Exam 4 Biol1520

A shift to the right of the oxygen-hemoglobin equilibrium curve correlates with: increased oxygen delivery to a tissue cooperative binding decreased oxygen delivery to a tissue noncooperative binding

A when shifted to the right, at any particular tissue partial pressure of oxygen, hemoglobin has a lower affinity for oxygen than in the original curve. this means that hemoglobin is more likely to release oxygen to tissues under the Bohr shift (low pH)

Select all of the factors below that will INCREASE oxygen levels in water. cooler temperature less salinity greater depth into the water body more wind at the surface less rugged terrain (smoother stream flow)

A, B, and D warmer water holds less oxygen than cold water. saltier water holds less oxygen than less salty water. oxygen diffuses into water from the air; thus a greater surface area for water-air interface means more oxygen in the water. wind and turbulence (such as waterfalls, rugged terrain) increases the amount of water exposed to the air surface. once in the water, oxygen moves by diffusion; water that is deeper below the surface will thus have less oxygen due to slow movement by diffusion.

Your friend wants to apply a topical cream containing retinol to improve their skin. However, an excess of vitamin A interferes with fetal development, and your friend is currently pregnant. To be safe, which of the following foods would be good for her to eat instead of using the cream? dark green leafy vegetables Vitamin C dairy yellow-orange fruits green fruits egg yolks

A, C, and D

If a person has a pancreatic disorder, which of the following might they be unable to digest? Lipids Proteins Fats Vitamins Minerals

B The pancreas secretes proteases to break down protein.

Clay in soils represents a trade-off in nutrient availability, such because oxygen levels are exceptionally high, but much of the nitrogen leaches away nitrogen levels are exceptionally high, but much of the nitrogen leaches away cations are less likely to leach out of soil but are difficult for plants to extract anions are less likely to leach out of soil but are difficult for plants to extract

C anions are readily soluble in soil water, and thus easily washed (leached) away during heavy rains.. in contrast, cations associate tightly with clay particles in soil, which are negatively charged. this means cations remain bound to clay during rains and do not wash way. plants compensate via a process called cation exchange, where plant cells pump protons into the soil to displace cations from the negatively-charged clay particles, thus freeing the cations for absorption by the plant.

What is the importance of consuming an adequate amount of proteins in the diet? They are used as cofactors for metabolic reactions and are required in minute quantities. Proteins are necessary to produce urea and other important metabolites. Proteins serve a variety of functions, and the body does not store excess quantities of amino acids. They are most commonly used to meet energy demands of cells.

C proteins carry out the bulk of chemical reactions and are also essential for structural support in cells. they make up the primary component of muscle and many other tissues. proteins are composed of amino acids, some of which can be synthesized by the body from but some of which cannot. unlike fats and sugars, the body does not store excess amino acids. dietary sources of protein are absolutely required for the essential amino acids and helpful for preventing malnutrition for the nonessential amino acids. vitamins (organic molecules) and mineral (inorganic molecules) are required in minute quantities and often function as cofactors in metabolic reactions cellular energy demands are typically met by either fats or sugars, combined with oxygen as the terminal electron acceptor for oxidative phosphorylation

Some of the "dead stuff in our food" makes it into our food chain through the activity of decomposers such as fungi. Fungi are photoautotrophs photoheterotrophs chemoautotrophs chemoheterotrophs

D chemoheterotrophs are organisms which use energy from chemical bonds (chemo) and organic carbon molecules (hetero) to meet their nutritional needs. fungi break down dead organic matter for their source of energy and carbon and thus are chemoheterotrophs

A friend wants better hair, skin, and nails. Assuming your friend has a deficiency in a vitamin, which of the following supplements should you suggest they try? Magnesium Vitamin C Iodine Biotin Iron

D biotin prevent or treat: hair loss. brittle nails. seborrheic dermatitis, a skin condition that affects infants

Why are respiratory systems necessary for complex, multicellular organisms?

Simple diffusion is inadequate to deliver oxygen and remove carbon dioxide from tissues more than a few cell layers removed from the air interface

Plants have been subjected to strong selection for increasing access to nitrogen. List three adaptations that increase plant access to nitrogen.

association with nitrogen-fixing bacteria (legumes), assosiation with fungi (mycorrhizae), parasitism, carnivory nitrogen is often the most critically limiting nutrient, as it can only be made biologically available by a few species of bacteria. thus plants which live in extremely nitrogen-poor environments often have carnivorous adaptations to provide an additional sources of nitrogen from other living organisms. Parasitism allows plants to directly 'steal' nutrients such as nitrogen from other plants. A few species of bacteria are the only organisms capable of reducing ("fixing") atmospheric nitrogen to make it biologically available. Just as plants and other photosynthesizers are essential as a source of carbon and oxygen for most other forms of life, these bacteria are essential as a soruce of nitrogen for most other forms of life. Nitrogen is used for synthesis of nucleic acids and proteins. Fungi use nucleid acids and proteins from the soil organic matter; they decompose organisms containgin nitrogen which was orginally made available by the nitrogen-fixing bacteria.

Crop

expanded, muscular pouch near the gullet or throat. It is a part of the digestive tract, essentially an enlarged part of the esophagus. As with most other organisms that have a crop, the crop is used to temporarily store food

Fish gills are said to be very efficient because they use counter-current flow, as opposed to other systems, which often use cross-current flow. Explain the difference between counter- and crosscurrent flow in terms of efficiency of gas exchange.

when a concentration gradient exists between two adjacent fluids that flow in the same direction, the solutes and water quickly exchange through diffusion (and osmosis) until the concentrations have equalized. once they have equalized, no more net exchange occurs. the end result is 50/50 distribution of solutes across the two adjacent liquids. in contrast, when a concentration gradient exists between two adjacent fluids that flow in OPPOSITE directions, the concentration gradient is maintained across the entire length of the adjacent flow. the gradient is never as strong as the initial gradient that would be seen in concurrent flow; however, because it is maintained across the entire length of the adjacent flow, this means that the final distribution of solutes can be strongly asymmetric such as 90/10.

Many plant roots have specialized associations with specific species of bacteria or fungi to increase access to nitrogen. Which of the following is TRUE of these relationships ? The plant provides sugars to the fungi and the bacteria in exchange for access to nitrogen The plant relationship with the fungus is mutualistic; the relationship with the bacteria is pathenogenic Plant-associated bacteria and fungi both acquire nitrogen from the atmosphere All of the above are true None of the above are true

A

Which of the following is an advantage of a complete digestive tract? Large pieces can be ingested Digestive steps co-occur in the same place A separate opening is not needed for waste Digestive enzymes are not needed

A

O2 binding by hemoglobin is cooperative. Which model is more effective for delivery of oxygen to tissues during exercise, when O2 demands are high? (cooperative = exponential and then levels off, noncooperative = linear then levels off) cooperative noncooperative both are equally effective

A By comparing these two graphs at a low tissue partial pressure (for example, 20 mm Hg), you can see in the cooperative binding model that oxygen saturation for hemoglobin is approximately 5%. in contrast, in the non-cooperative binding model, the oxygen saturation for hemoglobin is approximately 20% at this same partial pressure. this means in the non-cooperative binding model the hemoglobin keeps more oxygen rather than delivering it to tissues in need.

Where is partial pressure of CO2 the highest? skeletal muscle capillary bed in alveolus veins alveolus (lung air sac) all are equal

A carbon dioxide is produced as a result of cellular respiration. all cells use oxygen and produce carbon dioxide as a waste product, but muscle cells can have extremely high levels of cellular respiration, and thus produce large amounts of carbon dioxide, when doing work. in order to move out of the body, the gas must move to areas of lower partial pressure

In digestion, which of the following is most likely to be digested in a rumen or cecum for a grazer? cellulose fat-soluble vitamins oxygen chitin fatty-acids

A cellulose, the primary structural carbohydrate in plants, cannot broken down by any animal enzymes. only certain microorganisms produce an enzyme capable of digesting cellulose. thus herbivores rely on a host of mutualistic microorganisms that reside in their digestive tracts to digest cellulosic material. the specialized digestive tract chambers of cows (rumen) and horses (large cecum) house these microorganisms. the rumen is present in foregut fermenters such as cows, the cecum is present in hindgut fermenters such as horses and rabbits. the crop can serve different purposes in different animals. in some animals it functions in food storage for later digestion, but in some herbivorours birds, it functions analogously to the cecum or rumen by housing mutualistic microorganisms that break down cellulosic material.

What is the force behind the process known as "transpiration" in plants? Cohesion-tension pulls water up via evaporation from leaves. Carbon dioxide is absorbed through stomata. Water is absorbed into the leaves through stomata. Water is absorbed into the roots through root hairs.

A cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. when water evaporates out of the stomata in the leaves, it deepens the meniscus causing greater pull on the water below the meniscus (tension) and thus an upward force on all the water in the entire water column, which all interact with each other via hydrogen bonds (cohesion). thus transpiration is driven by evaporation in combination with cohesion and tension in the plant water column from leaf cell to root hair.

Water potential is generally most negative in which of the following parts of a plant? mesophyll cells of the leaf root hairs xylem vessels in leaves xylem vessels in roots

A in most cases, water potential follows a gradient where it is highest in the soil and lowest in the leaves. specifically, it is lower in the mesophyll cells of the leaf than in xylem, and because of this gradient it is pulled from the soil into the root hairs, then into the xylem in the roots, up to the xylem in the leaves, and finally into the mesophyll cells of the leaf.

How does a longer alimentary canal (digestive tract) create an advantage in processing plant material? Increased time of digestion allows for more processing. More volume means more food can be consumed. It creates positive feedback for decreased enzymatic activity.

A much of the plant matter an animal eats is not broken down by the animal itself, but by the mutualistic microorganisms which reside in its gut. digestion of plant matter, especially cellulosic material, is time-consuming and inefficient, even by the organisms with the necessary enzymes to carry out the reactions. thus a longer alimentary canal provides longer processing time for these microorganisms to digest the plant matter and, importantly, also time for the animal to then absorb the nutrients released (and produced) by the microorganisms.

How does mineral mobility affect the symptoms of deficiency in plants? Deficiency of a mobile nutrient usually affects older organs more than young ones Deficiency of a mobile nutrient usually affects younger organs more than older ones

A plants are constantly competing for access to light; often older leaves become shaded by competitors over time, and new leaves develop in new locations where the plant can exploit a new source of light. thus when a nutrient becomes limiting, the plant will typically break down structures in old leaves to release nutrients to move into new leaves. any mobile nutrient (present in a structure which can be broken down) in limiting supply will thus move to new leaves at the expense of old leaves; old leaves suffer for lack of mobile nutrients when those nutrients are in short supply. in contrast, any immobile nutrient (present in a structure which cannot be broken down) in limiting supply is stuck in the old leaf and cannot be moved to the new leaves; new leave suffer for lack of immobile nutrients when those nutrients are in short supply.

Which of the following is required for acquisition of nutrients from clay-rich soils? proton pumps facilitated diffusion direct diffusion osmosis none of these

A plants pump protons into the soil to create a high concentration of protons outside the plant. this allows plants to use co-transporters to couple the movement of protons back into the cell (down their concentration gradient) and necessary nutrients into the cell (against their concentration gradients) via a 'coat-tail' effect. the proton pumps also are used to add protons to the soil to 'compete' with cations for binding to negatively-charged clay particles; thus protons will displace the cations from the clay in a process called 'cation exchange', which allows plants to more easily absorb the cations

Plants use proton pumps, cation channels, and anion cotransporter channels to acquire nutrients from the soil. Which of the following requires a direct energy expenditure by the plant? proton pump cation channel anion cotransporter channel

A plants pump protons into the soil to create a high concentration of protons outside the plant. this allows plants to use co-transporters to couple the movement of protons back into the cell (down their concentration gradient) and necessary nutrients into the cell (against their concentration gradients) via a 'coat-tail' effect. the pumping of protons out of the cell requires consumption of ATP. no energy is required by the co-transporter, as the movement of protons back into the cell down the proton concentration gradient allows movement of the nutrient in question against its concentration gradient.

Root pressure can best be described as A high pressure potential driven by accumulation of ions and water by osmosis The loss of water molecules from menisci, creating a large negative pressure The adhesion of water molecules to the sides of xylem, creating a pull upward, and by cohesion with water molecules below The movement of water from a region of low water potential to high water potential

A plants typically have a higher solute concentration (lower water potential) than the soil, causing water to move into the plant from the soil. during the day, stomata are open and plants are transpiring as they synthesize sugars from carbon dioxide. at night, in the absence of sunlight to drive photosynthesis, stomata close and transpiration stops. water continues moving into the roots at night because of the lower solute potential in the roots compared to the soil. as water continues to move in but is not transpired out, pressure builds up in the xylem eventually forcing water up the xylem. in short plants, this pressure is strong enough to push water out of the leaves in a process called guttation. root pressure is sufficient to move water up xylem at night and in short plants; however, it is not strong enough to move water up tall trees. movement of water up tall trees occurs as a result of the cohesion-tension model. cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. when water evaporates out of the stomata in the leaves, it deepens the meniscus causing greater pull on the water below the meniscus (tension) and thus an upward force on all the water in the entire water column, which all interact with each other via hydrogen bonds (cohesion). thus transpiration is driven by evaporation in combination with cohesion and tension in the plant water column from leaf cell to root hair. adhesion (attraction of water to the cell walls of the xylem) combined with cohesion and surface tension together cause capillary action, or the movement of water up a narrow tube. capillary action alone is also not sufficient to move water the length of a tall tree.

Which transport pathway does NOT involve a "filtering" step by a selectively permeable membrane? Apoplast Symplast Transmembrane

A plasmodesmata are junctions between plant cell wells that allow continuous cytoplasm. water moving through plasmodesmata is moving within the symplastic route (within-plasm). aquaporins on plasma membranes are channels that allow water to pass in or out of the cell cytoplasm. water moving through aquaporins is moving through the transmembrane route (through the membrane). there are gaps between cells and within the cell wall where water can also move. water moving between cells or within the cell walls is moving through the apoplast rout (outside of the plasm). water moving through the apoplast eventually encounters the waxy barrier called the Casparian strip. the Casparian strip is comprised of cell walls that are filled with wax. was is an effective barrier to movement of water and dissolved solutes, thus forcing water in the apopolast to enter cells via the symplast or the transmembrane pathways. a selective membrane is anything that allows some materials through but not others. the Casparian strip does not represent a selective membrane, because it does not let anything through. when water is forced into either the symplast or the transmembrane, it passes through a selective membrane. in these cases, the selective membrane is the plasma membrane, which allows some molecules through via simple diffision, facilitated difusion, or active transport.

Which is likely happening when PO2 is at 30? (exponentional then levels off graph) O2 is offloading into the tissues O2 is loading onto the hemoglobin CO2 is offloading into the tissues CO2 is offloading into the lungs

A the curve shows the affinity of hemoglobin for oxygen at different partial pressures of oxygen in the tissue (how likely it is to be 'saturated' or be bound to 4 oxygen molecules). at PO2 40 mm Hg, hemoglobin is approximately 40% saturated, so it is more likely to release oxygen than to keep it. this would be occurring where tissues are depleted of oxygen and thus oxygen is offloading from hemoglobin into the tissues.

Water moves from an area of [blank] water potential to [blank] water potential. high; low low; high concentrated; dilute dilute; concentrated

A water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential).

A friend comes to you for dietary advice. Your friend is experiencing cracks and sores on the outer surface of their lips. Which of the following might be a nutrient your friend is lacking? Vitamin B2 Vitamin B9 Vitamin C Vitamin D Iron

A B2 rich in riboflavin include eggs, organ meats (kidneys and liver), lean meats, and milk [2,4]. Green vegetables also contain riboflavin

Certain nutrients are considered "essential" in the diets of some animals because _____. (multiple) the nutrients are required for normal organismal function only certain foods contain them these animals are not able to synthesize these nutrients only those animals use those nutrients

A and C any essential nutrient is one that is absolutely required for normal function and which the organism cannot synthesize.

Which of the following would decrease the flow of water in xylem? (multiple) Coastal soils Warm summer day in temperate region Desert soils Hydrated soil

A and C anything that decreases the water potential in the soil will decrease uptake of water by root hairs and thus decrease the flow of water in xylem. desert soils are typically very dry and thus have very low water potentials. coastal soils typically have high salt concentrations and thus have very low water potentials. a warm sunny day would be expected in increase evaporation of water from stomata, which would increase transpiration rates and pull water up from the roots via the cohesion-tension model.

Where is oxygen content the LOWEST? (multiple) In venous blood In arterial blood near the heart In arterial blood further from the heart In capillaries just before they reach tissues

A and D Arterial blood and venous blood don't engage in oxygen/carbon dioxide exchange. all exchange occurs in capillaries. Respiration causes oxygen to be extracted from hemoglobin so veins has the lowest oxygen content, after passing through capillaries in tissues with very low oxygen partial pressures, resulting in maximal offloading of oxygen from the hemoglobin into the tissues.

Under which of the following conditions would the rate of transpiration INCREASE? When the weather changes and air becomes drier When the temperature of a leaf decreases When stomata close at night When atmospheric pressure is low

A and D anything that increases evaporation of water from leaves increases transpiration. drier air will increase evaporation, and thus increase traspiration. in addition, low atmospheric pressure increases transpiration in much the same way that water moves from areas of high pressure to areas of low pressure. temperatures decrease in leaves as a RESULT of transpiration, not a cause of it (much like evaporation causes cooling for animals) transpiration occurs through stomata, and thus stomata must be open for transipration to occur. closing stomata at night, or during a drought, decreases transpiration rates.

Which of the following is likely to be a sink? (multiple) Fruit Flower Apical meristem New leaf Mature leaf Root during the middle of the growing season Root at the start of the growing season

A, B, C, D, and F a source is any location with a high concentration of sugar that is mobilized to a site in need of sugar. during the growing season, sugar is synthesized via photosynthesis in the leaf mesophyll cells, and transported to locations of new growth and/or sites of storage such as roots. over the course of the growing season, large amounts of sugars are stored in roots and other storage sites. at the end of the growing season, the plant loses leaves and goes dormant, similar to hibernation in some mammals. when the next season begins, sugars in the roots and other storage sites are rapidly mobilized and used to promote growth of new leaves which will then repeat the cycle. bulbs are one specialized sugar storage site; they are a source during the start of the growing season and a sink after new leaves are established by the middle of the growing season. any growing tissue, such as a new leaf, a growing root, an apical meristem, or a developing fruit, is a sink. a mature leaf is a source due to its high rates of photosynthesis.

Soil consists of: rock particles of various sizes minerals microorganisms organic matter from dead organisms

A, B, C, and D all of these are components of soil. rock is broken down into smaller and smaller fragments through weathering (combined effects of wind, temperature changes, rain, activity of organisms); minerals such as iron, zinc, and copper are released from rock particles as it is broken down; microorganisms such as a fungi, bacteria, protists, and invertebrates help break down organic matter from dead organisms present in the humus layer of the soil.

What would be different if the sink were a newly growing leaf instead of a mature storage root cell?

ATP would not be required, because sugar would be immediately metabolized for growth instead of stored (it would not have to be moved against its concentration gradient)

Some plants obtain nitrogen from symbiotic fungi or bacteria.What was the original source of N for the bacteria? urea in the soil N2 gas carbohydrates in the soil lipids in the soil proteins in the soil

B A few species of bacteria are the only organisms capable of reducing ("fixing") atmospheric nitrogen to make it biologically available. Just as plants and other photosynthesizers are essential as a source of carbon and oxygen for most other forms of life, these bacteria are essential as a soruce of nitrogen for most other forms of life. Nitrogen is used for synthesis of nucleic acids and proteins. Fungi would use nucleid acids and proteins from the soil organic matter; they decompose organisms containgin nitrogen which was orginally made available by the nitrogen-fixing bacteria.

Which of the following correctly describes why water is more difficult to respire in compared to air? Water is warmer than air, and thus holds less oxygen. Water is about 1000x more dense than air, and thus requires more energy to ventilate the respiratory surface (inhale/exhale). Water has a higher partial pressure of O2, and thus O2 constantly diffuses into the air (away from aquatic organisms). Respiratory surfaces work better in drier conditions, not in moist (or wet) conditions.

B air is less dense and thus takes less work (energy) to move through the respiratory organ. water has a lower partial pressure of oxygen than air does. warmer water holds less oxygen than colder water, but the temperature of a body of water is often cooler than the air. respiratory surfaces tend to be lined in thin mucus, and thus drier air conditions cause drying of these surfaces which can interfere with respiratory function.

The absorption of fats differs from that of carbohydrates in that _____. the processing of fats does not require any digestive enzymes, whereas the processing of carbohydrates does most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood fat absorption primarily occurs in the stomach, whereas carbohydrates are absorbed from the small intestine carbohydrates need to be emulsified before they can be digested, whereas fats do not

B because fats are hydrophobic, they aggregate into globules that are resistant to enzymatic breakdown. thus fats must first be emulsified (broken up and dissolved into aqueous solution with the aid of amphipathic molecules such as bile salts). the emulsified fats are then digested by the enzyme lipase. the resulting fatty acids and monoglycerides are then packaged into protein-coated globules. these globules are large enough that their diffusion into capillaries would clog the capillaries and stop blood flow. thus the globules are instead transported into the lymphatic system, where they eventually join the bloodstream at large veins where there is much less risk of clogging the vessels. digestion of all nutrients requires enzymatic breakdown. the stomach is not involved in absoprtion of any nutrients; its role is purely mechanical and chemical digestion. it is fats that require emulsification, due to their hyrdophobicity, not carbohydrates which are hydrophilic.

The only animals that use skin as a significant portion of their respiratory surface (ie, use skin for gas exchange) are largely aquatic/amphibious. Yet water is a less efficient medium for gas exchange than air. Why do you suppose all skin-ventilated animals reside in/near water? having a lot of skin surface area exposes you to greater changes in temperature and other environmenal risks the thin membranes required for efficient gas exchange increases the risk of dehydration natural selection has increased the efficiency of gas exchange in aquatic animals compared to terrestrial animals it is an evolutionary 'accident' based on lack of common ancestry between aquatic and terrestrial vertebrates

B efficient gas exchange requires a thin barrier to diffusion. thus respiratory surfaces are covered by extremely thin membranes. as a consequence, these membranes are also extremely susceptible to evaporation as the same principles that promote efficient diffusion of gasses also promote efficient movement of water.

Where is partial pressure of CO2 the highest? atmosphere skeletal muscle capillary bed in alveolus alveolus (lung air sac)

B partial pressure is the pressure of a particular amount of gas in a mixture of gasses. it is different from percent because gas is compressible; thus the percent of a gas in a mixture can be the same, but its partial pressure can change based on the overall pressure of the system. just like water's response to pressure, gasses move from areas of high partial pressure to areas of low partial pressure. the partial pressure of carbon dioxide is highest at locations where carbon dioxide is being produced and oxygen is being consumed. of the choices above, this would be at the skeletal muscles.

Iron deficiency is often indicated by yellowing in newly formed leaves. This suggests that iron is _____. concentrated in the xylem of older leaves relatively immobile nutrient in plants concentrated in the phloem of older leaves found in leghemoglobin and reduces the amount available to new plant parts tied up in formed chlorophyll molecules

B plants are constantly competing for access to light; often older leaves become shaded by competitors over time, and new leaves develop in new locations where the plant can exploit a new source of light. thus when a nutrient becomes limiting, the plant will typically break down structures in old leaves to release nutrients to move into new leaves. any mobile nutrient (present in a structure which can be broken down) in limiting supply will thus move to new leaves at the expense of old leaves; old leaves suffer for lack of mobile nutrients when those nutrients are in short supply. in contrast, any immobile nutrient (present in a structure which cannot be broken down) in limiting supply is stuck in the old leaf and cannot be moved to the new leaves; new leave suffer for lack of immobile nutrients when those nutrients are in short supply.

Moderate soil acidity means there are protons in the soil. Protons help nutrient availability by _____. increasing the cation binding to soil particles promoting cation exchange promoting cellular respiration in root cells leaching away the cations from soil after heavy rains

B plants can easily absorb anions from the soil because anions are readily soluble in soil water. in contrast, cations associate tightly with clay particles in soil, which are negatively charged. this makes it difficult for plants to absorb cations from the soil. protons in the soil will 'compete' with cations for binding to negatively-charged clay particles; thus protons will displace the cations from the clay in a process called 'cation exchange', which allows plants to more easily absorb the cations

Which is happening when PO2 is at 100? (exponential curve up and then levels off at PO2 100) O2 is offloading from hemoglobin into the tissues O2 is loading onto the hemoglobin in the lungs CO2 is loading onto hemoglobin in the tissues CO2 is loading onto hemoglobin in the lungs

B the curve shows the affinity of hemoglobin for oxygen at different partial pressures of oxygen in the tissue (how likely it is to be 'saturated' or be bound to 4 oxygen molecules). at PO2 100 mm Hg, hemoglobin is approximately 100% saturated, so it is more likely to take up/keep oxygen than to release it. this would be occurring in the lungs where hemoglobin is taking up oxygen from the air.

If ΨP = 0.3 MPa and ΨS = -0.45 MPa, the resulting Ψ is _____. +0.15 MPa -0.15 MPa -0.75 MPa +0.75 MPa -0.42 MPa

B Ψ (water potential) is the sum of ΨP (pressure potential) and ΨS (solute potential). water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential).

Why is it harder to breathe at high elevations? The air is "thicker" and more dense. The air is "thinner" and holds less oxygen per unit volume. The atmospheric pressure is higher, making it more difficult to breathe. The atmospheric pressure is lower, resulting in a lower partial pressure for O2.

B and D partial pressure is the pressure of a particular amount of gas in a mixture of gasses. it is different from percent because gas is compressible; thus the percent of a gas in a mixture can be the same, but its partial pressure can change based on the overall pressure of the system. just like water's response to pressure, gasses move from areas of high partial pressure to areas of low partial pressure. because the air is less dense at higher altitudes, the partial pressure of oxygen is lower at higher altitudes. efficient exchange across the respiratory surface depends on a high gradient of partial pressures, but the lowered partial pressure of oxygen at higher altitudes is not much greater than the partial pressure of oxygen in the blood in the alveolar capillaries; thus there is much less exchange of oxygen across the respiratory surface at high altitudes.

A friend comes to you for dietary advice. Your friend is experiencing symptoms of anemia. Which of the following might be a nutrient your friend is lacking? (Hint: Use the table in your reading for help) Vitamin B2 Vitamin B9 Vitamin C Vitamin D Iron

B and E B9 is important for the production and maintenance of new cells. Dark Leafy Greens, Asparagus,Broccoli, Citrus Fruits, Beans, Peas, and Lentils Iron substance in red blood cells that carries oxygen from your lungs to transport it throughout your body

Which of the following organs play an accessory role in the digestion of food? (multiple) esophagus pancreas stomach small intestine gall bladder liver large intestine

B, E, and F Accessory digestive organ: An organ that helps with digestion but is not part of the digestive tract. The accessory digestive organs are the tongue, salivary glands, pancreas, liver, and gallbladder.

Nitrifying bacteria can have a strong impact on the nutrient content of soils because: they add to the total pool of N by converting N2 to NH3 they convert biologically available N into inert N2 they transform biologically available N to a form that that washes out of soil easily they can outcompete plants for the biologically available N None of the above

C

Which of the following statements about mycorrhizae is/are FALSE? Mycorrhizae are mutualistic associations of roots and fungi The fungus component in mycorrhizae benefits by receiving sugar from plants The hyphae of arbuscular mycorrhizae extend into the root cortex. while the hyphae of ectomycorrhizae do not The fungus component in mycorrhizae benefits plants by supplying water and minerals absorbed by the fungal hyphae All of the above are true

C

Where does chemical digestion of proteins begin? esophagus pancreas stomach small intestine gall bladder liver large intestine mouth

C Although proteins are physically broken down in the mouth, the stomach begins the chemical breakdown of proteins.

Where is oxygen content the LOWEST? In venous blood during rest In arterial blood during exercise In venous blood during exercise In arterial blood during rest

C Arterial blood and venous blood don't engage in oxygen/carbon dioxide exchange. all exchange occurs in capillaries. exercise causes more oxygen to be extracted from hemoglobin so venous blood during exercise has the lowest oxgyen content, after passing through capillaries in tissues with very low oxygen partial pressures, resulting in maximal offloading of oxygen from the hemoglobin into the tissues.

Where does the mass of a tree come from? Soil Sunlight Air Water

C all biological compounds contain carbon. plants are capable of 'fixing' atmospheric carbon dioxide to produce sugars, which are the source of carbon for synthesis of biological molecules in the plant. thus the mass of a plant comes from the carbon dioxide in the air.

Which of the following is NOT a key component of the cohesion-tension process in xylem? Lignin in xylem cell walls Open stomata Use of ATP Water between mesophyll cells

C cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. adhesion is attraction among unlike molecules; in this case the attraction of water to the cell walls of the xylem. when water evaporates out of the stomata in the leaves, it deepens the meniscus causing greater pull on the water below the meniscus (tension) and thus an upward force on all the water in the entire water column, which all interact with each other via hydrogen bonds (cohesion). thus transpiration is driven by evaporation in combination with cohesion and tension in the plant water column from leaf cell to root hair. because the water column in a plant is continuous from root to leaf, the menesci (plural of meniscus) are present between the mesophyll cells, not actually within the xylem tubes. thus it is evaporation at these menisci inbetween the leafe mesophyll cells that drive movement via the cohesion-tension process. the cohesion-tension process puts strong negative pressure on the xylem, like sucking on a straw. lignin reinforces the walls of the xylem, which would otherwise collapse as a result of this negative pressure this cohesion-tension model does not require any input of energy on the part of the plant (energy that causes water to evaporate comes from the sun); there is no active transport to move water through xylem. this is because, in most cases, water potential in plants follows a gradient where it is highest in the soil and lowest in the leaves. specifically, it is lower in the mesophyll cells of the leaf than in xylem, and because of this gradient it is pulled from the soil into the roots.

How does hemoglobin binding work? Hemoglobin molecules form clumps and accumulate extra oxygen in the pile-up. Conformational changes in red blood cells allow for additional oxygen molecules once one is picked up. Hemoglobin is more likely to bind to oxygen once one O2 is bound. When O2 is bound to hemoglobin, a CO2 molecule can also bind to hemoglobin.

C each hemoglobin protein can bind four oxygen molecules at a time. cooperative binding is the phenomenon where the binding of the first oxygen changes the conformational shape of the rest of the protein and makes it easier for the second, third, and four oxygen molecules to bind. once the hemoglobin protein is fully saturated (bound to 4 oxygen molecules), the reverse is also true: loss of the first oxygen molecules makes it easier for the second, third, and fourth oxygen molecules to leave the hemoglobin protein. each red blood cell contains ~280 million hemoglobin molecules. the phenomenon of cooperative binding occurs at the level of hemoglobin, not red blood cells. most of the carbon dioxide in the bloodstream is converted to carbonic acid by the enzyme carbonic anhydrase. the carbonic acid then dissociates into bicarbonate and a proton. the protons tend to bind to deoxygenated hemoglobin, and the bicarbonate remains in the plasma; thus hemoglobin acts as a pH buffer. if hemoglobin proteins were to clump together, this would distort the shape of the red blood cells and interfere with oxygen binding to hemoglobin. this is what occurs in individuals who suffer from the genetic disorder sickle cell anemia, which results from a mutation in the hemoglobin protein that causes the hemoglobins to clump together.

Why are plants like the venus fly trap and pitcher plant carnivorous? The need additional carbon than is present in the soil They need additional protein than what is present in the soil They need additional mineral nutrients than what is present in the soil They need additional energy than what is present in the soil

C plants get carbon from carbon dioxide and energy from the sun. they synthesize their own amino acids (building blocks of proteins) from carbon and other nutrients. they also use other nutrients for many other biological functions. these other nutrients are typically minerals obtained from the soil such as nitrogen, potassium, calcium, etc. nitrogen is often the most critically limiting nutrient, as it can only be made biologically available by a few species of bacteria. thus plants which live in extremely nitrogen-poor environments often have carnivorous adaptations to provide an additional sources of nitrogen from other living organisms.

Which of the following promotes oxygen release from hemoglobin? A decrease in temperature in body tissue A decrease in CO2 levels in body tissue A decrease in pH in body tissue A decrease in carbonic anhydrase in RBCs

C the Bohr shift causes the hemoglobin-oxygen equilibrium curve (the plot comparing oxygen saturation of hemoglobin against partial pressure of oxygen in the body tissues) to shift toward the right. this means that hemoglobin becomes MORE likely to 'give up' oxygen at any particular partial pressure of oxygen in the body tissue (decreases the affinity of hemoglobin for oxygen). this shift occurs because of lower pH. blood pH can be lowered as a result of increased carbon dioxide; carbon dioxide is converted into carbonic acid in the blood. hemoglobin binds many of the protons released by carbonic acid to buffer the blood, but excess protons beyond what are bound by hemoglobin will lower the blood pH. this occurs when tissues are heavily utilizing oxygen such as during exercise, thus causing greater release of oxygen to the tissues. increased temperature causes a similar effect on the release of oxygen from hemoglobin, but the response to increased temperature is not called the Bohr effect. a decrease in carbonic anyhdrase would decrease the likelihood of Bohr effect occurring, because carbon dioxide would not be converted to carbonic acid as quickly.

The difference between positive pressure ventilation (PPV) and negative pressure ventilation (NPV) is that: in PPV, organisms exchange gases only during inhalation; in NPV, organisms exchange gasses only during exhalation in PPV, respiration is coupled to a circulatory system; in NPV, respiration occurs through direct gas exchange with tissues PPV occurs when air is pushed into the respiratory organ; NPV occurs when air is pulled into the respiratory organ PPV occurs only in animals with gills or tracheae, NPV occurs only in animals with lungs

C this is the definition of positive vs negative ventiliation. whether an organism can engage in gas exchange during inhalation only or inhalation and exhalation has to do with the organization of the airways, not the mechanism for bringing air into the airways (review bird vs mammal airway organization). organisms that use direct gas exchange through the skin have no need to 'pump' air anywhere. amphibians are an examples of lunged organisms that use PPV rather than NPV.

Concurrent flow is not as efficient in exchange as countercurrent flow because countercurrent flow provides: more diffusion at the beginning of capillary flow than at the end of the capillary by maximizing the concentration gradient at the beginning. more diffusion at the end of capillary flow than at the end of the capillary by maximiizing the concentration gradient at the end. consistent diffusion across weaker concentration gradients through the entire capillary. thinner capillary walls to promote diffusion. greater surface area for diffusion.

C when a concentration gradient exists between two adjacent fluids that flow in the same direction, the solutes and water quickly exchange through diffusion (and osmosis) until the concentrations have equalized. once they have equalized, no more net exchange occurs. the end result is 50/50 distribution of solutes across the two adjacent liquids. in contrast, when a concentration gradient exists between two adjacent fluids that flow in OPPOSITE directions, the concentration gradient is maintained across the entire length of the adjacent flow. the gradient is never as strong as the initial gradient that would be seen in concurrent flow; however, because it is maintainied across the entire length of the adjacent flow, this means that the final distribution of solutes can be strongly asymmetric such as 90/10.

Root hairs absorb nutrients from soil against the nutrient concentration gradient. Depending on the nutrient, which of the following can play a role in this process? (multiple) osmosis direct diffusion facilitated diffusion electrochemical gradient co-transport

C, D, and E plants pump protons into the soil to create a high concentration of protons outside the plant. this allows plants to use co-transporters to couple the movement of protons back into the cell (down their concentration gradient) and necessary nutrients into the cell (against their concentration gradients) via a 'coat-tail' effect. the proton pumps also are used to add protons to the soil to 'compete' with cations for binding to negatively-charged clay particles; thus protons will displace the cations from the clay in a process called 'cation exchange', which allows plants to more easily absorb the cations

Why are many digestive enzymes produced in an inactive form and then activated in the lumen of the digestive tract? It helps to break down macromolecules(proteins, carbohydrates, nucleic acids, lipids) faster. The temperature of organism changes when food falls into digestive tract, that helps to activate digestive enzymes. Digestive enzyme have an inherent inactive period, only after that period can they become activated. Digestive enzymes would destroy the cells that produce and secrete them if they were produced in an active form.

D animals eat biological materials and use digestive enzymes to break the material down. thus digestive enzymes are designed to break down nutrients which in many cases are extremely similar to components of the animal cells (lipids, proteins, carbohydrates). if the enzymes were active as soon as a cell produced them, the enzymes could immediately begin digesting components of the cells that made them. the two major strategies for avoiding this type of cell self-destruction are producing enzymes in an inactive form and compartmentalizing digestive reactions when enzymes are active (for example, compartmentalizing the initial digestion of polypeptides to the stomach). the digestive systems of most animals display both of these strategies.

What is the adaptive function of specialized digestive tract chambers in vegetarian animals like cows and horses? maintain low pH for stomach enzymes. mixing of bile and pancreatic enzymes with food. for storage of partially digested plant material. housing symbiotic bacteria required for cellulose digestion. consolidation of undigested waste before defecation.

D cellulose, the primary structural carbohydrate in plants, cannot broken down by any animal enzymes. only certain microorganisms produce an enzyme capable of digesting cellulose. thus herbivores rely on a host of mutualistic microorganisms that reside in their digestive tracts to digest cellulosic material. the specialized digestive tract chambers of cows (rumen) and horses (large cecum) house these microorganisms.

What forces are responsible for capillarity? high pressure potentials created by the entry of ions and water during the night, when transpiration rates are low, followed by an influx of water cohesion of water molecules in a continuous flow from leaf to root gravity and wall pressure (from the sides of xylem cells) adhesion of water molecules to the sides of xylem cells, cohesion of water molecules to each other, and surface tension

D cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. adhesion is attraction amon unlike molecules; in this case the attraction of water to the cell walls of the xylem. adhesion combined with cohesion and surface tension together cause capillary action, or the movement of water up a narrow tube. capillary action alone is also not sufficient to move water the length of a tall tree. root pressure occurs because plants typically have a higher solute concentration (lower water potential) than the soil, causing water to move into the plant from the soil. during the day, stomata are open and plants are transpiring as they synthesize sugars from carbon dioxide. at night, in the absence of sunlight to drive photosynthesis, stomata close and transpiration stops. water continues moving into the roots at night because of the lower solute potential in the roots compared to the soil. as water continues to move in but is not transpired out, pressure builds up in the xylem eventually forcing water up the xylem. in short plants, this root pressure is strong enough to push water out of the leaves in a process called guttation. root pressure is sufficient to move water up xylem at night and in short plants; however, it is not strong enough to move water up tall trees. movement of water up tall trees occurs as a result of the cohesion-tension model. when water evaporates out of the stomata in the leaves, it deepens the meniscus causing greater pull on the water below the meniscus (tension) and thus an upward force on all the water in the entire water column, which all interact with each other via hydrogen bonds (cohesion). thus transpiration is driven by evaporation in combination with cohesion and tension in the plant water column from leaf cell to root hair. the cohesion-tension process puts strong negative pressure on the xylem, like sucking on a straw. lignin reinforces the walls of the xylem, which would otherwise collapse as a result of this negative pressure

Which of the following is NOT a reason that an animal's gut is a favorable habitat for mutualistic microorganisms? Constant temperature Ready supply of nutrients Inhospitable conditions for many micro-competitors Easy access to bloodstream

D like all life, microorganisms survive better in 'ideal' growth conditions and are in constant competition for access to resources. the gut represents an 'ideal' growth condition for microorganisms because of controlled temperature and ready supply of nutrients, in addition, the inhospitable conditions (high acidity of the stomach, presence of immune cells in the intestines) reduce competition. the gut does not provide easy access to the bloodstream except in cases where the lining of the gut becomes compromised. this can occur in cases of infection, where the tight junctions between intestinal cells becomes compromised. microorganisms which enter the bloodstream can cause massive, systemic infection in the host organism, resulting in an overwhelming immune response that either destroys the microorganism or causes death of the host. neither of these outcomes is advantageous for the microorganism.

Which organism do you think has the most efficient respiratory organ? snail bird snake fish human

D the partial pressure of oxygen in water is lower than the partial pressure of oxygen in air. in addition, air is less dense and thus takes less work (energy) to move through the respiratory organ. thus fish gills are much more efficient at removing oxygen from water than terrestrial lungs are at removing oxygen from the air as a result of this selective pressure.

Which of the following is not a major activity of the stomach? Mechanical digestion HCl secretion Mucus secretion Nutrient absorption Enzyme secretion

D the purpose of the stomach is digestion, not absorption. digestion is breakdown of nutrients into smaller components. stomach digestion processes include 1) mechanical breakdown via muscular contractions of the stomach that churns and mixes the food particles and 2) chemical breakdown via enzymatic digestions. stomach enzymes are secreted into the stomach compartment when food enters, and hydrochloric acid is also secreted which activates the protein digestive enzyme pepsin. mucus is also secreted by stomach cells to protect the lining of the stomach from HCl.

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis, the volume of the cell increases until it bursts. This does not happen to plant cells, because _____. certain gated channel proteins embedded in their plasma membranes open as osmotic pressure decreases, allowing excess water to leave the cell they have cell walls, which prevent the entry of water by osmosis they have large central vacuoles, which provide abundant space for storage of incoming water they have cell walls, which provide pressure to counteract the pressure of the incoming water

D water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential). in the case above, the wall of the plant cell exerts pressure potential against water moving in to cell that balances against the solute potential driving water into the cell. there is no such pressure potential in the case of a mammalian cell that lacks a cell wall, which means water continually moves into the mammalian cell until it bursts.

Compared to plants from other environments, the cells of many desert plants contain high concentrations of solutes. This helps them survive in their arid surroundings because the high solute concentrations create relatively [blank], which helps retain water and prevent reverse flow of water from roots to soil. low pressure potentials high pressure potentials high solute potentials low solute potentials

D Ψ (water potential) is the sum of ΨP (pressure potential) and ΨS (solute potential). water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential). desert soil is very dry and thus has very low water potential; this makes it difficulty for plants to absorb water from the soil because the soil may have lower water potential than the plant; this would cause water to move out of the plant and into the soil. as a result of selection in a dry environment, one adaptation in desert plants is very high solute concentrations in their tissues. the higher the solute concentration, the lower the solute potential, and thus the more likely water is to move into the plant from the soil: this low solute potential in the plant can drive the water potential of the plant lower than the water potential of the dry soil.

Carnivorous plants have evolved mechanisms that trap and digest small animals. The products of this digestion are used to supplement the plantʹs supply of . carbohydrates minerals water energy proteins

E

What is the function of proton pumps localized in the plant plasma membrane? to provide channels for ion diffusion to transfer phosphorus groups from ATP to proteins to transfer metal ions across the plasma membrane to transfer anions across the plasma membrane to create a membrane potential

E

in a root nodule, the nitrogenase: regulates the amount of oxgyen available is inactivated by leghemoglobin is absent in active bacteroids protects the nodule from nitrogen is encoded by the Rhizobium genome is encoded by the plant genome

E

Some plants obtain nitrogen from symbiotic fungi or bacteria.What were the original sources of N that the FUNGI obtained? urea in the soil N2 gas carbohydrates in the soil lipids in the soil proteins in the soil

E A few species of bacteria are the only organisms capable of reducing ("fixing") atmospheric nitrogen to make it biologically available. Just as plants and other photosynthesizers are essential as a source of carbon and oxygen for most other forms of life, these bacteria are essential as a soruce of nitrogen for most other forms of life. Nitrogen is used for synthesis of nucleic acids and proteins. Fungi would use nucleid acids and proteins from the soil organic matter; they decompose organisms containgin nitrogen which was orginally made available by the nitrogen-fixing bacteria.

Which of the following soil minerals is most likely leached away during a hard rain (ie, dissolve easily in soil water)? H+ Ca++ K+ Na+ NO3-

E anions are readily soluble in soil water, and thus easily washed (leached) away during heavy rains.. in contrast, cations associate tightly with clay particles in soil, which are negatively charged. this means cations remain bound to clay during rains and do not wash way.

Which elements are most often the limiting nutrients for plant growth? carbon, nitrogen, oxygen carbon, potassium, sodium carbon, sodium, chlorine nitrogen, oxygen, hydrogen nitrogen, potassium, phosphorus

E nitrogen, potassium, and phosphorus are all essential macronutrients for plants, meaning they are required in relatively large quantities. macronutrients are typically major components of nucleic acids, proteins, and/or phospholipids, and are thus required for normal function in all cells. nitrogen is highly abundant in the atmosphere as nitrogen gas; however, nitrogen gas is not usable for most organisms. only a few species of bacteria are capable of reducing or 'fixing' nitrogen to become biologically available. oxygen is produced by plant photosynthesis, and required by plant respiration. plants produce enough that it is not limiting. carbon dioxide is required by plants to produce sugars via photosynthesis. it is not limiting in the atmosphere. sodium is not required for most plants.

The Bohr* shift on the oxygen-hemoglobin dissociation curve is produced by changes in _____. hemoglobin concentration the partial pressure of oxygen the partial pressure of carbon monoxide salts pH

E the Bohr shift causes the hemoglobin-oxygen equilibrium curve (the plot comparing oxygen saturation of hemoglobin against partial pressure of oxygen in the body tissues) to shift toward the right. this means that hemoglobin becomes MORE likely to 'give up' oxygen at any particular partial pressure of oxygen in the body tissue (decreases the affinity of hemoglobin for oxygen). this shift occurs because of lower pH. blood pH can be lowered as a result of increased carbon dioxide; carbon dioxide is converted into carbonic acid in the blood. hemoglobin binds many of the protons released by carbonic acid to buffer the blood, but excess protons beyond what are bound by hemoglobin will lower the blood pH. this occurs when tissues are heavily utilizing oxygen such as during exercise, thus causing greater release of oxygen to the tissues. increased temperature causes a similar effect on the release of oxygen from hemoglobin, but the response to increased temperature is not called the Bohr effect.

Place the following digestion events in sequential order. If two events occur in the same organ, you should set them as equal to one another. Pepsinogen is cleaved to form pepsin Polypeptides are cleaved into individual amino acids by proteases Salivary amylase hydrolyzes starch Digested food material is compacted and most remaining water absorbed Parietal cells secrete HCl Bile salts and pancreatic amylase are secreted

Salivary amylase hydrolyzes starch < Parietal cells secrete HCl = Pepsinogen is cleaved to form pepsin < Bile salts and pancreatic amylase are secreted = Polypeptides are cleaved into individual amino acids by proteases < Digested food material is compacted and most remaining water absorbed this sequence of steps occurs from mouth to large intestine. in the mouth, salivary amylase breaks down complex carbohydrates during chewing. once the food is swallowed and passes through the esophagus into the stomach, the stomach secretes both HCl and pepsinogen. The HCl activates the pepsinogen into pepsin, which breaks down large proteins into polypeptides (shorter chains of amino acids). after digestion in the stomach, the bolus of food moves into the small intestine where the gall bladder secretes bile salts (produced in the liver, stored in the gall bladder) to digest lipids, and the pancreas secretes pancreatic amylyase and other digestive enzymes. these enzymes cause further digestion of material into individual components such as polypeptides broken down into individual amino acids. these nutrients are then absorbed into the blood stream (or moved into the lymph in the case of lipids) in the small intestine. after absorption of nutrients in the small intestine, the digested material moves into the large intestine where water is reabsorbed and the material is compacted for elimination.

process of the formation of a root nodule

Step 1 - Root produces flavenoids Step 2 - Bacteria produce Nod factors Step 3 - Root growth of a nodule begins Step 4 - Vesicles form in root cells containing Rhizobium bacteria Step 5 - Root creates and regulates low oxygen environment

You decide to feed your rabbit, an herbivore, a series of different antibiotics to get over an illness. It temporarily gets better, but then begins to show symptoms of malnutrition. Why might this be?

Symbiotic gut bacteria aid in digestion by breaking down molecules the host cannot digest and making them available to the host. In some cases, the host organisms provide essential vitamins that otherwise cannot be accessed from the food, such as vitamin K. The anitbiotics likely killed both the 'bad' bacteria making the rabbit sick, and the 'good' gut bacteria needed for nutrient acquisition.

Fetal hemoglobin (encoded by a different gene than adult hemoglobin) has a higher affinity for oxygen than maternal hemoglobin. is this shift beneficial or detrimental to the developing fetus, and why?

The oxygen-dissociation curve shift to the left, with the Sigmoidal shape maintained and near 100% saturation still achieved at high PO2. This is beneficial, because it means the fetal hemoglobin binds oxygen more tightly (has a higher affinity for oxygen) than adult hemoglobin. This higher affinity means that oxygen is transferred from the maternal hemoglobin to the fetal hemoglobin in the placenta, where maternal and fetal blood supplies are in close proximity. This process is necessary to provide oxygen to the developing fetus.

what happens to the hemoglobin-saturation curve when pH is decreased compared to the "normal" curve.

The oxygen-dissociation curve shift to the right, with the Sigmoidal shape maintained and near 100% saturation still achieved at high PO2.

Fick's law of diffusion describes the rate of diffusion across a respiratory surface. rate of diffusion = k * A * (P2-P1)/D where k is a diffusion constant (dependent on the gas and T) A is surface area P is partial pressure in either side (1, 2) of the surface D is depth of surface The structures of respiratory organs have been evolutionarily selected to maximize gas exchange. What aspect(s) of respiratory organ structure are most likely to be MAXIMIZED/LARGEST to increase the rate of diffusion?

area for gas exchange, partial pressure difference area for gas exchange: large surface area in lungs/gills/tracheae; partial pressure difference: efficient respiratory organs maintain a high partial pressure difference across the respiratory medium (e.g. cross-current or counter-current flow) depth of the surface (barrier to diffusion) is MINIMIZED in respiratory organs; the greater the depth, the less efficient diffusion is.

Describe the role of the gizzard in digestion. What types of animals have gizzards? What digestive structure do these organisms lack?

mechanical disruption of food; animals with crops lack teeth adapted for chewing the gizzard functions in mechanical breakdown in organisms that lack teeth. it is present in may different types of organisms including birds, reptiles, earthworms, some fish, and crustaceans. many types of animals swallow stones or sand that is stored in the gizzard to aid in mechanical disruption of food.

apoplast

outside the cell, via the cell wall

where passive transport is responsible for bulk flow in phloem.

sieve tube once sugars have been transported into companion cells, their movement within phloem is driven by turgor pressure and diffusion. turgor pressure in phloem increases as a result of water movement into phloem from xylem, due to the negative solute potential caused by high concentrations of sugar in the cytoplasm of the phloem cells. because water moves from areas of high pressure to low pressure, the high turgor pressure drives movement of sugar from source to sink.

Sodium is not an essential nutrient for plants, but is essential for animals. Given what you know from previous modules, why is this the case?

sodium is required for generating action potentials in the nervous system; plants don't have nervous systems

where energy is required during the loading of the sieve-tube members

source to companion cell

where sucrose is moved by a co-transporter.

source to companion cell an H+ gradient outside the companion cells is used to transport sugars against their concentration gradient into the the companion cells. ATP-powered pumps move H+ out of the companion cells to establish this H+ gradient. sucrose-H+ symporters are then responsible for moving sucrose from the mesophyll source cells into the companion cells. thus the movement of sucrose into the companion cells from the source requires energy (indirectly) because of the energy cost to establish the proton gradient.

"Germ-free" laboratory mice birthed and reared in completely sterile environments (this is difficult but possible!) have higher nutritional needs compared to normal mice. Explain why.

symbiotic gut bacteria aid in digestion by breaking down molecules the host cannot digest and making them available to the host symbiotic gut bacteria aid in digestion by breaking down molecules the host cannot digest and making them available to the host. in some cases, the host organisms provide essential vitamins that otherwise cannot be accessed from the food, such as vitamin K.

transmembrane

through the cell membrane, via water channels

symplast

through the shared cell cytoplasm, via plasmodesmata

where energy is required for the unloading of sucrose into root storage cells

tonoplasts transport of sugar into storage sites requires energy, because the concentration of sugar is constantly increasing at the storage site. similar to the H+ gradient outside the companion cells that is used to transport sugars against their concentration gradient into the the companion cells, ATP-powered pumps first move H+ into specialized vacuoles (tonoplasts) in storage cells; this hydrogen gradient is used transport sugars from the cytoplasm of these cells into the tonoplasts via antiporters.