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BIOL370 Midterm 1 Practice Question Answers
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BIOL370 Midterm 1 Practice Question Answers
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Learning Goals- Describe the importance of homeostasis
Homeostasis is the process whereby the body maintains steady internal conditions. Homeostasis
is important because enzymes and tissues in the body require optimal temperature, pH conditions,
salinity conditions, etc in order to maintain their proper structure remains and thus function. If the
body is unable to maintain homeostasis, then they will not be able to operate optimally.
- Explain how feedback loops allow organisms to maintain homeostasis
Feedback loops (especially negative) are essential to allowing organisms to maintain homeostasis because
they consist of a sensor, and integrator and an effector. The sensors allow the organism the organism to
observe internal conditions, this information is sent to the integrator. The integrator looks like the specific
variable and compares it to a baseline or set point for which that variable is supposed to be at. If there is
deviation from the set point, then the integrator sends a signal to an effector which brings about a
compensatory response and moves the variable towards the set point. The compensatory response then
acts as signal for the sensor which will send a single to the integrator which will once again compare the
variable to the set point and determine that the variable has been adjusted and then cause a reduction in
the effector’s compensatory response. As such, the feedback loops are required to maintain homeostasis
because sensors allow for constant monitoring of internal conditions, integrators allow for comparison
between the variable and the set-point. Finally, the effector enables a compensate response to move the
variable towards the desired set-point maintaining homeostasis. Furthermore, the effectors of feedback
loops usually have opposing effects like a gas pedal and a brake which to ensure the variable can be
changed to the appropriate set-point.
- Compare and contrast different type of membrane transport
There are three main types of membrane transport and they are simple diffusion, facilitated diffusion, and
active transport
Simple Diffusion Compare Simple Facilitated Compare Facilitated Active transport
Diffusion and Diffusion Diffusion and
Facilitated Active transport
Diffusion
• Small, hydrophobic • No ATP required; • Small hydrophilic • Require a • ATP required;
molecules can pass through molecule follows molecules can pass transporter molecule moves
the membrane concentration through the (channel, gated against
• No transporter gradient membrane channel, or carrier) concentration
requirement • Open channels, gradient
• Fast when molecules are Gated channel • Primary active
small, membrane is thin, (ligand, voltage, transport
and follows Fick’s Law mechanical) • Secondary active
• Carriers (uniport; transport
cotransporters =
antiport and
symport)
, - Compare and contrast the different types of intercellular signalling
Paracrine Juxtacrine (gap Endocrine Neuroendocrine Pheromones
junctions)
• Indirect signalling • Direct signalling • Indirect signalling • Indirect signalling • Indirect
• Short range signalling • There is direct • There signalling signalling
between close cells contact between factors (hormones • Neurotransmitters are • Signalling
• Will affect only a few cells through gap are released into the released into the between
cells (example is junctions (connexin circulation bloodstream and can organisms
neurotransmitters) = vertebrates, • May affect several possibly have an affect • Affect
innexins = hundreds or on several hundreds of organismal
invertebrates) thousands of cells cells behaviour
• Materials are
shared between
cells, this is allows
for two way
signalling, this is
seen in electrical
synapses
• Affecting only the
cells directly
touching
- Predict the physiological effect of different types of drugs based on their effects on receptors
There are several different types of receptors and the binding of a receptors to a ligand will generate a
specific response. Upon binding a ligand, a receptor can cause downstream effects on the cell. There are
several types of receptors but the ones that I will focus on below are metabotropic receptors and the
ionotropic receptors. Receptors are specific to their ligands and only the proper ligand (or its agonist) will
activate the receptor. Similarly shaped antagonists, block receptors by binding to the receptor and
preventing the ligand from binding.
The metabotropic receptors are receptors are also GPCRs an initiate several steps otherwise known as the
second messenger pathway to regulate the activity of a cell. They can involve PLC or adenyl cyclase as
the second.
In the phospholipase C pathway, the activated alpha G-protein subunit induce PLC to remove a
phospholipid from the membrane and cleave it molecules DAG and IP3, which in turn individual trigger
signalling cascades. IP3+ induces the release of Ca2+ from internal stores, which in turn increase the
[Ca2+] intracellularly. The increase in intracellular Ca2+ activates calmodulin which will induces a
conformational change in a protein – activating it and therefore bring about a cellular response. As
mentioned earlier, DAG will bring about a separate second messenger cascade. If the drug is an agonist, it
will not change the response that the receptor would produce when bound to the ligand, However, if the
drug is an antagonist of the receptor, there will be a decrease in the G-protein activity and therefore no
induction of PLC thus preventing the removal of a phospholipid from the membrane and preventing the
cleavage of the phospholipid into DAG and IP3. As a result, there will be no signalling cascades
triggered. IP3+ will not induce the opening of Ca2+ from internal stores and internal calcium
, concentration and membrane will remain constant, thus calmodulin will remain inactive and therefore no
cellular response will be produced.
Upon the binding of the proper ligand or agonist, In the adenyl cyclase pathway, the activated
stimulatory alpha G-subunit influences the adenyl cyclase activity by causing it to be phosphorylated.
Activated adenyl cyclase will increase cAMP production by converting ATP, which will act as a second
messenger and activate protein kinase A (PKA) which will later phosphorylate a downstream protein; in
turn altering the proteins shape and therefore function. Once the function of the protein is altered it will
bring about a particular cellular response. The opposite is true for inhibitory G protein, there is a decrease
in cAMP production. If the drug us an agonist, then there will be a similar effect seen in the agonist as the
ligand. However, if the drug is an antagonist, then the receptor will not activate the alpha G-subunit. As
such, adenyl cyclase activity will remain inactive. As a result of being inactive, adenyl cyclase will not be
able to convert ATP to cAMP and there will be a decrease cAMP levels which will signalling the
inactivating of protein kinase A (PKA). Inactivated PKA prevents the phosphorylation of a downstream
protein. As a result, the cellular response will not be initiated, the opposite is true if the cell has an
inhibitory G-protein.
The ionotropic receptors are ligand gated channels that receptors that upon binding the ligand will open
and allow for the ligand to enter the cell. If the drug is an agonist, the effect of the drug will be like the
effect of the ligand. If the drug is an antagonist, then then the drug will bind to the receptor and prevent
the ligand from bind, therefore, blocking the entrance of the ligand into the cell.
- Compare and contrast the functions of different neurotransmitters and their receptors
Receptor Type
Acetylcholine Muscarinic Nicotinic
• Found as the preganglionic • Metabotropic (GPCR) • Iontropic receptor (Na+)
neurotransmitter throughout the • Excitation = gut • Excitatory (depolarization)
autonomic nervous system • Heart = inhibition • Found at the neuromuscular
• Found as the postganglionic • Bronchioles = excitation junction, neuronal ganglion, adrenal
neurotransmitter for the • Sweat glands = activation medulla
parasympathetic nervous system • Blood vessels of muscle muscle = • Agonists = ACh, nicotine,
• Necessary for the basic inhibition carbochol
maintenance of systems and • Found in the gut, heart, • Antagonists = curare
operations (homeostasis) bronchioles, sweat glands, and blood
vessels of skeletal muscle
• Agonists = muscarine, ACh,
carbochol
• Antagonists = atropine,
scopolamine
Dopamine Receptors D1 to D5
• Secreted from dopaminergic
neurons in the brain
• Associated with reward sensations
and drug addiction
• Deficiency in dopamine associated
with Parkinson’s
• Other disorders = ADHD and
restless leg syndrome
Serotonin There are 9 receptor subtypes
• Associated with sleep, mood, pain,
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