Bio 203 exam 1

What is the osmolarity, in mOsM, of a solution composed of 0.1 M NaCl, 0.1M sucrose and 0.1M glucose?

400mOsm To find the osmolarity, you must add up the molarities of each solute. Ionic substances like NaCl contribute one mole of solute for each mole of ion, so NaCl contributes 0.2 OsM (200 mOsM.) Substances that do not contain ionic bonds contribute in proportion to their molarity. 0.1 M of sucrose contributes 0.1 OsM, and same is true for glucose.

From which of the following blood vessels would the most heat be lost through the skin?

A blood vessel with a diameter of 1mm that was 1mm from the skin. Heat is most easily transferred from large diameter blood vessels that are close to the skin

A cell containing only pure water is placed into a solution containing 1M Na+. The cell's membrane is impermeable to both water and sodium ions. How could you make the cell isosmotic to the outside solution?

Add NACl to the inside of the cell until it contains 0.5M NaCl Add sodium ions to the cell until there are 1mole ions/liter of ICF Increase the number of sodium channels on the cell membrane Add sucrose to the cell until it contains 1M sucrose. In order to make the cell isosmotic, you need to make the total number of dissolved solutes in the cell equal to the number outside of the cell. You could do this in two basic ways: 1) add an appropriate number of solutes to the inside of the cell OR 2) make the cell permeable to one or more solutes and allow them to reach an osmotic equilibrium

Suppose that animals living at 20°C are moved to a new environment at 10°C. Which of the following animals would have the greatest decrease in MR compared to its MR at 20°C?

An ectotherm, after 30 minutes at 10°C An endotherm, if its thermoneutral zone stretched from 5°C to 15°C Heat is most easily transferred from large diameter blood vessels that are close to the skin

Heat Transfer

An increase in thermal conductivity between two objects will result in an increase in the rate of heat transfer only if the temperatures of the objects are different. For a human in a cold environment, forced convection leads to increased heat loss (compared to free convection) because the driving force for heat loss from the skin is greater. Unlike heat transfer by conduction, evaporation can produce heat loss from an organism but not heat gain.

Action potentials (APs)

At the peak of an AP inactivation gates in some voltage-gated Na+ channels begin to spontaneously close, other voltage-gated Na+ channels are open, and the membrane begins to repolarize because there is a ↓PNa Toward the end of the absolute refractory period, inactivation gates in many voltage-gated Na+ channels are closed, some voltage-gated Na+ channels are in the closed state and voltage-gated K+ channels are in open and closed states The hyperpolarization phase of the AP is a time when the membrane potential is more negative than the resting membrane potential and is the result, primarily, of the fact that PK is greater in value than when all voltage-gated channels in the membrane are closed During the relative refractory period suprathreshold depolarization of the membrane is required to generate an AP because PK is higher than at the rest and many voltage-gated Na+ channels are in the closed configuration

Fever - Humans

At the very end of a fever, the thermoregulatory response is essentially the same as the response to an increase in body temperature. Fever is initiated by an increase in the body temperature set point leading to increased heat retention and endogenous heat production. Placing someone with a fever into a cold bath lowers body temperature without changing the temperature set point.

Basic Principles

Body fluids of all animals have the same general composition. A fundamental challenge for all multicellular organisms is maintaining the asymmetric distribution of ions between different compartments. While all animals must deal with the same fundamental problems, different animals may have different solutions.

Synaptic transmission

Ca++ binding to synaptotagamin is necessary for hormone containing vesicles to alter their conformations to allow vesicle fusion and exocytosis of arginine vasopressin from nerve terminals Alpha-bungarotoxin is an exogenous agonist that, acting as a ligand, opens ion channels that are necessary and sufficient for the generation of suprathreshold end- molecules that bind to integral proteins which function either as ligand-gated ion channels or as G protein-coupled receptors that indirectly open ion channels

What is the importance of the axon hillock region?

Contains the trigger zone. Graded potentials can generate a depolarization in this region that can trigger an AP Closing the inactivation gate of the sodium channel prevents more sodium from coming in to hyperpolarize the membrane (make it become even MORE positive.) Opening of the activation gate of the potassium channels allows potassium to move into the cell and depolarize it (make it less positive or closer to 0mv) and subsequently to repolarize it below 0 mV

Which of the following organ systems are important for the exchange of vital substances between and organism and its environment?

Digestive system Respiratory system Integumentary system Excretory system Circulatory system

The largest increase in sodium permeability occurs at the peak of the action potential waveform

False. The largest increase occurs during the rising phase of the action potential

Describe 2 differences between the chloride cells in freshwater and saltwater fish. One difference should be a structural difference (what is found in the cell) and one difference should be a functional difference.

Functional difference: chloride cells in saltwater fish transport chloride ions out of the gills, but in saltwater fish they bring chloride into the gills. Structural differences: Saltwater chloride cells export both sodium and chloride ions, so they have a triporter protein on the basolateral side that brings sodium in along with chloride, and a channel to allow passive loss of sodium on the apical side. Freshwater chloride cells do not import sodium (that's done by the pavement cells), so they do not possess the same channels. You could also find other proteins that differ between the two types of chloride cells, but Dr. Collins mentioned these in particular.

G protein-coupled cell signaling

G protein-coupled receptor activation of membrane associated phospholipase C increases intracellular IP3 resulting in the opening of ligand-gated Ca++ channels in the membranes of the endoplasmic reticulum Bronchiolar smooth muscle relaxation in response to epinephrine binding to receptors is the result of the alpha subunit of G protein activating the amplifier enzyme adenylate cyclase which in turn increases intracellular cAMP levels Arteriolar smooth muscle contraction in response to epinephrine binding to receptor results in the alpha subunit of G protein exchanging GDP for GTP and a subsequent increase in intracellular Ca++ If the βγ-subunit of G protein opens a peripheral membrane ion channel, and the cellular response is hyperpolarization, then the first messenger could be ACh

Which of the following are channel proteins that can move substances across membranes with no energy expenditure.

GLU Aquaporin K+ leak channel CFTR Voltage gated sodium channel

Which of the following statement(s) are true with respect to graded potentials?

Graded potential amplitude decays over distance Graded potentials are not regenerative Graded potentials can summate in space and time Graded potential amplitude increases with stimulus strength

Homeostasis and Feedback

Homeostasis is the process of maintaining the internal conditions of a n organism within tolerable ranges for the cells in the organism. All homeostatic feedback systems have the same basic components; the sensor, the integrator and the effector. Homeostasis requires communication and negative feedback between the cells in an organism. In a homeostatic feedback system, a decrease in the sensor measurement has the same effect on the output of the system as an increase in the set point.

Equilibrium potentials

If intracellular and extracellular concentrations of a cation were equal, then the Nernst potential for that ion would be 0 mV. The equilibrium potential for an ion will remain constant following changes in intracellular and extracellular ion concentrations so long as the ratio of ( [ion]out / [ion]in ) remains constant. The Nernst potential for an anion whose extracellular concentration is greater than its intracellular concentration will be negative.

Osmolarity and Tonicity Solution A: 0.2 M sucrose Solution C: 0.1 M glucose + 0.1 M NaCl Solution B: 200 mM NaCl ICF= 300mOsm

If solutions A and B were separated by a membrane permeable only to water, there would be net movement of water from solution A to solution B. Solution B is hypertonic to a cell that is permeable to water but impermeable to sodium and chloride ions. If solutions A and C were separated by a membrane permeable only to water, there would be net movement of water from solution A to solution C.

Organization of Complex Biological Organisms

In a small simple organism, individual cells obtain vital substances directly from the interstitial fluid. A group of cells of different types that perform a specific function is referred to as a tissue. Biochemical substances comprise 0.25% of the molecules in the human body. The production of ATP by anaerobic metabolism is fast but inefficient compared to aerobic metabolism.

The membrane associated with the synaptic release of neurotransmitter is different from the membrane of the axon. List one unique feature of the bouton.

It has no voltage-gated sodium channels. In has no voltage-gated potassium channels. It does not generate action potentials.

Which of the following animals would be most likely to be ammonotelic?

Most fish are ammonitelic. Excreting wastes as ammonia does not require any energy expenditure, but a large amount of water to get rid of the toxic ammonia; fish have plenty of water to use in their environments.

Place the neurons in order of their typical speed of conduction, from fastest to slowest

Myelinated axon, diameter 20μm (fastest) Unmyelinated axon, diameter 20μm Unmyelinated axon, diameter 200μm Myelination increases conduction velocity. Axons with larger diameter have faster conduction than small diameter axons.

osmoconformers

Osmoconformers adopt the same osmolarity as their environment and are always found on an isosmotic line in a graph like this one. A and C are not on the isosmotic line, so they are not osmoconformers. They are osmoregulators. Organism B may be an osmoconformer; to test if it was you could place it in an environment with a different EnvOC and measure its BFOC. If it allowed its BFOC to fluctuate to the new EnvOC, it would be an osmoconfomer, but if it maintained its original BFOC it is an osmoregulator.

What does passive mean with respect to the transport of a substance across a membrane? What does passive mean in referene to water gain or loss by an animal?

Passive transport of a substance does not require energy, and the substance is always moved down a gradient. For solutes, this would be down a chemical gradient, and for water it would be down an osmotic gradient. Passive water gain or loss is involuntary (beyond the animal's control.) An example of passive water loss would be respiratory water loss. An example of water gain that would not be passive would be drinking water.

Distribution of ions between compartments

Sodium concentration is high in plasma compared to inside red blood cells. Calcium concentration is high in plasma compared to intracellular fluid. Potassium concentration in plasma is high compared to calcium concentration in intracellular fluid. Potassium concentration in plasma is low compared to interstitial fluid.

If you change the selective permeability of a membrane to an ion, what information do you need to know to predict the direction in which the membrane potential will change?

The equilibrium potential for the ion; this is determined by the intracellular and extracellular concentrations of the ions.

Solution B is hypertonic to a cell that is permeable to water but impermeable to sodium and chloride ions. Solution A: 0.2 M sucrose Solution B: 200 mM NaCl Solution C: 0.1 M glucose + 0.1 M NaCl ICF = 300 mOsM

This statement is correct. A solution is hypertonic to a cell if it contains more dissolved solutes per unit volume than the cell. Solution B is 400mOsm (Na+ and Cl+ ions each contribute 200mOsM to this total.) The osmolarity of most intracellular fluids is 300 mOsm, so solution B is hypertonic to the cell. If the cell were placed in solution B, water would tend to move out of the cell causing it to shrink.

With respect to an animal's thermal budget, evaporation is the only type of heat transfer that cannot lead to heat gain

This statement is correct. An animal's thermal budget is all of the processes that lead to heat loss or gain from an animal. Convection, conduction and radiation can contribute to both gain and loss, while endogenous heat production can only contribute to heat gain. In evaporation, only heat loss can occur. During the phase change from liquid to gas that occurs in evaporation, heat is always dissipated from an animal.

If the βγ-subunit of G protein opens a peripheral membrane ion channel, and the cellular response is hyperpolarization, then the first messenger could be ACh

This statement is correct. As discussed in the cell signaling echo recording, in one of the protein gating of ion channel example, one subtype of muscarinic ACh receptor, increases the permeability to K+, hyperpolarizing the cell. The activation of the muscarinic ACh receptor (a G protein coupled receptor) by ACh leads to the opening of a chemically gated ion channel that increase the permeability to K+. Once ACh binds to this G protein coupled receptor βγ-subunits activates an ion channel that allows K+ to flow out of the cell.

Living cells in terrestrial organisms exist in an aqueous environment

This statement is correct. Life evolved in water, and the intracellular and extracellular fluids of all living things have a composition that is very similar to ocean water. The fluid surrounding cells, called the extracellular fluid, in terrestrial organisms is similar in composition to sea water, so those cells are surrounded by an aqueous environment. The extracellular fluid (which includes plasma and interstitial fluid) and the intracellular fluid both contain water, salts, and biological molecules in roughly the same amounts.

If Solutions A and C were separated by a membrane permeable only to water, there would be net movement of water from Solution A to Solution C. Solution A: 0.2 M sucrose Solution B: 200 mM NaCl Solution C: 0.1 M glucose + 0.1 M NaCl ICF = 300 mOsM

This statement is correct. Solution A is 0.2 OsM because sucrose does not contain ionic bonds and does not separate into ions in water. Solution C is 300 OsM because glucose contributes 0.1 OsM and NaCl, due to its ionic nature, contributes 0.2OsM. Water tends to move down its osmotic gradient, from compartments that have more water (and more solutes) to compartments that have less water and more solutes, so water would move from solution A to solution C. Solution A is hypoosmotic with respect to solution C.

Assume the following: [K+]in = 150 mM [K+]out = 5 mM [Na+]in = 5 mM [Na+]out = 150 mM If one poisoned all Na+,K+ ATPase antiport carriers in the peripheral membrane of the cell above, the resting membrane potential would be equal to log(([K+]in + [K+]out) / ([Na+]in + [Na+]out))

This statement is correct. The sodium potassium antiport carrier (a.k.a. Na+/K+ pump) is responsible for generating the driving force for movement of both sodium and potassium across the cell membrane. If it was poisoned so that it did not work, the sodium and potassium would travel through leak channels down their gradients until there were equal concentrations of each ion on each side of the membrane (80mM). If you put this value in for all 4 of the ion concentrations into the Goldman Equation, it would look like this: Vm = 61mV * log [(Pk(80mM)+ Pna (80mM))/(pK(80mM) + Pna(80mM)] Simplified and rearranged, this is Vm = 61mV*log(1) **log1=0** This equation gives a resting membrane potential of 0 mV, and so does the equation in the statement. Here's another way to look at this one: If you poisoned the Na+/K+ pump, there would be no driving force for the movement of ions for reasons mentioned above. The ions would reach both electrical and chemical equilibrium, so the membrane voltage would be 0. The statement above gives a membrane voltage of 0, too.

In a hot environment, an endotherm's metabolic rate will increase if physiological and behavioral thermoregulatory mechanisms are insufficient to maintain body temperature.

This statement is correct. Within the thermoneutral zone of an endotherm, low-energy physiological and behavioral thermregulatory mechanisms are sufficient to maintain body temperature. Examples of physiological mechanisms include vasoconstriction and vasodilation, and examples of low-energy behavioral mechanisms include thermal windows, changing posture, huddling, etc. When these mechanisms are not enough to keep the body temperature constant, the animal is outside of the thermoneutral zone and must use energy-costly mechansims that increase the metabolic rate in order to maintain the body temperature. If the ambient temperature is above the thermoneutral zone, it will spend energy on sweating or panting, for example, and if colder than the thermoneutralzone it could spend energy on shivering or non-shivering thermogenesis

α-bungarotoxin is a nicotinic ACh receptor antagonist that binds to nonspecific cation channels, preventing simultaneous increases in PK and PNa in excitable membranes

This statement is correct. α-bungarotoxin binds irreversible to nicotinic ACh receptors, blocking the action of ACh, inhibiting the flow of ions (Na+ and K+) through the channel.

Organisms living in different environments have to deal with different fundamental problems.

This statement is incorrect, because all organisms have to deal with the same fundamental problems, including reproduction, energy generation, homeostasis, and maintaining asymmetric distribution of substances. Different organisms have evolved unique solutions to these same fundamental problems, and the study of these solutions is called comparative physiology.

In a hot dry environment, allowing body temperature to fluctuate is an effective water conservation strategy for both large mammals (e.g., camel) and small mammels (e.g., kangaroo rat.)

This statement is incorrect. Fluctuations in body temperature are effective in large mammals but not small mammals. Since small mammals have a very large SA/V ratio, they are good at exchanging substances and bad at retaining them. The rat would tend to lose much more water per unit mass than the camel and it would also be much more susceptible to heat gain from the environment because of its small size and large SA/V. It uses other strategies to minimize water loss, including producing metabolic water, excreting dilute urine and rectal water absorption

In cold environments, mammals and birds use counter-current heat exchange in their extremities to keep the extremities from becoming too cold.

This statement is incorrect. Mammals and birds do use use CCE, but use it in order to minimize the driving force for heat loss from the extremities so as to keep the core temperature warm. As the arterial blood gets closer to the extremities it is cooled as it looses some heat to the veins that are close to the arteries. By the time the blood reaches the extremity, it is close to the temperature of the environment, so there is little driving force for heat loss. The venous blood is warmed by the arterial blood close by, and it is close to the core temperature by the time it reaches the torso. The animal therefore needs to only spend a small amount of energy heating it back up to body temperature. The trade-off for maintaining a warm core temperature is that the extremities can actually get quite cold.

In cell signaling, the first messenger or ligand determines the intracellular response.

This statement is incorrect. Specificity is defined by the receptor, and not by the first messenger or ligand. As discussed in the cell signaling echo recording, " the first messenger is not going to determine the response, is always going to be the receptor that does that". "The action of the ligand on the receptor is going to determine the response"(Not the ligand by itself) Several different kinds of cells can respond to the same first messenger in very different ways.

Establishing the Nernst potential for all major cations and anions is sufficient to make an accurate prediction of the resting membrane potential

This statement is incorrect. The Nernst potential (or equilibrium potential) is the potential at which there is no net movement of an ion across the cell membrane because the internal and external concentrations are equal. It only deals with the ion concentrations. In order to use the Goldman equation to predict the resting membrane potential, you would need to know the concentrations of each ion extracellularly and intracellularly, BUT you would also need to know the permeability of the membrane to each of those ions.

assume a cell has [K+]in = 150 mM [K+]out = 5 mM [Na+]in = 5 mM [Na+]out = 150 mM If the cell above was selectively permeable to Na+ and K+, and the ratio of PNa / PK = 40, the Goldman Equation would predict that Vm (resting membrane potential) ≈ -70 mV (± 6 mV)

This statement is incorrect. The resting membrane potential for most cells is around -70mV, and this is mainly a consequence of the relatively high permeability of the cell to potassium compared to other ions. The membrane permeability of potassium is actually 40 times higher than the permeability to sodium. The statement suggests that a cell that was 40 times more permeable to sodium than to potassium would have the same membrane potential as a normal cell, and this is not correct. If the cell was more permeable to sodium the membrane potential Vm would be much closer to the sodium equilibrium potential (+50mV) than to the potassium equilibrium potential (-90mV.)

An action potential in a particular cell has the same amplitude, same duration and same shape every time.

True. These facts are not true about graded potentials.

Acetylcholine (ACh) as a ligand

When ACh binds to the nicotinic ACh receptor, membrane PK increases and a graded depolarization occurs Muscarine is an exogenous ACh receptor agonist that increases membrane Pk by opening G protein coupled receptors, nonspecific cation channels Alpha-bungarotoxin is an ACh receptor antagonist that prevents an increase in membrane PNa that is normally associated with ACh receptor-mediated opening of nonspecific cation channels If ACh opened a chemically-gated channel that only increased membrane PK, systemic administration of an antagonist to this ACh receptor-mediated response would increase heart rate

action potentials

all or nothing, even if you keep increasing the initiator past the threshold it doesnt change it anymore. cannot be summated, has a threshold 15mV + depolarized relative to the resting potential. has a refractory period, conducted without decrement.

Nicotinic

ionotropic, fast reaction, respond best to nicotine. nicotine ACh receptor is also Na+ and K + ion channel. form the ligand gated nicotinic channel. in neuromuscular junction.

An animal has a high whole animal metabolic rate which remains constant over a large range of temperatures. Which of the following is probably true about the animal? Choose all of the correct answers.

it is an endotherm it has a low unit metabolic rate it uses behavioral thermoregulation it is a large animal Because the animal maintains a constant body temperature over a wide range of ambient temperatures, it is an endotherm. For endotherms, the whole animal metabolic rate and unit metabolic rate tend to be opposite - large animals have a large whole animal metabolic rate, but a small unit metabolic rate because of their low surface area to volume ratio. Both ectotherms and endotherms use behavioral thermoregulation

Musarinic

metabotropic, slow reacting because activates many processes that have to be carried out. respond best to muscarine. G protein coupled receptors that act through 2nd messengers

Cells use energy to move a substance from a compartment with a low concentration of the substance to a compartment with a higher concentration. Which of the following processes would require a cell to expend energy? Choose all of the correct answers.

moving sodium ions out of cells Moving potassium ions into cells Moving calcium ions out of cells Moving calcium ions out of the cytoplasm and into an organelle Moving an ion from a compartment where it has a low concentration to a compartment where it has a high concentration requires energy. Sodium and calcium are more concentrated extracellularly than intracellularly, and potassium is more concentrated intracellularly than extracellularly. While the cytoplasmic concentration of calcium is very low, some organelles have a very high concentration of calcium.

Graded potentials

no saltatory conduction, can summate, amplitude varies with size of the initiating event, no threshold no refractory period, conducted decrementally in terms of amplitude, decreases with distance, can be hyperpolarized or depolarized. initiated by environment stimulus (receptor) by neurotransmitter

In a hot environment, and endotherm's metabolic rate will increase if physiological and behavioral thermoregulatory mechanisms are insufficient to maintain body temperature - these statements are all valid to varying degrees, but some more than others.

physiological and behavioral thermoregulatory mechanisms are not energy costly so an organism relies on those mechanisms first. An endotherm's MR will increase afterwards if an organism cannot maintain body temperature because it is energy costly. physiological and behavioral thermoregulatory mechanisms were sufficient, the metabolic rate would stay constant as the animal would be in the thermoneutral zone. Metabolic rate increases because sweating/panting require energy. In a hot environment, an endotherm's metabolic rate will increase if physiological and behavioral thermoregulatory mechanisms are insufficient to maintain body temperature. Endotherms can use vasodilation/vasoconstriction (physiological changes) at any point in Tamb. They also can utilize behavioral thermoregulation at any point. An endotherm will alter its metabolic rate to maintain body temperature when it is not in the thermoneutral zone.

During a fever, which of the following is increased compared to before the onset of the fever?

temperature setpoint in the hypothalamus Core body temperature Thermogenesis Vasoconstriction Basal Metabolic Rate During fever, pyrogens raise the setpoint of the body. The integrator in the hypothalamus compares the difference between the body temperature and the setpoint, then signals to various effectors to increase heat production and minimize heat loss. Shivering and non-shivering thermogenesis increase to increase endogenous heat production, and vasoconstriction occurs to minimize heat loss. This leads to an increase in body temperature. The metabolic rate also increases because shivering in particular is very energy costly; the body is also spending a lot of energy on fighting off the infection as well.