MOLECULAR BIOLOGY EXAM: LATEST A+ QUESTIONS
AND ANSWERS BREAKDOWN
Four principle groups of organic compounds that contribute to much of the structure and
function of a cell.
Carbohydrates, lipids, nucleic acids and proteins
Carbohydrate primary function
source of energy (short term) and recognition molecule (glycoproteins) and as a structural
component (part of DNA/RNA)
Lipids what are they + primary function
Non-polar, hydrophobic molecules which may come in a variety of forms (simple, complex or
derived)
Functions: major component of cell membranes (phospholipids and cholesterol), long term
energy storage molecule (fats and oils), function as a signalling molecule (steriods)
Nucleic acids - what are they + main functions
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
Protein functions GENERAL
- Make over 50% of the dry weight of cells; are composed of C, H, O and N atoms (some may
include S) CHO + N
- 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)
- Amino acids
Metabolism describes
the totality of chemical processes that occur within a living organism in order to maintain life
Metabolic reactions two key functions
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
,Anabolism describes
the set of metabolic reactions that build up complex molecules from simpler ones
Anabolism condensation or hydrolysis
condensation
Condensation reactions
occur when monomers are covalently joined and water is produced as a by-product
Example: gluconeogenesis
(metabolic pathway that results in the generation of glucose from certain non-carbohydrate
carbon substrates)
- Monosaccharides --> disaccharides and polysaccharides
- Amino acids --> polypeptide chains
- Glycerol and fatty acids --> triglycerides
- Nucleotides --> polynucleotide chains
Monosaccharides are joined via... to form disaccharides and polysaccharides
Monosaccharides are joined via glycosidic linkages to form disaccharides and polysaccharides
Amino acids are joined via... to make polypeptide chains
Amino acids are joined via peptide bonds to make polypeptide chains
Glycerol and fatty acids are joined via an.... to create triglycerides
Glycerol and fatty acids are joined via an ester linkage to create triglycerides
Nucleotides are joined by ... to form polynucleotide chains
Nucleotides are joined by phosphodiester bonds to form polynucleotide chains
Catabolic reaction
Catabolic reactions describe the set of metabolic reactions that break complex molecules down
into simpler molecules
Hydrolysis reactions require the consumption of water molecules to break the bonds within the
polymer. H20 —> H + OH. The H fills the 'empty spot on the C atom of one of the small
molecules and the OH does the same on the other small molecule)
example --> glycolysis
(the metabolic pathway that converts glucose into pyruvate.)
, maltose --> 2 glucose
polypeptide --> amino acid
triglyceride --> glycerol and 3 fatty acids
Catabolism condensation or hydrolysis
hydrolysis
Vitalism
a doctrine that dictated that organic molecules could only be synthesised by living systems
How was vitalism disproven
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
Glucose diagram
Ribose diagram
Saturated fatty acid
Generalised amino acid
Formation of a dipeptide
Water type of bond
covalent
Water polar explanation
While this covalent bonding involves the sharing of electrons, they are not shared equally
between the atoms
- Oxygen (due to having a higher electronegativity) attracts the electrons more strongly
- The shared electrons orbit closer to the oxygen atom than the hydrogen atoms resulting
in polarity
Oxygen is... charged, hydrogen is... charged
AND ANSWERS BREAKDOWN
Four principle groups of organic compounds that contribute to much of the structure and
function of a cell.
Carbohydrates, lipids, nucleic acids and proteins
Carbohydrate primary function
source of energy (short term) and recognition molecule (glycoproteins) and as a structural
component (part of DNA/RNA)
Lipids what are they + primary function
Non-polar, hydrophobic molecules which may come in a variety of forms (simple, complex or
derived)
Functions: major component of cell membranes (phospholipids and cholesterol), long term
energy storage molecule (fats and oils), function as a signalling molecule (steriods)
Nucleic acids - what are they + main functions
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
Protein functions GENERAL
- Make over 50% of the dry weight of cells; are composed of C, H, O and N atoms (some may
include S) CHO + N
- 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)
- Amino acids
Metabolism describes
the totality of chemical processes that occur within a living organism in order to maintain life
Metabolic reactions two key functions
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
,Anabolism describes
the set of metabolic reactions that build up complex molecules from simpler ones
Anabolism condensation or hydrolysis
condensation
Condensation reactions
occur when monomers are covalently joined and water is produced as a by-product
Example: gluconeogenesis
(metabolic pathway that results in the generation of glucose from certain non-carbohydrate
carbon substrates)
- Monosaccharides --> disaccharides and polysaccharides
- Amino acids --> polypeptide chains
- Glycerol and fatty acids --> triglycerides
- Nucleotides --> polynucleotide chains
Monosaccharides are joined via... to form disaccharides and polysaccharides
Monosaccharides are joined via glycosidic linkages to form disaccharides and polysaccharides
Amino acids are joined via... to make polypeptide chains
Amino acids are joined via peptide bonds to make polypeptide chains
Glycerol and fatty acids are joined via an.... to create triglycerides
Glycerol and fatty acids are joined via an ester linkage to create triglycerides
Nucleotides are joined by ... to form polynucleotide chains
Nucleotides are joined by phosphodiester bonds to form polynucleotide chains
Catabolic reaction
Catabolic reactions describe the set of metabolic reactions that break complex molecules down
into simpler molecules
Hydrolysis reactions require the consumption of water molecules to break the bonds within the
polymer. H20 —> H + OH. The H fills the 'empty spot on the C atom of one of the small
molecules and the OH does the same on the other small molecule)
example --> glycolysis
(the metabolic pathway that converts glucose into pyruvate.)
, maltose --> 2 glucose
polypeptide --> amino acid
triglyceride --> glycerol and 3 fatty acids
Catabolism condensation or hydrolysis
hydrolysis
Vitalism
a doctrine that dictated that organic molecules could only be synthesised by living systems
How was vitalism disproven
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
Glucose diagram
Ribose diagram
Saturated fatty acid
Generalised amino acid
Formation of a dipeptide
Water type of bond
covalent
Water polar explanation
While this covalent bonding involves the sharing of electrons, they are not shared equally
between the atoms
- Oxygen (due to having a higher electronegativity) attracts the electrons more strongly
- The shared electrons orbit closer to the oxygen atom than the hydrogen atoms resulting
in polarity
Oxygen is... charged, hydrogen is... charged
