2.1

Question 1

Molecular biology

Answer 1

Molecular biology is a field of study that focuses on investigating biological activity at a molecular level

Question 2

Molecular Biology includes…

Answer 2

elucidating the structure and function of chemical substances and determining their interactions as parts of living processes

Question 3

Biological processes are regulated by

Answer 3

by enzymes, whose expression is controlled by gene activation (DNA)

Question 4

changes in activity

Answer 4

Changes in activity are typically determined by signalling molecules (either endogenous or exogenous in origin)

Question 5

organic compounds

Answer 5

An organic compound is a compound that contains carbon and is found in living things

Question 6

organic compound exceptions

Answer 6

Exceptions include carbides (e.g. CaC2), carbonates (CO32–), oxides of carbon (CO, CO2) and cyanides (CN–)

Question 7

carbon

Answer 7

• Carbon forms the basis of organic life due to its ability to form large and complex molecules via covalent bonding
• Carbon atoms can form four covalent bonds, with bonds between carbon atoms being particularly stable (catenation)

Question 8

Main Classes of Carbon Compounds

Answer 8

carbohydrates, lipids, nucleic acids, proteins

Question 9

Carbohydrates

Answer 9

• Most abundant organic compound found in nature, composed primarily of C,H and O atoms in a common ratio – (CH2O)n
• Principally function as a source of energy (and as a short-term energy storage option)
• Also important as a recognition molecule (e.g. glycoproteins) and as a structural component (part of DNA / RNA)

Question 10

Lipids

Answer 10

• Non-polar, hydrophobic molecules which may come in a variety of forms (simple, complex or derived)
• Lipids serve as a major component of cell membranes (phospholipids and cholesterol)
• They may be utilised as a long-term energy storage molecule (fats and oils)
• Also may function as a signalling molecule (steroids)

Question 11

Nucleic Acids

Answer 11

• Genetic material of all cells and determines the inherited features of an organism
• DNA functions as a master code for protein assembly, while RNA plays an active role in the manufacturing of proteins

Question 12

Proteins

Answer 12

• Make over 50% of the dry weight of cells; are composed of C, H, O and N atoms (some may include S)
• Major regulatory molecules involved in catalysis (all enzymes are proteins)
• May also function as structural molecules or play a role in cellular signalling (transduction pathways)

Question 13

macromolecules may commonly be comprised of…

Answer 13

smaller, recurring subunits called monomers

Question 14

what contains monomers?

Answer 14

Carbohydrates, nucleic acids and proteins are all comprised of monomeric subunits that join together to form larger polymers

Question 15

what doesn’t contain monomers?

Answer 15

Lipids do not contain recurring monomers, however certain types may be composed of distinct subunits (e.g. triglycerides)

Question 16

carbohydrate structure

Answer 16

Carbohydrates are composed of monomers called monosaccharides (‘single sugar unit’)

• Monosaccharides are the building blocks of disaccharides (two sugar units) and polysaccharides (many sugar units)
• Most monosaccharides form ring structures and can exist in different 3D configurations (stereoisomers)
• structure of complex carbohydrates may vary depending on the composition of monomeric subunits

Question 17

lipid structure

Answer 17

Lipids exist as many different classes that vary in structure and hence do not contain a common recurring monomer

• However several types of lipids (triglycerides, phospholipids, waxes) contain fatty acid chains as part of their overall structure
• Fatty acids are long chains of hydrocarbons that may or may not contain double bonds (unsaturated vs saturated)

Question 18

protein structure

Answer 18

Proteins are composed of monomers called amino acids, which join together to form polypeptide chains

• Each amino acid consists of a central carbon connected to an amine group (NH2) and an opposing carboxyl group (COOH)
• A variable group (denoted ‘R’) gives different amino acids different properties (e.g. may be polar or non-polar, etc.)

Question 19

nucleic acid structure

Answer 19

Nucleic acids are composed of monomers called nucleotides, which join together to form polynucleotide chains

• Each nucleotide consists of 3 components – a pentose sugar, a phosphate group and a nitrogenous base
• The type of sugar and composition of bases differs between DNA and RNA

Question 20

Glucose monomer combinations

Answer 20

Glucose monomers can be combined to form a variety of different polymers – including glycogen, cellulose and starch

Question 21

lipid classes

Answer 21

Lipids can be roughly organised into one of three main classes:

• Simple (neutral) lipids – Esters of fatty acids and alcohol (e.g. triglycerides and waxes)
• Compound lipids – Esters of fatty acids, alcohol and additional groups (e.g. phospholipids and glycolipids)
• Derived lipids – Substances derived from simple or compound lipids (e.g. steroids and carotenoids)

Question 22

how do amino acids join?

Answer 22

Amino acids join together by peptide bonds which form between the amine and carboxyl groups of adjacent amino acids

• The fusion of two amino acids creates a dipeptide, with further additions resulting in the formation of a polypeptide chain
• The subsequent folding of the chain depends on the order of amino acids in a sequence (based on chemical properties)

Question 23

how do nucleotides form?

Answer 23

Nucleotides form bonds between the pentose sugar and phosphate group to form long polynucleotide chains

• In DNA, two complementary chains will pair up via hydrogen bonding between nitrogenous bases to form double strands
• This double stranded molecule may then twist to form a double helical arrangement

Question 24

vitalism

Answer 24

Vitalism was a doctrine that dictated that organic molecules could only be synthesised by living systems

• It was believed that living things possessed a certain “vital force” needed to make organic molecules
• Hence organic compounds were thought to possess a non-physical element lacking from inorganic molecules

Question 25

how was vitalism disproven

Answer 25

Vitalism as a theory has since been disproven with the discovery that organic molecules can be artificially synthesised

• In 1828, Frederick Woehler heated an inorganic salt (ammonium cyanate) and produced urea
• Urea is a waste product of nitrogen metabolism and is eliminated by the kidneys in mammals
• The artificial synthesis of urea demonstrates that organic molecules are not fundamentally different to inorganic molecules

Question 26

metabolism

Answer 26

Metabolism describes the totality of chemical processes that occur within a living organism in order to maintain life
- It is the web of all enzyme-catalysed reactions that occur within a cell or organism

Question 27

metabolism key functions

Answer 27

• They provide a source of energy for cellular processes (growth, reproduction, etc.)
• They enable the synthesis and assimilation of new materials for use within the cell

Question 28

anabolism

Answer 28

building up

Question 29

Anabolic reactions describe…

Answer 29

the set of metabolic reactions that build up complex molecules from simpler ones

Question 30

anabolic reactions occur

Answer 30

via condensation reactions

- Condensation reactions occur when monomers are covalently joined and water is produced as a by-product

Question 31

catabolism

Answer 31

breaking down

Question 32

Catabolic reactions describe…

Answer 32

the set of metabolic reactions that break complex molecules down into simpler molecules

Question 33

catabolic reactions occur

Answer 33

via hydrolysis reactions

- Hydrolysis reactions require the consumption of water molecules to break the bonds within the polymer