Why are organic macromolecules so
important to consume in the diet?
Why are organic macromolecules so
important to consume in the diet?
The body utilizes these
macromolecules to yield energy.
Energy-Yielding Molecules
• Carbohydrates
• Fats
• Proteins
Describe the fate of each of these molecules
following digestion.
Energy-Yielding Molecules
• Carbohydrates
• Fats
• Proteins
Describe the fate of each of these molecules following
digestion.
Sugars are utilized in CR first, then excess gets converted to
glycogen or fat. Fats are usually stored as a longer-term
energy reserve. Proteins (amino acids) are utilized as
necessary, but cannot get stored.
Nitrogenous Waste = Metabolic Waste
Metabolic Wastes
•
•
•
•
Nitrogenous
Carbon dioxide
Water
Salts (phosphates, sulfates, etc.)
Organisms must EXCRETE metabolic waste.
Considering evolutionary history,
organismal systems were simple and
became more complex.
The need to excrete metabolic wastes
(nitrogenous) efficiently evolved as
organisms transitioned from water to
land.
Evolution of Metabolic Wastes
Important Factors




Need to conserve water
Solubility in water
Toxicity
Energy Cost
Body Fluid Regulation
• The Excretory system is involved in regulating
body fluid concentrations.
• How? By retaining or eliminating certain ions
and water
• OSMOSIS: Water moves from on area of
higher concentration (less solute) to an area of
lower concentration (higher solute).
Forms of Nitrogenous Waste
Ammonia
– Very soluble
– Very toxic
– Found in organisms that
do not need to conserve water
Urea
– Soluble
– Toxic
– Found in organisms that conserve
some water
Uric Acid
– Not Toxic
– Not Soluble
– Found in organisms that
must conserve all water
some waste
Considering the type of environment
that the organism of interest lives in,
you can predict the nitrogenous waste
form that is excreted.
Let’s consider the excretion of nitrogenous wastes
in the Paramecium
Which nitrogenous waste form is most likely excreted by the
Paramecium?
How are wastes excreted in the Paramecium?
Let’s consider the excretion of nitrogenous wastes
in the Paramecium
Which nitrogenous waste form is most likely excreted by the
Paramecium? AMMONIA
How are wastes excreted in the Paramecium?
SIMPLE DIFFUSION
Which Nitrogenous Waste form is
excreted by the Cnidarians?
How is the life process of excretion
enabled in the Cnidarians?
Which Nitrogenous Waste form is
excreted by the Cnidarians?
AMMONIA
How is the life process of excretion
enabled in the Cnidarians?
Phylum: Cnidaria
•Excretion
•excrete metabolic wastes
by diffusion
•between cell layers
•out through mouth
•excrete salt into
gastrovascular cavity
•regulate water balance
Which Nitrogenous Waste form is
excreted by the Platyhelminthes?
How is the life process of excretion
enabled in the Platyhelminthes?
Which Nitrogenous Waste form is
excreted by the Platyhelminthes?
Aquatic- Ammonia, Terrestrial- Urea
How is the life process of excretion
enabled in the Platyhelminthes?
The simplest tubular excretory system
is the flame-cell system of flatworms.
These animals have neither circulatory
systems nor coeloms, and so the
flame-cell system must regulate the
contents of the interstitial fluid
directly.
Phylum: Platyhelminthes
Class: Turbellaria
•simple excretory system- protonephridia
•consists of flame cells (specialized ciliated cells)
•move fluid through branched ducts to outside via
excretory pores
•maintains osmotic balance
Which Nitrogenous Waste form is
excreted by the Mollusks?
How is the life process of excretion
enabled in the Mollusks?
Which Nitrogenous Waste form is
excreted by the Mollusks?
Aquatic- Ammonia, Terrestrial- Urea
How is the life process of excretion
enabled in the Mollusks?
Heart. Most molluscs have an open circulatory
system. The dorsally located heart pumps
circulatory fluid called hemolymph through arteries
into sinuses (body spaces). The organs of the
mollusc are thus continually bathed in hemolymph.
Nephridium. Excretory organs
called nephridia remove metabolic
wastes from the hemolymph.
The long digestive tract is
coiled in the visceral mass.
Visceral mass
Coelom
Intestine
Gonads
Mantle
Stomach
Mantle
cavity
Shell
Radula
Anus
The nervous
system consists
of a nerve ring
around the
esophagus, from
which nerve
cords extend.
Figure 33.16
Gill
Foot
Nerve
cords
Esophagus
Mouth
Mouth
Radula. The mouth
region in many
mollusc species
contains a rasp-like
feeding organ
called a radula. This
belt of backwardcurved teeth slides
back and forth,
scraping and
scooping like a
backhoe.
Annelids have similar
excretory structures
as the Mollusks
Anatomy of the earthworm
-Contain two nephridia in each segment
-
Earthworm Nephridia
• Nephridia: Tubule with
ciliated opening an an
excretory pore.
• Fluid from the coelom is
propelled through the
tubule by beating cilia,
nutrient substances are
reabsorbed and carried
away by a network of
capillaries surrounding
the tubule.
• Urine: Contains metabolic
wastes, salts, water
How does the habitat of insects (e.g.
grasshoppers) differ to that of the
other organisms discussed prior?
How does the habitat of insects (e.g.
grasshoppers) differ to that of the
other organisms discussed prior?
Insects tend to live in drier habitats
and require more water to be
conserved.
Which Nitrogenous Waste form is
excreted by the Arthropods?
How is the life process of excretion
enabled in the Arthropods?
Which Nitrogenous Waste form is
excreted by the Arthropods?
Aquatic- Ammonia, Terrestrial- Uric Acid
How is the life process of excretion
enabled in the Arthropods?
Grasshopper Anatomy
Malpighian Tubules
• These specialized tubules are attached to the
gut of arthropods.
• Uric acid flows from the surrounding
hemolymph into these tubules, and water
follows a salt gradient established by active
transport of K+.
• Water and other useful substances are
reabsorbed at the rectum. Excrete a dry,
semisolid mass of uric acid.
Excretion in Insects and Arachnids
Organisms utilize some form
of excretory structure to
excrete nitrogenous
waste.
IMPORTANT
The form of nitrogenous
waste is completely
dependent on the
environment and the
need to conserve water.
Human Excretory System
(HES)
Urea is made in the mitochondrion of
liver cells.
Urea then circulates in the
bloodstream until it reaches the
structures of the HES.
Identify the structures of the
Human Excretory System
that enable the function of the
removal of nitrogenous waste.
Filtration of blood begins in the
kidneys.
Why does blood need to be filtered?
How is the kidney structured to enable
the function of filtration?
The functional unit of the kidney is the
Nephron.
Whole blood traveling from renal
artery enters into the Glomerulus
(small capillary structures arranged
into a cup-like structure).
Which molecules are going to easily
enter into Bowman’s capsule?
Capsular urine
•
•
•
•
•
•
Amino acids
Nutrients
Electrolytes
Water
Gases
Nitrogenous waste
WHAT IS THE PROBLEM WITH CAPSULAR URINE?
Capsular urine
•
•
•
•
•
•
Amino acids
Nutrients
Electrolytes
Water
Gases
Nitrogenous waste
WHAT IS THE PROBLEM WITH CAPSULAR URINE?
There is good stuff that is potentially going to be
excreted and released in urine.
Proximal convoluted tubule is the site
of selective reabsorption.
Tubular Reabsorption
• Substances that are biologically important
move from the proximal convoluted tubule
into the surrounding peritubular capillaries.
• Sodium and chloride ions are actively pumped
from PCT to the PTC, enabling water to follow.
• Glucose and amino acids are selectively
reabsorbed by carrier proteins- Active
transport.
Urine formation and Concentration
There are three hormones critical in
maintaining the water content of the
blood.
Hormones
• Antidiuretic Hormone (ADH)- Makes the collecting duct
more permeable. It is secreted by the posterior
pituitary gland in response to an increase in the
osmotic pressure of the blood.
• Aldosterone- Acts on the kidneys to retain sodium ions,
therefore water is reabsorbed and blood pressure rises
as a result of increased blood volume.
• Renin- Kidneys release renin in the event of low blood
pressure. The presence of renin causes the release of
angiotensin II, which causes the adrenal cortex to
release aldosterone.