MOLECULAR BIOLOGY EXAM: LATEST A+ QUESTIONS
AND ANSWERS BREAKDOWN
Most frequently occurring chemical elements in living things
Carbon, hydrogen, oxygen, nitrogen
Carbon atoms
Ability to form long chains of carbon - carbon-carbon bonds are extremely strong
The simplest form of an organic molecule is the hydrocarbon—a large family of organic
molecules that are composed of hydrogen atoms bonded to a chain of carbon atoms.
Covalent Bonds
Chemical bonds formed by the sharing of a pair of electrons between atoms. The nuclei of two
different atoms are attracting the same electrons.
Carbon can form single, double and triple bonds
Carbohydrates
Carbohydrates are composed of carbon, hydrogen and oxygen
The general formula for carbohydrates is (CH2O)n.
All carbohydrate contain C, H and O
Many carbohydrates are used for energy or structural purposes
Lipids
Lipids are compounds that are insoluble in water but soluble in non-polar solvents.
Lipids contain C, H and O, but much less O than carbohydrates.
Some lipids function in long-term energy storage. Animal fat is a lipid that has six times more
energy per gram than carbohydrates.
Lipids are also an important component of cell membranes.
Examples of lipids are triglycerides, steroids, waxes and phospholipids
Animal fats (saturated) are solid at room temperature and plant fats (unsaturated) are liquid at
room temperature
Proteins
Proteins are composed of one or more chains of amino acids
All proteins are composed of carbon, hydrogen, oxygen and nitrogen. Some proteins also
contain S in their R-groups
Proteins are distinguished by their "R" groups. Some of these also contain sulphur
Nucleic Acids
,Nucleic acids are composed of smaller units called nucleotides, which are linked together to
form a larger molecule (nucleic acid).
Each nucleotide contains a base, a sugar, and a phosphate group. The sugar is deoxyribose
(DNA) or ribose (RNA). The bases of DNA are adenine, guanine, cytosine, and thymine. Uracil
substitutes for Thymine in RNA
They are made from carbon, hydrogen, oxygen, nitrogen and phosphorus
Amino Acid
Composed of an amine (NH2) group, a carboxyl (COOH) group, and an R group.
20 amino acids exist that compose all proteins
Each amino acid differs because the R groups are different
Glucose
Is a reducing sugar that contains C6 H12 O6
Most commonly found in a ringed structure and is the main product formed by photosynthesis
Energy molecule used in aerobic respiration
Monomer of starch, glycogen, and cellulose
Ribose
Pentose (5 carbon) sugar of RNA
C5 H10 O5
Differs from Deoxyribose (sugar in DNA) because it has an extra -OH group on the 2nd carbon of
the ring
Fatty Acids
Main component of triglycerides and phospholipids
Fatty acids are non-polar and therefore hydrophobic
Chains consist of covalently bonded carbon with hydrogen
Saturated Fatty Acid
Saturated - are all single bonds and are therefore saturated with hydrogen.
Unsaturated Fatty Acid
Unsaturated - contain a double bond or double bonds.
Metabolism
Metabolism is the set of life-sustaining chemical reactions within the cells of living organisms.
These reactions are catalyzed by enzymes and allow organisms to grow and reproduce,
maintain their structures, and respond to their environments.
, Many of these reactions occur in the cytoplasm, but some are extracellular including digestion
and the transport of substances into and between different cells
Anabolism and catabolism
Metabolism is divided into two components; anabolism (building large molecules from smaller
ones) and catabolism (breaking down of large molecules into their component parts)
Anabolic reactions require energy as you are building large molecules from small ones (takes
energy to build things)
Some anabolic processes are: condensation, protein synthesis, photosynthesis
Catabolism are reactions that break down larger molecules into smaller ones or their
component parts
Catabolic reactions release energy (sometimes captured in the form of ATP)
Some examples of catabolic reactions are: hydrolysis, cellular respiration, and break down of
carbon compounds by decomposers
Other elements are needed by living organisms and their functions
Sulphur (Found in certain amino acids)
Calcium (Found in bones and teeth)
Phosphorus (Component of nucleic acids)
Iron (Found in haemoglobin - oxygen transport)
Sodium (generation of nerve impulses in neurons)
Structure of a Water Molecule
Water (H2O) is made up of two hydrogen atoms covalently bound to an oxygen atom
The oxygen atom are slightly negative and the hydrogen atoms are slightly positive
Water is also bent so the positive charge exists more or less on one side and the negative
charge from the O exists on the opposite side
Hydrogen Bonding between Water Molecules
Covalently bonded molecules that have a slight potential charge are said to be polar
The slightly charged regions of the water molecule can attract other polar or charged
compounds
Water molecules can associate via weak hydrogen bonds (F/O/N bonding with H)
Thermal properties of water
Water has a high specific heat capacity (amount of energy needed to raise temperature of a
substance by a certain temperature level) - water can absorb a lot of heat and give off a lot of
heat without drastically changing the temperature of water.
Water's high specific heat capacity results from the extensive hydrogen bonding between the
water molecules.
Water also has a high heat of vaporization which means it takes a lot of heat to evaporate
AND ANSWERS BREAKDOWN
Most frequently occurring chemical elements in living things
Carbon, hydrogen, oxygen, nitrogen
Carbon atoms
Ability to form long chains of carbon - carbon-carbon bonds are extremely strong
The simplest form of an organic molecule is the hydrocarbon—a large family of organic
molecules that are composed of hydrogen atoms bonded to a chain of carbon atoms.
Covalent Bonds
Chemical bonds formed by the sharing of a pair of electrons between atoms. The nuclei of two
different atoms are attracting the same electrons.
Carbon can form single, double and triple bonds
Carbohydrates
Carbohydrates are composed of carbon, hydrogen and oxygen
The general formula for carbohydrates is (CH2O)n.
All carbohydrate contain C, H and O
Many carbohydrates are used for energy or structural purposes
Lipids
Lipids are compounds that are insoluble in water but soluble in non-polar solvents.
Lipids contain C, H and O, but much less O than carbohydrates.
Some lipids function in long-term energy storage. Animal fat is a lipid that has six times more
energy per gram than carbohydrates.
Lipids are also an important component of cell membranes.
Examples of lipids are triglycerides, steroids, waxes and phospholipids
Animal fats (saturated) are solid at room temperature and plant fats (unsaturated) are liquid at
room temperature
Proteins
Proteins are composed of one or more chains of amino acids
All proteins are composed of carbon, hydrogen, oxygen and nitrogen. Some proteins also
contain S in their R-groups
Proteins are distinguished by their "R" groups. Some of these also contain sulphur
Nucleic Acids
,Nucleic acids are composed of smaller units called nucleotides, which are linked together to
form a larger molecule (nucleic acid).
Each nucleotide contains a base, a sugar, and a phosphate group. The sugar is deoxyribose
(DNA) or ribose (RNA). The bases of DNA are adenine, guanine, cytosine, and thymine. Uracil
substitutes for Thymine in RNA
They are made from carbon, hydrogen, oxygen, nitrogen and phosphorus
Amino Acid
Composed of an amine (NH2) group, a carboxyl (COOH) group, and an R group.
20 amino acids exist that compose all proteins
Each amino acid differs because the R groups are different
Glucose
Is a reducing sugar that contains C6 H12 O6
Most commonly found in a ringed structure and is the main product formed by photosynthesis
Energy molecule used in aerobic respiration
Monomer of starch, glycogen, and cellulose
Ribose
Pentose (5 carbon) sugar of RNA
C5 H10 O5
Differs from Deoxyribose (sugar in DNA) because it has an extra -OH group on the 2nd carbon of
the ring
Fatty Acids
Main component of triglycerides and phospholipids
Fatty acids are non-polar and therefore hydrophobic
Chains consist of covalently bonded carbon with hydrogen
Saturated Fatty Acid
Saturated - are all single bonds and are therefore saturated with hydrogen.
Unsaturated Fatty Acid
Unsaturated - contain a double bond or double bonds.
Metabolism
Metabolism is the set of life-sustaining chemical reactions within the cells of living organisms.
These reactions are catalyzed by enzymes and allow organisms to grow and reproduce,
maintain their structures, and respond to their environments.
, Many of these reactions occur in the cytoplasm, but some are extracellular including digestion
and the transport of substances into and between different cells
Anabolism and catabolism
Metabolism is divided into two components; anabolism (building large molecules from smaller
ones) and catabolism (breaking down of large molecules into their component parts)
Anabolic reactions require energy as you are building large molecules from small ones (takes
energy to build things)
Some anabolic processes are: condensation, protein synthesis, photosynthesis
Catabolism are reactions that break down larger molecules into smaller ones or their
component parts
Catabolic reactions release energy (sometimes captured in the form of ATP)
Some examples of catabolic reactions are: hydrolysis, cellular respiration, and break down of
carbon compounds by decomposers
Other elements are needed by living organisms and their functions
Sulphur (Found in certain amino acids)
Calcium (Found in bones and teeth)
Phosphorus (Component of nucleic acids)
Iron (Found in haemoglobin - oxygen transport)
Sodium (generation of nerve impulses in neurons)
Structure of a Water Molecule
Water (H2O) is made up of two hydrogen atoms covalently bound to an oxygen atom
The oxygen atom are slightly negative and the hydrogen atoms are slightly positive
Water is also bent so the positive charge exists more or less on one side and the negative
charge from the O exists on the opposite side
Hydrogen Bonding between Water Molecules
Covalently bonded molecules that have a slight potential charge are said to be polar
The slightly charged regions of the water molecule can attract other polar or charged
compounds
Water molecules can associate via weak hydrogen bonds (F/O/N bonding with H)
Thermal properties of water
Water has a high specific heat capacity (amount of energy needed to raise temperature of a
substance by a certain temperature level) - water can absorb a lot of heat and give off a lot of
heat without drastically changing the temperature of water.
Water's high specific heat capacity results from the extensive hydrogen bonding between the
water molecules.
Water also has a high heat of vaporization which means it takes a lot of heat to evaporate
