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ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
1. What are the three most commonly occurring elements?
carbon (C), Hydrogen (H) and Oxygen (O)
[the fourth is nitrogen (N)]
2. State one function of each of these elements:
a. Iron
function: Used in all organisms in enzymes in aerobic respiration
b. Sulphur
function: A part of two amino acids, essential in most proteins.
c. Calcium
function: Important messenger in cells including transcription of
DNA. Also in nerve impulses, muscle contraction and bone
formation in animals.
d. Phosphorous
function: Part of the phosphate group in ATP and DNA molecules.
e. Sodium
function: important in osmotic regulation of cells. Also important
for nerve impulses and muscle contractions in animals.
3. Define organic molecule.
Organic molecule is a molecule containing carbon and is found in living organisms.
4. What are three carbon-containing groups or molecules that are not organic?
Hydrogen carbonates, carbonates and oxides of carbons are considered to be inorganic.
5. In the space below, draw three water molecules attracted to one another by hydrogen
bonding. Include labels to show the polarity of the molecules.
Hydrogen bond between the slightly negative
oxygen atom in one water molecule and slightly
positive Hydrogen atom in another water molecule
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
http://sciencevideos.wordpress.com
ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
6. Water has many properties which are essential for life. Complete the table below.
Explanation
Significance to living things
Water is slow to gain and lose heat.
Organisms can keep the temperature
even if the environment increase or
decrease the temperature temporarily.
This is especially true for organisms
living in or close to water habitat.
The denser water at 4oC allows animals
to survive at the bottom of lakes during
the winter. The ice floats and insulates
the water below.
Mammals sweat, and plants in deserts
increase their transpiration, for
thermoregulation and preventing overheating.
Habitat for Insects like the Pond Skaters
(Skräddare). They can walk on the
surface film and feed on small organisms
trapped by surface tension of film.
Female mosquitoes land on water
surface and lay egg raft which floats.
Watery habitat dissolves ions that can
be absorbed by organisms.
Soluble excretory products can be
removed, for example urea). Soluble
substances can be transported within
the cytoplasm and in circulatory
systems.
Thermal Properties
Water freezes at 0oC and is most
dense at 4oC. Ice is less dense than
water.
Water requires a lot of energy to
evaporate (to break the bonds
between the molecules).
Cohesion
Solvent Properties
Hydrogen bonds link water molecules
together.
This creates a “skin” on the surface of
water, surface tension.
Many substances can form hydrogen
bonds with water and therefore
dissolve. Examples are sugars.
Ionic compounds may form ions in
water and dissolve. Example is sodium
chloride (NaCl) which forms sodium
ions Na+ and chloride ions Cl-.
(include uses as a coolant, medium for metabolic reactions, transport medium)
7. In the space below, draw the structure of a general amino acid. Include (and label) the
amino, carboxyl and ‘R’ groups.
amino group
carboxyl group
R group
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
http://sciencevideos.wordpress.com
ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
8. In the space below, draw the generalized structures of fatty acids and glycerol.
9. Draw the structures of glucose and ribose.
ribose
glucose
10. Complete the table below:
-saccharides
examples
Plant or animal?
Both
Glucose
Plant
Mono-
Di-
Poly-
Function/ uses
Broken down in cell respiration to
release energy
Part of sucrose that transport the
products from photosynthesis to
storing organs of plants.
Galactose
Animal
Fructose
Plant
Lactose
Animal
Sucrose
plant
The transport form of the products
from photosynthesis to storage
organs or where it will be used.
Maltose
animal
Dimer of glucose, broken down from starch.
Starch
plant
Glycogen
animal
Cellulose
plant
Insoluble storage of glucose
Insoluble storage of glucose
energy storage in liver an muscles
Insoluble compound - Main
component of cell wall
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
‘brain sugar’ – less sweet/ less soluble
Fruit sugar is used to make fruits
sweet-tasting, attracting animals
to disperse seeds n the fruit
Milk sugar that provides energy to
young mammals
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ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
11. Using labeled diagrams, describe how a monosaccharide (glucose) is converted to a
disaccharide (maltose). What is the name of this process?
Condensation reaction or dehydration reaction
glucose
glucose
12. What is the name of the process through which polypeptides, polysaccharides or
triglycerides are catabolised (broken down)?
Hydrolysis reactions
13. On a separate sheet of paper, outline condensation and hydrolysis in proteins, saccharides
and triglycerides. Label the reactions and bonds formed/ broken clearly.
2 amino acids
Proteins
Hydrolysis reaction
reaction
Condensation reaction
H2O
H2O
1 Dipeptide
Peptide linkage
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
http://sciencevideos.wordpress.com
ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
saccharides
2 monosaccharides
condensation reaction
1 disaccharide
glycosidic bond
triglycerides
Hydrolysis reactions
reactions
3 H2O
3 Ester bondings
Condensation
reactions
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
http://sciencevideos.wordpress.com
ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
Link
Extra Figure
Condensation
reactions
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
http://sciencevideos.wordpress.com
ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
14. Triglycerides can have saturated or unsaturated fatty acids attached.
Differentiate between saturated and unsaturated fats in terms of:
a. Bonds in the fatty acid chain
Saturated triglycerides only have single bonds in their fatty acids. Unsaturated
triglycerides have double bonds in their fatty acids.
b. Melting point/ state at room temperature
Saturated triglycrides are solid at room temperature.
Unsaturated triglycerides are liquid at room temperature.
c. Origin (plants or animals)
Saturated triglycerides are more common in animals, especially warm blooded
(homoithermic) animals. Unsaturated triglycerides are more common in plants and in
cold blooded (piokilothermic) animals.
15. State three functions of lipids:
1. Energy storage – fat in animals and oils in plants
2. Heat insulation – a layer of fat under the skin reduces heat loss
3. Boyancy – lipids are less dense than water so help animals to float
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
http://sciencevideos.wordpress.com
ESSENTIAL BIOLOGY 03: THE CHEMISTRY OF LIFE
16. Compare lipids and carbohydrates in terms of energy storage:
carbohydrates
lipids
Starch in plants and glycogen
in animals
Triglycerides or fat in animals and
oils in plants
Short time storage
Long time storage
Stored as…?
Long/short term storage?
Ease of digestion/ release
of energy?
Easily broken down to release More complex and so slower to
energy quickly.
brake down.
Energy per gram?
17 kJ per gram
38 kJ per gram
Solubility in water?
(and consequence)
Soluble in warm water and
insoluble in cold water
Insoluble in water
Use of oxygen in
metabolism?
(and consequence)
May be used for anaerobic
Only for aerobic respiration
respiration temporarily in
muscle cells. In this case lactic
acid will be produced.
Essential Biology Revision Series
(Chem of Life, inc. AHL and Option C)
Steve Taylor
Bandung International School
http://sciencevideos.wordpress.com