Download Assessment Statement

Topic 3: The Chemistry of Life
1.
Assessment Statement
Response
Campbell pages
3.1 Chemical elements and water: 2 hours
3.1.1 State that the most
Pg. 33
frequently occurring
chemical elements in
living things are
hydrogen, oxygen,
carbon, and nitrogen
3.1.2 State that a variety of
Pg. 33
other elements are
needed by living
organisms, including
sulfur, calcium,
phosphorus, iron, and
sodium
3.1.3 State one role for each
The major roles of these elements can be found
of the elements
throughout the textbook.
mentioned in 3.1.2
IB says: Refer to the roles in plants, animals, and
prokaryotes
Sample Test Questions
What element occurs in all proteins?
Nitrogen
What role does sulfur play in living organisms?
D. Component of proteins
3.1.4 Draw and label a
diagram showing the
structure of water
molecules to show their
polarity and hydrogen
bond formation
3.1.5 Outline the thermal,
cohesive, and solvent
properties of water
Pg 47-48
Draw and label a diagram, etc.
Pg. 48-52
Outline the thermal properties of water.
3.1.6 Explain the relationship Pg. 48-52
between the properties
of water and its uses in IB says: Limit the properties to those outlined in 3.1.5
living organisms as a
coolant, medium for
metabolic reactions, and
transport medium.
3.2 Carbohydrates, lipids, and proteins: 2hrs
3.2.1 Distinguish between
Pg 58. Campbell defines “organic compounds” as
organic and inorganic
“compounds containing carbon.” IB disagrees with that
compounds
definition
IB says: Compounds containing carbon that are found in
living organisms (except hydrogen-carbonates,
carbonates, and oxides or carbon) are regarded as
organic.
3.2.2 Identify amino acids,
glucose, ribose and
fatty acids from
diagrams showing their
structure
Pg. 70-78
IB says: Specific names of amino acids and fatty acids
are not expected.
3.2.3 List three examples
each of
monosaccharides,
disaccharides, and
polysaccharides.
IB says: The examples used should be: glucose,
galactose, and fructose; maltose, lactose, and sucrose;
and starch, glycogen, and cellulose.
3.2.4 State one function of
Pg. 70-72, does not include function of fructose
glucose, lactose, and
glycogen in animals,
and of fructose, sucrose,
and cellulose in plants.
3.2.5 Outline the role of
condensation and
hydrolysis in the
relationships between
monosaccharides,
disaccharides and
polysaccharides;
between fatty acids,
glycerol and
triglycerides; and
between amino acids
and polypeptides.
Pg. 68-69
The relationships between condensation and hyrdrolysis
reactions and the formation and disassembly of
macromolecules is discussed in general though not with
all the specific molecules at left.
Campbell uses the term “dehydration reaction” in some
places instead of “condensation”. These terms refer to
the same thing.
IB says: This can be dealt with using equations with
words or chemical formulas.
3.2.6 State three functions of
lipids
Pg. 76-77
IB says: Include energy storage and thermal insulation.
3.2.7 Compare the use of
carbohydrates and
lipids in energy storage
Can be inferred from 70-76
May 2006 PM (SL)
7c. Describe why carbohydrates and lipids are used as
energy stores
(c) carbohydrates and lipids contain a lot of chemical
energy;
carbohydrates are readily used in cell respiration /
sugars are quick access energy
stores;
lipid molecules contain about twice as much energy
as carbohydrates;
complex
carbohydrates/polysaccharides/starch/glycogen are
also long term energy
stores;
lipids are long term energy reserves;
complex
carbohydrates/polysaccharides/starch/glycogen and
lipids are insoluble /
will not diffuse out of cells;
complex
carbohydrates/polysaccharides/starch/glycogen/lipids
do not contribute
(significantly) to osmotic pressure;
complex
carbohydrates/polysaccharides/starch/glycogen can
be converted into
sugars by hydrolysis;
carbohydrates and lipids burn cleaner than proteins /
do not yield N waste; [6 max]
(Plus up to [2] for quality)
3.3 DNA structure: 1 hour
3.3.1 Outline DNA
nucleotide structure in
terms of sugar
(deoxyribose), base,
and phosphate.
3.3.2 State the names of the
four base pairs of DNA
3.3.3 Outline how DNA
nucleotides are linked
together by covalent
bonds into a single
strand
Pg. 87
IB says: Chemical formulas and the purine/pyrimidine
subdivision are not required. Simple shapes can be used
to represent the component parts. Only the relative
positions are required.
Pg 88
Pg 88
IB says: Only the relative positions are required.
3.3.4 Explain how a DNA
double helix is formed
using complementary
base pairing and
hydrogen bonds.
Pg 88
3.3.5 Draw and label a simple
diagram of the
molecular structure of
DNA
Can be inferred from pages 87 and 88.
IB says: An extension of the diagram in 3.3.3 is sufficient
to show the complementary base pairs of A-T and G-C
held together by hydrogen bonds and the sugarphosphate backbones. The number of hydrogen bonds
between pairs and details of purine/pyrimidines are not
required.
3.4 DNA Replication: 1 hour
3.4.1 Explain DNA
replication in terms of
unwinding the double
helix and separation of
the strands by helicase,
followed by the
formation of new
complementary strands
by DNA polymerase.
Pg. 89
Helicase and DNA polymerase are not mentioned until
pages 300-304 (Concept 16.2)
IB says: It is not necessary to mention that there is more
than one DNA polymerase.
3.4.2 Explain the significance Pg. 89
of complementary base
pairing in the
conservation of the base
sequence of DNA
3.4.3 State that DNA
Pg. 299
replication is semiconservative
6 May 2009 PM
6b Explain the process of DNA replication. [8]
2009 Specimen Paper
6. The diagram shows part of a molecule produced by
replication of DNA. What is the significance of the
shaded and the unshaded regions? (One strand is
shaded and the complementary strand is unshaded)
A. The shaded parts are DNA and the unshaded parts
are mRNA.
B. The shaded parts contain adenine and thymine and
the unshaded parts contain guanine
and cytosine.
C. The shaded part is a codon and unshaded part is
an anticodon.
D. One of the parts has been newly synthesized and
the other was part of a pre-existing
DNA molecule.
3.5 Transcription and Translation: 2 hours
3.5.1 Compare the structure
Pg. 88
of RNA and DNA
IB says: Limit this to the names of sugars, bases, and the
number of strands.
3.5.2 Outline DNA
transcription in terms of
the formation of an
RNA strand
complementary to the
DNA strand by RNA
polymerase
Pg. 311-315
6 May 2009 PM
6a Distinguish between DNA and RNA [3]
May 2006 PM (SL)
5. (a) Determine the strand of mRNA that is
transcribed from the DNA strand below.
A–T–C–C–A–G–G–T–C–A–A–G
[1]
(b) List three of the other molecules, apart from
mRNA, required for transcription.
[3]
5. (a) – U – A – G – G – U – C – C – A – G – U – U –
C – [1]
(b) DNA;
RNA polymerase;
(ribose) nucleotides / ribonucleotides / RNA
nucleotides;
transcription factors;
nucleoside/ribonucleoside triphosphates;
Any two of the following: A / C / G / U; [3 max]
3.5.3 Describe the genetic
code in terms of codons
composed of triplets of
bases.
Pg 314
3.5.4 Explain the process of
translation, leading to
polypeptide formation.
Pg 320-324
2009 Specimen Paper
IB says: Include the roles of messenger RNA (mRNA),
transfer RNA (tRNA), codons, anticodons, ribosomes
and amino acids.
7. If mRNA has a codon CAU, what is the
corresponding anticodon on the tRNA molecule?
A. CAT
B. GUA
C. CAU
D. GTA
3.5.5 Discuss the relationship
between one gene and
one polypeptide.
Pg. 310
IB says: Originally, it was assumed that one gene would
invariably code for one polypeptide, but many
exceptions have been discovered.
3.6 Enzymes: 2 hours
3.6.1 Define enzyme and
active site
3.6.2 Explain enzymesubstrate specificity
Pg. 150
Pg. 152
4 May 2006 PM (SL)
IB says: The lock-and-key model can be used as a basis
for the explantion. Refer to the three dimensional
structure. The induced-fit model is not expected at SL.
4. (a) State why each step in a biochemical pathway
often requires a separate enzyme.
[2]
4. (a) enzymes are specific for their substrate / lock
and key model / energy requirements
for reactions with substrates vary;
each step of the pathway is unique / different
substrate at each step;
finer control of metabolic pathways; [2]
3.6.3 Explain the effects of
temperature, pH, and
substrate concentration
on enzyme activity
Pg. 154
I did not find a mention in Campbell of how substrate
concentration affects enzyme activity.
8. Which graph shows the relationship between the
substrate concentration and the rate of an enzyme
controlled reaction?
May 2006 PM (SL)
4(b) Explain the effects of either changing
temperature or pH on enzyme activity.
[3]
(b) Either, temperature: [3 max]
each enzyme has an optimal temperature for its
maximum activity;
(small) temperature increases result in increased
enzyme activity to a
point/optimum;
increase activity due to increased movement of
molecules / increased kinetic
energy or conversely stated;
temperature increases above the optimum causes
(progressive) loss of activity due
to denaturation/shape changes
or, pH: [3 max]
each enzyme has an optimal pH for its maximum
activity;
as pH varies from optimal pH, enzyme activity
diminishes / becomes inhibited;
loss of activity is due to denaturation/shape
changes;
gain or loss of hydrogen ions distorts tertiary shape
of enzyme;
homeostatic mechanisms maintain optimal
conditions for enzyme activity; [3 max]
Credit marking points above if illustrated by a
suitably annotated graph.
3.6.4 Define denaturation
Pg 84
IB says: Refer only to heat and pH as agents.
3.6.5 Explain the use of
lactase in the
production of lactosefree milk
3.7 Cell respiration: 2 hours
3.7.1 Define cell respiration
3.7.2 State that, in cell
respiration, glucose in
the cytoplasm is broken
down by glycolysis into
pyruvate, with a small
yield of ATP.
Not discussed in Campbell.
Pg. 161
Important: Campbell uses the term “cellular
respiration” to refer ONLY to aerobic respiration. IB
uses the term “cell respiration” to refer to both aerobic
and anaerobic respiration.
Pg. 165
3.7.3 Explain that, during
anaerobic respiration,
pyruvate can be
converted in the
cytoplasm into lactate,
or ethanol and carbon
dioxide, with no further
yield of ATP.
Pg. 175
IB says: Mention that ethanol and carbon dioxide are
produced in yeast, whereas lactate is produced in
humans.
3.7.4 Explain that, during
aerobic cell respiration,
pyruvate can be broken
down in the
mitochondria into
carbon dioxide and
water with a large yield
of ATP.
Pg. 168-174
3.8 Photosynthesis: 3 hours
3.8.1 State that
photosynthesis involves
the conversion of light
energy into chemical
energy.
2009 Specimen Paper
9. Humans can respire aerobically and anaerobically.
Which are products of both aerobic cell respiration
and anaerobic cell respiration in humans?
A. pyruvate and ATP
B. pyruvate and lactate
C. ATP and carbon dioxide
D. lactate and carbon dioxide
Pg. 181
3.8.2 State that light from the
Sun is composed of a
range of wavelengths
(colours).
Pg. 186
3.8.3 State that chlorophyll is
the main photosynthetic
pigment.
3.8.4 Outline the differences
in absorption of red,
blue, and green light by
chlorophyll.
Pg. 182
IB says: Reference to actual wavelengths or frequencies
is not expected.
Pg. 187-188
IB says: Students should appreciate that pigments
absorb certain colors of light. The remaining colors of
light are reflected. It is not necessary to mention
wavelengths or the structure responsible for the
absorption.
3.8.5 State that light energy is Pg. 184-185
used to produce ATP,
and to split water
molecules (photolysis)
to form oxygen and
hydrogen.
3.8.6 State that ATP and
Pg. 184-185
hydrogen (derived from
the photolysis of water)
are used to fix carbon
dioxide to make organic
molecules.
3.8.7 Explain that the rate of
photosynthesis can be
measured directly by
the production of
oxygen or the uptake of
carbon dioxide, or
indirectly by an
increase in biomass.
Not specifically discussed in Campbell.
IB says: The recall of details of specific experiments to
indicate that photosynthesis has occurred or to measure
the rate of photosynthesis is not expected.
3.8.8 Outline the effects of
temperature, light
intensity, and carbon
dioxide concentration
on the rate of
photosynthesis.
Not specifically discussed in Campbell
May 2006 PM (SL)
7. (b) Explain how the rate of photosynthesis can be
measured. [7]
(b) CO2 +H2O (CH2O)n + O2 / suitable
photosynthesis equation;
amount of CO2 absorbed (per unit time) can be
measured;
measuring the increase of biomass (per unit time);
O2 excretion (per unit time) can be measured;
methods for measuring the above:
volume of O2 (bubbles) produced per unit time can
be measured;
dry mass can be weighed;
increase in starch concentration in leaves (as
measured by iodine);
use of pH indicator can monitor CO2 uptake in
water;
the rate of photosynthesis measured is relative
because some of the CO2 is
produced by the plant internally through respiration;
the rate of photosynthesis measured is relative
because some of the carbohydrates
are used internally by the plant for respiration; [7
max]
2009 Specimen Paper
5(b) Outline the role of chlorophyll and the effects of
temperature, light intensity and carbon
dioxide concentration on the rate of photosynthesis.
[6]
(b) chlorophyll is composed of a number of pigments;
absorb different colours of light;
mainly red and blue absorbed;
green light reflected;
temperature increases rate;
up to a point where enzymes denature;
light intensity increases rate;
up to a point where maximum absorbance can occur;
carbon dioxide increases rate;
up to a point where fixation is at a maximum; [6
max]