1. Entry slip: None
Unit 3 – Excretion and Waste
Management
Lesson 3.1- Identify the primary metabolic wastes
produced
in the cell and the human body and the source of
each.
(pp374-375) of Biology-McGraw-Hill Ryerson)
I. Terms:
a.Excretion: the process of discharging
waste matter from the blood, tissues and
organs.
i. Occurs by respiration (breathing out).
ii. Occurs by urination.

2. b. Metabolism: the collective term for all the
chemical reactions that occur inside the
cells of our body.
c. Metabolic Waste: the by-products of
chemical reactions in the body that need
to be excreted or else the build-up of
these compounds will sicken and
eventually kill the person.
II. Primary Metabolic Wastes:
a. Carbon Dioxide (CO2):
i. A by-product of the oxidation of
CHO’s and lipids for energy:
A. Ex C6H1206(glucose) + O2  H2O
+ CO2
ii. The water is not a waste; we need it
as a nutrient
iii. The CO2 is excreted by respiration
(see Unit 2: Respiration)
b.Urea:

3. i. From the de-aminization of excess
amino acids in the liver (see Lesson
1.7).
ii. The nitrogen is converted in the liver
to urea, a compound which is mildly
toxic. This means that as long as it is
excreted regularly and does not build
up in the body, it will not sicken you.
iii. Excreted by urination.
c. Uric Acid:
i. From the break-down of DNA and
RNA of old dead cells all over the
body.
A. DNA and RNA are very long
chains of amino acids which are
like instruction manuals for your
cells. Information stored in the
DNA and RNA tell the cells what
to do, the same way
information stored on the drives
of computer (software) instructs

4. your computer on how to
perform.
B. Because DNA and RNA are
composed of amino acids, they
contain N, which has to be
removed when the old cells die
off.
ii. Mildly toxic.
iii. Excreted by urination.
d.Creatinine:
i. From the breakdown of Creatine.
A. Made up of amino acids (N
again!)
B. Part of the process of chemical
reaction that allow your muscles
to move.
ii. Mildly toxic.
iii. Excreted by urination.
III. Assignment:

5. a. You are Sheriff Homeostasis of the Human
Body Police Services and there are some
primary metabolic wastes that you have
to drive out of town. Make up an all-
points-bulletin for each suspect so your
deputies will have descriptions to look out
for. Include any known aliases (names),
their histories, where in town they may
be found and how they should be driven
out.
b.Due the next day.