HL unit 2 test



Unit Test


Time allowed: 70 minutes

You may use a calculator

Write all answers on this paper


Section A: Multiple Choice (12 marks)

Section B: Structured Factual Recall (15 marks)

Section C: Structured Data Analysis (9 marks)

Section D: Extended Response (14 marks)



Name: _______________________

Date: _______________________


Score:   ___/ 50 =   ____ %      (IB Grade ___)





Section A: Multiple Choice (circle the correct answer)

1.     Which of the following is considered acellular or non-living?

A.     Eukaryote cell

B.     Prokaryote cell

C.     Amoeba

D.    Virus


2.     A plasma membrane is 10nm thick. On a diagram, a student draws it 20mm thick.

What is the magnification of the drawn image?

A.     X    5,000

B.     X    100,000

C.     X    2,000,000

D.    X    2,000



3.     Which of the following are fundamental statements of cell theory?

i. Cells come only from other cells

ii. Cells maximize their SA:Vol ratio

iii. All living things consist of cells

iv. Cells are the smallest units of life


A.     i and ii

B.     i, iii and iv

C.     ii, iii and iv

D.    i, ii, iii and iv


4.     Which of the following organelles are present in prokaryotes but not eukaryotes?

A.     Plasma membrane

B.     Cytoplasm

C.     Nucleoid

D.    Nucleus





5.     Which part of the plasma membrane is involved in recognition of other cells?

A.     Phospholipid bilayer

B.     Integral proteins

C.     Peripheral proteins

D.    Cholesterol



6.     The diagram below shows a channel protein in a plasma membrane.

Channel proteins allow polar molecules to pass through by facilitated diffusion.

Which labeled parts of the channel proteins are likely to be polar?

A.     I and II only

B.     III and IV only

C.     I and III only

D.    All parts




7.     How do animals use cholesterol?

A.     To store energy

B.     To form part of the plasma membrane

C.     To insulate neurons (nerve cells)

D.    To increase blood pressure


8.     Which cell organelle is responsible for the production of proteins to be exported from the cell?

A.     Rough endoplasmic reticulum

B.     Free ribsomes

C.     Mitochondrion

D.    Lysosome






9.     Which of the following correctly describes the process of osmosis?

A.     The passive movement of water molecules from areas of low solute concentration to high solute concentration, through a selectively permeable membrane.

B.     The passive movement of water molecules from areas of high solute concentration to low solute concentration, through a selectively permeable membrane.

C.     The active movement of water molecules from areas of high solute concentration to low solute concentration,  using a membrane pump protein.

D.    The passive movement of water molecules from areas of low solute concentration to high solute concentration, through a channel protein. 



10.  During which phase of the cell cycle is the plasma membrane divided to give two new daughter cells?

A.     Interphase

B.     Prophase

C.     Anaphase

D.    Cytokinesis


11.  Which labels match ‘i’ and ‘ii’ respectively?

A.     Centromere and chromosomes

B.     Centriole and chromosomes

C.     Centromere and sister chromatids

D.    Centriole and sister chromatids


12.  Which process is used to export a macromolecule from the cell?

A.     Exocytosis

B.     Endocytosis

C.     Facilitated diffusion

D.    Pinocytosis



End of Section A. 12 marks.




Section B: Structured Factual Recall



In the image, the scale bar represents 1µm.

a.     Calculate the length of the cell ‘A’.



2.5µm ± 2µm     (2)

                                                      [2.2µm – 2.8µm if work shown]

b.     By which method do prokaryotes reproduce?


……………………………Binary fission………………………………….  (1)


2.           a. Explain how the surface area to volume ratio influences cell size.

the rate of material / heat exchange / diffusion is proportional to surface area;
the rate of metabolism is proportional to mass / volume;
as a cell grows, the volume increases faster than the surface area / as a cell grows,
surface area to volume ratio decreases;
(without cell division) material / heat cannot be exchanged fast enough to meet the needs of the cell (3)


b.     Compare prokaryotic and eukaryotic cells with regard to three features: [3 max]

Award [1]for each of the following pairs.
Mark first answer only in boxes 1, 2 and 3.

Allow [1] only for a similarity.

prokaryotic cells      eukaryotic cells

          nucleoid / no nucleus / nuclear membrane     vs.     nucleus / nuclear membrane;
naked DNA / no histones     vs.     NA associated with protein /histone;     NA associated with protein / histone;
no mitochondria     vs.     mitochondria present;
no Golgi / no ER     vs.     Golgi / ER present;
circular DNA     vs.     linear DNA;
no / very few membrane-bound organelles     vs.     membrane-bound organelles;
ribosomes smaller / 70S     vs.     ribosomes larger / 80S;
no mitosis / meiosis     vs.     mitosis / meiosis;
flagella lack internal microtubules     vs.     flagella have microtubules (9+2);



c. State one function of each of the following organelles.

i.      lysosome: hydrolysis / digestion / break down of materials (macromolecules);

ii. ribosome: translation / site of synthesis of proteins

iii. Golgi apparatus: synthesis / sorting / transporting / secretion of cell products (3)          


3.     a.  Differentiate between diffusion and osmosis.


Must have both for [1]. diffusion is the movement of molecules from an area of high concentration to an area of low concentration; osmosis is the diffusion of water across a partially permeable membrane;             (2)


b.  An animal cell is placed in a hypotonic (very weak) sugar solution.

                    Will the cell increase or decrease in mass?


 ……………………… increase …………………………………………………………………………………………   (1)



End of Section B. 15 marks.


Section C: Structured Data Analysis

1.    A study was carried out to determine the relationship between the diameter of a molecule and its movement through a membrane. The graph below shows the results of the study.

[Source: Knox, et al., Biology, Mcgraw Hill, Sydney, 1994, page 65]


(a)        From the information in the graph alone, describe the relationship between the diameter of a molecule and its movement through a membrane.


as the diameter of the molecule increases the permeability / relative ability
to move decreases (accept converse);

the relationship is logarithmic / non-linear / negative;

for molecules above 0.6 (
± 0.1) nm relative ability to move changes little /
for molecules below 0.6 (
± 0.1) nm relative ability to move changes rapidly;        2 max


A second study was carried out to investigate the effect of passive protein channels on the movement of glucose into cells. The graph below shows the rate of uptake of glucose into

erythrocytes by simple diffusion and facilitated diffusion.


(b) Identify the rate of glucose uptake at an external glucose concentration of

           4 mmol dm-3by

(i)            simple diffusion.            10 mmol cm-3 hr-1 (accept ± 5)        (1)

(ii)            facilitated diffusion.            370 mmol cm-3 hr-1 (accept ± 10)                (1)

(c)            (i)            Compare the effect of increasing the external glucose concentration on glucose uptake by facilitated diffusion and by simple diffusion. (3 max)

• Rate of glucose uptake in facilitated diffusion levels out as external glucose concentration increases whereas uptake in simple diffusion does not level out / continues to rise.

• Rate of glucose uptake increases with both increasing external concentration in both. 

• Rate of glucose uptake is higher in facilitated diffusion (than in simple diffusion).

• Increase in rate of glucose uptake in simple diffusion is constant/ linear, whereas in facilitated diffusion the rate of uptake increases rapidly at the beginning / increase is not constant.

(ii)            Predict, with a reason, the effect on glucose uptake by facilitated diffusion of increasing the external concentration of glucose to 30 mmol dm-3. (2 max)

Little/ no change in glucose uptake

because all/most (protein) glucose channels in use


2.    Data based question

1) State the time of day when:

               (a) Most DNA replication occurs           02:00 ± 2 h       

              (b) mitosis is most likely to occur        04:00 – 07:00 ± 1 h        [2]


2) Identify the cell cycle stage when most of the increase in cell size

               is occurring.           G1        [1]


3)  Evaluate the claim that the timing of the cell cycle in Emiliania huxleyi is an adaptation to take advantage of light resources. [3]

[summary required; worth 1 point]

This phytoplankton takes advantage of light to make chemical energy and material / then in the dark it uses this stored energy and material for other processes like DNA duplication, mitosis and cell division / when the sun comes up there are now new cells ready to take advantage of the light and the cycle repeats.


[Must state two evidences with data explicitly taken from information above]

In this data most cells reach maximum size about 18:00 (end of daylight) / size means more energy storage and more organelles / more material in cell/ minimum size occurs at dawn 06:00 and this is because cells have divided and are at their smallest


DNA duplicated after midnight/ cell uses material from growth to duplicate DNA in next 2-4 hours/ Cycle reach maximum size about noon each day;


Within 2 hours of S phase/DNA duplication cell undergoes mitosis and divides;


                  End of Section C. 15 marks.                 

Section D: Extended Response                                    Answer these questions on the paper provided.


1. Draw labeled diagrams to show four stages of mitosis in an animal cell with 2 chromosomes. (5)

prophase showing spindle fibres;
prophase showing condensed chromatin;
prophase showing replicated chromosomes;
metaphase showing replicated chromosomes lining up at the equator;
anaphase showing chromatids moving to opposite poles;
telophase showing nucleus reforming;
telophase showing cytokinesis occurring;
           5 max

The four diagrams must have the name of the phase, otherwise award [3 max].
The four stages must be included to receive [5]. If correct number of
chromosomes is not shown award [4 max].


Explain how mitosis ensures that daughter cells are genetically identical. (4) (Note this can be combined as annotations to diagrams above.)


sister chromatids are two identical DNA molecules held together by centromere;


sister chromatids are separated during mitosis to form two genetically identical nuclei;


in prophase chromosomes shorten / thicken / become visible as double-stranded chromosomes / joined sister chromatids;


chromosomes condense by supercoiling;


chromosomes attach to spindle microtubules at centromeres;


chromosomes begin to move towards equator / centre of cell;


during metaphase all chromosomes lined up at equator separately / not in homologous pairs;


at start of anaphase centromeres divide separating sister chromatids;


separated sister chromatids known as (single stranded) chromosomes;


(identical sets of) chromosomes pulled to opposite poles;


move by contraction of microtubules;


nuclear envelope / membrane forms around each set of chromosomes;               

2.  Outline one therapeutic use of stems cells. (5)                                      

stem cells are cells that retain the capacity to divide and have the ability to differentiate along different paths into all types of cells / are pluripotent / totipotent;


stem cells are derived from blastocysts / human embryos, left over from IVF / placenta / umbilical cord / some adult tissues;


new techniques / technologies rely on replacing diseased / dysfunctional cells with healthy / functioning ones;


need to identify desired type of stem cell and grow in culture / special solutions / controlled conditions;


develop biochemical solution that will cause cells to differentiate into desired cell type;


develop means of implanting / integrating cells into patient’s own tissues so that they function with the body’s natural cells;


danger of rejection of cells therefore need to suppress immune system;


must make sure new cells do not become overgrown / develop into cancerous tumours;

Award [2 max] for a specific example ie: [1] for type of cells and [1] for proposed use:

eg retinal cells;

replace dead cells in retina to cure presently incurable diseases such as glaucoma

and macular degeneration;

eg graft new skin cells;     to treat serious burn victims;

eg nerve tissue;     help repair catastrophic spinal injuries / help victims of paralysis

regain movement;        6 max

(Plus up to [2] for quality)

                                                                              End of Section D. 14 marks.


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