Self-Test Questions (STQ) - Check your Progress
Unit 01 - The Biochemical Basis of Life
STQ 01.01 - a) What is the atomic number of carbon?
b) What is the mass number for chlorine?
ANS. 35 (17 + 18)
c) Is water an element or a compound?
ANS. - a compound of hydrogen and oxygen
d) Is oxygen an element or a compound?
ANS. an element
STQ 01.02 - a) What is an ion?
ANS. a charged atom or molecule
b) What is the difference between an anion and a cation?
ANS. an anion is negatively charged and a cation is positively charged
c) Give two key properties of ions
ANS. ions are charged and ions are stable
d) Has the magnesium ion (Mg2+) gained or lost two electrons?
ANS. it has lost two (negative) electrons
STQ 01.03 - a) What is the difference between ionic and covalent bonds?
ANS. an ionic bond is formed when oppositely charged ions are attracted. A covalent
bond is formed by atoms sharing electrons
b) Explain why water molecules have polarity
ANS. there is an imbalance of charge between the oxygen atom and the smaller hydrogen
atoms due to the distribution of electrons. The oxygen region is more negatively charged
than the hydrogen region.
c) How many oxygen atoms are there in 2HCO3-?
d) Balance this equation - H2 + O2 - H2O
ANS. 2H2 + O2 - 2H2O
STQ 01.04 - a) Is a solution of pH 5.0 more or less acidic than a solution of pH 6.0?
ANS. pH 5.0 is ten time more acidic than pH 6.0
b) Are there more or less hydrogen ions (H+) in a solution of pH 5.0
compared to a solution of pH 6.0?
ANS. more H+ in pH 5.0
c) Why might small changes in pH represent large changes in acidity?
ANS. the pH scale is a log scale so a small change in pH represents a large change in the
number of hydrogen ions
STQ 01.05 - a) What is the chemical difference between a monosaccharide, a
disaccharide and a polysaccharide?
ANS. a monosaccharide is a single sugar. A disaccharide is two monosaccharides and a
polysaccharide is a polymer (chain) of monosaccharides
b) Give an example of a monosaccharide, a disaccharide and a polysaccharide
ANS. monosaccharide - glucose, fructose and galactose
disaccharide - maltose, sucrose and lactose
polysaccharide - glycogen, starch and cellulose
c) Why does glycogen not increase the osmolarity of cells?
ANS. because it is insoluble
STQ 01.06 - a) Explain the chemical difference between a saturated and unsaturated fat.
ANS. a saturated fat has all its fatty acid carbon atoms bonded to the maximum number
of hydrogen atoms. An unsaturated fat has some double bonds between its fatty acid
carbons - and so less hydrogens
b) Give one source of saturated and unsaturated fat in the Western diet.
ANS. most animal fats are saturated and most plant oils are unsaturated
c) Why will lipids not dissolve in water?
ANS. because lipids are non-polar molecules and there is no ionic attraction between the
non-polar lipid and the polar water molecules. Lipids molecules have no tendency to
disperse in water
STQ 01.07 - a) Name a type of protein that protects us against pathogens.
ANS. antibodies (immunoglobulins)
b) Name a type of protein that allows distant parts of the body to communicate.
ANS. hormones (note that not all hormones are proteins)
c) Name two proteins that produce movement in muscles.
ANS. actin and myosin
d) What are the main components of proteins?
ANS. amino acids
STQ 01.08 - a) List the four stages in the structure of a protein
ANS. primary, secondary, tertiary and quaternary
b) What is a biochemical pathway?
ANS. the conversion of one substance into another in a series of steps, each catalysed by
c) What are the main fuels for energy production in cells?
ANS. lipids and glucose
d) What is the process called where these fuels are broken down to produce
ANS. cellular respiration
STQ 01.09 - a) Is ADP phosphorylated or dephosphorylated to form ATP?
b) What process in plants uses sunlight, CO2 and H2O to make glucose?
c) Energy cannot be destroyed so what happens to the waste energy released
when ATP takes part in a biochemical reaction?
ANS. waste energy is converted into heat which maintains our steady internal
d) What is the fate of atmospheric oxygen (O2) in the process of oxidative
ANS. atmospheric oxygen combines with hydrogen ions to form water
STQ 01.10 a) Which contains more stored energy - a gram of fat or a gram of
ANS. a gram of fat which contains 39 kj/g energy compared to 17kj/g
b) When amino acids are broken down for energy, what happens to the
nitrogen from the amine group?
ANS. transformed into urea
c) What substance produced in anaerobic respiration may cause angina pain?
ANS. lactic acid