, like the collagen in your skin, serve as structural supports. Others, like the motor protein myosin, enable muscles to relax and contract. Others adopt compact ‘globular’ shapes and can store or transport smaller molecules around, control cellular metabolism by speeding up particular chemical reactions or even recognize and bind other molecules. Some proteins, like insulin, act as intercellular signals, while others regulate bodily processes by chemically modifying other proteins to adjust how they function. Yet proteins are comprised of only 20 basic building blocks called amino acids, so named because they all contain a central carbon atom bonded to an amine group and an acid group. The central carbon is also bonded to a third variable group called a side chain, which may be polar, nonpolar, small, large, acidic, or basic. Amino acids can string together to form long polymers whose properties can vary widely based on the exact sequence of these side chains. Interactions between the side chains at different points along the polymer with each other and with surrounding water causes the protein to wriggle and fold into specific shapes, which in turn determine the functions they can perform.
3-SECOND NUCLEUS
Amino acids can be strung together into protein chains that fold into a diverse array of shapes and carry out many biological functions.
3-MINUTE VALENCE
When you take a breath the oxygen you breathe becomes bound to a protein called haemoglobin in your red blood cells, which transports the oxygen to your muscles and other tissues where it is used to ‘burn’ fats and carbohydrates in interconnected sequences of protein-catalyzed reactions. These generate the energy your body needs to move, synthesize other biomolecules and produce the electrical signals needed for nerve cells to function.
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REACTION RATES & CHEMICAL KINETICS
3-SECOND BIOGRAPHIES
GERARDUS JOHANNES MULDER
1802–80
Dutch chemist who first described the composition of proteins
JOHN KENDREW & MAX PERUTZ
1917–97 & 1914–2002
British biochemist and Austrian-born molecular biologist who determined the first 3D structures of proteins
30-SECOND TEXT
Stephen Contakes
Some proteins fold into globular shapes (centre), while others have more linear structures (bottom).
THE BIOLOGICAL BLUEPRINT: NUCLEIC ACIDS
the 30-second chemistry
DNA is a long, chain-like molecule containing units called nucleotides. Each nucleotide unit contains a negatively charged phosphate group attached to a carbohydrate ring, which is itself attached to a wedge-like nitrogen-containing group called a base. Bases come in four varieties, all of which are flat and nonpolar on top and bottom, but have specific patterns of polar nitrogen, oxygen and hydrogen atoms along their edges. These patterns allow bases to recognize ‘complementary’ bases, namely those which have the right pattern of polar groups to interact strongly, giving a base pair. Therefore, when deoxyribonucleic acids’ sugar-phosphate groups are linked together into long polynucleotide chains, the bases along the chain can generate another polynucleotide strand with a sequence of bases complementary to the first. Some base sequences in DNA encode instructions for making proteins. These, along with nearby base sequences that tell the cell’s machinery when to make those proteins, make up the units of heredity called genes. However, nucleic acids aren’t only used to store and transmit genetic information. The cell’s main energy currency, adenosine triphosphate (ATP), is a ribonucleotide in which the phosphate has been replaced by a chain of three linked phosphate groups.
3-SECOND NUCLEUS
Nucleic acids form chains of alternating phosphates and carbohydrates with attached wedge-like nitrogen-containing bases, the sequence of which encodes biological information.
3-MINUTE VALENCE
Life’s information-bearing molecule is deoxyribonucleic acid or DNA. DNA contains within it the chemical code for protein synthesis and is passed from parent to offspring, which is why you have characteristics similar to your parents. In 2003, scientists successfully mapped the entire human genome, a chemical code containing about 3 billion units (base pairs).
RELATED TOPICS
See also
THE FORCES THAT HOLD MATTER TOGETHER
3-SECOND BIOGRAPHIES
OSWALD AVERY
1877–1955
Canadian-born medical researcher who demonstrated that DNA is genetic material
JAMES WATSON & FRANCIS CRICK
1928– & 1916–2004
American and British molecular biologists who determined DNA’s double-helical structure
30-SECOND TEXT
Stephen Contakes
DNA has a double helical structure in which complementary bases connect along the middle.
BIOTECH DRUG SYNTHESIS
the 30-second chemistry
Before 1922, diabetes was fatal. Then a 14-year-old diabetes patient on the verge of death was given insulin (a protein that regulates blood sugar) derived from animal sources. The patient recovered – and survived. Soon insulin (harvested mostly from pigs) became available for widespread use, changing diabetes into a manageable long-term disease. However, some patients did not tolerate pig insulin very well. In the 1980s a company called Genentech figured out a way to synthesize human insulin by inserting the gene for human insulin into the DNA of bacterial cells. When the bacteria reproduced, they copied the human insulin gene and passed it on to their offspring. Furthermore, as the genetically modified bacteria synthesized the proteins they needed to survive and reproduce, they also synthesized human insulin. The insulin was harvested from the bacterial cultures, purified and administered to diabetics. Today diabetics take human insulin, synthesized in this way. The DNA instructions for making desired proteins can also be inserted into the DNA of plants or animals. For example, in 2015 the FDA approved a drug to treat Wolman disease, a rare but fatal disease caused by a deficiency of an enzyme called LAL. The drug is harvested from the eggs of chickens that have been genetically modified to produce LAL.
3-SECOND NUCLEUS
Human proteins can be synthesized by inserting the human gene for the desired protein into bacterial, plant or animal cells. As these cells grow and divide, they synthesize the desired protein.
3-MINUTE VALENCE
Genetic engineering – the process of modifying an organism’s genome for a particular purpose – has been used, not only to produce life-saving medicines but also to produce animals or plants with desirable characteristics. Genetic modification of soybeans, tomatoes and rice has resulted in crops with more resilience and higher nutritional value. In spite of rigorous scientific testing, the controversy surrounding some of these products has resulted in increased scrutiny of their safety.
RELATED TOPICS
See also
THE BIOLOGICAL BLUEPRINT: NUCLEIC ACIDS
3-SECOND BIOGRAPHIES
FREDERICK BANTING
1891–1941
Canadian physician who was awarded the 1923 Nobel Prize in Medicine for his discovery of insulin
FREDERICK SANGER
1918–2013
British biochemist who was awarded the Nobel Prize in Chemistry in 1958 for his determination of the structure of insulin
PAUL BERG
1926–
American biochemist awarded the 1980 Nobel Prize in Chemistry for his work on recombinant DNA technology
30-SECOND TEXT
Nivaldo Tro
Human insulin is synthesized by the genetic modification of bacteria.
