Which of the following statements is incorrect?

A. Active immunity is the stimulation of the immune system to produce antigen-specific antibodies.
B. Vaccines produce immunological memory similar to that acquired by having the natural disease.
C. The most common way to acquire passive immunity is to have the natural disease.
D. Killed forms of a microorganism can act as an antigen.

C

This question was a good discriminator which the less able candidates found difficult.  

Where are microvilli located in the nephron?

A. Glomerulus

B. Proximal convoluted tubule

C. Loop of Henle

D. Collecting duct

B

Most good candidates correctly answered that microvilli are found in the proximal convoluted tubule.

What is secreted after implantation of the blastocyst in the uterine wall?
A. Estrogen which stimulates the degeneration of the corpus luteum
B. HCG which prevents the degeneration of the corpus luteum
C. Estrogen which prevents the degeneration of the corpus luteum
D. HCG which stimulates the degeneration of the corpus luteum

B

Thank you to those who spotted the new HGC hormone in place of HCG. Fortunately the candidates were not put off by this with over two thirds gaining the mark.

What is the role of HCG in early pregnancy?

A. It prevents the degeneration of the corpus luteum.
B. It initiates the development of the uterus lining.
C. It inhibits the production of estrogen.
D. It stimulates the degeneration of the corpus luteum.

A

N/A

In the production of monoclonal antibodies, B-cells are fused to tumour cells to make hybridoma cells. What can hybridoma cells do?

A. Divide endlessly

B. Ingest antigens

C. Become memory cells

D. Bind to antibodies

A

There has been a complaint that this topic is not in the guide. In section 11.1.5 the guide says to "Describe the production of monoclonal antibodies", so the production of hybridoma can be tested. This question is a good discriminator.

What first happens to a B lymphocyte when it becomes activated?

A. It divides by mitosis producing a clone of cells.
B. It begins transcription and produces antigens.
C. It differentiates into memory cells.
D. It produces antibodies using its extensive rough endoplasmic reticulum (rER).

A

N/A

What is clonal selection?

A. Production of memory B cells
B. Production of a group of identical organisms
C. Passive immunity as a result of inoculation with antibodies
D. Mitotic division of B cells activated in response to an infection

D

N/A

What is the role of HCG in early pregnancy?

A. HCG stimulates FSH secretions.
B. HCG stimulates ovarian estrogen secretion.
C. HCG stimulates ovarian progesterone secretion.
D. HCG stimulates uterine contractions.

C

Options B and C are both correct, and therefore both answers were accepted.

What is the correct order of events in fertilization?
A. fusion of gametes, acrosome reaction and then cortical reaction
B. cortical reaction, fusion of gametes and then acrosome reaction
C. acrosome reaction, fusion of gametes and then cortical reaction
D. fusion of gametes, cortical reaction and then acrosome reaction

C

Which event takes place during normal fertilization?

A. The acrosome fuses with the egg membrane.
B. The entire sperm cell enters the egg cytoplasm.
C. The egg divides to form a blastocyst.
D. The cortical granules fuse with the egg membrane.

D

The acrosome reaction is in the guide in section 11.4.9 so candidates should have known that it is the cortical granules and not the acrosome that fuse with the membrane.

Which process is part of the mechanism that controls muscle contraction?

A. Troponin enables actin heads to attach to ATP and slide along myosin.
B. Myosin heads attach to troponin and tropomyosin pulls on actin filaments.
C. Tropomyosin attaches to calcium and breaks the bond between actin and myosin.
D. Calcium frees actin filaments for myosin heads to attach.

D

This was one of the best discriminatory questions. Good candidates had obvious studied section 11.2 well.

Which kidney adaptation would be expected in the desert kangaroo rat (Dipodomys deserti)?

A. Increased nephron density
B. Longer proximal convoluted tubule
C. Longer loop of Henle
D. Increased ADH receptors on the collecting duct

 

C

Which hormone is inhibited during pregnancy in order to prevent contractions of the uterus?

A. Oxytocin

B. Progesterone

C. Estrogen

D. FSH

A

What happens during muscle contraction?
A. The number of light bands is reduced.
B. The width of the dark bands is reduced.
C. The lengths of the sarcomeres are reduced.
D. Actin and myosin filaments coil up.

C

In a mammal that had just ingested a large volume of water, what would be secreted into the bloodstream?

A. More ADH (vasopressin)
B. Less epinephrine (adrenaline)
C. More epinephrine (adrenaline)
D. Less ADH (vasopressin)

D

N/A

A skeletal muscle contains bundles of elongated muscle fibre cells. What is the longest structure within each fibre?

A. A myosin filament

B. The sarcomere

C. A myofibril

D. The Z line

C

What is required to produce monoclonal antibodies?

A. T-lymphocytes and oocytes
B. T-lymphocytes and early embryo cells
C. B-lymphocytes and tumour cells
D. B-lymphocytes and stem cells

C

N/A

What is the role of testosterone in spermatogenesis?

A. It stimulates interstitial cells.
B. It stimulates Sertoli cells.
C. It inhibits the germinal epithelium.
D. It inhibits the prostate gland.

B

Many teachers complained that the question was too specific and too much detail about the role of testosterone was expected. 42% of the candidates incorrectly answered A and 58% correctly answered B.

What would result from drinking large quantities of water?

D

Only about a third of candidates answered question 38 correctly. All of the distracters attracted substantial numbers of candidates, suggesting rather weak understanding of the topic of ADH secretion and collecting duct permeability to water.  

Which is the sequence of events in muscle contraction?

I. Use of ATP
II. Formation of cross bridges
III. Release of calcium ions from the sarcoplasmic reticulum
IV. Actin filament moves towards the centre of the sarcomere

A.    I    →    II    →    III    →    IV
B.    III    →    II    →    IV    →    I
C.    IV    →    I    →    II    →    III
D.    II    →    IV    →    I    →    III

B

There were several G2 comments on the answer choices for the sequence of events in muscle contraction. As release of calcium is the first stage, B is the only correct answer. The placement of ATP at the end of the list was confusing and many candidates chose A, making the assumption that use of ATP must be at the beginning of the sequence.  

Which structure is acted upon by ADH (vasopressin)?

A. Proximal convoluted tubule
B. Bowman’s capsule
C. Loop of Henle
D. Collecting duct

C

N/A

The Bowman’s capsule is a cup-shaped structure that is part of the nephron. What is the source of glucose in the fluid in the Bowman’s capsule?
A. Blood in the glomerulus
B. Urine in the renal pelvis
C. Filtrate in the distal convoluted tubule
D. Interstitial fluid in the medulla

A

Although this was considered a very difficult question, it was an excellent discriminator.

Which ions are released from the sarcoplasmic reticulum when a skeletal muscle fibre contracts?

A. Sodium
B. Potassium
C. Calcium
D. Chloride

C

N/A

What does the blastocyst secrete?

A. HCG

B. Estrogen

C. ADH

D. Progesterone

A

Which of the following best describes what happens in the glomerulus?

A. Selective reabsorption of water and molecules by active transport
B. Ultrafiltration introduces water and other molecules into the capillaries
C. Regulation of salt balance leading to the production of urine
D. High blood pressure forces water and other molecules into the tubule lumen

D

Was another relatively difficult question that discriminated well. The term tubule lumen was unfamiliar to candidates and is an unusual way to refer to the space inside the Bowman‟s capsule, but even so, the more able candidates were able to reject answers A, B and C and choose D correctly.

From where is human chorionic gonadotropin (HCG) secreted in early pregnancy?
A. Embryo
B. Corpus luteum
C. Ovary
D. Pituitary gland

A

This was a poorly answered question with less than 30% of candidates knowing that the embryo itself is the source of the HCG that is needed to maintain the pregnancy. The program requires that the role of HCG should be known (Assessment statement 11.4.10) but this inevitably includes the idea that the embryo signals its presence to the mother by means of secreting this hormone.

What is an example of active immunity?
A. Antibodies passed from the mother to fetus across the placenta
B. Antibodies produced by another organism and injected to protect against a disease
C. Antibodies passed from the mother in colostrum during breastfeeding
D. Antibodies produced after the defence mechanisms have been stimulated by antigens

D

What is directly responsible for allergic symptoms, including a runny nose or itchy eyes?

A. Pathogens
B. Histamine
C. T-lymphocytes
D. Antigens

B

What is required for a skeletal muscle to exert force?

A. Extensor and flexor muscles
B. Synovial joints
C. Attachment to bones
D. Ligaments

C

In a healthy kidney which of these substances would you expect to find in the tubular fluid entering the loop of Henle?

I. Glucose 

II. Sodium ions 

III. Proteins

A. I only
B. I and II only
C. II only
D. II and III only

C

N/A

What is the function of the knee joint?

A. It permits movement in one plane.
B. It allows bones to glide over each other.
C. It facilitates movement in all planes.
D. It allows a wide range of movement.

A

N/A

What is the function of the epididymis in the male reproduction system?
A. To stimulate sperm production by secreting testosterone
B. To store the sperm in the final stages of maturation
C. To provide fluids to nourish the sperm
D. To transport the sperm from the testes to the urethra

B

What is a function of synovial fluid in the elbow joint?

A. Joins the humerus to the radius and ulna

B. Grows red blood cells

C. Protects the biceps

D. Allows easy movement

D

Which of the following events form the basis of immunity upon which the principle of vaccination is based?

D

Eight teachers objected to this question. Student performance on the question was poor with only 30% answering it correctly. The choice of incorrect response was spread between responses A, B and C. Students should have been easily able to rule out A and B as clonal selection is a clear part of the outcome. If students understand the clonal selection process correctly, then they would know that injection with an attenuated virus would result in polyclonal antibodies.

During urine production, what happens if the water content of the blood is too low?

A. Membrane channels are produced in the cells of the collecting duct.
B. The pituitary gland stops secreting ADH.
C. The collecting duct becomes less permeable to water.
D. Large volumes of dilute urine are formed.

A

This was surprisingly the hardest question by difficulty index showing that candidates didn't know this topic. While there were concerns about the wording of answer A, the other three choices were the opposite of what happens in this situation given.

During muscle contraction, what is the role of calcium ions ( Ca²⁺) which are released from the sarcoplasmic reticulum?

A. To cause ATP hydrolysis on myosin filaments
B. To bind to both actin and myosin filaments forming a cross-bridge
C. To cause the cross-bridge to detach itself and start a new cycle
D. To cause binding sites on the actin filaments to be uncovered

D

This was another question with a very high discrimination index and a relatively low percentage of candidates answering correctly. More candidates than expected thought that calcium ions bind to actin and myosin filaments forming a cross-bridge. Although the candidates are not expected to know the roles of troponin and tropomyosin, they should understand that calcium ions cause the binding site for myosin heads to be uncovered on actin filaments.

What helps to prevent polyspermy?

A. The unequal division of oocytes

B. The placental barrier

C. The contraceptive pill

D. The cortical reaction

D

What is a blastocyst?

A. An unfertilized egg surrounded by follicle cells
B. An unfertilized egg cell expelled by menstruation
C. The follicle when it has swelled up with fluid
D. The embryo when it has become a hollow ball of cells

D

N/A

Which cells activate helper T-cells by antigen presentation?
A. B-cells
B. Bacteria
C. Macrophages
D. Plasma cells

C

How are B-cells activated?
A. An antibody binds to a B-cell which is activated by a helper T-cell.
B. An antigen binds to a B-cell which is activated by a helper T-cell.
C. An unattached antigen binds to a helper T-cell which activates the B-cell.
D. An antibody binds to a plasma cell which is activated by a helper T-cell.

B

This raised a few comments on the G2 forms. The correct answer of B was only given by half the number of the candidates who gave the incorrect answer of C. It was decided that the wording was perhaps too subtle and in the end both B and C were deemed worthy of the mark.

A secondary immune response occurs when an antigen is encountered on a second occasion, due to exposure to a pathogen that previously caused infection. Which property of some viruses explains the lack of a secondary immune response?

A. Viruses fail to induce a primary response.

B. Viruses can have a high mutation rate.

C. B cells do not interact with viruses.

D. Antibodies cannot interact with viruses.

B

How can active immunity be acquired?

A. By having the disease
B. Injection of antibodies
C. Through colostrum
D. Via placenta

A

N/A

What are fused in the production of monoclonal antibodies?

A. Tumour cells and T-cells
B. Tumour cells and B-cells
C. B-cells and T-cells
D. Antibodies and antigens

B

N/A

What happens immediately after the penetration of the egg membrane by a sperm during fertilization?

A. The acrosomal reaction
B. The secondary oocyte develops
C. The blastocyst divides by mitosis
D. The cortical reaction

D

N/A

The diagram below shows the side view of the arm joint.

Which letter is pointing to the ulna?

A. W
B. X
C. Y
D. Z

D

N/A

Which of these statements about the human placenta is incorrect?

A. The placenta is the site of nutrient and gas exchange between the mother and fetus.
B. The placenta produces hormones, such as estrogen.
C. The placenta begins to develop after implantation of the blastocyst.
D. The mother’s blood and the baby’s blood mix in the placenta.

D

While D was obviously the correct response as the mother‟s blood and baby‟s blood do not mix in the placenta, many were distracted by the B. In 11.4.12, the secretion of both estrogen and progesterone by the placenta is to be included. 

What is the role of ligaments in humans?

A. Linking bones together at a joint
B. Preventing friction at a joint
C. Contracting to move a joint
D. Attaching muscles to bones

A

N/A

Which is the correct sequence of stages in fertilization?

D

N/A

Which processes are required for the reabsorption of glucose in the kidney tubules?

I. Simple diffusion
II. Facilitated diffusion
III. Active transport

A. I and II only
B. II and III only
C. I and III only
D. I, II and III

B

This question turned out to be a very bad discriminator but many candidates had the correct answer.

What is a difference between spermatogenesis and oogenesis?

D

N/A

Which hormone increases in concentration in the mother’s blood during early pregnancy?

A. ADH
B. FSH
C. HCG
D. LH

C

There was some concern on the terminology used in the question. The term early pregnancy is not too scientific but a more definite time span might have confused candidates, which is why it was not used. This question proved to be a very good discriminator, so it probably did not distract candidates, as the more able candidates were getting this question right.

Which of the following is a term for muscle cell?

A. Muscle bundle
B. Muscle fibre
C. Myofibril
D. Sarcomere

B

This question was very difficult for most candidates. C and D should have been eliminated by candidates as they do not have a membrane.  

In which region of the kidney is the glomerulus found?
A. Cortex only
B. Medulla only
C. Cortex and medulla
D. Pelvis

A

What occurs in the body after the injection of a vaccine containing antigens?

A. Activated B-cells divide to form memory cells.
B. The receiver of the vaccine develops passive immunity.
C. Helper T-cells produce specific antibodies.
D. Macrophages are cloned and destroy the antigen.

A

N/A

What is produced in the body during HIV infection?

A. Anti-HIV antibiotics
B. Anti-HIV anticodons
C. Anti-HIV antibodies
D. Anti-HIV antigens

C

N/A

Which processes require calcium?

I. Muscle contraction
II. Movement of an action potential along an axon
III. Production of the skeleton of hard corals

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

B

Where is human chorionic gonadotrophin (HCG) produced?

A. Ovary
B. Anterior pituitary
C. Embryo
D. Posterior pituitary

C

N/A

What is the role of ligaments in humans?

A. To hold bones together
B. To hold muscles together
C. To attach bones to muscles
D. To attach nerves to muscles

A

N/A

What is the role of calcium in muscle contraction?

A. To release tropomyosin from myosin

B. To bind to troponin so myosin-binding sites on actin are exposed

C. To bind to tropomyosin so ATP can bind to actin

D. To release ATP from actin so myosin can bind to troponin

B

What is the role of ATP during contraction of a skeletal muscle fibre?

A. To uncover the myosin binding sites on actin filaments
B. To make cross-bridges between actin and myosin filaments
C. To break cross-bridges and re-set myosin heads
D. To cover the myosin binding sites on actin filaments

C

In question 37 a substantial minority of candidates thought that ATP is used to make cross bridges rather than break them. The development of rigor mortis is an indicator that energy from ATP is directly used to break rather than make cross bridges.

What is the function of the synovial fluid in the elbow joint?

A. It removes waste products from the surrounding tissue.
B. It provides glucose and oxygen to the cartilage.
C. It lubricates the joint and prevents friction.
D. It prevents the bone from becoming brittle.

C

Some teachers criticised 37 on the grounds that synovial fluid both lubricates the joint and supplies glucose and oxygen to the cartilage. Nearly 95% of candidates chose the former answer, which was the expected one. As a result this question hardly discriminated between the candidates.  

What is the role of calcium ions during muscle contraction?

A. To block the myosin binding site on actin when the muscle is not contracting
B. To move the molecules blocking the myosin binding site on actin
C. To form cross-bridges between the actin and myosin filaments
D. To provide the energy for resetting the myosin heads

B

In question 39, substantial numbers of candidates thought that calcium ions form cross bridges between actin and myosin filaments during muscle contraction. The expected answer was that they move the molecules blocking the myosin bonding sites on actin. Teachers need to be aware that some You Tube clips on this topic are misleading and of course all material taken from the internet should be treated with circumspection.

What results from the fusion of tumour cells with B-cells?

A. The inability of B-cells to divide
B. The production of monoclonal antibodies
C. The production of antigens
D. The activation of helper T-cells

B

This question was a good discriminator and good candidates clearly understood that fusing tumour cells and B lymphocytes serves the purpose of producing monoclonal antibodies.

What is indicated by the letters X, Y and Z?

D

N/A

When a pathogen is ingested by a phagocyte, which event occurs first?

A. T-cell activation
B. Memory cell proliferation
C. Antigen presentation by the phagocyte
D. B-cell activation

C

This question also had a high discrimination index, where the good candidates knew that antigen presentation by the phagocytes is the first event after a pathogen is ingested by a phagocyte, although the word phagocyte in the answer possibly gave the answer away.

Which types of immunity are acquired by each of the following actions?

D

N/A

What is the role of HCG (human chorionic gonadotrophin) in early pregnancy?

A. It stimulates the release of FSH (follicle stimulating hormone).
B. It maintains the corpus luteum.
C. It inhibits the release of progesterone.
D. It stimulates implantation of the blastocyst.

B

N/A

What is the main role of nerves in human movement?

A. To cause muscles to stretch
B. To move joints
C. To transport pain signals that indicate muscle injuries
D. To stimulate muscle contraction

D

N/A

Through what process does a spermatid become a functioning spermatozoan?

A. Mitosis

B. Differentiation

C. Fertilization

D. Meiosis

B

What forms the basis of immunity after vaccination?

D

The graph shows the daily amount of the residue of a drug in the wastewater of a hospital.

What can be deduced from these data?

A. The drug is not fully reabsorbed by the proximal convoluted tubules.

B. The glomeruli are not permeable to the drug.

C. The collecting ducts reabsorb all of the drug.

D. The drug is catabolized by the liver.

A

Which pair of statements best describes oogenesis and spermatogenesis?

D

This was criticized on some G2 forms for unclear wording but three quarters of candidates answered it correctly and it discriminated well between the stronger and weaker candidates. Well-prepared candidates were able to answer it without needing to look at the second column of the table, although the advice is still to always look at all the information provided in a question before choosing an answer.  

Which sequence of events leads to the production of antibodies?

A

Although the presentation of the information was quite novel, candidates were able to answer this question without problems.

What are the roles of the following structures in the production of semen?

C

N/A

The diagram shows the exchange processes that take place in the placenta between the maternal and fetal blood. Which process requires endocytosis?

D

The image shows the male reproduction system.

Where is prostate cancer likely to start developing?

A. In X only
B. In Y and Z only
C. In Z only
D. In X, Y and Z

C

Candidates found this question very easy.

The diagram shows the nephron in a kidney. Which labelled part is permeable to sodium and not to water?

C

N/A

What is bone X and muscle Y in the diagram of the elbow joint?

B

The diagram shows the female reproductive system.

[Source: © International Baccalaureate Organization 2017]

Which structures do K and L identify?

B

The diagram below shows a human egg.

What are the structures labelled I, II and III?

D

In which part of the nephron is salt secreted from the tubule to increase osmotic potential?

B

Two teachers objected to the use of the term osmotic potential. 74% of students answered correctly. Knowledge of the meaning of the term can be inferred from the question.

The diagram shows a nephron from a human kidney. In what part of the nephron would most glucose be reabsorbed?

A

In the diagram of the nephron below, what structures are indicated by the letters Y and Z?

C

There were some complaints about the level of depth that the candidates must know. This question was a very good discriminator and the question did not seem too hard for most candidates.

The table shows solute concentrations in normal blood plasma and the fluid in one section of the nephron.

In which section of the nephron would you expect to fi nd these concentrations?

A

The diagram below shows a longitudinal section through a kidney. What is the structure labelled Z and what is its function?

C

This question did not discriminate well with many able candidates choosing the incorrect response.  Candidates knew that Z was the cortex and were split in their choice of A and C. Osmoregulation refers to the whole kidney and is more related to distal convoluted tubule in the medulla. Bowman‟s Capsules in the cortex carry out ultrafiltration. In retrospect, this was not a good question.

In the following diagram of the kidney, which structure contains urine?

D

N/A

Where are structures I, II and III found in the human body?

B

N/A

The following is a diagram of the elbow joint.

What structures are indicated by the letters X, Y and Z?

C

Where does the acrosome reaction occur?

C

The image shows a section of a seminiferous tubule.

What is shown by the letter X?

A. Meiosis I in a primary spermatocyte
B. A spermatogonium undergoing mitosis
C. Meiosis II in a secondary spermatocyte
D. A spermatid undergoing meiosis

A

Most candidates recognized cell X as a primary spermatocyte. There were some complaints that the chromosomes were not very clear, but this did not seem to be the case.

The micrograph shows the structure of a testis undergoing spermatogenesis.

What is the structure labelled X?

A. Sperm
B. Sertoli cell
C. Leydig cell
D. Germinal epithelium cell

B

This attracted the most comments from teachers, with many saying that the quality of the micrograph was poor and that the Sertoli cell did not show clearly. The examining team reevaluated the micrograph, because the statistics for this question were very unusual, but it was decided that the Sertoli cell showed about as clearly as it they ever do. The cytoplasm does not usually stain densely so can appear as a gap between other cells rather than a strong feature itself. The possible answers to the question allowed candidates to identify the cell by eliminating the incorrect answers. The cell was clearly not a sperm or a Leydig cell, so two answers could easily be eliminated. The remaining answers were Sertoli cell and germinal epithelium. Although more candidates chose the former, large numbers of candidates decided that the cell was a germinal epithelium cell. This is not possible, because the cell is about half way through the wall of the seminiferous tubule, not in its outer layer of cells.  
Many of the stronger candidates thought that the cell was in the germinal epithelium and there was therefore a negative discrimination index. On average, weaker candidates answered the question slightly better than strong candidates. This is an area of the programme that should be emphasized more by teachers to ensure that candidates' knowledge is better. Perhaps as it comes at the end of the AHL it is sometimes neglected.

The diagram below shows some stages in the production of monoclonal antibodies. What are stages X, Y and Z?

D

The word hybridoma does not appear in the guide. This did not affect the candidates' performance, as it had a good discrimination index.

Which letter correctly identifies the medulla?

C

N/A

What structure is indicated by the arrows?

[Source: Courtesy Roger Craig, University of Massachusetts]

A. One muscle fibre

B. One sarcomere

C. One myofibril

D. One Z line

B

The images below show muscle tissue.

Which image shows contracted muscle tissue?

A. I because the dark band is narrower.
B. II because the Z lines are closer together.
C. II because there is less overlap between actin and myosin.
D. I because the dark bands are darker.

B

N/A

What does label X indicate?

A. Sarcolemma
B. Sarcomere
C. Sarcoplasmic reticulum
D. Endoplasmic reticulum

B

N/A