BioAP Chapter 32 (Packet) Homeostasis and Endocrine Signaling

Osmoregulation

The general term for processes by which animals control solute concentrations in the interstitial fluid and balance water gain and loss; required by homeostasis.

Homeostasis

"Steady state" → maintenance of internal balance. For example, steady body temperature of river otter and stable concentration of solutes of freshwater bass.

Epinephrine (Adrenaline)

("fight-or-flight") A hormone secreted by the adrenal glands which lie atop the kidneys. When you are in a stressful situation (running to catch a bus), the release of epinephrine rapidly triggers responses that help you (chase the departing bus): raising blood glucose levels, increasing blood flow to muscles, and decreasing blood flow to the digestive system.

Your knowledge of biology from previous chapters should make understanding how ADH works easy to understand. Describe the four steps of ADH action.

(1) Drop in ADH secretion to a very low level (2) Decreases in number of aquaporin channels (3) Permeability of collecting ducts drops (4) Water reabsorption is reduced

The basic process of excretion usually requires four steps. Explain the four processes in Figure 32.17.

(1) Filtration (2) Reabsorption (3) Secretion (4) Excretion

The process of converting blood filtrate to urine requires five steps as shown in Figure 32.20. Explain the key processes that occur in each step.

(1) Proximal tubule - reabsorption which is critical for the recapture of ions, water, and valuable nutrients (pH reg) (2) Descending limb of the loop of Henle - numerous water channels formed by aquaporin proteins make the transport epithelium freely permeable to water (3) Ascending limb of the loop of Henle - Epithelial membrane that faces filtrate is impermeable to water (4) Distal tubule - key role in regulating the K+ and NaCl concentrations of body fluids (pH reg) (5) Collecting duct - carries filtrate through the medulla to the renal pelvis

Response

A physiological activity that helps return the variable to the set point, triggered when a control center generates output.

Neuroendocrine Pathway

(1) Stimulus of sensory neurons causes a receptor to transmit a neural signal to neurons in the CNS/generates nerve impulses that reach the hypothalamus (2) Cell in the CNS releases a hormone such as oxytocin (3) Hormone acts on a effector cell (4) Effector cell generates a response from the glands

Osmoconformer

(One of two ways an animal can maintain water balance) To be isoosmotic with its surroundings; all are marine animals.

Osmoregulator

(One of two ways an animal can maintain water balance) To control internal osmolarity independent of the environment; enables animals to live in environments that are inhabitable for osmoconformers, such as fresh water and terrestrial habitats.

Testes (in males) Hormones

- Androgens*- support sperm formation; promote development and maintenance of male secondary sex characteristics

Ovaries (in females) Hormones

- Estrogens*- stimulate uterine lining growth; promote development and maintenance of female secondary sex characteristics - Progestins*- promote uterine lining growth

Hypothalamus Hormones

- Hormones released from posterior pituitary - Releasing and inhibiting hormones- regulate anterior pituitary

Pancreas Hormones

- Insulin- lowers blood glucose level - Glucagon- raises blood glucose level

What are some forms of connective tissue in vertebrates?

- Loose connective tissue- holds skin and other organs in place - Fibrous connective tissue- found in tendons and ligaments - Adipose tissue- stores fat - Blood- consists of cells and cell fragments suspended in plasma (a liquid) - Cartilage- provides flexible support in the spine and elsewhere - Bone- a hard mineral of calcium, magnesium, and phosphate ions in a matrix of collagen

Pineal Gland Hormone

- Melatonin- participates in regulation of biological rhythms

Parathyroid Glands Hormones

- Parathyroid hormone (PTH)- raises blood calcium level

What three major regions of the nephron does filtrate pass through during processing?

- Proximal tubule - Loop of Henle - Distal tubule

Thyroid Gland Hormones

- Thyroid hormone (T3 and T4)- stimulates and maintains metabolic processes - Calcitonin- lowers blood calcium level

Hypothalamus

A brain region which consists of a group of nerve cells functioning as a thermostat, responding to body temperatures outside a normal range by activating mechanisms that promote heat loss or gain.

Urinary Bladder

A common sac through which the two ureters drain.

Negative Feedback

A control mechanism that reduces, or "damps," the stimulus and is largely relied upon by homeostasis.

Bowman's Capsule

A cup-shaped swelling formed by the blind end of the tubule, and surrounds the glomerulus.

Pancreas

A gland located behind the stomach. Target cells here respond by releasing bicarbonate into ducts leading to the duodenum which raises the pH in the duodenum, neutralizing the stomach acid.

What is the role of the hypothalamus in temperature regulation?

A group of nerve cells within the hypothalamus functions as a thermostat, responding to body temperatures outside a normal range by activating mechanisms that promote heat loss or gain.

Loop of Henle

A hair-pin turn with a descending limb and an ascending limb.

Oxytocin

A hormone that regulates milk release during nursing in mammals as part of the neuroendocrine pathway. Stored and released in the posterior pituitary.

Urea → Describe the characteristics of this nitrogenous waste molecule and the animal groups that excrete them

A nitrogenous waste. In vertebrates, is the product of a metabolic cycle that combines ammonia with carbon dioxide in the liver. Its main advantage for nitrogenous waste excretion is its very low toxicity. - Urea → Mammals, most amphibians, sharks, some bony fishes

The example in the text is related to temperature regulation. Would ectotherms be regulators or conformers?

A nonliving example of temperature regulation: control of room temperature Ectotherms → conformers Endotherms → regulators

Renal Cortex & Renal Medulla

A part of each kidney which is supplied with blood by a renal artery and drained by a renal vein. Tightly packed excretory tubules and associated blood vessels lie within this.

Set Point

A particular value → maintaining at or near this allows an animal to achieve homeostasis

Angiotensin II

A peptide that is made when renin initiates a sequence of chemical reactions.

Acclimatization

A physiological adjustment to environmental changes--contributes to thermoregulation in many animal species. Example: - Response to seasonal temperature changes in birds and mammals often includes adjusting insulation--growing a thicker coat of fur in the winter and shedding it in the summer.

Antidiuretic Hormone (ADH or Vasopressin)

A posterior pituitary hormone which opposes a state of high level urine production (diuresis), the reason for its name.

Glomerulus

A single long tubule and a ball of capillaries in each nephron.

Juxtaglomerular Apparatus (JGA)

A specialized tissue consisting of cells of and around the afferent arteriole, which supplies blood to the glomerulus.

Countercurrent Multiplier System

A system which expends energy to create a concentration gradient.

Urethra

A tube through which urine exits during urination. Empties to the outside near the vagina in females and through the penis in males.

Vasodilation

A widening of superficial blood vessels (those near the body surface) due to nerve signals that relax the muscles of the vessel walls. This results in increased blood flow to the skin; in endotherms--warms skin and increases transfer of body heat to environment by radiation, conduction, and convection; sweating or panting. In short- increase in vessel diameter

Why do species vary tremendously in makeup, complexity, organization, and appearance?

Adaptation: Natural selection favors those variations in a population that increase relative fitness. Frequently results in a close match of form to function.

What endocrine gland secretes epinephrine?

Adrenal gland

Adrenal Gland Hormones

Adrenal medulla - Epinephrine & norepinephrine- raise blood glucose level; increase metabolic activities; constrict certain blood vessels Adrenal cortex - Glucocorticoids- raise blood glucose level - Mineralocorticoids- promote reabsorption of NA+ and excretion of K+ in kidneys

Osmosis

Allows water to enter and leave cells, occurs whenever two solutions separated by a membrane differ in osmolarity. The diffusion of water across a selectively permeable membrane.

Why do animals that excrete nitrogenous wastes as ammonia need access to lots of water?

Ammonia can be tolerated only at very low concentrations

Animals excrete nitrogenous wastes as __________, __________ or __________.

Ammonia, urea, or uric acid.

Throughout the text, a common theme has been regulation of homeostasis by feedback loops. We discuss feedback loops again as we look at hormone levels. What is meant by a set point?

An animal achieves homeostasis by maintaining a variable, such as body temperature, at or near a particular value, or set point.

Conformer

An animal is this for a particular variable if it allows its internal condition to change in accordance with external changes. (Bass → conforms to temperature of the lake it inhabits--as the water warms or cools, so does the bass's body)

Regulator

An animal is this for an environmental variable if it uses internal mechanisms to control internal change in the face of external fluctuation. (Otter → keeps its body at a temperature largely independent of that of the water in which it swims)

Fever

An elevated body temperature. Many experiments have shown this to reflect an increase in biological thermostat's set point.

Posterior Pituitary

An extension of the hypothalamus which stores and releases two hormones, oxytocin and antidiuretic hormone (ADH), synthesized by neurosecretory cells of the hypothalamus.

Afferent Arteriole

An offshoot of the renal artery that branches and forms the capillaries of the glomerulus; supplies blood to each nephron.

Explain the difference between animals that are regulators and those that are conformers.

Animals that are regulators use internal mechanisms to control internal change in the face of external fluctuation--they are indep. Animals that are conformers match their internal conditions to change in accordance with external changes. Note that an animal may regulate some internal conditions while allowing others to conform to the environment.

Skeletal (Striated) Muscle

Attached to bones by tendons and is responsible for voluntary movements. The arrangement of contractile units along the cells gives them a striped (striated) appearance.

Anatomy

Biological form

Physiology

Biological function

Renal Pelvis

Collects urine from the excretory tubules and passes it to the urinary bladder.

Connective Tissue

Consists of cells scattered through an extracellular matrix, often consisting of a web of fibers embedded in a liquid, jellylike, or solid foundation. Within the matrix are numerous cells called fibroblasts and microphages.

Sensor (Receptor)

Detects the stimulus, fluctuations in the variable either above or below the set point.

Ureter

Ducts through which urine produced by each kidney exits.

Does endothermy or ectothermy require less energy?

Ectothermy b/c gain heat from the environment

The two major communication systems differ in signal type, transmission, speed, and duration. What different functions are each especially adapted to as a result?

Endocrine System → coordinating gradual changes that affect the entire body (such as growth, development, reproduction, metabolic processes, and digestion) Nervous System → directing immediate and rapid responses to the environment (especially in controlling fast locomotion and behavior)

Endocrine Pathway

Endocrine cells respond directly to an internal or environmental stimulus by secreting a particular hormone. The hormone travels in the bloodstream to target cells, where it interacts with its specific receptors. Signal transduction within target cells brings about a response.

Explain the difference between an endocrine gland and an exocrine gland. Give an example of each.

Endocrine glands secrete hormones (or chemical "messengers") that travel through the blood to regulate the activity of a target organ. Ex: Hypophysis (pituitary) and the adrenals Exocrine glands have ducts (tubes) to send their secretions to their target externally. Ex: Sebaceous glands and the salivary glands

The body has two long-distance regulating systems. Which involves chemical signals by hormones?

Endocrine system

Describe the difference between endothermy and ectothermy, and give an animal that exhibits each.

Endothermy is gaining heat through metabolism (humans) and ectothermy is gaining heat through external sources (turtles).

Microphages

Engulf foreign particles and cell debris; present within an extracellular matrix.

What four main types are animal tissues commonly grouped into?

Epithelial, connective, muscle, and nervous

What is the key function of juxtamedullary nephrons?

Essential for production of urine that is hyperosmotic to body fluids.

Stimulus (Sensor)

Fluctuations in the variable above or below the set point which are detected by a receptor (sensor).

Peritubular Capillaries

Formed by branches of the efferent arteriole; surrounds the proximal and distal tubules.

Efferent Arteriole

Formed when the capillaries converge as they leave the glomerulus.

Organs

Functional units in which different types of tissues are organized.

Nervous Tissue

Functions in the receipt, processing, and transmission of information. Contains glial cells (glia). In many animals, a concentration of this forms a brain, an information-processing center.

Tissues

Groups of cells with a similar appearance and a common function.

Organ System

Groups of organs that work together to provide another level of organization and coordination.

Vasa Recta

Hairpin-shaped capillaries that serve the renal medulla and surround the loop of Henle.

What facilitates specialization for animals/multicellular organisms?

Having many cells

Aldosterone

Hormone from the adrenal glands stimulated by angiotensin II.

One hormone can have several different effects. For example, epinephrine can cause the release of glucose from liver cells, dilate blood vessels to skeletal muscles, and constrict intestinal blood vessels. All these effects prepare the body for "fight or flight." Explain how these multiple effects are possible.

Hormones set off varying chain of reactions as they interact with different parts of the body. This is possible because different parts of the body have different target cells, receptors, or signal transduction pathways that only they express.

Glial Cells (Glia)

In nervous tissue. Support cells present in various types which help nourish, insulate, and replenish neurons in some cases modulate neuron function.

Kidney → (Figure 32.19) be able to label: renal medulla, renal cortex, and renal pelvis

In vertebrates and some other chordates, a specialized bean-shaped organ which functions in both osmoregulation and excretion. Transports and stores urine. Consists of numerous tubules arranged in a highly organized manner and closely associated with a network of capillaries.

Piloerection

Involuntary erection or bristling of hairs due to a sympathetic reflex typically triggered by cold, shock, or fright or due to a sympathomimetic agent.

Smooth Muscle

Lacks striations and has spindle-shaped cells. Is found in the walls of many internal organs. Responsible for involuntary activities, such as churning of the stomach and constriction of arteries.

Epithelium (plural, epithelia)

Lines the intestines, secretes digestive juices and absorbs nutrients. Polarized, meaning they have two different sides-- - the apical surface faces the lumen (cavity) or outside of the organ and is thus exposed to fluid or air - the basal surface is attached to a basal lamina, a dense mat of extracellular matrix that separates this from the underlying tissue

Pituitary Gland

Located at the base of the hypothalamus and receives signals from it. Has discrete anterior and posterior parts.

Immune and Lymphatic System

Main Functions: Body defense (fighting infections and cancer) Main Components: Bone marrow, lymph nodes, thymus, spleen, lymph vessels, white blood cells

Skeletal System

Main Functions: Body support, protection of internal organs, movement Main Components: Skeleton (bones, tendons ligaments, cartilage)

Excretory System

Main Functions: Disposal of metabolic wastes, regulation of osmotic balance of blood Main Components: Kidneys, ureters, urinary bladder, urethra

Circulatory System

Main Functions: Internal distribution of materials Main Components: Heart, blood vessels, blood

Muscular System

Main Functions: Locomotion and other movement Main Components: Skeletal muscles

Reproductive System

Main Functions: Reproduction Main Components: Ovaries or testes and associated organs

Digestive System

Main functions: Food processing (ingestion, digestion, absorption, elimination) Main Components: Mouth, pharynx, esophagus, stomach, intestines, liver, pancreas, anus

Figure 32.21 in the text shows the increasing osmolarity of the kidney, moving from cortex to outer medulla to inner medulla. Why does the kidney expend great energy to maintain this gradient?

NaCl needs to be actively transported into the interstitial fluid.

Tropic Hormones (Tropins)

Name given to anterior pituitary hormones in hormone cascade pathways because such pathways in a sense redirect signals from the hypothalamus to other endocrine glands.

Describe an example of a negative feedback loop. Clearly identify the set point, the stimulus, and the response.

Negative feedback is a control mechanism that reduces the stimulus. For example: when you exercise vigorously, you produce heat which increases your body temperature. Your nervous system detects this increase and triggers sweating. As you sweat, the evaporation of moisture from your skin cools your body, helping return your body temperature to its set point.

Cortical Nephrons

Nephrons which reach only a short distance into the medulla.

How does the nervous system differ from the endocrine system?

Nervous system conveys info by the PATHWAY the signal takes. For example, a person can distinguish different musical notes because each note's frequency activates different neurons connecting the ear to the brain.

What is the other major communication and control system? How does it work?

Nervous system-- Usually involves multiple signals. (Transmission is very fast) - Nerve impulses travel along axons, sometimes over long distances, as changes in voltage - Passing info from one neuron to another often involves very short-range chemical signals

Nephrons

The functional units of the vertebrate kidney which weave back and forth across the renal cortex and medulla.

Nervous System

Neurons transmit signals along dedicated routes connecting specific locations in the body. Main Functions: Coordination of body activities; detection of stimuli and formulation of responses to them Main Components: Brain, spinal cord, nerves, sensory organs

Ammonia (NH₃) → Describe the characteristics of this nitrogenous waste molecule and the animal groups that excrete them

Nitrogen is removed by enzymes in this form when proteins and nucleic acids are broken apart for energy or converted to carbs or fats. Very toxic partly b/c its ion interferes with oxidative phosphorylation. Many species expend energy to convert it to a less toxic compound, urea or uric acid, before excretion. - Ammonia → most aquatic animals including most bony fishes

Where are the receptors for the water-soluble proteins found? Explain this difference for the two types of hormones.

On cell surface → diff b/c can not diffuse across lipid bilayer.

Transport Epithelia

One or more layers of epithelial cells specialized for moving particular solutes in controlled amounts in specific directions. Typically arranged in complex tubular networks with extensive surface areas. Some face the outside environment directly, while others line channels connected to the outside by an opening on the body surface. Relied on in most animals by osmoregulation and metabolic waste disposal.

Why does a hormone elicit a response only with target cells?

Only (target) cells that have receptors for a particular hormone respond.

Ectothermic

Organisms that gain most of their heat from external sources (amphibians, many fishes, nonavian reptiles)

Endothermic

Organisms warmed mostly by heat generated by metabolism (mammals such as humans, birds)

Explain the difference between osmoconformers and osmoregulators.

Osmoconformers maintain water balance by being isoosmotic with their surroundings (marine animals) while osmoregulatrs do so by controling internal osmolarity independent of the environment.

Secretion

Other substances, such as toxins and excess ions, are extracted from body fluids and added to the contents of the excretory tubule.

We sometimes say that in negative feedback "more gets you less," and in positive feedback "more gets you more." Describe an example of a positive feedback loop.

Positive feedback reinforces a stimulus, leading to an even greater response (changes from the normal point and amplifies it). Help drive processes to completion. For example: - Blood clot formation (amplifies chemicals in the clot promote further clotting UNTIL it's sealed) - Milk released in response to oxytocin leads to more suckling and more stimulation as a result (as long as baby is nursing, milk is produced UNTIL baby is done) - Uterine contractions during childbirth (contraction UNTIL placenta out/no more stimulus) - Fever (virus/bacteria, body heats itself to counter fever UNTIL it's destroyed)

Pituitary Gland Hormones

Posterior pituitary - Oxytocin- stimulate contraction of uterus and mammary gland cells - Vasopressin (antidiuretic hormone, ADH)- promotes retention of water by kidneys; influences social behavior and bonding

Integumentary System

Protects against infection and helps regulate body temperature. Main Functions: Protection against mechanical injury, infection, dehydration; thermoregulation. Main Components: Skin and its derivatives (such as hair, claws, skin glands)

Aquaporin

Proteins that create water channels making the transport epithelium freely permeable to water.

What are the four processes by which heat is exchanged with the environment?

Radiation, evaporation, convection, and conduction

Proximal Tubule

Reabsorption here is critical for the recapture of ions, water, and valuable nutrients from the huge volume of initial filtrate.

Collecting Duct

Receives processed filtrate from many nephrons and transports it to the renal pelvis.

Vasoconstriction

Reduces blood flow and heat transfer by decreasing the diameter of superficial vessels; shivering or goosebumps.

Explain the role of antidiuretic hormone (ADH) in maintaining blood osmolarity.

Reduction in blood osmolarity below the set point causes a drop in ADH secretion to a very low level. The number of aquaporin channels decreases, lowering permeability of the collecting ducts. Water reabsorption is reduced, resulting in discharge of large volumes of dilute urine.

Renin-Angiotensin-Aldosterone System (RASS)

Second regulatory mechanism acting on the kidney.

Fibroblasts

Secretes fiber proteins; present within an extracellular matrix.

Epithelial Tissue

Sheets of closely packed cells covering the outside of the body and lining organs and cavities. Functions as a barrier against mechanical injury, pathogens, and fluid loss. It also forms active interfaces with the environment.

Portal Vessels

Short blood vessels into which the hypothalamic hormones secreted near capillaries at the base of the hypothalamus are drained. Connect directly to a second capillary bed in the anterior pituitary.

Signaling in the endocrine and nervous systems (Note: both use same pathway)

Signaling by hormones- (1) Stimulus → (2) Signal travels everywhere via the bloodstream → (3) Response: Limited to cells that have the receptor for the signal Signaling by neurons- (1) Stimulus → (2) Signal travels along axon to a specific location → (3) Response: Limited to cells that connect by specialized junctions to an axon that transmits an impulse

Endocrine System

Signaling molecules released into the bloodstream by endocrine cells are carried to all locations in the body. Main Functions: Coordination of body activities (such as digestion and metabolism) Main Components: Pituitary, thyroid, pancreas, adrenal, and other hormone-secreting glands

Nerve Impulses

Signals in the nervous system which travel to specific target cells along communication lines consisting mainly of axons. Can be received by four types of cells: other neurons, muscle cells, endocrine cells, and exocrine cells.

Hormone Cascade Pathway

Signals to the brain stimulate the hypothalamus to secrete a hormone that regulates the release of an anterior pituitary hormone. The anterior pituitary hormone in turn acts on another endocrine organ, stimulating secretion of yet another hormone, which exerts effects on specific target tissues. Such pathways redirect signals from the hypothalamus to other endocrine glands.

Filtrate → process of filtration: what the filtrate contains

Solution formed when water and small solutes (such as salts, sugars, amino acids, and nitrogenous wastes) cross the selectively permeable membrane of a transport epithelium.

What regulates urination?

Sphincter muscles near the junction of the urethra and bladder.

Recall that target cells have receptors for specific hormones. Where are the receptors for lipid soluble hormones found?

Steroids → located within target cells

Cardiac Muscle

Striated like skeletal muscle, forms the contractile wall of the heart.

Neurons

The basic units of the nervous system which receives impulses from other neurons via its cell body and multiple extension called dendrites. Transmit impulses to neurons, muscles, or other cells via extensions called axons, which are often bundled together into nerves.

What happens when the body loses water?

The blood becomes more concentrated, and thus hyperosmotic.

Conduction

The direct transfer of thermal motion (heat) between molecules of objects in contact with each other.

Radiation

The emission of electromagnetic waves by all objects warmer than absolute zero (sun).

Filtration → process of filtration: explain where and how it occurs

The excretory tubule collects a filtrate from the blood. Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule.

Duodenum

The first part of the small intestine. During digestion, partially digested food passes through this from the stomach.

Interstitial Fluid

The fluid surrounding body cells.

Uric Acid → Describe the characteristics of this nitrogenous waste molecule and the animal groups that excrete them

The primary nitrogenous waste of insects, land snails, and many reptiles, including birds. Relatively nontoxic and does not readily dissolve in water → can be excreted as a semisolid paste with very little water loss. More energetically expensive to produce than urea. - Uric acid → Many reptiles (including birds), insects, and land snails

Thermoregulation

The process by which animals maintain an internal temperature within a normal range; a physiological example of homeostasis.

Excretion

The process that rids the body of nitrogenous (nitrogen-containing) metabolites and other metabolic waste products.

Juxtamedullary Nephrons

The remainder of cortical nephrons which extend deep into the medulla, and are essential for production of urine that is hyperosmotic to body fluids.

Evaporation

The removal of heat from the surface of a liquid that is losing some of its molecules as gas.

Signal Transduction

The series of changes in cellular proteins that converts the extracellular signal to a specific intracellular response. This type of pathway typically has multiple steps, each involving specific molecular interactions.

Hormones

The signaling molecules broadcast throughout the body by the endocrine system. Different types cause distinct effects and only cells that have receptors for a particular hormone respond. Often long-lasting effects because they can remain in the bloodstream for minutes or even hours.

Anterior Pituitary

The synthesis and release of hormones here are triggered by hormonal signals from the hypothalamus. These hormones in turn often regulate other endocrine glands.

Countercurrent Exchange

The transfer of heat (or solutes) between fluids that are flowing in opposite directions. Reduces heat loss in extremities.

Convection

The transfer of heat by the movement of air or liquid past a surface. For example, when a breeze contributes to heat loss from skin or blood moves heat from the body core to the extremities

Reabsorption

The transport of epithelium reclaims valuable substances from the filtrate and returns them to the body fluids.

Why do many organisms have a body fluid composition adapted to the salinity of their environment?

They are osmoconformers and have adapted to their environments.

Osmolarity (Osmotic Pressure)

Total solute concentration expressed as molarity, or moles of solute per liter of solution (tonicity). The unit of measurement is milliOsmoles per liter (mOsm/L).

Muscle Tissue

Vertebrates have three types: skeletal, smooth, and cardiac. Its cells all consist of filaments containing the proteins actin and myosin, which together enable muscles to contract.

How is filtrate formed?

When blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman's capsule.

Why are nitrogenous wastes lipids or carbohydrates?

When proteins and nucleic acids are broken apart for energy or converted to carbohydrates or fats, enzymes remove nitrogen in the form of ammonia.

Notice the slight switch in terms when dealing specifically with osmolarity. a. Explain water movement in an isoosmotic condition. b. When two solutions differ in osmolarity, in which direction does water flow?

a) No net movement → water continually moves across membrains evenly between two isoosmotic solutions across the permeable membrane b) Water flows to higher concentration of solutes [from a hypoosmotic solution (higher concentration of water) to hyperosmotic solution higher concentration of solutes)]