Tricky revision questions

Question 1

A 62 year old man visits his GP complaining of abdominal pain, dark coloured faeces, unexplained weight loss and a persistent change in his bowel habits. The GP suspects that the man may have bowel cancer. The most common type of bowel cancer is adenocarcinoma, a malignant neoplasm originating from gland forming cells. From what type of tissue do most glands originate from?

Answer 1

Epithelial tissue

Most glands begin to develop in utero, approximately 5 weeks after fertilisation. The process of formation is as follows:

1. Fibroblast Growth Factor is produced by mesenchymal cells
2. This FGF stimulus is received by epithelial cells, causing them to proliferate downwards, towards the source of the FGF.
3. The migrating epithelial cells produce extracellular protein degrading enzymes, allowing them to proliferate further downwards.
4. What happens next depends on whether the gland is exocrine or endocrine:
   a. In an endocrine gland, epithelial cells in the centre of the downward growth undergo apoptosis. This leaves a duct in the middle of the growth. Cells at the base (apex) of the growth differentiate into secretory cells.

b. In an exocrine gland, all cells that link the migratory cells to the original epithelium apoptose, leaving just a group of epithelial cells surrounded by an extracellular matrix. These epithelial cells then differentiate into secretory cells and induce the formation of capillaries around the gland.

Question 2

Women in Chad have a lifetime risk of maternal death of 1 in 16 whilst in the UK this same risk is around 1 in 10,000. Mother and baby What is this difference an example of?

Answer 2

Inequity

Question 3

inequity

Answer 3

refers to differences in the quality of health and healthcare across different populations. Health inequity is different from health inequality. For example, if one population dies younger than another because of genetic differences, this would be health inequality. On the other hand, if a population has a lower life expectancy due to lack of access to medications, this would be health inequity.

Question 4

A competitive inhibitor

Answer 4

competes with the substrate for the active site of the enzyme: This means that increasing the concentration of substrate will decrease the chance of inhibitor binding to the enzyme. Hence, if the substrate concentration is high enough the enzyme will reach the same Vmax as without the inhibitor. However, it will require a higher concentration of substrate to achieve this and so the Km of the enzyme will also be higher.

Question 5

A stereotype is a thought that someone has about specific types of individuals that may or may not accurately reflect reality. Stereotypes can also be thought of like caricatures, which are pictures that exaggerate certain features while oversimplifying others and end up distorting the essence of an individual. Many stereotypes are widely held but they are also overgeneralised images or ideas about a particular type of person. Any time we group individuals together and make a generalisation or judgment about them without knowing them, this is an example of a stereotype. People who encounter the threat of being judged by negative stereotypes related to weight, age, race, gender, or social class in health care settings are more likely to have hypertension, be depressed, and rate their own health more poorly. They are also more distrustful of their doctors, feel dissatisfied with their care, and are less likely to use preventive care.

Answer 5

a thought that someone has about specific types of individuals that may or may not accurately reflect reality. Stereotypes can also be thought of like caricatures, which are pictures that exaggerate certain features while oversimplifying others and end up distorting the essence of an individual. Many stereotypes are widely held but they are also overgeneralised images or ideas about a particular type of person. Any time we group individuals together and make a generalisation or judgment about them without knowing them, this is an example of a stereotype. People who encounter the threat of being judged by negative stereotypes related to weight, age, race, gender, or social class in health care settings are more likely to have hypertension, be depressed, and rate their own health more poorly. They are also more distrustful of their doctors, feel dissatisfied with their care, and are less likely to use preventive care.

Question 6

The Km is

Answer 6

the substrate concentration (in this case glucose) that gives half maximal velocity

Question 7

Which of the following vitamins is water soluble? vit A, C, D, E, K

Answer 7

Vitamin C

Question 8

A biochemist studying the function of the enzyme glucokinase fits a graph of experimental data using the Michaelis-Menten equation.

Which option represents this equation ?

Answer 8

Question 9

Identity work refers to

Answer 9

the establishment and maintenance of an acceptable identity

Question 10

A 23 year old man attends the accident and emergency department with a stab wound on the left side of his groin. The femoral nerve, artery and vein are undamaged but the doctor believes that the stab wound may have damaged the lymphatic system by cutting through the lymphatic vessels that supply the man’s inguinal lymph nodes.

In what order does lymph flow through this system from cells to blood?

Answer 10

A

Question 11

“inverse care law”

Answer 11

That the availability of good medical care tends to vary inversely with the need of the population served

Question 12

What type of exocrine glands are the mammary glands?

Answer 12

A compound acinar gland is a type of exocrine gland that has a duct with multiple duct branches. The duct branches have smaller branches leading from them to the secretory portion of the gland. The secretory portion of the duct has a berry shape. An example of this type of gland is the mammary gland.

Question 13

What is co-dominance?

Answer 13

Pair of alleles in heterozygote are equally dominant and so the resulting phenotype is a mix

Question 15

What is the pattern of inheritance in G6PD deficiency?

Answer 15

X linked recessive

Question 16

What pathway is this glucose-6- phosphate dehydrogenase involved in?

Answer 16

pentose phopshate pathway

Question 17

What is NADPH required for ?

Answer 17

• reducing power for biosynthesis • maintenance of GSH levels
• detoxification reaction

Question 18

Why are red blood cells particularly affected in G6PD deficiency?

Answer 18

RBC’s are particularly affected since the pentose phosphate pathway is the only source of NADPH in these cells and their role as oxygen carriers puts them at increased risk of oxidative damage.

Question 19

What abnormality is commonly found in a blood sample of a patient with this deficiency and briefly explain why they are formed ?

Answer 19

1- Heinz bodies

2- Haemoglobin become crosslinked due to inappropriate disulphide

bonds which form insoluble aggregates called Heinz bodies.

Question 20

Enzymes can be classed into two different groups: fibrous and globular

State two differences between these two groups?

Answer 20

1- Fibrous Globular Support,

2- shape,

3- protection Catalysis,

4- regulation Long strands or sheets

5- Compact shape

6- Single type of repeating secondary structure

7- Several types of secondary structure

Question 21

examples of DNA damage

Answer 21

Mismatches, deamination, single strand breaks, double strand breaks, inter-strand crosslink, bulk adducts

Question 22

what is DNA replication stress- definition

Answer 22

Inefficient replication that leads to replication fork slowing, stalling and or breaking

Question 23

Explain how repetitive DNA can lead to replication stress

Answer 23

Repetitive DNA can lead to fork slippage. If the template strand has repetitive DNA and loops out, there is a forwards slippage and DNA polymerase will miss out nucleotides

Question 24

Explain how base excision repair takes place?

Answer 24

1. Deamination converts a cytosine base into uracil.
2. The uracil is detected and removed, leaving a base-less nucleotide. This is then removed leaving a hole in the DNA backbone.
3. This is then filled with the right base by DNA polymerase and the gap is sealed by DNA ligase.

Question 25

A 17-year-old female presents to the GP with her mother. The mother describes the whites of her eyes to be blue. You are accompanying the GP and note the girl to be significantly taller than the mother.

History reveals the father is about the same height as the mother. What condition do you suspect to be most likely?

Answer 25

Marfans

Question 26

What else would you expect to find upon inspection without further testing or imaging?

Answer 26

Slender limbs; long fingers; long toes; big hands; big feet.

Question 27

Many people with this condition live a normal-length life. What however, may develop and how might this cause sudden death?

Answer 27

Dilated aorta; aortic aneurysm; ruptured aortic aneurysm; (catastrophic) haemorrhage.

Question 28

State what gene is likely to be defective

Answer 28

Fibrillin-1 gene.

Question 29

State the inheritance pattern of this genetic defect- Marfans

Answer 29

Autosomal dominant.
Half-a-point for: Autosomal only; dominant only.
Do not accept: Only one parent has to carry the gene.

Question 30

An 8-year-old male presents to A&E with difficulty breathing and coughing up a mucoid secretion. His father is accompanying him.

Respiratory examination and CXR reveal no cause for immediate concern. You suspect cystic fibrosis and refer the boy to his GP. State which test the GP would order to confirm the diagnosis and state what the test would look for.

Answer 30

Accept for one point each: PCR; genetic abnormality. Brownie

points if specific gene mutations are mentioned. Do not accept: Genetic testing.

Question 31

State the inheritance pattern of cystic fibrosis.

Answer 31

Autosomal recessive

Question 32

Jaqen H’ghar, a 63 year old male presented to the GP with complaints of fatigue that increases during periods of activity and improves after rest. The patient also reports of having double visions. Myasthenia Gravis is suspected.

What investigation would the GP request, and what you be looking for in the results of this investigation?

Answer 32

Blood test (1/2)
Acetylcholine receptor antibodies (1/2)

Question 33

Myasthenic patients can experience myasthenia crisis. Why is this manifestation of the disease life threatening?

Answer 33

Function of respiratory muscles can decrease (1) which causes a loss of control in breathing (1)

Question 34

Myasthenia gravis is a pathology which occurs at the Neuromuscular Junction (NMJ). NMJ is an area between a communicating motor neurone and muscle fibre. Describe the sequences that occur at the NMJ which leads to a muscular contraction. (6x1⁄2 marks)

Answer 34

1. Nerve impulses arrive at the NMJ which causes Acetylcholine,
2. ACh to be released into the synaptic cleft (1/2).
3. ACh binds to Nicotinic Acetylcholine Receptors (nAChR) on the post-synaptic membrane which causes depolarisation of the sacrolemma (1/2).
4. Voltage-gated Sodium channels open and sodium enters cell (1/2). This causes depolarisation waves to spread over over the sacrolemma and into T tubules (1/2).
5. Voltage gated Calcium Channels of terminal cisternae opens and calcium is released into sacroplasm (1/2).
6. Calcium Binds to troponin C and contractile cycle is initiated (1/2)

Question 35

A week later, the GP prescribe Jaqen some medications to relieve his symptoms. Name the two classes of drugs that are commonly used to treat Myasthenia Gravis.

Answer 35

Acetylcholinesterase inhibitors (1) Immunosuppressive drugs (1)

Question 36

Apart from Myasthenia gravis, organophosphate poisoning can also affect the NMJ. Name a common source of organophosphates (1 mark) and describe the pathophysiology(2 x 1⁄2)

Answer 36

(Insecticides, nerve gases) (1)
Organophosphate inhibits acetylcholinesterase(1) which causes continuous acetylcholine activity at the NMJ (1)

Question 37

Which type of tissue fixing takes place in this procedure for immediate intraoperative microscopy? (1 mark)
Describe the process of staining (3x1/2 marks) and importance of this tissue staining whilst still in surgery (1x1⁄2 marks)

Answer 37

Frozen Section (1)
Surgical specimen is frozen to -20 to -30 dc. (1/2)
A cryostat is then used to slice the tissue. (1/2)

Haematoxylin and Eosin is used to stain the tissue. (1/2) Importance: To visualise architure of cells. (1/2)

Question 38

Two regions of the body include five layers of skin. Name all the five layers (1 mark) and state where are these layers found. (1 mark)

Answer 38

Stratum corneum, stratum lucidum, stratum ganulosum, stratum spinosum, stratum basale (1) *Come Lets Get Some Beer mnemonic

Soles of hands and feet (1)

Question 39

Apart from epithelial cells, name two other cells that are found in the epidermis and state their function (4x1⁄2 marks)

Answer 39

Keratinocyte (1) which is involved in keratin synthesis (1)

Melanocyte (1) which produces melanin for skin pigment (1) Langerhans cell (1) which is an antigen presenting cell (1) Merkel cell (1) which is a mechanoreceptor cell (1)
*Accept any of the two cells and functions

Question 40

What are the two common types of Hyperkeratosis?

Answer 40

Eczema

Psoriasis

Question 41

State the definition of the Lay referral system

Answer 41

The chain of advice-seeking contacts which the sick make with other lay people instead of seeking help from healthcare professionals

Question 42

Why is it important for healthcare professionals to understand the Lay referral system?

Answer 42

Helps doctors understand the role they play in a patient’s health (1) Understand why people might delay in seeking help (1) Understand how, why and when people consult a doctor (1) Identify whether patients use alternative medicines (i.e. traditional medicine, herbs, etc) (1)

Identify patients’ awareness of available health services and medication (1)

Question 43

in developming fetal occipital bone, where can osteoprogenitor cells be found?

Answer 43

as part of the peruostium

• as the bone develops further, they differentiate into osteoblasts that line the endosteum

Question 44

what is the most probable cause of the aneursym

Answer 44

too little eleastin in the tunica media

Question 45

what process in collagen synthesis does vitamin C specifically increase

Answer 45

intracellular production of procollagen

Question 46

what is the primary factor for providinf bone strength

Answer 46

regular exercise

Question 47

sacrum is what type of bone

Answer 47

irregular

Question 48

which cells contract to aid rthe secretory portion of eccrine sweat glands

Answer 48

myoepithelial cells

Question 49

which structure in an embryo is destined to become the umbilical cord

Answer 49

the conencting stalk

Question 50

Studies have shown that about half of the energy requirement of the human brain can be accounted for by the activity of the Na+-K+-ATPase (the Na+pump).

Approximately how much of the resting membrane potential in neurones is attributable to the electrogenic activity of this pump?

Answer 50

5-10mV

Question 51

A 79 year old man with a 40 pack-year history of smoking presents at the accident and emergency department with shortness of breath and persistent chest infections. A junior doctor conducts a chest X-ray of the patient and to his surprise discovers that the patient’s heart is on the right side of his chest and the stomach and spleen are on the patient’s right side. The patient has undiagnosed situs inversus.

Answer 51

Immotile ciliated cells at the primitive node on the dorsal surface of the trilaminar disc results in the lack of left-ward flow of signalling molecules in the trilaminar disc during gastrulation.

Situs inversus is a developmental disorder where there is a complete mirror image of visceral organs; the heart will be on the right side of the thorax the stomach and spleen will be on the left side of the abdomen and the liver will be on the right of the abdomen. Situs inversus occurs due to the absence of the wafting of the signalling molecules as the cilia at the primitive node (which are responsible for the wafting) are immotile. These signals lead to the initiation of signalling cascades that correspond for the development of ‘left-sidedness’. The absence of these signals leads to the development of ‘right sidedness’. If the ciliated cells are immotile, then these signals are not wafted in a leftward direction, leading to the development of Situs Inversus.

Question 52

A 16 year old boy with a 12 month history of dystonia, sleep disturbance and difficulty walking is referred to the metabolic medicine department. After further testing, Niemann-Pick type B disease is diagnosed. This disease results from deficiency in the enzyme sphingomyelinase.

What effect does this enzyme have on the reaction it catalyses?

Answer 52

Enzymes lower the activation energy for the reaction they catalyse. Enzymes do not however change the difference in energy levels between reactants and products.

Question 53

A 56 year old man on the cardiology ward is bradycardic and the doctor records an electrocardiogram (ECG). A pattern of regular PR Intervals with a sudden drop of a QRS interval is observed in a regular pattern. The doctor believes that the patient is suffering from Type II 2nd Degree heart block, which normally occurs as a result of a defect in the His-Purkinje conduction system.

What characteristics do the cells that make up this conduction system posses?

Answer 53

Lots of glycogen, few myofibrils and many gap junctions

Purkinje fibres are a specialised type of cardiomyocyte found in the ventricles of the heart. Their role is to increase the electrical activity of the heart. They contain a high amount of glycogen and have large number of intercalated discs which contain many gap junctions. This allows these cells to rapidly pass action potentials through the myocardium of the ventricles; they conduct action potentials between cells at a rate of 4m/s whereas normal cardiomyocytes conduct action potentials at only 0.5ms. They have little role in contraction; therefore, they have few myofibrils.

Question 54

A pharmaceutical company is developing a new inhibitor of the sodium-calcium exchanger (NCX) for protection against myocardial ischemia/reperfusion injury.

What is the normal stoichiometry of this exchanger working in forward mode?

Answer 54

3 Na+ ions in : 1 Ca2+ ion out

Question 55

Histones are proteins found in eukaryotic cell nuclei where they form part of chromatin. The isoelectric point of histones is very high at about 10.8 and this facilitates strong interactions with DNA.

Which amino acids are in abundance in this type of protein allowing interactions with DNA?

Answer 55

Lysine (K) and Arginine (R)

Histones are proteins found in eukaryotic cell nuclei, tightly bound to DNA which has many negatively charged phosphate groups. The pI of histones is very high, about 10.8, and contains an abundance of the positively charged amino acids lysine and arginine that contribute to the strong of histones to DNA. Important point to remember: DNA is negatively charged.

Question 56

The Global Burden of Disease project produces comparable estimates of ill health and injury around the world and allows quantification of the many risk factors which contribute to premature mortality in different countries.

Which risk factor currently has the greatest impact on this measure in the UK?

Answer 56

tobacco smoking then dietary risk

Question 57

Recent Office for National Statistics data show that life expectancy at birth of males living in England’s most deprived areas was lower than that in the most affluent areas.

What is the approximate size of this difference?

Answer 57

9 years