Nutrition in Animals

Learning Objectives:

 Determine how animals obtain nutrients

 Understand the process happening on human
alimentary canal
 Determine the important functions of the parts of
alimentary canal
 Understand how the digestive tract adapt to the
body of the organism.
Pointers

 Different Biological Molecules

 Major Food Groups
 Food Tests
Biological Molecules

 Food Groups
 Food Tests
 Biological Molecules
Major Food Groups

 Carbohydrates
 Proteins
 Fats
Biological Molecules

 Carbohydrates
 Proteins
 Fats
Nutrients
Carbohydrates

Monosaccharide Disaccharide Polysaccharide

(simple sugar) (double sugar) (complex sugar)

e.g. glucose, e.g. maltose, e.g. starch,

galactose, lactose, glycogen,
fructose sucrose cellulose
Nutrients
Proteins

Amino Acids Polypeptide Proteins

Chains

e.g. adenine, e.g. enzymes,

methionine antibodies
Nutrients
Fats

Fatty Acids Fats/Lipids

Glycerol
e.g. adipose tissues,
phospholipids
The Alimentary Canal

 Parts of the Human Alimentary Canal

 Functions of the Human Alimentary Canal
 Peristalsis
The Human Alimentary Canal
Nutrition in Human
Human Alimentary Canal
Processes and Functions
 Ingestion – the process of taking in food into
the alimentary canal through the mouth.

 Digestion - the process of the breaking down

of large, complex and insoluble substances
into small, simple and soluble molecules by
the action of enzymes; so as to facilitate the
absorption of nutrients into the body.
Human Alimentary Canal
Processes and Functions
 Absorption – the process where digested
food substances are taken up by the body
through the blood stream.

 Assimilation – the process where the

nutrients absorbed are converted into new
protoplasm and/or used to release energy for
the body
Human Alimentary Canal
Processes and Functions
 Egestion – the process where indigestible
and unabsorbed material are removed from
the alimentary canal through the anus.

 Egestion = Excretion*

*Excretion is the removal of metabolic waste products from the body through
the excretory system (to be covered in later topics)
Buccal Cavity
 Food is broken down into
smaller bits by chewing
(physical digestion).
- increases surface area of food
substances.

 Salivary glands produce

Salivary glands
salivary amylase that breaks
down starch into maltose.

 The bolus is swallowed and

being pushed along the
Salivary amylase
Starch → Maltose
Oesophagus oesophagus by peristalsis.
Peristalsis
Peristalsis
Longitudinal muscles

Epidermal layer

Lumen

Circular muscles

Antagonistic muscles
Stomach  Gastric juices is secreted into
the stomach.

 Gastric juices contain

hydrochloric acid, pepsin and
rennin.
- hydrochloric acid kills bacteria.
- hydrochloric acid lowers the pH
in the stomach (pH 2~3).
- pepsin breaks down protein to
polypeptides.
- rennin curdles the milk.
- salivary amylase action stops
Pepsin due to the low pH. (non-optimal
Protein → Poly-peptides pH conditions)
Small intestine and peripheral organs
 Liver makes bile
 Bile is stored in gall bladder
and secreted into the
Liver duodenum via the bile duct.
Gall
bladder - bile increases the pH (pH
9~10)
Bile duct - bile emulsifies fat.
- emulsification of fat increases
Pancreas the surface area for fat
digestion.
Duodenum - lipases will break down the fats
into fatty acid and glycerol.

Lipase
Fats → Fatty acid + Glycerol
Small intestine and peripheral organs
 Pancreas produces pancreatic
juices.
Liver
 Pancreatic juices are secreted
into the duodenum via the
Gall
pancreatic duct.
bladder

Bile duct - pancreatic juices increases the

Pancreas pH (pH 9~10).
- pancreatic juices contains
Duodenum pancreatic amylase, pancreatic
lipase, and trypsin.
- trypsin breaks down protein to
Trypsin
Protein → Poly-peptides polypeptides.
- gastric juices actions stop.
Small intestine and peripheral organs
 Small intestine produces
intestinal juices.
Liver
 Small intestine absorbs most of
the nutrients at the end of
Gall
ileum.
bladder

Bile duct - intestinal juices contains

Pancreas erepsin, lipases and
carbohydrases.
Duodenum - erepsin breaks down
polypeptides into amino acids.
Erepsin
Poly-peptides → Amino acids
Large intestine, rectum and anus.
 Colon absorbs the remaining
water content and mineral
salts.
colon
 Rectum serves as a
temporary storage for
indigestible material and
appendix
unabsorbed material.
 The anus is the opening
rectum where faeces is egested out
of the body.
anus
Digestion (pancreatic enzymes)

amylase
 Starch maltose
 Protein trypsin polypeptides
 Fat lipase fatty acids and glycerol
Digestion (intestinal enzymes)

maltase
 Maltose glucose
 Polypeptides erepsin amino acids
 Fats lipase fatty acids and glycerol
Absorption and Adaptation of Parts

 Absorption of nutrients
 Roles of the liver
Absorption of nutrients

Nutrients absorbed in the Digestive

System would be carried to parts of
the body via the Circulatory System
(Blood).
Adaptations in the Alimentary Canal
 The Human Alimentary Canal (from the mouth to the
anus) is approximately 6.5 metres long. Why?

-Food takes time

to be digested.
-The longer food
stays in the body,
more nutrients
can be absorbed.
Adaptations in the Alimentary Canal

Increased surface area

can help increase the rate
of absorption of nutrients.

The intestinal walls are

lined with networks of folds
blood capillaries.
Adaptations in the Alimentary Canal
Diagram of a villus showing
the blood capillary network
and the lacteal.

microvilli

Blood
folds capillaries

Lacteal
The hepatic portal vein

Nutrients absorbed from Nutrients absorbed from

the small intestine is the large intestine is
transported to the liver transported to the liver
via the hepatic portal via the hepatic portal
vein vein
Roles of the Liver
 Metabolism of Glucose
 Metabolism of Amino Acid (Formation of
Urea)
 Metabolism of Fats
 Breakdown of Red Blood Cells
 Breakdown of Alcohol
 Production of heat.
Metabolism of Glucose
 Insulin and Glucagon are secreted
by the pancreas to regulate the
blood glucose levels in the body.
 In a healthy individual, insulin is
secreted when blood-glucose level
is high.
- Insulin promotes the uptake of
glucose into the liver and the
Insulin will promote conversion of glucose into
the conversion of glucose glycogen.
into glycogen in the liver  In a healthy individual, glucagon is
secreted when blood-glucose level
is low.
Glucagon will promote
the conversion of glycogen
- Glucagon promotes the conversion
into glucose in the liver of glycogen into glucose and the
release of glucose into the
bloodstream.
Metabolism of Amino Acids
 Excess amino acids will be found in
the human body after the person
has taken in large amount of
protein.
 The excess amino acids will be
deaminated to form urea.
 Urea is toxic and is removed from
the body via the kidney.
 Urea is a metabolic waste product.
The liver will deaminate excess
amino acids to form urea.
Breakdown of Alcohol
 Alcohol is broken down in the liver
into harmless substances through
detoxification.
 When there is surplus of nutrients
in the body, alcohol is converted
into fats and stored in the body.
 When there is a shortage of
nutrients in the body, alcohol is
The liver will detoxify broken down by enzymes to
alcohol to form other release energy.
harmless products.
Summary of Digestion

Carbohydrates Proteins Fats/Lipids

(polysaccharides) (polypeptides) (polymer)

Glucose Amino Acids Fatty Acids/Glycerol

(monosaccharides) DIGESTION
(monomers) (monomers)

e.g. Glycogen e.g. Enzymes e.g. Adipose Tissue

(polysaccharides) ASSIMILATION
(polypeptides) (polymers)
Reflection time…

DO NOT WASTE FOOD

File Case 00129042009

Annabel: found dead at home in

her room by her mother at 3pm.
Suspect 1: Joanne (Annabel’s
mother)

Recently divorced, Status complicated

Has depression and suicidal tendency
Suspect 2: Nicholas (Annabel’s
brother)

Studies at SARS University:

Life-Sciences undergrad, specializing in toxins
On bad terms with Annabel, Sibling rivalry.
Suspect 3: Bruce (Joanne’s
boyfriend)

Bought all the food ate by

Annabel before she died.
Annabel finds him unworthy of
her mother.
Coroner’s Report
Cause of death:
 Acute food poisoning due to presence of neurotoxin produced by
mutant bacterial strain;
 Mutant bacterial strain is similar to Pseudoalteromonas tetraodonis,
a well-known marine bacterium that produces a neurotoxin that is
very potent, usually found in puffer fish and other venomous marine
animals.
Other evidences gathered
 Unpublished blog posting from Annabel.
 Recorded statements from suspects.
 Preliminary food test results.
 Food test results for the presence of mutant bacterial strains.
(currently in progress)
Directives:
 1. Which are the food product/s that should be tested for the
presence of the mutant bacterial strain?

 2. Which are the food product/s likely to be utilized by the mutant

bacterial strain for its metabolism?

 3. Suggest a possible reason for the observation in the Iodine test

performed on the food samples collected from the body of the
deceased.
3. Suggest a possible reason for the observation in the Iodine test performed
on the food samples collected from the body of the deceased.
Directives:
 4. Examine the results for the food test for presence of mutant
bacterial strain so as to determine the cause of acute food
poisoning.

 5. Suggest who might be responsible for poisoning Annabel,

indicating the contaminated food item, and support your deduction
with logical reasoning.