chapter 25: control of the internal environment

Chapter 25: Control of the Internal EnvironmentNEW AIM: How do organisms deal with metabolic waste?

a. produced from breakdown of proteins and nucleic acids

I. Excretion

A. removal of metabolic wastei. Carbon dioxideii. Nitrogenous waste

iii. Water


Fig. 25.8

b. Forms of nitrogenous waste

1. Ammonia (NH3)

- highly toxic- highly water soluble- formed by deamination of AAs- secreted by most aquatic animals- Must be secreted immediately or will denature proteins and cause death

Land animals do not have the luxury of being able to secrete waste continuously due to water loss…how do we get around this?

Adide: NH3 (ammonia) can get protonated to NH4+ (ammonium) in aqueous solution and vice versa. NH3 < - - > NH4+ ; pKa = 9.23


Fig. 25.8

b. Forms of nitrogenous waste2. Urea

- 100,000X less toxic than NH3

- mammals, adult amphibians, sharks, some fish

- convert NH3 to urea (occurs in liver – site of deamination)

- why don’t all organisms just make urea??

- urea travels in blood and is removed by kidneys

- Highly water soluble

- certain toads switch back and forth depending if they are in water where they can get rid of NH3 quickly or on land.

It is not free, costs ATP



- 100,000X less toxic than NH3

- mammals, adult amphibians, sharks, some fish

- convert NH3 to urea (liver – site of deamination)

- why don’t all organisms just make urea??

- urea travels in blood and is removed by kidneys

- Highly water soluble

You thought Krebs and Calvin were awesome, but what about THE UREA (ornithine) CYCLE…

It is not free, costs ATP

Formation of urea requires many enzymes (which take lots of ATP to make) and additional ATP to power endergonic reactions!!

Aside: This was the first metabolic cycle discovered by…wait for it…Hans Krebs!!


Fig. 25.8


Compare hypothetical storage of NH3 to storing urea in bladder.

Ammonia (NH3), cannot be stored at high concentration as it is too toxic and would destroy the bladder. Therefore, it must be gotten rid of immediately

2. If you live in water, you just let the ammonia diffuse across the epithelium into the water…

1. If you live on land you would need to constantly be urinating to get rid of it and you would thus be constantly losing water…dehydration (on top of constantly urinating…).


Fig. 25.8


What about birds (no bladder) or many insects / reptiles that are highly susceptible to drying out – desiccation)?


Fig. 25.8

b. Forms of nitrogenous waste3. Uric acid

- relatively non-toxic

- birds, insects, many reptiles, land snails, amphibians in deserts

- secreted as a paste or dry powder- costs a lot of ATP to make

- Largely INSOLUBLE in water

- savings is in water- great for external development (egg) – why?

Birds don’t urinate!


Fig. 25.8

b. Forms of nitrogenous waste

Form of nitrogenous waste

toxicity Solubility in water

Energy cost to make

NH3

(ammonia)

high high none

urea low high high

Uric acid Very low low Very high

Summary

Chapter 25: Control of the Internal EnvironmentAIM: How do organisms deal with metabolic waste?

II. Excretion in other organisms

A. Protists- diffusion through membrane

- ammonia and CO2

- Some use contractile vacuoles to remove water waste



B. Cnidaria (hydra)- entire body in contact with water

- diffusion of ammonia and CO2 directly into surrounding water


C. Annelida (Earthworm)- Nephridia = excretory organs of Earthworm

- one pair (2) in each segment- excrete urine (urea, ammonia, salts dissolved in water) out the nephridopores

- CO2 excreted through skin (skin-breathers)


(nephridopores)

Body fluid from one segment containing waste enters the funnel of the nephridia in the next segment. Capillaries surround the nephridia. Some of the solutes like salts, and water (the solvent of course) diffuse back into the blood (reabsorbed). The fluid, now mostly waste products like urea and ammonia dissolved in water, continues to the bladderlike storage organ and will then be excreted through the nephridopores.


F. Arthropod (Grasshopper)- CO2 diffuses into tracheal tubes and expelled through spiracles- Malpighian tubules = excretory organs closely associated with the intestines that removes uric acid and excess salts from hemolymph and put it into the intestines…


- excretes URIC ACID with fecal matter



Organism Form of nitrogenous waste

Method of excretion

Protist NH3 (ammonia) diffusion

cnidaria NH3 diffusion

annelida Urea, NH3 nephridia

arthropoda Uric Acid Malpighian tubules

Humans Urea kidneys

Summary


Fig. 25.9

*LIVER - makes urea from ammonia from deamination of amino acids

**Skin (urea with sweat) and lungs (CO2) also involved in excretion

III. Human Excretory System

In addition:



Fig. 25.9

A. Kidneys

ii. maintains the homeostatic balance of blood

iii. 1100-2000L of blood filtered per day

i. Site of urine formation

-filters out metabolites (urea)2. Regulates osmolarity

1. Regulates metabolic waste

- filters out minerals (salts) /water

3. Regulates blood pressure

4. Regulates pH



i. Blood enter via renal arteryB. Flow of the excretory system

ii. Urea, water and salts extracted by nephrons of kidneys (filtrate)

iv. Blood leaves via renal vein

iii. Filtrate drains into renal pelvis (urine now) -> ureter -> bladder -> urethra -> toilet



Fig. 25.9

C. How does the kidney extract filtrate?

i. Functional unit of the kidneyii. ~1,000,000 per kidney

1. The Nephron



Fig. 25.9

iii. Each extracts tiny amount of filtrate


i. Functional unit of the kidney (tiny filtering unit)ii. ~1,000,000 per kidney

1. The Nephron



** Fig. 25.9

C. How does the kidney extract filtrate?1. The Nephron



Fig. 25.9

- Flow chart through nephron


1. The Nephron

http://www.biologymad.com/resources/kidney.swf



C. nephron

Fig. 25.9

Practice Labeling

http://www.biologymad.com/resources/kidney.swf



C. nephron

Fig. 25.10

Urine is produced in 4 major processes

IMPORTANT: Water, urea, salts, monomers, toxins, etc… are forced out of the glomerulus capillaries by high blood pressure into Bowman’s capsule and enter the nephron tubule non-selectively. The only selective filter is the size of the molecule. Glucose and smaller enters automatically. The kidney can only control what is taken back (reabsorbed) into the blood, NOT what goes into Bowman’s and the nephron tubule!!



C. nephron

Fig. 25.11

A closer look at urine formation



D. Regulating the nephron (water reabsorption)i. Under hormonal controlii. The kidneys regulates blood osmolarity (solute concentration of blood)

A diuretic is any drug that elevates the rate of urination.

a. If blood is hypertonic, cells will lose water and crenate.

b. If blood is hypotonic, cells will gain water and lyse.- The kidney must controls how much water is in the blood by removing it or not removing it from the nephron tubule…

****By default, monomers and smaller will enter Bowmans. The only selecive criteria is size!! The kidney cannot stop these molecules from entering!! Therefore it can only control what it takes back. If you are dehydrated, hypertonic, it will take back water. If your blood is hypotonic, they will NOT take back water. It is all about reabsorption.



D. Regulating the nephron (water reabsorption)i. Under hormonal controlii. The kidneys regulates blood osmolarity (solute concentration of blood)

A diuretic is any drug that elevates the rate of urination.

a. If blood is hypertonic, cells will lose water and crenate.

b. If blood is hypotonic, cells will gain water and lyse.- The kidney must controls how much water is in the blood by removing it or not removing it from the nephron tubule…

iii. Kidneys also regulate blood pressure (BP)

- Low blood volume = low BP, add water to blood- BP is controlled by controlling blood volume

- high blood volume = high BP, take water out of blood

Diuresis = urinationWater reabsorption by the kidneys is contolled by AntiDiuretic Hormone (ADH), also called vasopressin

- Renin – angiotensin – aldosterone system



D. Regulating the nephron (water reabsorption)iv. How does ADH accomplish this?

-Solute sensor cells are located in the hypothalamus of the brain(ex. too little solute = too much water; BP to high = too much water)

-What if you eat a lot of salty food (food high in sodium) and your blood volume increases because ADH is secreted and your kidneys are reabsorbing water from the nephron tubules to maintain the osmotic balance so your cells do not crenate?

-Your blood pressure will be high and your kidneys really can’t do anything about it because if they remove water, the blood will become hypertonic relative to your cells…



D. Regulating the nephron (water reabsorption)iv. How does ADH accomplish this?



D. Regulating the nephron (water reabsorption)

Alcohol inhibits release of ADH

1. Drink alcohol,2. Inhibit ADH release3. Water not reabsorbed from nephron

tubule 4. Urinate a lot.5. Dehydration occurs…

Caffeine has the same affect

Therefore alcohol and caffeine are called diuretics (make you pee)



D. Regulating the nephron (water reabsorption)i. Under hormonal controlii. Solute sensors in brain (too little solute = too much water)

Negative feedback

Alcohol inhibits release of ADH

iii. Regulates blood pressure

High [water] = high BP

ADH = vasopressin



D. dialysisi. Kidneys are damaged

a. toxic waste builds up, unregulated BP, unregulated pH, unregulated salt/water concentrationb. causes

- hypertension and diabetes (60%)

-prolonged use of pain relievers, alcohol, other drugs and medicines

ii. Dialysis machine “Artificial kidney”

a. Dialysis = separationb. 3 times a week, 4 to 6 hours a session



D. dialysis



E. gouti. Hyperuricemia

- elevated levels or uric acid in blood (we do make some uric acid when we break down purines)- causes

1. Accelerated generation of uric acid

2. Impaired excretion in kidney

- crystals of uric acid can form in joints (pain) = GOUT

3. Consumption of purine-rich diet as uric acid is breakdown product of purines

Humans make a small amount of uric acid when we break down adenine and guanine (purines), which is put into the urine by the kidneys.



E. gout



F. Kidney Stones (for Joel)i. AKA renal calculi

ii. Form inside kidneys or bladder

iii. Most made of Calcium oxalate crystals


IV. The liver

A. More functions than any other organi. Bile productionii. Deamination and synthesis of urea from ammonia

iii. Detox of alcohol and other drugs

iv. Synthesize blood clotting factorsv. Involved in blood glucose regulation (stores glucose as glycogen)

vi. Forms lipoproteins

- transport fat and cholesterol to body tissues


IV. The liver

A. More functions than any other organi. Bile productionii. synthesis of urea from ammonia


iv. Synthesize blood clotting factors

vi. Forms lipoproteins Lipoprotein (ex. LDL)


IV. The liver

A. More functions than any other organi. Bile productionii. Deamination and synthesis of urea from ammonia


iv. Synthesize blood clotting factorsv. Involved in blood glucose regulation (stores glucose as glycogen)

vi. Forms lipoproteins

- transport fat and cholesterol to body tissues

So where do you think your blood goes straight after absorbing molecules at the small intestines?


IV. The liver

A. More functions than any other organ

First “stop”…the liver.

Fig. 25.13

The hepatic portal express- nutrients and harmful chemicals go straight to liver from duodenum

- detox before entering body, and modify nutrients (deamination, lipoprotein synthesis, etc…)


IV. The Skin (not in book)

Fig. 25.13


IV. The Skin

a. epidermisi. Top layer of skinii. Protects body, keeps in moistureiii. Couple layers of living cells topped with many layers of dead cellsiv. Holds skin pigment


IV. The Skin

b. dermisi. Layer underneath epidermis

ii. Connective tissue

iii. Nerve endings for heat/pressure/painiv. Exocrine Glands (pores)

- sebaceous (oil) gland - associated with hair- eccrine (sweat) gland

v. Blood vessels

-sweat = 99% water, bit of NaCl, waste products (urea)

- thermoregulation, excretion, protection (slightly acidic to prevent bacterial and fungal growth)

chapter 25: control of the internal environment

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nh3 ammonia

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forms of nitrogenous

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