AS- Biology Student
Guide
Topic 1 Biological MoleculesCarbohydrate and Lipids
Effective Learning 1-Excellent; 2-Good; 3-Needs to improve; 4-Cause for concern
Independent Learning
• Do you work outside of formal learning sessions?
• Are you able to demonstrate independent learning?
Questioning
• Do you interrogate material/resources
• Ask your LT / peers sensible, in depth questions
• Question sources of information
Planning
• Do you read additional material in preparation for the session
• Plan your work in advance
• Use assessment criteria to plan your tasks
Review/Amend
• Do you look back at notes/tasks and review them regularly
• Amend tasks having spoke/discussed with others or read more widely
• Amend/review after advice from LTs
Active listening
• Listen to understand
• Be proactive and contribute in sessions/activities
• Listen to other students in the group
Collaboration
• Work effectively with others in the group
• Take part in group work to ensure that everyone is involved
• Take a range of roles within group work to encourage effective collaboration
Biological molecules
All life on Earth shares a common chemistry. This provides indirect evidence for
evolution.
Despite their great variety, the cells of all living organisms contain only a few groups
of carbon-based compounds that interact in similar ways.
Carbohydrates are commonly used by cells as respiratory substrates. They also form
structural components in plasma membranes and cell walls.
Lipids have many uses, including the bilayer of plasma membranes, certain
hormones and as respiratory substrates.
SPECIFICATION
Assessable Learning Outcomes
3.1.1 Monomers and polymers
The variety of life, both past and present,
is extensive, but the
biochemical basis of life is similar for all
living things.
Monomers are the smaller units from
which larger molecules are
made.
Polymers are molecules made from a
large number of monomers
joined together.
Monosaccharides, amino acids and
nucleotides are examples of
monomers.
A condensation reaction joins two
molecules together with the
formation of a chemical bond and involves
the elimination of a
molecule of water.
A hydrolysis reaction breaks a chemical
bond between two molecules
and involves the use of a water molecule.
3.1.2 Carbohydrates
Monosaccharides are the monomers from
which larger carbohydrates are made.
Glucose, galactose and fructose are
common monosaccharides.
Covered
How did I review this
A condensation reaction between two
monosaccharides forms a
glycosidic bond.
Disaccharides are formed by the
condensation of two
monosaccharides:
•• maltose is a disaccharide formed by
condensation of two glucose molecules
•• sucrose is a disaccharide formed by
condensation of a glucose molecule and a
fructose molecule
•• lactose is a disaccharide formed by
condensation of a glucose
molecule and a galactose molecule.
Glucose has two isomers, α-glucose and
β-glucose, with structures:
Polysaccharides are formed by the
condensation of many glucose units.
•• Glycogen and starch are formed by the
condensation of α-glucose.
•• Cellulose is formed by the condensation
of β-glucose.
The basic structure and functions of
glycogen, starch and cellulose.
The relationship of structure to function of
these substances in animal
cells and plant cells.
Biochemical tests using Benedict's
solution for reducing sugars and
non-reducing sugars and
iodine/potassium iodide for starch.
3.1.3 Lipids
Triglycerides and phospholipids are two
groups of lipid.
Triglycerides are formed by the
condensation of one molecule of
glycerol and three molecules of fatty acid.
A condensation reaction between glycerol
and a fatty acid (RCOOH)
forms an ester bond.
The R-group of a fatty acid may be
saturated or unsaturated.
In phospholipids, one of the fatty acids of
a triglyceride is substituted
by a phosphate-containing group.
The different properties of triglycerides
and phospholipids related to
their different structures.
The emulsion test for lipids.
Students should be able to:
•• recognise, from diagrams, saturated
and unsaturated fatty acids
•• explain the different properties of
triglycerides and phospholipids.
KEY WORDS
keyword
Monomer
Polymer
Monosaccharide
Disaccharide
Condensation
Reaction
Hydrolysis Reaction
Alpha Glucose
Beta Glucose
Glycosidic bond
(1,4 and 1,6)
Starch
Cellulose
Hydrogen Bond
Glycogen
Amylose
Amylopectin
Triglycerides
Fatty Acid
Glycerol (glyceride)
Hydrophilic
definition
Hydrophobic
Phospholipid
Polar
Saturated
Mono- and PolyUnsaturated
Describe Benedicts
test
Describe test for Lipids
Define Osmosis using
the term water
potential
Resources and suggested Reading: find this document on the MLE to be able
to click the links.
Copies of Biological Science review can be found in the library : see the MLE for
the index of past articles
http://www.biologymad.com/
http://www.mrothery.co.uk/ecology/Mod5Notestrimmed.htm
http://www.freeeschool.blogspot.co.uk/
The awesome Bozeman Biology YouTube site: search for Carbohydrates and
Lipids
Practice Questions
Answer these practice questions and self assess them against the markschemes
published on www.drharrisbiology.com
Q1.
Cellulose is made from one type of monomer. The monomers are held
together by bonds. The diagram shows parts of three cellulose molecules in a cell wall.
(a)
Name the monomer present in cellulose.
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(1)
(b)
Name the type of reaction that converts cellulose to its monomers.
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(1)
(c)
Cotton is a plant fibre used to make cloth. Explain how cellulose gives
cotton its strength.
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(3)
(Total 5 marks)
Q2.
The diagram shows a cell from a potato.
(a)
Give two features which may be found in a prokaryotic cell which would
not be found in this cell.
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2 ...................................................................................................................
(2)
(b)
(i)
Describe how you could confirm that the granules contained starch.
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(1)
(ii)
Name one polysaccharide other than starch that would be found in
this cell.
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(1)
(c)
Explain one advantage of storing starch rather than glucose in potato cells.
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(2)
(Total 6 marks)
Q3.The glycaemic index (GI) is a measure of the increase in blood glucose concentration
after eating a given mass of a food compared with eating the same mass of pure glucose.
The GI of pure glucose has a value of 100.The GI of a food depends on several factors such
as how much starch and sugars it contains. High GI foods include those containing lots of
simple sugars or white flour. The carbohydrates in these foods are rapidly digested and
absorbed. Low GI foods include wholegrain bread and breakfast cereals that contain a lot of
fibre. The carbohydrates in these foods are digested and absorbed more slowly.
The following figure shows changes in blood glucose concentration after eating
meals of high GI food and meals of low GI food.
(a)
Complete the table below to give four differences between the effects of
high GI and low GI foods on blood glucose concentration.
High GI foods
Low GI foods
(4)
(b)
White bread and wholegrain bread contain similar proportions of starch.
White bread has a higher GI than wholegrain bread.
Suggest one explanation for the difference in GI.
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(2)
(Total 6 marks)
Q4.
(a)
fatty acid.
Figure 1 shows the structure of a molecule of glycerol and a molecule of
Figure 1
Draw a diagram to show the structure of a triglyceride molecule.
(2)
(b)
Explain why triglycerides are not considered to be polymers.
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(1)
(c)
Figure 2 shows two types of fat storage cell. Mammals living in cold
conditions have more brown fat cells than mammals living in tropical
conditions.
Figure 2
Using evidence from Figure 2 to support your answer, suggest how the
function of brown fat cells differs from that of white fat cells.
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(3)
(Total 6 marks)
Q5.
(a)
(i)
Starch and protein are biologically important polymers.
Explain what is meant by a polymer.
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(1)
(ii)
Give one example of a biologically important polymer other than
starch or protein.
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(1)
(b)
In an investigation, the enzyme amylase was mixed in a test tube with a
buffer solution and a suspension of starch. The amylase broke down the
starch to maltose. When all the starch had been broken down, a sample
was removed from the test tube and tested with biuret reagent.
(i)
Explain why a buffer solution was added to the amylase-starch
mixture.
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(2)
(ii)
What colour would you expect the sample to go when tested with
biuret reagent?
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(1)
(iii)
Give an explanation for your answer to part (ii)
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(2)
(Total 7 marks)