Topic 15: Carbohydrates and Related Substances
Introduction
The study of photosynthesis and respiration is fundamental to any appreciation of the relationship
of Chemistry to life, in particular, the role of both processes in maintaining the balance of gases
in the atmosphere, and the importance of photosynthesis in food production.
This topic introduces (or revises) these processes and extends chemical knowledge and
understanding of the synthesis and breakdown of carbohydrates. The production of alcohol by
fermentation is studied.
At General Level, the Learning Outcomes are based on:
 ability to apply the terms photosynthesis and respiration and explain their role in carbon
dioxide/oxygen balance
 knowledge of distinguishing tests for glucose and starch
 awareness that starch is a polymer and of its breakdown into smaller molecules (glucose)
 knowledge of the role of enzymes as biological catalysts
 knowledge that ethanol is produced by fermentation.
At Credit Level, in addition, the Learning Outcomes require an understanding of hydrolysis (of
starch); knowledge of the existence of simple carbohydrates other than glucose; the idea of
functional group in alkanols and the ability to write formulae for monosaccharides and
disaccharides (molecular only).
Topic 15: Carbohydrates and Related Substances
Learning Outcomes
GENERAL LEVEL (Grades 4, 3)
CREDIT LEVEL (Grades 2, 1)
Pupils should be able to:
and in addition to:
1 State that photosynthesis is the process by
which plants make carbohydrates from
carbon dioxide and water, using light
energy in the presence of chlorophyll;
oxygen is released in the process
2 State that the role of chlorophyll in
photosynthesis is to absorb light energy
3 State that the carbohydrates made in
plants during photosynthesis are an
important food for animals
4 State that respiration is the process by
which animals and plants obtain a supply
of energy by breaking down
carbohydrates (using oxygen) to give
carbon dioxide and water
GENERAL LEVEL (Grades 4, 3)
CREDIT LEVEL (Grades 2, 1)
5 State that carbohydrates release energy,
producing carbon dioxide and water when
burned
Explain why the production of carbon
dioxide and water, on burning, indicates
the presence of carbon and hydrogen in
a carbohydrate
6 Give examples of how energy can be used
by animals
7 Explain the importance of respiration and
photosynthesis in maintaining the balance
of carbon dioxide and oxygen in the air
8 Explain why the extensive clearing of
forests could present dangers to life on
earth
9 Give examples of carbohydrates to include
glucose, sucrose and starch
Explain why glucose/fructose and
maltose/sucrose are pairs of isomers
10 State that carbohyradtes contain the
elements carbon, hydrogen and oxygen
11 State that glucose is sweet and dissolves
in water and that starch is not sweet and
does not dissolve well in water
12 Explain what is seen when a beam of light
is passed through:
 glucose solution
 starch in water
13 State that it is possible to distinguish
starch from other carbohydrates using
iodine solution
14 State that Benedict’s or Fehling’s Reagent
is used to test for glucose but not for
sucrose
15 State that glucose is a carbohydrate built
up in photosynthesis
16 State that starch is a polymer made in
plants from glucose monomer units
state that the glucose molecules join together
with loss of water
State that Benedict’s or Fehling’s
Reagent is used to test for glucose,
fructose, maltose and other sugars but
not for sucrose
GENERAL LEVEL (Grades 4, 3)
CREDIT LEVEL (Grades 2, 1)
17 Explain that the joining up of glucose
molecules to form starch is an example of
polymerisation
Explain that the joining up of glucose
molecules to form starch is an example
of condensation polymerisation
18 State that during digestion starch
molecules are broken down in the body
into small glucose molecules which can
pass through the gut wall
19 State that the breakdown of starch can be
carried out in the laboratory using acid or
amylase
State that starch molecules break down
by reacting with water molecules
20
State what is meant by hydrolysis
21
Explain that the breakdown of starch
and sucrose are examples of hydrolysis
22 State the enzymes, eg amylase, act as
biological catalysts in the breakdown of
complex food molecules into smaller ones
in the digestive system
polymer.
23
Write the molecular formulae for
monosaccharides and disaccharides
24 State that glucose is the carbohydrate
which reacts with oxygen during
respiration
25 State that alcoholic drinks can be made
from any fruit or vegetable which is a
source of starch or sugars
26 Give examples to show that the type of
alcoholic drink varies with the plant
source of the carbohydrate
27 State that an enzyme produced by yeast, a
living organism, acts as a catalyst for the
reaction
28 State that fermentation is the breakdown
of glucose to form alcohol and carbon
dioxide
29 REMOVED FROM COURSE
describe the effect of changes in pH
and temperature on the optimum
efficiency of an enzyme
GENERAL LEVEL (Grades 4, 3)
CREDIT LEVEL (Grades 2, 1)
30 state that distillation is a method of
increasing the alcohol concentration of
fermentation products
explain why there is a limit to the
alcohol concentration of fermentation
products.
31 explain why water and alcohol can be
separated by distillation
32 state that alcohol is a member of the
alkanol family and is called ethanol