1. Unit 4: Excretion and Waste Management

2. 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?

3. 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

4. Waste Products Waste Product Origin Organ of Excretion Ammonia
Breakdown of amino acids in the liver
Kidney
Urea
Conversion of ammonia in the liver
CO2
Cellular respiration
Lungs
Water
Kidneys
Mineral Salts
Food and water
Lactic Acid
Anaerobic cellular respiration
Liver

5. Liver
Kidney

6. 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?

7. 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): HCO3-
Lactic Acid
Converted to pyruvate (aerobic respiration)
OR removed through conversion to glucose
Water

8. Cellular Respiration
Waste Products

10. 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

11. 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

12. Ammonia Deamination = the breakdown of amino acids
occurs in the liver.
byproduct = ammonia (NH3)
BUT ammonia is extremely toxic - a buildup of as little as mg is lethal!
In the liver, two molecules of ammonia combine with another waste product, CO2, to form urea

14. 3 Hydrogen atoms (H+) that can be donated to increase acidity
This acidity makes it a useful agent for household cleaners

16. Urea Urea is 100 000 times less toxic than ammonia.
The blood can dissolve 33 mg of urea per 100 mL of blood.

17. 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

18. 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

20. 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

21. 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.

22. 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.

24. Human Excretory System
Major structures:
Kidneys
Liver
Large Intestine
Lungs
Skin

25. Excretory System Structures
Class Activity
Structure (how is it built, where is it in the body)
Include a simple diagram
Role (in terms of waste removal)
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)