Biology
Long Question
Exercise
for HKDSE
(Supplement to Book 1-1st Edition)
Supplement to Book 1 -1st Edition
© Takka Education Books Co.
All rights reserved. No part of this book
may be reproduced in any form or by any
means, including electronic copies, without
the prior permission from the copyright owner.
Takka Education Books Co.
德嘉教育出版社
CONTENTS
Chapter 1
Molecules of life ......................................................... 3
Chapter 2
Cellular organisation .................................................. 5
Chapter 3
Movement of substances across a membrane ............... 7
Chapter 4
Enzymes ................................................................... 7
Answer ....................................................................................... 8
Chapter 1
3
Molecules of life
這本書主要修訂是在第一章大幅刪去 "molecular structure" (分子結構) 的部分, 原版第二冊
中的 "Energetic - respiration" 移到修訂版第一冊, 其餘變動不大。
Chapter 1
A)
Molecules of life
The following questions are removed from Chapter 1 of the previous edition:
1.9
1.11
1.13
1.15
1.17
1.18
1.19
1.20
1.21
1.22
1.27-(a)
1.28
1.31
1.33
1.35
1.36
1.37
1.39
1.41-(a)
1.44
1.58
1.59
1.63
1.64
These removed questions are chiefly related with the molecular structures of carbohydrates proteins, and fats.
B)
In the revised edition, biuret test for proteins was replaced by Albustix paper test.
C) Three questions are added to Chapter 1.
Proteins
1.1
Describe a test to find out if soybean contains protein.
(4 marks)
(這是原 1.25-c 的題目 , 答案中的 biuret test 改為 Albustix paper test.)
1.2
Globular proteins are proteins with a specific shape (conformation). Describe how globular
proteins can have different shapes and how these shapes enable them to have different
functions in a human body. (Description of fibrous protein is not required.)
(13 marks)
(This question requires answers in essay form. Some marks are given on the presentation of
the answers, which should be logical and with coherent layout.)
4
Chapter 1
Molecules of life
Food tests
1.3 The table below shows the results of some food tests on four foodstuffs.
(這是原題目 1.49, 修訂版將原本 biuret test 改為 Albustix paper test.)
Result of food test
Foodstuff
Colour on Albustix
paper test
Colour on Benedict’s
solution test
Appearance on
emulsion test
A
blue-green
blue
milky
B
yellow
blue
milky
C
yellow
brick-red
clear
D
yellow
blue
clear
(a)
Name the food types in foodstuffs (i) A , (ii) B , and (iii) C as indicated by the results of
the tests.
(3 marks)
(b)
Describe a further test to find out if foodstuff D contains non-reducing sugar.
(c)
Describe a test to find out if starch is present in foodstuff C.
(3 marks)
(1 mark)
Chapter 2
Chapter 2
5
Cellular Organisation
Cellular organisation
A) Question 2.10 is removed from the previous edition.
B) Three questions have been added to Chapter 2.
2.1
Draw a labelled diagram to show the structures of a biological membrane, such as the
plasma membrane. The following are some structures that you may have to include in your
diagram.
(7 marks)
phospholipid
2.2
glycoprotein
cholesterol
carrier protein
The vacuoles of the beetroot cells contain a red pigment. This red pigment would be
released if the cell membrane and the vacuole membrane have been damaged.
In an investigation, two beetroot cubes of similar size cut from a peeled beetroot were put
separately in two test tubes (X and Y) containing the same volumes of alcohol but of
different concentrations as shown in Diagram A. After 20 minutes, red colours of different
intensities appeared in the alcohol as that shown in Diagram B.
X
Y
X
alcohol of different
concentrations
beetroot
cube
Diagram A: at the start
beetroot
cube
Y
red colour
of different
intensities
Diagram B: after 20 minutes
6
Chapter 2
Cellular Organisation
(a)
From the result in Diagram B, explain which test tube contains alcohol with a higher
concentration.
(5 marks)
(b)
After two hours, it was found that the red colours in X and Y has the same intensity. Explain
why.
(2 marks)
2.3
At the 17th century with the invention of compound light microscopes, scientists at that
time found that the semi-fluid materials inside the cells could carry out all life activities
such as respiration, enzyme actions and cell divisions. They called this semi-fluid
"protoplasm", which was believed to be the basis of life.
After the invention of electron microscopes, scientists discovered that this semi-fluid
actually contained even smaller structures, which they named them "organelles". On
isolating these organelles, they confirmed that most life activities are actually carried out by
these organelles.
(a)
From the above information, explain why protoplasm is a term that is no longer appropriate
in modern biology.
(1 mark)
(b)
Explain why electron microscope with a magnification of 20 000x can see cell structures in
greater detail than a light microscope with the same magnification.
(2 marks)
(c)
In the following table, elaborate on how the above information demonstrates the nature of
science in the building of knowledge.
(3 marks)
Nature of Science
(i) Science is based on
existing evidence.
(ii) Scientific knowledge is
tentative and can be changed.
(iii) New technology adds
new knowledge to science.
Elaboration
Chapter 4
Chapter 3
A)
7
Enzyme
Movement of substances across a membrane
The following questions are removed from Chapter 3 of the previous edition:
3.6
3.8-(a)
B) cm3 and dm3 are replaced by mL and L.
C) No question is added to Chapter 3.
Chapter 4
Enzymes
A) The questions listed below are removed from Chapter 4. They are mainly those related
with competitive and non-competitive inhibitions.
4.17
4.18
4.19
4.20
B) One question is changed in Chapter 4.
4.1
(這代替原版中的 4.17。)
The diagram on the right shows an enzyme.
X and Y are two kinds of molecules that can
combine with the enzyme. X is the substrate.
(a)
Y
Draw a circle on the diagram to indicate the
active site.
(1 mark)
Enzyme
(b)
Explain how X is broken down by the
enzyme.
(4 marks)
(c)
Molecules Y is an inhibitor of the reaction between X and the enzyme.
(d)
X
Explain how Y leads to the inhibition.
(3 marks)
Explain why heating may cause an enzyme to lose its activities.
(4 marks)
End
Answer
8
Book 1 - Answer
1
Molecules of life
The answers below are split in separate
lines for the clarity of ideas. In the
examination, candidate should present them
in an essay form
1.1
Soak the soybeans overnight to soften it.
1
Grind with water to obtain an extract.
1
Test the extract with Albustix paper.
Positive result: If protein is present, the
reagents at the tip change from yellow
to [blue-green / blue / green]
1
(1) Role of DNA
There are about 20 kinds of amino acids.
1
1
These amino acids join with each other to
form a polypeptide, which will become a
protein with a specific conformation.
1
The type and sequence of amino acids in a
particular polypeptide is determined by
genetic codes, which are inherited from the
parents and are carried by the DNA in the
nucleus. A certain section of the DNA
constitutes a gene.
1
Each gene has a specific base sequence and
this sequence will direct the formation of a
specific polypeptide with a specific amino
acid sequence.
1
(Accept: Biuret test.)
1.2
Layout of the answer:
1. Having a special conformation
Role of DNA => Amino acids with a specific
sequence forming a polypeptide =>
coiling to form 3-dimentional shape.
(The concept is that different arrangements of amino acids in a polypeptide
would lead to different conformations.)
2. Different functions
Enzymes and active sites.
Antibodies for body defense.
(Reject "formation of a specific protein" at
this stage.)
(2) Folding to a 3-dimentional shape
Hydrogen bonds can be formed between the
amino acids in a polypeptide. These bonds
link up different parts of the polypeptide so
that the polypeptide folds into a 3dimensional shape, so forming a protein.
1
Since a polypeptide has its specific amino
acids sequence, the positions of the
hydrogen bonds are also specific. This gives
a specific conformation to the protein.
1
Haemoglobin for carrying oxygen.
Proteins on cell membrane, receptors
for neurotransmitters and hormones.
Note: Don't include hormones because
peptide or protein hormones are usually short
peptide chains with no special conformation.
Marks will be lost for including irrelevant
materials.
Maximum 4 marks for parts (1) and (2)
9
Answer
For example, the cell membrane of the postsynaptic cell has receptors for the neurotransmitters released from the pre-synaptic
cell. This allows nerve impulses to cross the
synapse.
(3) Different functions
Each protein, with its specific conformation,
can carry out a specific function that
depends on the conformation. The following
are some examples.
Enzyme:
Enzymes are biological catalysts that
control the reactions in a human body, from
cellular metabolic activities to the digestion
of foods.
Each enzyme has a location called active
site, which has a special shape that is
complementary to the shape of the substrate
molecules. Reaction occurs when the
substrate molecules have fitted into the
active site to form an enzyme-substrate
complex.
Antibodies:
Antibodies are a chief mechanism of body
defence.
When a pathogen with a special antigen has
entered a human body, antibodies with a
shape complementary to the antigen are
produced. The antibodies will bind to the
antigen and so making the pathogen
inactive.
Haemoglobin:
A haemoglobin molecule consists of four
polypeptide chains. There are sites which
can bind with oxygen.
At the lung, oxygen bind to haemoglobin,
which then carries the oxygen to other parts
of the body.
Cell surface receptors:
Some cells have protein receptors on the
cell membrane. These protein receptors
have special shapes that serve as a binding
site for the molecules with a shape
complementary to the binding site.
1
Another example is the receptors on the cell
membrane of the target cells of insulin (or a
hormone). These receptors have a special
shape that enables them to act as a binding
site for only insulin (or a particular
hormone). So insulin has effects only on its
target cells.
1
1
1
1
(Accept general description on hormones
instead of insulin.)
1
Maximum 6 marks for part (3)
1
Marks on communication:
Answers incoherent with many irrelevant
materials.
0 mark
1
Answers incoherent but still can be made
out by readers spending time on it. With
some irrelevant materials.
1 mark
Answers can be easily understood but still
with some irrelevant materials.
2 marks
1
Answers logical and coherent. With no or
negligible irrelevant materials.
3 marks
Maximum for total final = 13
1
1.3
(a) (i) A: protein and [triglyceride / fat /
oil / lipid]
1
1
(Both correct for one mark.)
(ii) B: triglyceride / fat / oil / lipid
1
(iii) C: reducing sugar
1
(Reject sugar's name such as glucose.)
1
(b) Boil the foodstuff with acid, then
neutralise with hydrogencarbonate.
1
10
Answer
(No mark if
neutralised.)
the
Heat the resulting
Benedict's solution.
solution
is
not
General quality of drawing and title:
Clear and large diagram, without shading.
solution
The appearance of a [red / brick-red /
orange] precipitate indicates the
presence of non-reducing sugar in the
foodstuff.
(c) Add iodine solution to the foodstuff. A
blue black colour indicates the
presence of starch.
1
A proper title for the diagram.
1
The following parts correctly drawn and
labelled:
Phospholipid molecules line up as a layer. 1
1
(Reject "iodine" instead of "iodine
solution". Reject "blue colour" instead
of "blue black colour".)
2
½
½
Neat guide lines without crossing.
with
1
Phospholipid bilayer with
orientations of the molecules.
correct
1
A transmembrane protein labelled as
[carrier / channel / transmembrane]
protein
1
A labelled glycoprotein shown on the
surface
1
A cholesterol among the hydrophobic
tail of the phospholipid molecules.
1
Cellular organisation
2.1
All that is required is a simple line drawing
showing the important structures and without
much touch up such as shading or too much
dotting.
For example:
glycoprotein
(or glycolipid)
phospholipid
molecule
cholesterol
carrier protein
(or channel protein)
Structures of a plasma membrane
2.2
(a) The alcohol in tube Y had a higher
concentration
1
because the alcohol in tube Y had
higher red colour intensity.
1
The alcohol dissolved the phospholipid
of the membranes. The red pigment in
the vacuole was released and dissolved
in the alcohol.
1
The alcohol in tube Y had a higher
concentration and so the membranes
were dissolved faster.
1
The alcohol could also reach the deeper
part of the beetroot cube faster.
1
In tube Y, more red pigment was
released.
1
Maximum 5
Answer
(b) In two hours time, all membranes in
both cubes had been dissolved and so
all pigments diffused and distributed
evenly in the alcohol.
1
Sine the two cubes came from the same
beetroot and had similar size, the
concentrations of the red pigment in
the two alcohols are similar.
1
2.3
(a) Because most life activities are carried
out by the organelles and not just by a
semi-fluid materials.
1
11
(ii) Protoplasm was once believed to be the
material responsible for life. Later it is
known that the organelles are
responsible for life activities after
scientists had identified the organelles
under electron microscope and studied
their activities.
(iii) Most organelle cannot be seen under
light microscope and so scientists know
the existence of organelles only after
the invention of electron microscope.
1
1
(Do not accept the general description
on the advantage of electron microscope. The answer must be focused on
the identification of organelles.)
(Accept any idea of the complexity of the
cell that is more than just protoplasm.)
(b) Because an electron beam has a shorter
wavelength than a light beam,
and so the electron microscopes can
have a higher resolution than the light
microscopes even both have the same
magnification.
1
4
Enzymes
1
4.1
(a) A circle around the active site
1
For example:
(c)
This type of question requires a candidate
just to select from the provided information
the material that fits the statement on the
left column and then write a comment on it.
No other materials are required unless
specified. And don't just copy the question
as the answer.
(i) Scientists believed that the protoplasm
was the basis of life because they found
that the protoplasm could show all life
activities.
(Or: Scientists isolated organelles and
found they showed life activities. So
life depends on these organelles.)
(b) The shape of X is complementary to
the shape of the active site.
1
1
(Reject "[same / similar] shape as the
active site".)
X fits into the active site,
1
forming an enzyme-substrate complex,
1
in which the activation energy is
lowered.
1
12
Answer
After the reaction, the products no long
fit the active site and they detach from
the active site.
1
Maximum 4
(c) Y can fit into the active site.
1
This blocks the active site and so X
cannot fit into the active site.
1
No enzyme-substrate complex can be
formed.
1
(d) Heating increases the kinetic energy of
the [molecules / atoms in the
molecule].
1
(Or: increases the vibrations of the
[molecules / atoms in the molecule].)
This causes the breaking of the
hydrogen bonds and ionic bonds in the
enzyme molecule,
which then leads to a change in the
[tertiary structure / configuration] of
the enzyme.
1
1
(or leads to denaturation).
The shape of the active site is changed.
1
The substrate cannot fit into the active
site. / Enzyme-substrate complex
cannot be formed.
1
Maximum 4
End