Oxbridge Medicine Academic Questions

• Consider things that we class as drugs e.g. paracetamol and what we don't class as drugs e.g. water

• Drugs don't have to necessarily have to be external to the body e.g. insulin injections are classed drugs but insulin is hormone made naturally by the body

• All 'drugs' seem to have something in common - they interact with major biological molecules in the body

• Examples to illustrate would be good: - Proteins: enzyme inhibitors such as aspirin - DNA: chemotherapy drugs e.g. cisplatin

• Typically have a therapeutic effect by affecting a physiological state

• Immediate changes - reduction in blood volume

• How would the body respond to this?

• Reasonable to suggest that it has to make sure that important organs are still perfused properly and it would prioritise conserving water

• Downstream effects - increase in heart rate, vasoconstriction to maintain blood pressure

• Could suggest hormones responsible for this such as adrenaline

• To conserve water the blood flow to the kidney would be reduced

• Increase in feeling of thirst

• SARS-CoV-2 is an RNA virus which translates its RNA into proteins upon infecting cells while also replicating its RNA

• mRNA in the vaccine contains code for the spike protein - the virus uses this to enter cells

• First the vaccine has to get into cells - it has to cross the cell membrane barrier

• In some vaccines the mRNA has a lipid coat to enable it enter without needed a protein

• Once translated the spike protein has to be recognised by the immune system - the cell achieves this by presenting it on its surface

• This stimulates the production of antibodies which are specific to the spike protein

• They prevent the spike protein from binding to its receptor

• There's no right answer here, consider the function of different organs and what would happen to the body without them

• Brain - processing of sensory information, generating motor commands, source of emotions, consciousness etc. Legal death is brain death therefore a favourite?

• Heart - pumping of blood to rest of body, without it other organs would die from hypoxia due to lack of oxygen

• Lungs - gas exchange surface, needed to get rid of carbon dioxide and take in oxygen for cells to respire

• Kidneys - osmoregulation, filtering of the blood. It's possible to live with just one so this suggests it's not as important as the others

• Liver - metabolism of harmful substances in the blood, filtering of substances, production of bile etc.

• Not all DNA forms part of of the coding sequence for proteins hence the term 'junk'

• While it's referred to as junk DNA, it is still important to suggest their purpose for being in the genome

• Within genes there are introns which are spliced out during post-transcriptional modification of RNA

• Exons can be arranged in different ways which increases the diversity of proteins which can be generated from the same gene

• Sequences upstream of the gene are needed to recruit RNA polymerase and transcription factors e.g. the promoter sequence

• Part of the DNA is required to recruit ribosomes when transcribed into mRNA (ribosome binding site)

• Some parts of the DNA have unknown function e.g. repetitive elements

• Some DNA sequences are remnants of past retroviral infections which have remained integrated into the genome

• Think about the main functions of a placenta and suggest features accordingly

• Each feature performs a function that the fetus' organs will perform post-natally (in brackets)

• Gas exchange surface - high surface area with rich blood supply to maximise transfer of oxygen from mother to fetus (lungs)

• Excretory functions, water balance, pH regulation - need someway to remove waste products from fetus (kidney)

• Synthetic and secretory functions - useful to coordinate pregnancy changes in mother and fetus since it acts as the interface between the two (most endocrine glands)

• Immunological interactions and protection - the fetus is a foreign body so placenta needs to ensure that the mother doesn't reject the fetus during pregnancy

• Glucose is the substrate for respiration - cancer cells require more since they are constantly growing unregulated by the cell cycle

• Glucose eventually used to generate ATP

• ATP drives biosynthetic pathways such as nucleotide synthesis which cancer cells will be doing lots of

• Gives the cancer cell an evolutionary advantage over other cells if it's able to divide more

• It's a good idea to first outline how to describe the position of a sound in space

• (1) Vertical plane - elevation

• (2) Horizontal plane - azimuth

• The external ear itself (pinna) can affect elements of the sound depending on its elevation

• This is interpreted by the brain - how might this 'interpretation' work?

• Since we have 2 ears it would be reasonable to suggest that there is a time delay in the detection of sound between one ear and the other depending on the position of the sound in the horizontal plane

• This time delay can be used as a signal by the brain to locate sounds

• In addition, the head provides an acoustic shadow which reduces the intensity of sounds depending on which side of the head it originated from

• This difference in intensity between the 2 ears can also be used as a signal to pinpoint the location of a sound

• At altitude there is a reduction in barometric pressure

• This causes a reduction in the inspired partial pressure of oxygen (pO2) leading to hypoxia

• To compensate for this people tend to hyperventilate to increase their pO2

• However, this reduces their pCO2 since they are exhaling more CO2; this causes an increase in the pH of their cerebrospinal fluid (CSF)

• Changes in the composition of CSF brings pH back to normal

• Oxygen diffusion can be rate-limiting at altitude because there is a suppressed partial pressure gradient of oxygen

• Therefore, it takes longer for oxygen to diffuse into the blood

• Finally there is an increase in the concentration of 2,3-DPG which causes a right shift in the oxygen dissociation curve

• This facilitates unloading of oxygen since it has a lower affinity to haemoglobin

• For permanent residents at high altitude there is a physiological adaptation that occurs to increase oxygen content - a significant increase in the concentration of haemoglobin (polycythemia)

• Antibiotic - drugs used to kill microorganisms e.g. bacteria

• Anticancer - drugs used to treat cancer

• Main difference is in target: pathogens vs cancerous cells

• Different mechanisms of action, suggest some examples: - Antibiotics can target cell walls (bacteria), lipid within membranes (fungi), enzymes needed for replication (viruses), DNA etc - Anticancer drugs can be broadly split into cytotoxic and molecular targeted drugs - Cytotoxic drugs can target: DNA and its synthesis, enzymes needed for DNA replication, the mitotic spindle etc - Molecular targeted drugs can target: receptors, tyrosine kinases, hormone synthesis and many more

• Improvements in these drugs mostly come from making them more selective, particularly with anti-cancer drugs because they can be very toxic

• New drugs are also designed to counteract antibiotic resistance, making better antibiotics may include changing their structure so they bind with higher affinity to their targets

• Anti-cancer drugs can be made better by targeting molecules/markers specific to the cancer cell

• Some drugs upregulate the immune response (T cells in particular) to cancer by binding to certain inhibitory molecules on cancer cells, these have shown to be effective in some cancers