UNIT 4: EXCRETION AND WASTE MANAGEMENT

Excretion and Waste Management

 What would happen if you never threw out your garbage or leftover food?

 Be as detailed and exact as possible  Specific to your house and family  Why do we sweat?

 Why do we urinate?

Waste Removal

 One of the

7 life processes

= removal of waste products produced by the cells of our bodies  What are the waste products in the human body?

 Brainstorm on a piece of paper  Compile your ideas into the following table on chart paper:

Waste Product Origin Organ of Excretion

Waste Products

Waste Product

Ammonia Urea CO 2 Water Mineral Salts Lactic Acid

Origin

Breakdown of amino acids in the liver Conversion of ammonia in the liver Cellular respiration Cellular respiration Food and water Anaerobic cellular respiration

Organ of Excretion

Kidney Kidney Lungs Kidneys Kidneys Liver

Kidney Liver

Excretory System

   Why is feces not included in the list of metabolic wastes?  Feces is not a product of cellular metabolism. It is a “leftover” after the body absorbs what nutrients it needs from the intestines Brainstorm: the relationships between the excretory system and the respiratory system, and the digestive system.

How might the excretory system be involved in homeostasis?

Waste Products: Cellular Respiration

    We obtain energy by converting complex organic compounds into simpler compounds.

 BUT some of these simpler compounds can be harmful

Carbon Dioxide

 Humans produce an average of 1kg per day!

 If levels become too high = our blood becomes acidic  Leads to breakdown of enzymes, etc…  Most is converted to bicarbonate ions (less harmful): HCO 3 -

Lactic Acid

  Converted to pyruvate (aerobic respiration) OR removed through conversion to glucose

Water

Cellular Respiration Waste Products

Waste Products: Metabolism

 The large intestine removes toxic waste from the digestive system.

 The liver transforms these ingested toxins into soluble compounds that can be eliminated by the kidneys  Alcohol, heavy metals (Fe, Al, Hg)  The liver also transforms the hazardous products of protein breakdown to be eliminated by the kidneys

Waste Products: Metabolism

Why are

proteins

so harmful?

 Fact: The average Canadian consumes more protein than is required to maintain tissues and promote cell growth.

 Excess protein is often converted into carbohydrates  BUT proteins, unlike carbohydrates, contain

nitrogen

.

 When amino acids (the protein building blocks) are broken down we get the by-product:

ammonia

Ammonia

 Deamination = the breakdown of amino acids  occurs in the liver.

 byproduct =

ammonia

(NH 3 )  BUT ammonia is extremely toxic - a buildup of as little as 0.005 mg is lethal!

 In the liver, two molecules of ammonia combine with another waste product, CO 2 , to form

urea

3 Hydrogen atoms (H + ) that can be donated to increase acidity This acidity makes it a useful agent for household cleaners

Urea

 Urea is 100 000 times less toxic than ammonia.

 The blood can dissolve 33 mg of urea per 100 mL of blood.

Excretion: Simple Organisms

 For ALL organisms, getting wastes out of the cell is just as important as bringing in nutrients  Otherwise toxins would build up and the cell would soon die  In unicellular organisms and in primitive multicellular organisms (e.g. a sponge) every cell is in direct contact with the external environment  Therefore, wastes are released directly from the cell and water currents carry the waste away

Excretion: Simple Organisms

 BUT, unicellular organisms must regulate their internal fluids  More dissolved solutes then their freshwater surroundings  Therefore, these cells should draw in water, expand, and eventually burst  Fluid Regulation: a

contractile vacuole

expels excess water, preventing this swelling

Excretion: Complex Organisms

   Complex multicellular organisms are faced with the same problem but on a much bigger scale.

Not every cell is in direct contact with the external environment  Therefore, wastes must be collected and temporarily stored A secondary problem: our cells are so specialized that not every cell is designed to remove wastes  Wastes must be transported to cells that are capable of excretion

The earthworm uses a series of

tubules

to remove wastes from the blood and body cavity. Cells lined with

cilia

surround a funnel-like structure (the nephrostome) and draw fluids from the body cavity into tiny tubules. The wastes are stored as urine and are released through small

pores

(nephridiopores) along the body wall.

Malpighian tubules that run throughout the body cavity of an insect absorb wastes by

diffusion

. Wastes are released into the gut and eliminated with solid wastes from the anus.

Human Excretory System

 Major structures:  Kidneys  Liver  Large Intestine  Lungs  Skin

Excretory System Structures

Class Activity

1.

2.

 Structure (how is it built, where is it in the body) Include a simple diagram Role (in terms of waste removal) 3.

4.

5.

One way in which it is related to one of the other structures in the excretory system One way in which it is related to digestive, respiratory, and circulatory system How it helps to maintain homeostasis (include one feedback loop/process)