NUTRITION
• Food is a source of energy and building
materials for heterotrophs.
• Energy is needed for daily chemical
activities (metabolism) and the building
materials needed for growth and the
repair of tissues.
1
You are a tube inside a
tube…
The tube starts
here:
And although
there are a few
twists and turns
along the way…
It comes out here:
This tube is
called the GUT.
THROUGH-GUT.
Anything that goes
in the top hole
(mouth) does not
become part of the
body until it is
absorbed (taken in)
in a part called the
small intestine.
2
BASIC STRUCTURE AND FUNCTION
of the human digestive system.
different parts of the digestive system have
different _______________
functions
SPECIALISED
3
Autotrophic nutrition
Heterotrophic nutrition
1 Make their own food
1 Cannot make their
own food
2 Made by
2 Have to find their
food made by others
3 Forms the primary
producers in food
chains
3 Forms the Primary
consumers (herbivores),
Secondary and tertiary
consumers (carnivores)
photosynthesis or
chemosynthesis
4
Examples of heterotrophs
paramecium
5
Obviously, a heterotroph!
6
Enzymes
• They need to be broken down chemically
by ENZYMES.
• Enzymes are biological catalysts. They
speed up chemical reactions in the body.
• Digestive enzymes speed up the breaking
down process by holding the large particle
(substrate) in place
7
Enzymes (Chemical Digestion)
Remember :
• Large particles cannot be
absorbed in the small intestine
INSIDE THE
BODY (BLOOD)
GUT
starch
starch
G
starch
G
G
G
Large particles
(e.g. starch) are
left in the gut and
small particles
(e.g. glucose) go
through into the
blood.
G
G
starch
BUT large particles can be
broken down into small particles.
This is called DIGESTION
8
Amylase
enzyme
Starch
molecule
The enzyme fits over
the substrate
perfectly – like a key
fits a lock.
It holds the starch
molecule in place as
a water molecule
breaks the bond
between two glucose
particles
9
This continues until
the molecule has
been broken down
completely
10
Digestive Enzymes
• There are 3 main types of digestive
enzymes:
– Carbohydrases breaks carbohydrates down
into glucose.
– Protease breaks protein down into amino
acids.
– Lipase breaks fats down into fatty acids and
glycerol
11
Digestive Enzymes
carbohydrase
Glucose
Starch
Protease
Protein
Amino
Acids
12
Digestive Enzymes
Lipase
Fatty Acid
Glycerol
Fatty Acid
Fatty Acid
Fat
Fatty Acids
and Glycerol
13
Tour guide
• Mouth - saliva (contain enzyme)
– Teeth
– Amylase enzyme (What are enzymes???)
• Oesophagus
– peristalsis
• Stomach – Gastric juice (contain enzyme)
– Protease enzyme
– Enzymes and pH
• Pancreas Pancreatic juice (contain enzyme)
– Amylase, Protease and Lipase Enzymes
• Small intestine - Intestinal juice (contain enzyme)
– Amylase, Protease and Lipase Enzymes
– Absorption
• Large intestine
– egestion
14
1
4
2
3
6
7
5
8
9
10
11
13
12
14
15
15
Salivary gland
16
Types of teeth
(Mechanical digestion)
There are different types of teeth for different
Sharp pointed teeth
functions:
for cutting and
tearing food
DENTAL FORMULA
2.1.2.3.
2.1.2.3
Grinding and
mashing food
Crushing and
grinding food
Cutting and chopping food
17
Salivary glands
18
19
Saliva
• Water softens food and moistens food,
facilitating chewing (mastication)
• Is neutral (or slightly alkaline for enzyme
action (pH 8)
• Contains enzyme carbohydrase
(salivary amylase) for digesting cooked
starch.
20
• The lining of the mouth cavity is able to
"tell" when food is "ready". The tongue and
palate mould the food into a small ball or
bolus
____________that
is then ready for
swallowing.
reflex
• Swallowing is a __________
action of
the tongue, palate, pharynx and glottis.
21
Swallowing & Peristalsis
1 The bolus is pushed downwards by peristalsis
circular
2 ____________
muscles above the bolus
contract
3 The tube above the bolus narrows
longitudinal
4 The ______________muscles
below the
bolus relax.
22
STOMACH
23
Gastric pits
Gastric juice contains...
protease enzymes which act
upon proteins.
water enabling easy movement
of the food.,
mucin which forms a thick
protective layer against the
action of the enzymes in gastric
juice.
hydrochloric acid which
provides an acid medium for
enzyme action as well as acts
as an antiseptic destroying
"germs" taken in with the food.
24
GASTRIC PIT
25
ACCESSORY GLANDS
26
Gall bladder
liver
Common bile
duct
Hepaticopancreatic duct
pancreas
27
ACCESSORY GLANDS
28
NORMAL LIVER
SECTION THROUGH LIVER
HEPATIC PORTAL VEIN
HEPATIC VEIN
29
30
Liver Functions
2. Liver detoxifies
3. Liver
1. DEAMINATION
(makes harmless)
forms and
OF EXCESS
harmful substances,
stores fat
AMINO
as
alcohol
6. TheACIDS
liver is able to convert
glucose
to(has
glycogen that is
5such
The liver
Those
aa stored
not used
enzyme
alcoholic
then
in the liver
(It as
can
serves
a also convert glycogen
for the
synthesis
dehydrogenase).
back
into glucose when
the body needs it).
storehouse
7. Secretes bile
of proteins are
for minerals
deaminated,
such as iron.
forming UREA
4. Storage
organ for the
Vitamins A,
D and B12
Bile
•Water keeps the food fluid for easy
movement.
•Alkaline bile salts neutralize the acid food
from the stomach.
•Emulsifies fats increasing the surface area
for enzyme action.
Bile salts help in the absorption of fat and 31
vitamins A, D, E and K that are fat-soluble.
Liver
Stomach
Gall
bladder
Bile
Duodenum
Pancreas
32
• Like the liver, the pancreas is also an associated
gland of the alimentary canal that opens up into
the small intestine. It is a large gland that lies in
the loop of the ____________________
of the
duodenum
small intestine. It secretes pancreatic juice that
is carried by the pancreatic duct. The pancreatic
duct joins the common bile duct and forms the
hepato-pancreatic duct before it enters the
duodenum.
• Specialized cells called islets of
_____________________,
amongst the ordinary
Langerhans
cells of the pancreas, secrete the hormones
_____________
and ____________
that play an
insulin
glucagon
important role in controlling the blood
glucose
___________
(sugar) level.
33
Tour guide
• Mouth
– Teeth √
– Amylase enzyme (What are enzymes???) √
• Oesophagus
– Peristalsis √
• Stomach
– Protease enzyme
– Enzymes and pH √
• Pancreas
– Amylase, Protease and Lipase Enzymes
• Small intestine
– Amylase, Protease and Lipase Enzymes
– Absorption
• Large intestine
– egestion
34
35
Pancreas
• Secretes
• Pancreatic juice (containing digestive
enzymes)
• Hormones: insulin and glucagon
36
Pancreatic juice
• Pancreatic juice is important since ...
• water keeps the food fluid enabling easy
movement of the food.
• sodium bicarbonate neutralizes the acid
food coming from the stomach so that the
enzymes can function efficiently in the
small intestine.
• it contains the following enzymes
o carbohydrases to digest carbohydrates.
o proteases to digest proteins
o Lipases to digest lipids/fats
37
38
The duodenum
• The first part of the small intestine is called
the duodenum.
• Food, still mixed with gastric juice is
squirted into it from the stomach.
• The food is now a semi liquid, highly acidic
mush called chyme.
• It needs to be neutralised and digestion
needs to be continued…
39
jejenum
• The ________________
is a short
intermediate tube that follows the
duodenum. It leads into the ileum.
ileum
• The _____________
is the longest part of
the small intestine. It runs from the
jejunum to the sac-like caecum that is the
first part of the large intestine.
40
•
•
•
•
SEROSA
– the ______________ on the outside.
– the muscular region, assisting in peristalsis, made up
of:
o an outer layer of ___________________
muscles.
LONGITUDINAL
CIRCULAR
o an inner layer of _______________
muscles.
SUBMUCOSA
a ______________________
made up of connective
tissue with blood vessels, lymph vessels and nerves.
MUCOSA
a ______________________
or mucous membrane
which is the Innermost layer. It is lined with columnar
epithelium with goblet cells that secrete mucous.
41
The small intestine has a large area for digestion
and absorption because:
• It is very long and folded in the
abdomen.
• The inner mucosa is folded.
• On the surface of the mucosa are millions
of microscopic villi
42
Small Intestine wall
•
•
•
•
serosa
– the ______________
on the outside.
– the muscular region, assisting in peristalsis, made
up of:
longitudinal
o an outer layer of ___________________
muscles.
circular
o an inner layer of _______________
muscles.
Sub-mucosa
a ______________________
made up of
connective tissue with blood vessels, lymph vessels and
nerves.
mucosa
a ______________________
or mucous membrane
which is the Innermost layer. It is lined with columnar
epithelium with goblet cells that secrete mucous.
43
Villi
• These are small finger
like structures that stick
out into the small
intestine tube.
• They help to increase
the surface area of the
small intestine.
44
Villi
Outer wall
Pathway
for Food
Inner wall
45
VILLI
46
HOW TO DRAW A VILLUS
ENLARGED
LACTEAL
CAPILLARY NETWORK
CRYPT OF LIEBERKUHN
BRUNNER’S GLAND
AFFERENT VESSEL
EFFERENT VESSEL
TO LYMPHATIC SYSTEM
47
How is the villus well-adapted to the
functions of digestion and absorption in
the small intestine?
1. Finger-like, increasing surface area for
absorption of nutrients
2. Villi wave motion mixes food with
enzymes.
3. Crypts of Lieberkuhn secrete digestive
enzymes to complete food digestion.
4. Brunner’s glands and mucous epithelium
secrete mucus to aid peristalsis in the
movement of food and to protect the
48
intestinal wall.
How is the villus well-adapted to the
functions of digestion and absorption in
the small intestine?
5. Simple columnar epithelium is thin for
short distances for absorbed foods to
travel.
6. The Epithelium also actively absorbs the
digested food
7. Brush border (microvilli) of simple
columnar epithelium increases the
absorptive surface area.
8. Capillary network efficiently carries away
the absorbed food.
9. Lacteal carries away the absorbed
49
products of lipid digestion.
A
Simple Columnar Mucous
epithelium with micovilli
VENULE
B
C
ARTERIOLE
D
LACTEAL
CAPILLARY NETWORK
E
F
G
I
CRYPT OF LIEBERKUHN
BRUNNER’S GLAND
H EFFERENT VESSEL
AFFERENT VESSEL
The lining of the villus contains simple
columnar epithelium which contains:
GOBLET
• _______________
cells which secrete
mucus, which serves as a lubricant and
which is alkaline and protects the lining of
the small intestine against acid chyme.
MICROVILLI
• __________________
which enlarge the
surface area for absorption of digested
foods.
51
The small intestine has a large area for digestion
and absorption because:
• It is very long and folded in the
abdomen.
• The inner mucosa is folded.
• On the surface of the mucosa are millions
of microscopic villi
• Microvilli
52
The small intestine
• The small intestine produces 3 enzymes to
complete digestion:
– Carbohydrase (maltase, lactase and
sucrase) breaks disaccharides down into
glucose.
– Protease breaks protein down into amino
acids.
– Lipase breaks fats down into fatty acids and
glycerol
53
FOOD
ENZYME(S)
1 CARBOHYDRATES
1.1 STARCH
AMYLASE
PRODUCT
CARBOHYDRASE Disaccharide
1.2 MALTOSE
1.3 SUCROSE
MALTASE
SUCRASE
1.4 LACTOSE
LACTASE
1.5 CELLULOSE
None
2. LIPIDS
LIPASE
2. PROTEINS
Glucose
Glucose +
fructose
Glucose +
galactose
Glucose
Glycerol + 3
fatty acids
PROTEASE
Amino
acids
WHERE (JUICE)
Mouth (saliva)
Pancreas (juice)
Small intestine
Small intestine
Small intestine
Bacteria in SI
Pancreas (juice)
Small intestine
Stomach
(gastric juice)
Pancreas (juice)
54
Enzyme summary
Enzyme
Substrate
Product
Amylase
STARCH
GLUCOSE
Where it is
produced
Where it acts
Saliva
Mouth
Pancreas
Duodenum
Amino Acids
PROTEASE
PROTEINS
Fat
LIPASE
Pancreas
GLYCEROL
FATTY ACIDS
Duodenum
Pancreas
Duodenum
Small
intestine
Small
intestine
55
Absorption
• The digested food is ABSORBED through
the wall of the small intestine into the
blood stream.
• To do this effectively, the small intestine
needs to have a large surface area.
• This is achieved in the following ways:
56
Absorption: Villi
The digested food
passes through the wall
of the villi (epithelium).
Why does the epithelium have
to be thin?
The glucose and amino
acids pass into the blood
capillary. From here they
go to the liver in the
HEPATIC PORTAL VEIN
57
Absorption: Villi
Lymph is a fluid that is
made when the liquid
part of blood comes out
of blood vessels and
washes over the cells.
Lymph drains into
lymphatic vessels before
joining the blood again.
The fatty acids and glycerol go
into one of these lymphatic
vessels in the villus.
58
Absorption of carbohydrates
• Glucose is the product of carbohydrate
digestion and it is absorbed by diffusion,
assisted by active transport (using a
carrier molecule)
59
Absorption of amino acids
• Amino acids are the products of protein
digestion and are absorbed by diffusion,
assisted by active transport (using a
carrier molecule)
60
Absorption of fats
Fatty acids and glycerol, are absorbed as follows:
• Fatty acids combines with bile salts to form a fatty acidbile salts complex so that they can diffuse through the
epithelium into the lacteal.
• Glycerol is soluble and is actively absorbed into the lacteal.
FATTY ACIDS
+BILE SALTS
GLYCEROL
Fatty acid-Bile
Complex
Glycerol
Active transport across
cell
1 FATTY ACIDS
LIPID DROPLETS
BILE SALTS
2 GLYCEROL
Columnar Epithelium
LACTEAL
61
Hepatic Portal System
62
Liver Functions
1. DEAMINATION OF
EXCESS AMINO ACIDS
Amino acids not used for
the synthesis of proteins
are deaminated
4. LIVER FORMS AND
STORES FAT
2. SECRETES BILE
5. LIVER DETOXIFIES
(MAKES HARMLESS)
HARMFUL SUBSTANCES
6. STORAGE
ORGAN FOR
THE
VITAMINS A,
D AND B12
63
64
65
66
Control of Blood Glucose
67
68
CORRECTIVE MECHANISM
Blood glucose
level rises
Insulin, secreted by Beta
cells of Islets of Langerhans
of Pancreas, enters blood
and stimulates the cells to
take up glucose from blood
and to convert excess
glucose into glycogen to be
stored in liver and muscles.
Normal level of blood glucose
Blood glucose
level drops
NEGATIVE FEEDBACK
MECHANISM
Normal level of blood glucose
CORRECTIVE MECHANISM
Glucagon, secreted by alpha
cells of Islets of Langerhans of
Pancreas, convert the stored
glycogen liver and muscles to
be converted into glucose and
be released into blood.
Ingestion of a meal rich in
glucose
NEGATIVE FEEDBACK
MECHANISM
69
Digestion Products:
• Proteins
• Carbohydrates
• Lipids
•
•
•
•
•
•
•
•
•
Amino acids subunits
Muscle, enzymes,Hb
Last use for food
Simple sugar
(glucose)
Quick energy food
1st used
Fatty acids &
glycerol
Long term food,
insulation,protection
2nd used for food 70
Balanced Diet: Carbohydrate
67%
Carbohydrates
(sugar, sweets,
bread, cakes)
71
Protein
33% Protein
(eggs, milk,
meat, poultry,
fish)
72
Fat
33% Fats (dairy
products, oil)
73
• A balanced diet is one which provides the correct
proportions of all nutrients required for good health.
• It contains about
• 2/3 carbohydrates. Simple sugar (glucose) Quick
energy food 1st used. A 50kg athlete who trains for 2
hours each day needs 343 grams of carbohydrates
per day.
• 1/6 proteins Amino acids subunits. Important for
muscle, enzymes, Hb. Last use for food. A 50kg
athlete who trains for 2 hours each day needs 80
grams of proteins per day.
• 1/6 lipids as well as Fatty acids & glycerol Long
term food, insulation, protection. 2nd used for food. A
50kg athlete who trains for 2 hours each day needs
80 grams of lipids per day.
74
•
•
•
•
vitamins,
minerals,
water and
Roughage (or fibre): The indigestible
material in food which slows down
peristalsis and makes digestion and
absorption of food more efficient.
75
Daily Energy Requirements
• Basic energy requirements (BER)
includes your basal metabolic rate
(BMR) and general daily activities.
• For every Kg of body weight 1.3
Calories is required every hour. (An
athlete weighing 50Kg would require 1.3
× 24hrs × 50Kg = 1560 calories/day
• 1560 x 4.2 = 6552 Kilojoules (Kj)
76
•Extra energy requirements (EER)
•For each hours training you require an
additional 8.5 Calories for each Kg of
body weight.
•(For a two hour training session our 50Kg
athlete would require 8.5 × 2hrs × 50Kg =
850 Calories) = 3570kJ
An athlete weighing 50Kg who trains for two
hours would require an intake of
approximately 10 122 kilojoules (kJ) (BER
+ EER = 6552 + 3570)
77
Energy yield of foods
• The energy yield per gram is as follows:
Carbohydrate – 16,8 kJ, Fats – 37,8 kJ and
Protein – 16,8 kJ.
• What does a 50 kg athlete require in terms of
carbohydrates, fats and protein?
• Carbohydrates - 67% of 10 122 = 6782 kJ - at
16,8 kJ /gram = 6782 ÷ 16,8 = 403 grams
• Fats - 33% of 10 122 = 3260 kJ - at 37,8 kJ
/gram = 3260 ÷ 37,8 = 86 grams
• Protein - 33% of 10 122 = 3260 kJ - at 16,8
kJ/gram = 194 grams
• Our 50kg athlete requires 403 grams of
Carbohydrates, 86 grams of Fat and 194 grams78
of Protein
BALANCED DIET
• CARBOHYDRATES: 2/3 = 403 g
• FATS: 1/6 = 86g
• PROTEINS: 1/6 = 194 g
79
2436 kJ in a big Mac Hamburger
(of the 10 122 an athlete of 50kg needs)
80
3/80 = 3.75%
1/78 = 1.282%
24/343 = 6.99%
235/10122 = 2.32%
81
82
83
Malnutrition
Obesity
This man is digging his own grave
with his teeth
84
Malnutrition
KWASHIORKOR
• This is caused by a diet
high in carbohydrates
and low in proteins.
• Swollen belly, puffy face,
stick-like arms and legs,
skin sores,
• reddish hair, stunted
physical and mental
growth.
85
Malnutrition
MARASMUS
• This is due to a general
lack of energy foods.
• SYMPTOMS are:
• Monkey-like face with
sunken eyes, thin body,
tight skin, lethargy.
86
Malnutrition
Anorexia Nervosa
•This is a psychological disease in which the person REFUSES to eat and
sees himself/herself as fat.
•SYMPTOMS are:
•Extreme loss of body mass, sterility, brain damage, possibly death.
87
Malnutrition
Bulimia
88
QUESTION 2
1 Small Intestine√
2.1 Deamination √
2.2 When you have an excess of amino
acids because they cannot be stored √
2.3 The urea is poisonous √ (acidic) and is
excreted √ by the kidneys √
3.1 Cell respiration √
3.2 Catabolic √
89
Effect of Saliva on Starch
An experiment will contain
The factor being measured
(SALIVARY AMYLASE)
No hydrolysis. Starch
remains. IODINE
TURNS BLUE-BLACK
No starch after 1 hour, all
hydrolysed by amylase.
IODINE STAYS BROWN
90
– What is the aim of the experiment above?
(2)
– Give ONE precautionary measure you would
take when setting up the experiment and
provide a reason for your answer.
(2)
– What would be put into container B while
setting up the experiment?
(2)
– What would happen if, after some time, a
few drops of an iodine solution were added
to A and B. Give ONE reason for your
answer.
(4)
[10]
91