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 Origin Organ of

Excretion

Ammonia Breakdown of amino acids in the liver Kidney

Urea Conversion of ammonia in the liver Kidney

CO2 Cellular respiration Lungs

Water Cellular respiration Kidneys

Mineral Salts Food and water Kidneys

Lactic Acid

Anaerobic cellular respiration Liver

Liver

Kidney

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):

HCO3-

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 (NH3)

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, CO2, 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 StructuresClass Activity1. Structure (how is it built, where is it in the

body) Include a simple diagram

2. Role (in terms of waste removal)3. One way in which it is related to one of the

other structures in the excretory system4. One way in which it is related to digestive,

respiratory, and circulatory system5. How it helps to maintain homeostasis (include

one feedback loop/process)