BSCI207 Exam 3

Osmolarity

-A 1 osmolar= 1 Osm solution has 6 x 10^23 dissolved entities (e.g., glucose molecules, protein molecules, Na+ ions) per liter. 1 osmolar = 1000 milliosmolar = 1000 most -For compounds that dissociate in solution, osmolarity and molarity are different. 1 molar (mol/L) solution of NaCl is a 2 osmolar (2 osmol/L) solution. But 1 molar solution of glucose is also 1 osmolar because glucose does not dissociate in solution.

Renal papilla

-A projection of medulla into the renal pelvis (expanded end of the ureter that drains the kidney) and is composed of largely long loops of Henle. -There is little or no development of the renal papilla in freshwater aquatic species. However, the renal papilla is highly developed in species native to arid habitats, so much that it often penetrates well into the ureter.

Summary of single effect in loop of Henle

-Active transport of NaCl out of ascending limb -Decreases NaCl concentration and osmotic pressure of fluid in ascending limb -Increases NaCl concentration and osmotic pressure of both adjacent interstitial fluid and adjacent descending limb fluid

Kangaroo rats

-Adult kangaroo rats typically don't drink at all -They live in deep, cool burrows during heat of day -Very little evaporation from skin, dry feces -Soluble waste very concentrated (osmotic U/P: 10-20) -Obtain small amount of water from seeds, but most important water source is metabolic water from oxidation of organic molecules, like glucose.

Which way will water and ions tend to move between freshwater and animal?

-All freshwater animals are hyperosmotic to fresh water. -Water breathing freshwater animals face problems opposite to those of marine fishes. They tend to gain water by osmosis from freshwater environment, bloating them, tend to lose ions by diffusion to the environment, and body fluids tend to become too dilute. -To maintain hyperosmotic state, kidneys produce large volume of urine each day to get rid of excess water. In most cases, kidneys produce urine far more dilute than blood plasma (U/P<1). -Lost salts replaced by active transport cells that use ATP to pump Na+ and Cl- directly from fresh water environment into blood-although these ions are scarce in freshwater.

Distal tubule of nephron

-As in proximal tubule, Na+ and Cl- are pumped out of tubule back into blood ( active transport) -Unlike proximal tubule, wall of distal tubule has variable permeability to water. Where aquaporin proteins are inserted in epithelial cell membrane, water permeability is high. Insertion of aquaporins is controlled by antidiuretic (decreases blood flow) hormone (ADH= vasopressin) secreted by the hypothalamus of the brain.

Ultrafiltration

-Blood enters each glomerulus at a pressure high enough that fluid from blood plasma is forced through tiny openings in walls of glomerular capillaries and then through inner wall of Bowman's capsule. Fluid enters lumen (central cavity) of Bowman's capsule: primary urine. -Blood cells and proteins dissolved in plasma are left behind in plasma -Water, salts, and small organic molecules such as glucose and amino acid pass through freely, entering nephron

Salmon transition

-Born in freshwater, grow in ocean, return to freshwater to spawn -In freshwater, do not drink; in ocean, start to drink and activate intestinal ion transport -In freshwater, use ATP to pump ions from surrounding water into blood in gills; in ocean, use ATP to pump ions out of blood in gills into seawater

Countercurrent multiplication in Loop of Henle

-Can imagine as a series of alternating steps, with successive applications of single effect amplifying concentrating effect. -Osmotic pressures paralleled by NaCl concentrations. -The single effect is generated, fluid moves in countercurrent fashion through loop, the single effect is again generated, the fluid concentration at the inner endow the loop is higher in step 4 than in step 2, moreover it is even higher by step 8 Fluid concentrated in descending limb moves around into the ascending limb. This sets the stage for single effect (from active transport of NaCl out of ascending limb) to produce an increasing osmotic concentration in interstitial fluid and descending limb toward inner (medullar) end of loop. -Successive applications of single effect amplify concentration. -Osmotic pressure of interstitial fluid at outer end of loop is kept near 300 mOsm by steady influx of 300 mOsm fluid into start of descending limb, and dilution of fluid in ascending limb as it flows from deep in medulla to top of ascending limb. -Difference in osmotic pressure between cortical and medullar ends of the loop becomes greater and greater to a point where it much exceeds the between limb difference generated by the single effect.

Kidneys and nitrogenous waste

-Carbohydrates and fats break down during metabolism to CO2 and H2O, which are easy to get rid of. -Proteins and nucleic acids contain nitrogen atoms, and nitrogenous waste can be toxic.

Generation of "single effect" in loop of Henle

-Cell walls of ascending thick segment actively transport NaCl from tubular fluid to adjacent interstitial fluid in medulla (active transport of NaCl out of ascending limb) -Consequences of this transport result from permeabilities of ascending limb and adjacent descending limb. Walls of ascending limb essentially impermeable to water, so active transport of NaCl out of ascending limb decreased NaCl concentration of fluid inside ascending limb and increases NaCl concentration in interstitial fluid. -Permeability of descending limb varies among spp, but fluid in descending limb approaches equilibrium with interstitial fluid with respect to pressure and ion concentrations.

Countercurrent multiplication

-Countercurrent exchange systems are passive and merely preserve gradients (ex heat exchangers in mammal limbs). -Countercurrent multiplier systems use metabolic energy within the system itself to induce flux into or out of the fluid streams, plus countercurrent exchange to maximize end to end gradient. -Use energy plus countercurrent exchange. E.g., loops of Henle, which use energy to transport NaCl out of the ascending limb, generating the single effect (the concentration difference between the ascending and descending limbs) -plus countercurrent flow in descending and ascending limbs, accounting for the "multiplier effect" (the much higher top-to-bottom gradient)

Glucose transport (for cells not in the small intestine and kidneys)

-Does not involve active transport -Carrier proteins facilitate glucose diffusion

Marine bony fishes solutions

-Drink seawater and expend energy pumping ions across intestinal wall so water will enter blood from gut -Use energy to excrete excess ions. Max U/P is 1.0- too low to keep body fluids more dilute than seawater, so vigorous extra renal salt excretion. Specialized cells in gills use ATP to actively transport Cl- and Na+ out of blood directly into more concentrated sea water. -They expend 8-17% of daily energy budget on osmoregulation

Summary of non-urea solute concentration

-Fluid travels down descending limb. Concentration of solutes increases, peaking at bend. -Fluid travels up ascending limb, concentration of solutes decrease, exiting loop more. -Fluid travels down collecting duct, reaching final concentration before entering. -Solute concentration increases toward medulla, peaks at bend -Solute concentration decreases toward cortex -Final non-urea solute concentration in definitive urine exiting collecting duct depends on NaCl concentration of innermost medulla. This concentration depends, in turn, on size of single effect, rate of flow through loops of Henle, and lengths of loops.

Kidneys adjust U/P ratio to regulate blood plasma

-If urine is less concentrated than blood plasma (U/P ratio < 1), the kidneys are making the plasma become more concentrated. -If urine is more concentrated than blood plasma (U/P ratio >1, the kidneys are making the plasma become more dilute.

Loop of Henle length

-In mammals that achieve high concentrations, at least 15-20% of nephrons have long loops. In contrast, hippos and muskrats for example have only short loops and can't make highly concentrated urine. -Loops of Henle and kidney work together to increase osmotic pressure of tissue fluids deep in medulla. Do not themselves concentrate urine, but set stage by increasing osmotic pressure of tissue fluids around collecting ducts. -Flow of tubular fluid in opposite directions in descending and ascending limbs multiples effects of active ion transport. Countercurrent multiplier

Relative osmolarity of water breathing aquatic animals

-Isosmotic animals have body fluids with same osmotic pressure as water in which they live. (osmoconformers: includes most marine inverts) -Hyperosmotic animals have body fluids with higher osmotic pressure than water in which they live -Hyposmotic animals have body fluids with lower osmotic pressure than water in which they live.

Large vs. small mammals and heat stress

-Large body size is advantageous for conserving water because of surface to volume ratio (exogenous heat absorption, evaporative water loss for cooling) -Allometric relationship between body size and mass specific metabolic rate (respiratory water loss, endogenous heat production, evaporative water loss for cooling) -Large arid adapted mammals that are drinking water dependent cannot wander more than 25 km from standing water.

Loop length

-Mammal species that produce highly concentrated urine tend to have high kidneys with more long loops of Henle. -Longer loops tend to produce larger maximum end to end NaCl gradients, thus increasing inner medulla NaCl concentration. -Among related species of similar body sizes, species with relatively thick medullas and prominent renal papillae tend to be capable of producing more concentrated urine. -Thickness of medulla provides a measure of the lengths of longest loops of henle. The thicker the medulla, the higher the max urine concentration

Beyond kidneys: Extrarenal salt excretion

-Many birds and non-avian reptiles associated with oceans or deserts have salt glands in their heads that excrete a highly concentrated salt solution. -Some terrestrial lizards and birds have cranial salt glands that secrete Na+, K+, and Cl- with higher ion concentrations than urine. -Marine fish have salt excreting glands in their gills. But marine mammals manage with just their ordinary mammalian high performance kidneys

Nonmigratory aquatic animals may also encounter varying salinity

-Most marine interest are osmotic conformers, but a minority are osmotic regulators. Most osmoconformers can't survive at low salinity. Of marine inverts that can do well in low salinity, most are hyper osmotic regulators when in such situations. -Most osmoconformers do not survive in water much more dilute than salt water. But marine mussels are osmoconformers that can thrive at a wide range of salinities.

Sharks

-Most sharks and relatives have ion concentrations similar to those of marine bony fishes and much lower than seawater (hypoionic) -But osmotic pressure of blood is slightly higher than that of seawater (hyperosmotic). Body fluids have high concentrations of two organic solutes, urea and trimethylamine oxide (TMAO) -They gain water across gills by osmosis, while marine bony fish lose water across gills by osmosis. -Because blood is hyperosmotic to seawater, sharks experience slight osmotic influx of water. -Nearly all sharks and relatives synthesize urea as main nitrogenous product of protein catabolism, while nearly all bony fish use ammonia. -40% of blood osmotic pressure is attributable to urea and TMAO. In most aquatic animals, blood osmotic pressure mostly due to inorganic ions dissolved in plasma, so if animals tends to gain water by osmosis, tends to lose ions by diffusion and vice versa. -Sharks tend to gain water by osmosis and ions by diffusion

Nephron

-Open at one end, closed on the other -Urine formation starts at closed end, which consists of the cup-shaped Bowman's capsule enclosing a dense cluster of blood vessels known as glomerulus

Human kidney U/P ratios

-Osmotic U/P can range from 0.1 (very dilute) to 4.0 (very concentrated) -Drink a lot, blood plasma too dilute, so kidneys make dilute urine (pulling more water than solutes from blood) -Sweat a lot/don't drink enough, blood plasma too concentrated, so kidneys make more concentrated urine (pulling more solute than water from blood) -Urine volume is also adjusted

Vasa recta maintains osmotic gradient

-Osmotic pressure gradient in medulla is created bloop of Henle countercurrent multiplier. Countercurrent arrangement of renal blood flow through vasa recta (flowing in, then back out the same way) maintains gradient. -If blood vessels flowed unidirectionally from cortex through medulla and out of kidney, blood traveling deeper into medulla would encounter even more concentration interstitial fluids. Blood would lose water osmotically and take up NaCl and urea by diffusion. It would then exit the kidney, leaving the water behind and taking solutes away, thereby diluting medullar fluids.

Evolution of digestive abilities

-Plant-eating insect host shift - Lactase production in human babies, but usually not in adults. Lactase breaks lactose molecules into monosaccharides galactose and glucose. Several cattle raising African tribes, as well as northern Europeans, have independently evolved the ability to digest lactose as adults.

What happens in the nephron

-Primary urine is isosmotic with blood plasma -During passage through nephron, half of water an ions are typically reabsorbed into blood plasma. -Equivalent of all the plasma water in body enters nephrons every 30 minutes -Human kidneys each day process ~180 liters of filtrate to 1.5 liters of urine. Opportunity to remove wastes or toxins quickly and make rapid adjustments to plasma volume and composition

How can mammal kidneys make such concentrated urine?

-Proximal convoluted tubules function like those of other vertebrates, so what do they do to volume and osmotic pressure of fluid within? They reduce volume of urine without changing osmotic pressure. -Distal convoluted tubules similar to those of other vertebrates in concentrating urine more or less depending on ADH levels. -However, in a mammal kidney, deeper portions of collecting ducts are surrounded by tissue fluid that is far more concentrated than blood plasma.

Proximal tubule of nephron

-Proximal tubule has nephron wall loaded with aquaporins, so highly permeable to water. -Na+ and Cl- (also glucose and amino acids) are retuned to blood by active transport and water follows by osmosis. Result is that as fluid moves through proximal tubule, volume is greatly reduces, but osmotic pressure is unchanged and still matches that of blood plasma -The water permeability of the tubular wall (epithelium) is always high. Water osmoses out of tubular fluid so it stays isosmotic with plasma as NaCl is pumped out. Output it isosmotic with plasma but greatly reduced value compared to input.

Insulin and glucagon

-Regulate storage and release of nutrients in the body. -Both hormones are released by endocrine portion of pancreas, known as "islets of Langerhans." Pancreas has exocrine portion as well, secreting digestive juices and bicarbonate into the midgut via pancreatic ducts, as discussed earlier. -As blood glucose rises, secreted insulin causes cells to take up glucose, stabilizing blood glucose concentration and stimulating glucose storage when it is abundant. Liver and muscle cells store glucose as glycogen. -Insulin also stimulates storage of fatty acids as lipids in fat cells and use of amino acids in protein synthesis -Between meals, pancreas produces glucagon instead of insulin, with reverse effects. Breakdown of glycogen into glucose and release into blood; breakdown of stored lipids and release of fatty acids into blood.

Glucose transport in the small intestine an kidneys

-Secondary active transport of glucose (a polar molecule) from lumen of small intestine into intestine cells. Na+-K+ pumps keeps Na+ concentration higher outside cells. This concentration gradient allows glucose plus Na+ to move reliably into intestine cells by facilitated diffusion with cotransporter (symporter) protein (Na+- glucose symporter). Glucose would normally enter cells by diffusion anyhow-but more slowly. -Glucose moves from intestinal cells into blood by facilitates diffusion (glucose uniporter protein)

Marine bony fishes problems

-Strongly hyposmotic, with body fluid osmolarity of ~300-500 mOsm They lose water to environment by osmosis, dehydrating them. For these hyposmotic fish, living in the ocean is like living in the desert. -Gain ions (such as Na+, Cl-) by diffusion from seawater, making body fluids too concentrated.

Loop of Henle

-The portion of a mammalian nephron connecting the proximal and distal convoluted tubules. -Main function is to create a concentration gradient in the medulla (innermost portion) of kidney, increasing the osmotic pressure around collecting ducts. -Nephrons in mammalian kidney oriented so all loops of Henle are parallel. Bowman's capsules and convoluted tubules in renal cortex, Loops of Henle and collecting ducts in renal medulla.

Mammal kidney collecting ducts

-Tubular fluid passes through a collecting duct just prior to exiting kidney -At start of collecting duct, osmotic pressure of surrounding tissue fluid is like that of blood plasma -Moving through the collecting duct, however, surrounding tissue fluid has increasingly high osmotic pressure -At distal end, the surrounding fluid has osmotic pressure much greater than that of blood plasma. -Na+ and Cl- cannot easily diffuse across wall of collecting duct (although they can cross via ion pumping when pumps are active), but depending on conditions, permeability to water can be high

Dehydration: a major challenge for terrestrial animals

-Typical terrestrial vertebrates have blood osmotic pressure ~300-350 mOsm -Some terrestrial animals have outer body covering highly permeable to water, so must stay moist -Many others have outer lipid layer that minimizes evaporation -Some animals can even live in deserts

How vertebrate kidneys work: Big picture

-Vertebrate kidney tubule= nephron. ~1 million nephrons in a human kidney -Fluid from blood plasma enters nephron at one end (=primary urine) -Volume and composition of fluid are modified as it passes through kidney and final product (=definitive urine) is passed out of the body. Along the way, materials can be both reabsorbed and secreted into the urine -All about surface area

Vasa recta in mammal kidney

-Vessels of vasa recta carry blood from cortex into medulla, then back out to cortex. -Blood entering medulla from cortex passively picks up solutes and loses water -Blood returning to cortex from medulla passively loses solutes and gains water -Blood vessels exit kidney at junction between cortex and medulla, where interstitial fluid is isosmotic to blood.

Mammal kidney with ADH

-When ADH level is high, collecting duct walls are highly permeable to water, so water moves by osmosis to concentrated tissue fluids around tubule, and then blood takes up this water. -Solution in tubular fluid is thus concentrated, reaching osmotic equilibrium with the most concentrated tissue fluids just before leaving collecting duct -This process yields a low volume of highly concentrated urine-osmotic pressure far higher than that of blood plasma -When ADH level is low, collecting duct walls have low permeability to water, so little water is lost through osmosis to surrounding tissue fluid as tubular fluid moves through collecting ducts. In addition, Na+ and Cl- are actively transported out of tubular fluid as it moves through collecting duct. This process yields a high volume of dilute urine.

ADH and aquaporins

-When ADH level is high, walls of distal convoluted tubule have high aquaporin density and are highly permeable to water. Functions like proximal tubule (ions pumped back into blood and water follows, yielding reduced volume of urine that is isosmotic with blood plasma) -When ADH level is low, walls of distal convoluted tubule have low aquaporin density and thus low permeability to water. Na+ and Cl- still pumped back into blood, but water can't follow so urine is dilute and volume is high

Human blood

0.3 Osm/L

Sea water

1 M total dissolved stuff (1 Osm/L)

Sea urchin body fluid

1 Osm/L

Summary of active transport of ions into plant cells

1. A proton pump generates differences in H+ concentration and electric charge across the membrane. 2. The difference in electric charge causes cations such as K+ to enter the cell. 3. A transport protein couples the diffusion of H+ to the transport (against an electrochemical gradient) of anions such as Cl- into the cell. It is secondary active transport because energy from ATP is used for transport indirectly: primary active transport sets up electrochemical gradient which then drives transport of molecules of interest.

Basic steps for nutrient assimilation in animals

1. Eat (macroscopic) 2. Digest (break down into small molecules + waste) 3. Absorb/import small molecules 4. Excrete whats left.

Osmoregulation and excretion topics

1. Osmosis and fluids homeostasis 2. Excretion of nitrogenous wastes

How is proton concentration in soil around the root increased to help with ion exchange

1. Proteins in root cell membranes actively pump protons out of the cells. 2. Cellular respiration in root released CO2, some of which dissolves in soil water, forms carbonic acid, and dissociated (ionizes) to form bicarbonate and free protons. A clay particle, which is negatively charged, binds mineral cations. Protons are pumped from the roots or freed by the ionization of carbonic acid. The protons bind to the clay particles, which releases the cations into the soil solution.

Functions of the vertebrate stomach

1. Stores food before processing 2. Secretes hydrochloric acid, which helps break down food. In humans or dogs digesting a meal, stomach contents can reach pH of 0.8, like battery acid. 3. Begins protein digesting by secreting pepsin 4. Mechanically squeezes food, mixes it with acid and digestive systems

Symbiosis with gut microbes in ruminant mammals

1. The content of the rumen are periodically regurgitated into the mouth for rechewing (rumen is in the stomach) 2. The rumen and reticulum serve as fermentation vats for the mixed microbial community. The microbes ferment cellulose, forming short chain fatty acids that diffuse into the blood. 3. The mixture of fermentation and micro organisms passes through the omasum where it is concentrated by removal of water. 4. The abomasum functions similarly to our stomach. It secreted hydrochloric acid and protein digesting enzymes. The microbes are killed and partly digested here, then passed on to the small intestine where digestion is completed and absorption occurs.

Nitrogen fixation (reduction of nitrogen gas)

1. The enzyme nitrogenase binds a molecule of nitrogen gas. 2. A reducing agent (e.g., ferrodoxin) transfers three successive pairs of hydrogen atoms to N2. 3.The final products- two molecules of ammonia- are released, freeing the nitrognase to bind another N2 molecule. This reaction requires a large input of energy.

Essential elements

6 macronutrients and 8 micronutrients. 6 macronutrients are nitrogen, phosphorus, potassium, sulfur, calcium, and magnesium.

Carnivorous plants

>500 species of plants that get at least some of their nutrients (but not energy) by digesting insects and arthropods. They often live in boggy soils where little nitrogen or phosphorus are available- light and water are not limiting. Most famous is the venus flytrap, with folding leaves that entrap prey, which is then digested by enzymes. Evolved independently.

Secondary active transport

A form of active transport that does not directly use ATP as an energy source. Instead, transport is coupled to ion diffusion down a concentration gradient that was established by primary active transport.

Proton pumps and ion channels

Active transport needed to move mineral ions across cell membrane against electrochemical gradient. Concentrations of many mineral ions are lower in soil solution than within plant cells. May need to move negatively charged ions into a negatively charged cellular component

Guttation

Active transport of ions into xylem continues at night, xylem sap swells with water. when soil is wet and humidity of air is high, root pressure can result in guttation. In short plants with low evaporation rates, water is literally pushed out of the leaves. Guttation is often mistaken for morning dew.

Osmoregulators

Actively maintain osmolarity of body fluids within narrow range.

Water movement in plants

Always moves from roots to leaves, moves through xylem

Parasites

Another way plants get nutrients. ~1% of flowering plant species get some or all of their nutrients and sometimes energy from other plants. Parasitic lifestyle evolved independently

Studying phloem using aphids

Aphids are insects that feed on plants by drilling into a sieve tube element with a specialized organ, the stylet. Pressure potential in a sieve tube is higher than outside, so phloem sap is forced though the stylet and into the aphid's digestive tract. A feeding aphid can be frozen and separated from its stylet, leaving phloem sap flowing from the stylet for hours. Overall, movement in phloem is bidirectional, but individual sieve tubes move fluid in just one direction. In contrast to xylem, movement of fluid in phloem required living cells. Phloem solute is 90% sucrose, and flow rate can exceed 100 cm per hour.

Solutions to the challenge of water mineral ions crossing a root cell cell membrane and entering cells

Aquaporin proteins (water channels) increase membrane permeability to water, so rate of osmosis can be regulated (though direction is always toward region of more negative water potential) Ion channels and protein pumps

Relative medullar thickness

Arid species tend to have thicker medullas compared to mesic and aquatic animals.

How and why do such huge animals feed on such tiny prey?

Because of the second law of thermodynamics, which is a transformation does not change the total amount of energy within a closed system, but after any transformation the amount of energy available to do work is always less than the original amount of energy. Big animals, like whales, feed on such small prey because the small prey have the most energy value. For example, algal cells like phytoplankton grow and reproduce sufficiently to produce 10,000 energy units of new biomass per month, and small crustaceans can produce 1000. Whales eat these because they have much more energy to give compared to fish, which only produce from 1-100 energy units.

What do kidneys make urine from?

Blood plasma. Tubular structures that discharge fluid directly or indirectly to outside environment. -single tube in crayfish or lobster -many microscopic tubules (nephrons) in vertebrate kidney. ~1 million nephrons in a human kidney. Nephrons ultimately discharge into a single tube, the ureter, that carries fluid out of the kidney (in mammals, via the bladder and urethra) Primary function of vertebrate kidney is to regulate composition and volume of blood plasma. Selectively removes water and ions from blood plasma

Osmoconformers

Body fluids isotonic with surrounding water

Xylem overview

Bulk flow of water from roots to leaves mediated by continuous water potential gradient. Tension (pulling from above) on xylem accounts for most of flow. Osmotic contribution (pushing from below) is limited to roots, contributes little to flow in tall plants.

Sugar movement in plants

Can move up or down, made in leaves and stored in roots, moves through phloem.

How to plants solve problems related to accessing mineral nutrients in soil?

Cations bound to soil particles: Clay particles are often covered by negatively charged chemical groups, which bind the cations important for plant nutrition. These cations are thus retained in soil, but unavailable to plants. So, plants do ion exchange to make cations available to them. Protons bind more strongly to clay particles than do mineral cations, so they swap places, releasing mineral nutrients into soil solution.

Challenges of water and mineral ions crossing a root cell cell membrane and entering cells

Cell membrane is hydrophobic, but water and mineral ions are polar. Some mineral ions must move against their concentration gradient.

Apoplast

Cell walls (which lie outside the cell membranes) and intercellular spaces. Continuous meshwork through which water and solutes can flow without ever having to cross a membrane. One way in which water and ions from soil pass though roots to reach xylem.

Phloem

Cells, which are generally living, transport carbohydrates (mainly sugars) from sources like leaves, tubers, and seeds, to sites where they are used or stored (sinks, e.g., growing tissues, roots, developing flowers and fruits). It is the innermost layer of tree bark.

Xylem

Conducting cells, which are dead when mature, distribute water and mineral ions taken up by the roots to all the cells of the roots and shoots.

A horizon, Topsoil

Contains most of the soil's living and dead organic matter

Water potential

Describes the tendency of a solution to take up water from pure water across a membrane. Solute potential + Pressure potential. Water flows from higher to lower water potential. It is lowered by addition of solute (i.e, making solution more attractive to water), and increased by higher hydrostatic pressure (pressure potential is zero when it equals atmospheric pressure)

Transpiration-Cohesion-Tension model process

During transpiration, water vapor diffuses out of the leaf through pores called stomata. Water evaporates from mesophyll cell walls. Tension pulls water from the veins into the apoplast surrounding the mesophyll cells which in turn pulls water in the veins of the leaves upward and outward, which in turn pulls the water column in the xylem of the shoot and root upward. Cohesion between water molecules forms a continuous water column from the roots to the leaves. Water moves into the xylem by osmosis, and enters the root from the soil by osmosis.

Bulk feeding

Eat relatively large pieces of food (humans do this).

Suspension feeding

Example is that many aquatic animals sift small food particles from the water. Other examples are whale sharks, basking sharks, baleen whales, and bryozoans. Includes the use of gill rakers, which are skeletal elements covered with ordinary epidermic and not involved in gas exchange. In suspension-feeding species, specialized arrays of long, closely spaced gill rakers are employed hydrodynamical to concentrate particulates for swallowing. Uses crossflow filtration so that water flows parallel to the gill rakers and is bled off.

Symbiosis with chemosynthetic autotrophs (chemoautotrophs)

Example: Hydrothermal vent worms living in total darkness in the deep sea are symbiotic with chemoautotrophic bacteria. The hydrothermal vent worm Riftia pachyptila has no mouth, gut, or anus. Its food comes from sulfur-oxidizing chemoautotrophic bacteria, living in its trophosome, that require H2S. The worms must live near hydrothermal vents because the vents are their source of H2S. SO4- made in the trophosome is voided across the gills. Blood flowing through the gills picks up H2S and )2 from sea water, and carries them to the bacteria in the trophosome. The bacteria in the trophosome obtain energy for the synthesis of organic compounds by oxidizing the reduced sulfur in H2S to form compounds such as SO4-. Organic compounds made by the bacteria pass to the animal cells of the worm. Cold seawater containing So4 2- seeps into cracks. SO4 2- is reduced to S 2- by complex reactions under heat and pressure. Heated water containing H2S rises to be spewed out in plumes.

Symbiosis with photosynthetic autotrophs (photoautotrophs)

Example: Reef-building corals. Each coral is made up of many individual polyps. Populations of symbiotic algae live in the gastrodermis. Photosynthetic products from the algae pass directly to the animal cells in each polyp.

Volume

Example: goldfish gains (and must expel_ a third of its weight per day by osmosis.

Osmosis

Flow of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration. Osmotic potential (solute potential) is an important component of water potential. If solute cannot diffuse, water will move to equalize concentration.

Digestion overview

Food is complex. Different parts of digestive system specialize in different tasks. Animals lacking teeth often have crops and gizzards to grind food.

Mycorrhizae

Fungus, found in soil, helps plants get nutrients. Fungal partner gets organic compounds such as sugars and amino acids from plant. Up to 20% of photosynthate produced by terrestrial plants goes to arbuscular mycorrhizal fungi. Fungal partner has huge surface area to volume ratio and ability to penetrate fine structure of soil, dramatically increasing access to water and minerals, especially phosphorus. Mycorrhiza increases root surface area 10 fold to 1000 fold and fungal hyphae are much finer than root hairs. Mycorrhizae are essential for normal growth of many plants, and many plants without chlorophyll form mycorrhizae that may be shared with photosynthetic plants, indirectly sponging off of them (mycoheterotrophy)

Late distal convoluted tubule during antiduresis

High ADH, tubule wall permeable to water, as NaCl is reabsorbed, water is readily reabsorbed with it, meaning that only a small fraction of the water remains in the tubule- resulting in a small volume of relatively concentrated urine.

Hyperosmotic side

Higher solute concentration Lower free water concentration. Water flows to this side.

U/P ratio relationship

Higher the U/P ratio, the less watery the urine and the lower the osmotic pressure of the blood. Lower U/P ratio, the more watery the urine and the higher the osmotic pressure of the blood.

Vampire bat urine

Highly dilute when feeding, highly concentrated when roosting and digesting.

Urine/plasma (U/P) ratio

Imagine that an animal's blood plasma has an overall osmotic pressure of 100 and that its urine has an osmotic pressure of 25. What is the U/P ratio? U/P ratio = 0.25 (25/100) Kidney must be pulling out more water than solutes from plasma, so plasma is becoming more concentrated (i.e the kidney is increasing the osmotic pressure of the blood plasma)

Mineral cations vs. anions

Important anions such as nitrate (NO3-) and sulfate (SO4 2-) are not bound to clay particles as cations are. This means that they are more accessible to plants, but more easily leached from soil.

Ionic composition

In biological solutions, Na+, K+, Cl- especially prominent. Each ion diffuses in response to its own concentration gradient.

Digestive enzymes in vertebrates

In mammals, amylase in saliva begins to break down starches. Food travels to stomach, which has four major functions in most vertebrates.

Midgut and hindgut

In mammals, midgut has smaller diameter than hindgut. In mammals: Foregut= mouth, esophagus, stomach Midgut= small intestine Hindgut= large intestine Some herbivorous vertebrates are midgut or hindgut fermenters. Including some fishes, as well as horses, elephants, zebras, rabbits, guinea pigs, rhinos, apes, geese, chickens, ostriches, and others.

B horizon, Subsoil

Includes material from topsoil above and parent rock below

U/P ratio: phylogenetic diversity

Kidneys of most animals can produce urine more dilute than blood plasma (U/P <1). But kidneys of most animals cannot produce urine more concentrated than plasma (U/P >1). These kidneys cannot correct problem if blood plasma is becoming too concentrated (ex. are fish, amphibians, lizards, snakes, turtles, most aquatic invertebrates) But mammals, birds, and insects can produce concentrated urine with U/P >1

Phenotypic plasticity of digestion

Lab rat switched from low-protein to high-protein diet increases production of protein digesting enzyme within 24 hours. In a week, secretion rate of these enzymes may increase 5 fold. Switched from high protein to low protein diet, production of protein digesting enzymes will drop. Similar findings for carbohydrates and lipids Absorption efficiency also ramps up and down

Avian mammalian nephrons

Large glomerulus, long convoluted tubules, loop of henle

Cover crops

Leguminous plants are often planted as cover crops to help replenish soil. Soybeans, which are a legume, are often rotated with corn to cut fertilizer use and maximize overall profit.

What do plants need to live?

Light, carbon, hydrogen, oxygen (from air an water), mineral nutrients (from soil solution around roots)

What stimulates opening of stomata?

Light, low CO2 levels, and time of day (circadian rhythm)

Substrate feeding

Live in or on their source. example is a leaf mining caterpillar in oak leaf, internal parasites, and external parasites

Translocation (movement of phloem sap) requires metallic energy for what two steps?

Loading and unloading

Late distal convoluted tubule during diuresis

Low ADH, tubule wall poorly permeable to water, as NaCl is reabsorbed into the blood, relatively little water is reabsorbed with it, meaning that a large fraction of water remains in the tubule, resulting in voluminous, dilute urine.

Hypoosmotic side

Lower solute concentration Higher free water concentration. Net water flow is to the hyper side.

Human in hot desert

Maintains 37 degrees celsius by sweating profusely (up to 2 L/h). While an oryx in a hot desert varies body temperature to conserve water. Essentially stores heat rather than panting or sweating to get rid of it, then losing it nonevaporatively at night. Reducing temperature gradient during the day between oryx tissue and very hot environment.

What phloem solute do many of us eat as a sweet treat?

Maple syrup, demonstrates bidirectional movement of sugar in the phloem. Summer and fall: sugar made in leaves, stored in roots. Late winter: sap rises back to shoot to support leaf development (when trunks are tapped)

If stranded on a desert island, should you drink sea water?

Max Cl- concentration in urine produced by human kidney is lower than Cl- concentration in saltwater. So must use additional water to excrete Cl- taken in with sea water. Some other animals can excrete salts at higher concentrations than humans can, thus able to take in seawater and excrete the salts in less water than they ingested. Many marine bony fish excrete pure ions from gills.

Translocation

Method of moving carbohydrates. Phosphosynthatue in leaves (mainly sucrose) is actively transported into sieve tube elements in phloem and moved throughout the plant. Carbohydrates and other solutes are translocated via phloem from sources to sinks.

Symbiosis with gut microbes

Microbes in ruminant guts break down cellulose into usable molecules, produce essential vitamins and amino acids, and recycle waste nitrogen from host metabolism into microbial protein; digested by host into amino acids used to make host proteins. Ruminants chews cud ("ruminates") to expose more surface to microbes; added saliva keeps pH from dropping too low in rumen. Growing evidence of major importance of gut microbes ("gut micro biome") in nutrition and health of all animals, not just ruminants.

Plant vascular tissue

Most plants have vascular tissue, like xylem and phloem, through which materials are distributed throughout the plant.

Nitrogenous waste

Most water breathing aquatic animals excrete ammonia. Breakdown of proteins and nucleic acids yields ammonia groups (NH2), which are easily converted to ammonia (NH3) or ammonium (NH4+) with no energy investment. Ammonia is quite toxic, so concentration in body fluids must be kept very low. Most terrestrial animals excrete urea, uric acid, or compounds related to uric acid, but not ammonia. These compounds are far less toxic than ammonia, so they can be stored, but cost ATP to make.

How anions move into the cell

Movement of anions into the cell does not offset the charge difference. To make this favorable, reimport of a proton (which is favorable) is coupled to import of the anion, so that the net effect is no change in charge.

Movement of cations summary

Movements of cations (e.g., K+) against a concentration gradient is possible if it neutralizes the charge difference across the membrane. Cation import against a concentration gradient thus required maintenance of a potential (charge) difference across the root membrane.

Effect of tension on water pressure

Negative pressure (tension) has a negative effect on water potential by pulling water. Applying tension to the right arm makes it lower there, resulting in net movement of water to the right arm.

Sink

Net consumer of carbohydrates (e.g flower developing in leaf)

Source

Net producer of carbohydrates (e.g photosynthesizing leaves or storage organs digesting stored reserves)

Bulk downward flow from leaves by positive pressure

Osmotic swelling of sap at source of sugar loading pushes surrounding phloem sap away. Unloading of sugar at sink allows sap to lose water. Result is similar to water potential gradient in xylem, but driven all by osmosis. Direction of gradient reversible (just flip source and sink tissue)

Symplast

Passes through the continuous cytoplasm of the living cells connected by plasmodesmata. Selectively permeable membranes of root cells control access to symplast, so movement of water and solutes into symplast is tightly regulated. One way in which water and ions from soil pass through roots to reach xylem, cross cell membrane and pass through plasmodesmata.

Why doesn't pepsin digest the cells that synthesize it?

Pepsin is secreted in an inactive form, activated by exposure to HCl in stomach lumen. Low pH converts pepsinogens to pepsins. Newly formed pepsins activate other pepsinogen molecules.

Plant circulatory systems

Plants are not very active and they have no muscles or heart, so they have evolved other ways to moves essential materials like water, minerals, and sugar. Their circulatory system does not transport gases.

Where does the mass of a plant come from?

Plants fix carbon in the leaves, and spread it to the stems and roots. While plants make their own sugars, they cannot make minerals, such as calcium, iron, potassium, and fixed nitrogen. These must come up from the roots.

Problems that plants have to solve when accessing mineral nutrients in soil

Problem 1: Most of the cationic molecules (Ca2+, Mg2+, K+) are bound to negatively charged soil particles, so they are mostly not in solution. How to release those cations? Problem 2: The concentration of minerals needed inside the plant is higher in the soil solution. Simple diffusion won't work.

Concentration of urea

Process of concentrating urea is a bit different from process of concentrating non-urea solutes.

Cotransporters

Proteins that move one cation and one anion at the same time

Stomata

Regulates gas exchange and transpiration. Guards cell membranes that are rich in aquaporins. In the light, stomata actively pump protons out, thus facilitating the entry of K+ and Cl-. Higher internal K+ and Cl- concentrations give these guard cells a more negative water potential, causing them to take up water. The resulting increase in turgor pressure stretched the cells and opens the stoma. In the absence of light, K+ and Cl- diffuse passively out of the guard checks, and water follows by osmosis. The guard cells shrink and the stoma closes. High [K+] in guard cells: H2O flows in by osmosis. Guard cells turgid, open. Low [K+] in guard checks: H2O flows out by osmosis, guard cell flaccid, closed.

C horizon, Weathering, parent rock (bed rock)

Rock from which soil arises

Pancreas function

Secretes digestive enzymes that hydrolyze proteins, carbohydrates, and lipids; also bicarbonate ions (HCO3-), which neutralize acidic material from stomach.

Liver function

Secretes emulsifying agents (bile). Bile helps enzymes access lipids, which are not water soluble, by breaking them into tiny droplets.

Amphibian nephron

Similar to those of freshwater fish, non-avian reptiles, and most bird nephrons. Discharge into a single collecting duct. All the collecting ducts in a single kidney discharge into a single ureter.

Avian reptillian nephrons

Small glomerulus, short proximal and distal convoluted tubules, no loops of henle.

Example of primary active transport in animals

Sodium potassium pump. 1. Cell begins when there is a high Na+ concentration and low K+ concentration outside the cell, and a low Na+ concentration and high K+ concentration inside the cell. 3 Na+ and 1 ATP bind to the protein pump. 2. Hydrolysis of ATP phosphorylates the protein pump and changes its shape. 3. The shape change releases Na+ outside the cell and enables K+ to bind to the pump. 4. Release of Pi returns the pump to its original shape releasing K+ to the cell's interior and once again exposing Na+ binding sites. The cycle repeats. Primary active transport because hydrolysis of ATP directly provides energy for transport.

Solute effect on water potential

Solutes have a negative effect on water potential by binding water molecules. Adding solutes makes the water potential lower, resulting in movement to where the solute was put.

Foregut fermenters

Some herbivorous vertebrates are foregut fermenters, with special non-acidic portions of foregut harboring symbiotic bacteria. Including ruminants like cattle, bison, sheep, goats, deer, giraffes, etc. Other foregut fermenters are kangaroos, hippos, sloths, colobus monkeys, hoatzin, etc. Lysosomes conversantly evolved, which indicates independent evolution of foregut fermentation in species (cow and langur)

Nitrogen fixing root nodules

Some plants, especially legumes, can form symbiotic relationships with certain bacteria that live in nodules that form on the roots, capture atmospheric N2, and make this nitrogen available to plants. Maintaining these nitrogen fixing bacteria can cost as much as 20% of a plant's photosynthetic output. Nitrogen fixation uses nitrogenase to transform N2 into ammonia (NH3). N2 + 6H --> 2NH3

Stomata response

Stomata can open and close quickly (in minutes) not only in response to light level, but also CO2 concentration and water loss. Over longer term, plants can change number of stomata in response to environmental conditions. Shed leaves, make new leaves with more or fewer stomata.

Nitrogenase

Strongly inhibited by oxygen Plant roots are typically an aerobic environment. - O2 levels in nodules regulated by leg hemoglobin, a plant produces O2 carrier protein related to hemoglobin. O2 levels are kept low enough for nitrogenase to function, but high enough for aerobic respiration by bacteria (necessary to supply energy for fixation reaction)

Pressure flow model

Sucrose loading: at source, sucrose actively transported into phloem companion by cells, from which is flows through plasmodesmata into sieve tube elements. These cells then have a high sucrose concentration (more negative solute potential), so water enters sieve tube elements by osmosis from xylem. Water entering sieve tube increases turgor pressure at source end of sieve tube (positive pressure potential)m so sieve tube contents are pushed toward sink end. Sucrose unloading: At sink, sucrose is unloaded both passively and by active transport. Water moved back into xylem, maintaining gradient of solute potential and pressure potential.

Loop diuretics

Suppress ion reabsorption in ascending limb. Used to rapidly reduce fluid buildup in lungs

Ontogenetic shifts in nitrogenous waste excretion

Tadpoles excrete ammonia across their gill membranes, but after metamorphosis adult frogs and toads generally excrete urea.

Vertebrate hindgut

Temporarily stores indigestible waste Completes reabsorption of water and salts. In humans, ~7 liters of watery solution with Na+,Cl-, and other ions is secreted from blood to gut each day as part of food processing-must be recovered. Failure to reabsorb can be deadly, like in cholera or dysentery.

Brain cooling in some hoofed mammals

The arterial blood is cooled by countercurrent heat exchange prior to entering the brain.

Parts of the gut lumen

The gut lumen is lined by the gut epithelium, a single layer of epithelial cells. Together, the gut epithelium and underlying connective tissue are termed the mucosa. The submucosa contains a neural network, plus blood vessels and lymph vessels. The enteric nervous system is a complex of nerve nets made up of neurons that reside entirely within the gut.

Midgut digestion

The midgut is where most digestion and absorption occur. The pyloric sphincter muscle opens and allows material to enter from the stomach in a controlled way. Pancreas and liver are connected via ducts to upper midgut. Proteins broken down into amino acids. Carbohydrates broken down into simple monosaccharides (glucose, galactose, fructose) Lipids broken down into fatty acids and glycerol (glycerin) These simple molecules can be absorbed by the gut.

Osmotic pressure

Total concentration of solutes (dissolved matter); water moves by osmosis from regions where osmotic pressure is low to where it is high. From a few molecules to a lot of molecules.

Transpiration-Cohesion-Tension model

Transpiration: Evaporation of water from cells within the leaves. Not only key to moving water through xylem, but also cools leaves. Cohesion: Cohesion of water molecules in the xylem sap as a result of hydrogen bonding Tension: Tension on the xylem sap as a result of transpiration

Unloading

Transport of sucrose and other solutes from sieve tubes into sinks. Maintains gradient of solute potential and pressure potential. Delivers sugars for storage or for growth.

Loading

Transport of sucrose and other solutes from sources into companion cells and then into sieve tubes.

Vertebrate digestion

Tubular gut with accessory glands. Salivary glands, liver, and pancreas are all accessory glands Human small intestine: ~7 m long Human large intestine: ~1.5 m long

Peristalsis

Two layers of smooth muscle surround the submucosa Inner layer of circular muscle constricts gut when it contracts Outer layer of longitudinal muscle shortens it when it contracts Between muscle layers is a network of neurons that coordinate muscle contractions to move through the gut. Sphincter muscles at key locations (e.g., entrances to stomach and small intestine) also control movement of food.

How baleen whales filter feed

Two sets of baleen plates hang from the upper jaw, one set on each side of the mouth cavity. The inner (medial) edge of each individual plate is frayed into fibers. The fibers of adjacent plates intermingle to form a tangled fibrous mat. Water enters the mouth, flows through an array of baleen plates on each side of the mouth cavity from the inside, and exits laterally. A thick fibrous mat on the inside face of each array of baleen plates forms a sieve. Small food items accumulate on the inside face of each mat because of sieving. To be swallowed, the food items are freed from the fibrous mats by backlashing, tongue licking, and vibrational movements that shake them free.

Nitrogen and symbiosis

Unlike other soil nutrients, nitrogen in soil is not from weathering of rocks. Instead, it comes from bacterial decomposition of dead organisms, and fixation of atmospheric nitrogen. Earth's atmosphere is 78% nitrogen, but plants cannot absorb it directly.

How does water not move through the xylem?

Upward pressure? NO, experiment that cut tree at base, cut off part placed in vat poison to kill living cells, poison continued rising up the trunk even though cells were killed, though once leaves were killed movement up trunk stopped. So neither living pump nor roots are needed to push xylem sap up tree, but living leaves are needed. Capillary action? NO, water molecules have strong cohesion, so a column of water can indeed rise a short distance in a narrow tube by capillary action, but calculations have shown that capillary action in a xylem vessel would raise a water column only a very small amount.

What do most mammals and amphibians excrete waste nitrogen as?

Urea. It is very soluble in water and relatively low in toxicity. Insects, spiders, and mainly reptiles (including birds) excrete waste nitrogen mainly as uric acid or related compounds. Uric acid has low solubility in water, so often excreted in solid or semi-solid forms. Bird feces is half feces from gut (the dark stuff) and half concentrated uric acid (the white stuff)

What if U/P ratio = 2.0? Is urine more or less watery than blood plasma?

Urine is less watery than blood plasma, so kidney is removing more solute than water from blood plasma, making blood plasma more dilute (the kidney is decreasing the osmotic pressure of the blood plasma)

How proton pumps work

Uses energy from ATP to move protons out of the cell against a concentration gradient (primary active transport), resulting in an electrical gradient such that the region just outside the cell is more positively charged than the inside of the cell, and a proton concentration gradient, with more protons just outside the cell than inside. The proton pump is an ATPase, so it uses energy from ATP to pump the protons out: chemical potential energy in ATP is converted into an electrochemical gradient that can drive other, non-favorable processes. Export of protons create both a proton gradient and a charge difference between inside and outside.

How do plants get help from soil organisms

Vast numbers of soil organisms (largely microscopic bacteria and fungi) break down organic material in soil, freeing up nutrients- and some have very important mutualistic relationships with plants, notably mycorrhizae, and nitrogen-fixing bacteria.

Glomerular filtration rate (GFR)

Volume of blood passing through glomeruli each minute. Measured indirectly with blood tests, like through creatinine levels. Important measure of kidney function.

From apoplast or symplast to xylem

Water and minerals in apoplast can travel only as far as the endodermis, the innermost layer of root cortex, before entering symplast. At the Caspian strip, water and solutes in apoplast must enter the symplast to cross the endodermic. Inside the stele, solutes are actively transported into the apoplast and water follows passively, forming the xylem sap. Minerals are actively transported into xylem, making water potential in the xylem more negative and water follows passively into the xylem by osmosis.

Soil solution

Water in spaces between soil particles, with dissolved minerals in it.

Regulation of water loss

Waxy cuticle on leaves and stems impermeable to water. Stomata in leaves can open and close to allow water, O2, and CO2 to move in and out of leaves. Some leaves have as many as 1,000 stomata per square millimeter.

Secondary active transport in proton pumps

With inside of the cell more negative now than outside, essential cations such as potassium (K+) move down the electrical gradient into cell through specific membrane channels. Essential anions such as chloride (Cl-) are moved against electrochemical gradient by a membrane "cotransporter" transport protein that couples their movement with that of H+.

Can sources and sinks change roles?

Yes

Are animal digestive systems diverse?

Yes. But, nearly all animal phyla are characterized by a tubular through gut. Most molecules ingested cannot pass through gut epithelium. Food must be broken down with the help of enzymes to yield smaller molecules that can cross gut epithelium and enter blood capillaries. Three enzymes hydrolyze the initial protein at the three places shown, producing four smaller molecules. In practice, the nutritional value of different foods depends on the specific digestive systems of the animals consuming them. Example, humans can't digest cellulose, but some insects produce cellulose-digesting enzymes, or like ruminant mammals, harbor symbiotic bacteria in their guts that do this work for them.

Salmon and osmoregulation

Young salmon in freshwater take up water by osmosis, loses salts to surroundings by diffusion. Tends to make blood more dilute. Once it migrates to the ocean, gains salts by diffusion from surroundings and loses water by osmosis to surroundings. Tends to make blood more concentrated.