VCE Biology Question Thread

[sweetcheeks]

would this be a

Before we answer, could you provide an explanation of why you think the answer is A? It will help you a lot more to try and justify your answer rather than have someone explain it to you.

[Billuminati]

would this be a

From the info you’re given, it looks like it’s B. They tell u the enzyme that produces pigmentation is tyrosinase II and it’s inactive at body temperature, so the centre mass of the cat will be lightly coloured. However, since the extremities are exposed to the cold environment (in a cold country), they will be pigmented as tyrosinase II is active

[Chocolatepistachio]

A local hyperpolarisation that changes the resting potential on a postsynaptic neuronal membrane from -70mV to -85mV
A a temporal stimulus
B an inhibitory postsynaptic potential (IPSP)
C an excitatory postsynaptic potential (EPSP)
D a saltatory stimulus

Would this be b

[Billuminati]

A local hyperpolarisation that changes the resting potential on a postsynaptic neuronal membrane from -70mV to -85mV
A a temporal stimulus
B an inhibitory postsynaptic potential (IPSP)
C an excitatory postsynaptic potential (EPSP)
D a saltatory stimulus

Would this be b

Correct because IPSPs (usually resulting from GABA binding to its receptor) makes action potential generation more difficult/less frequent by hyperpolarisation. Remember the closer the membrane potential is to -55mV (threshold), the more likely it is for an AP to be fired. Since -70mV is closer to that than -85mV, it's inhibitory and therefore IPSP.

[Chocolatepistachio]

Ok thanks

A newly developed pesticide is found to bind to an intracellular hormone receptor. If ingested, this pesticide could interfere with:
A cAMP second messenger pathway
B Ca2+ second messenger pathway
C transcription of particular genes
D G protein coupled receptors

Would this be a can someone explain the cAMP second messenger pathway

[-Lilac-]

Ok thanks

A newly developed pesticide is found to bind to an intracellular hormone receptor. If ingested, this pesticide could interfere with:
A cAMP second messenger pathway
B Ca2+ second messenger pathway
C transcription of particular genes
D G protein coupled receptors

Would this be a can someone explain the cAMP second messenger pathway

I don't think the details of G protein receptor pathways are really VCE knowledge. However, the key part of the information in this question is an intracellular hormone receptor. Both the cAMP and Ca2+ pathways are downstream of extracellular G protein-coupled receptors (as they are second messengers). Intracellular receptors are nuclear receptors.

Therefore, considering this information, what do you think the correct answer is here?

[Chocolatepistachio]

Oh ok so it would be c

[Billuminati]

Ok thanks

A newly developed pesticide is found to bind to an intracellular hormone receptor. If ingested, this pesticide could interfere with:
A cAMP second messenger pathway
B Ca2+ second messenger pathway
C transcription of particular genes
D G protein coupled receptors

Would this be a can someone explain the cAMP second messenger pathway

Extending on Lilac's answer without giving the answer away, once a steroid hormone has bound to the nuclear receptor, where does the nuclear receptor go and what factor does it serve as there?

To answer your question on the cAMP pathway, basically your exam-grade 2nd year biomed cAMP pathway explanation would be when the hormone binds to a GPCR, there is a conformation change in the receptor that allows it to act as a guanine exchange factor to the alpha subunit of a G protein. It activates the inactive, GDP bound alpha subunit of the G protein by causing the dissociation of the GDP and the association of GTP. The activated alpha subunit dissociates from the beta and gamma subunits (which remain dimerised) and activate adenylate cyclase. AC produces cAMP from ATP hydrolysis. There's a key enzyme in the phosphorylation transduction cascade that hasn't been activated yet called protein kinase A. It has 4 subunits, 2 catalytic ones and 2 regulatory ones, with the regulatory subunits bound to the catalytic ones in inactive form as an inhibitor of some sorts. When cAMP binds to the regulatory subunits, there's a conformation change that dissociates them from the catalytic subunits, which are now active and sets off a transduction cascade

[Chocolatepistachio]

Thanks

Would this be true
The process of ventilation includes both the transport of gases by bulk flow and the diffusion of gases into and out of the bloodstream

[Billuminati]

Thanks

Would this be true
The process of ventilation includes both the transport of gases by bulk flow and the diffusion of gases into and out of the bloodstream

This is partially correct, there’s this thing called V/Q (ventilation/flow) ratio you learn in 2nd year biomed physiology, it takes into account the amount of gas that diffuses across the alveolar membranes (ventilation usually refers to bulk flow) and the blood perfusion of the lung tissue. Smaller scale gas exchange referred to as tissue respiration occurs at your tissues and alveoli, hemoglobin loses its affinity for O2 when it encounters H+, AMP and CO2 (indicative of high metabolic activity in muscles) to deliver the bound O2 to the O2 poor muscles and take CO2 (in the form of HCO3- or H2CO3) to the lungs to be exhaled.

[Chocolatepistachio]

thanks
can you explain this calculation
isn't it just 101000 + (1000 x 9.8 x 30)= 395000 kpa

[Billuminati]

thanks
can you explain this calculation
isn't it just 101000 + (1000 x 9.8 x 30)= 395000 kpa

Both the given answer and your answer (however your answer needs to be in kPa) are correct, they just rounded some values ie they used 10 to approximate 9.8 for acceleration due to gravity

[Chocolatepistachio]

What would increase the amount of oxygen unloaded by haemoglobin into peripheral tissues
A decreased temperature
B decreased pH
C decreased levels of BPG
D decreased levels of pco2

Would this be d

[Billuminati]

What would increase the amount of oxygen unloaded by haemoglobin into peripheral tissues
A decreased temperature
B decreased pH
C decreased levels of BPG
D decreased levels of pco2

Would this be d

B is correct. I told you a few hours ago that hemoglobin loses affinity for O2 (and hence unloads it to tissues that need it) in the presence of indicators of high metabolic activity such as H+, CO2 and AMP. H+ is produced by anaerobic respiration (lactic acid is acidic and the CO2 produced will dissolve in blood to form H2CO3 which is also acidic), CO2 is a waste product of cellular respiration and AMP comes from the hydrolysis of ATP when the energy stored in ATP is required. Remember lower pH= higher [H+].

[Chocolatepistachio]

Which process of respiration relies on partial pressure gradients?
A pulmonary ventilation only
B pulmonary gas exchange and tissue gas exchange
C gas transport and pulmonary ventilation
D gas transport only

Would this be b