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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.
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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:
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.
This tube is called the GUT.THROUGH-GUT.
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BASIC STRUCTURE AND FUNCTIONof the human digestive system.
different parts of the digestive system have different _______________ functions SPECIALISED
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Autotrophic nutrition
Heterotrophic nutrition
1 1
2 2
3 Forms the primary producers in food chains
3 Forms the Primary consumers (herbivores), Secondary and tertiary consumers (carnivores)
Make their own food Cannot make their own food
Made by photosynthesis or chemosynthesis
Have to find their food made by others
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Examples of heterotrophs
paramecium
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Obviously, a heterotroph!
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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
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Enzymes (Chemical Digestion)Remember :• Large particles cannot be
absorbed in the small intestine
starchstarch
starch
starch G
G
G
GUT INSIDE THE BODY (BLOOD)
Large particles (e.g. starch) are left in the gut and small particles (e.g. glucose) go through into the blood.G
G
G
BUT large particles can be broken down into small particles. This is called DIGESTION
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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
Starch molecule
Amylase enzyme
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This continues until the molecule has been broken down completely
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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
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Digestive Enzymes
carbohydrase
StarchGlucose
Protease
ProteinAmino Acids
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Digestive Enzymes
Glycerol
Fatty Acid
Fatty Acid
Fatty Acid
Glycerol
Fatty Acid
Fatty Acid
Fatty Acid
Lipase
Fat Fatty Acids and Glycerol
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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
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Salivary gland
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Types of teeth (Mechanical digestion)
There are different types of teeth for different functions:
Cutting and chopping food
Sharp pointed teeth for cutting and tearing food
Crushing and grinding food
Grinding and mashing food
DENTAL FORMULA2.1.2.3.2.1.2.3
Salivary glands
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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.
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• 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 ____________that is then ready for swallowing.
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• Swallowing is a __________ action of the tongue, palate, pharynx and glottis.
reflex
bolus
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Swallowing & Peristalsis
1 The bolus is pushed downwards by peristalsis2 ____________ muscles above the bolus
contract3 The tube above the bolus narrows4 The ______________muscles below the bolus relax.
circular
longitudinal
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STOMACH
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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.
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GASTRIC PIT
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ACCESSORY GLANDS
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Gall bladderliver
pancreas
Common bile duct
Hepatico-pancreatic duct
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ACCESSORY GLANDS
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HEPATIC PORTAL VEIN
HEPATIC VEIN
NORMAL LIVER
SECTION THROUGH LIVER
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Liver Functions1. DEAMINATION OF EXCESS AMINO ACIDS Those aa not used for the synthesis of proteins are deaminated, forming UREA
2. Liver detoxifies (makes harmless) harmful substances, such as alcohol (has enzyme alcoholic dehydrogenase).
7. Secretes bile
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 vitamins A, D, E and K that are fat-soluble.
3. Liver forms and stores fat
4. Storage organ for the Vitamins A, D and B12
5 The liver serves as a storehouse for minerals such as iron.
6. The liver is able to convert glucose to glycogen that is then stored in the liver (It can also convert glycogen back into glucose when the body needs it).
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Liver
Gall bladder
Duodenum
Pancreas
Stomach
Bile
• 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 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 cells of the pancreas, secrete the hormones _____________ and ____________ that play an important role in controlling the blood ___________ (sugar) level. 33
duodenum
Langerhans
insulin glucagon
glucose
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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
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Pancreas
• Secretes• Pancreatic juice (containing digestive
enzymes)• Hormones: insulin and glucagon
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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 enzymeso carbohydrases to digest carbohydrates.o proteases to digest proteinso Lipases to digest lipids/fats
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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…
• The ________________ is a short intermediate tube that follows the duodenum. It leads into the 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.
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jejenum
ileum
– the ______________ on the outside.– the muscular region, assisting in peristalsis, made
up of:• o an outer layer of ___________________ muscles.• o an inner layer of _______________ muscles.• a ______________________ made up of connective
tissue with blood vessels, lymph vessels and nerves.• a ______________________ or mucous membrane
which is the Innermost layer. It is lined with columnar epithelium with goblet cells that secrete mucous.
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SEROSA
LONGITUDINALCIRCULAR
SUBMUCOSA
MUCOSA
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
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Small Intestine wall– the ______________ on the outside.– the muscular region, assisting in peristalsis,
made up of:• o an outer layer of ___________________
muscles.• o an inner layer of _______________ muscles.• a ______________________ made up of
connective tissue with blood vessels, lymph vessels and nerves.
• a ______________________ or mucous membrane which is the Innermost layer. It is lined with columnar epithelium with goblet cells that secrete mucous.
serosa
longitudinalcircular
Sub-mucosa
mucosa
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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.
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Villi
Outer wall
Inner wall
Pathway for Food
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VILLI
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HOW TO DRAW A VILLUS
ENLARGED
CAPILLARY NETWORK
TO LYMPHATIC SYSTEM
BRUNNER’S GLAND
LACTEAL
EFFERENT VESSELAFFERENT VESSEL
CRYPT OF LIEBERKUHN
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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 nutrients2. 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 intestinal wall.
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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 products of lipid digestion.
Simple Columnar Mucous epithelium with micovilli
A
B
C
D
E
F
GH
I
VENULE
ARTERIOLE
LACTEAL
CAPILLARY NETWORK
CRYPT OF LIEBERKUHNBRUNNER’S GLANDEFFERENT VESSEL
AFFERENT VESSEL
The lining of the villus contains simple columnar epithelium which contains:
• _______________ cells which secrete mucus, which serves as a lubricant and which is alkaline and protects the lining of the small intestine against acid chyme.
• __________________ which enlarge the surface area for absorption of digested foods.
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GOBLET
MICROVILLI
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
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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
FOOD ENZYME(S) PRODUCT WHERE (JUICE)1 CARBOHYDRATES1.1 STARCH AMYLASE
CARBOHYDRASE
1.2 MALTOSE MALTASE1.3 SUCROSE SUCRASE
1.4 LACTOSE LACTASE
1.5 CELLULOSE None Glucose
2. LIPIDS LIPASE
2. PROTEINS PROTEASE
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Mouth (saliva)Pancreas (juice)Small intestine
Small intestine
Small intestine
Bacteria in SI
Pancreas (juice)Small intestine
Stomach (gastric juice)Pancreas (juice)
Glycerol + 3 fatty acids
Amino acids
GlucoseGlucose + fructoseGlucose + galactose
Disaccharide
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Enzyme summary
Enzyme Substrate Product Where it is produced
Where it acts
Amylase Saliva Mouth
Pancreas Duodenum
Amino Acids
Fat
Small intestine
Small intestine
STARCH GLUCOSE
PROTEASE PROTEINS Duodenum
LIPASE GLYCEROLFATTY ACIDS
Pancreas
Pancreas Duodenum
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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:
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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
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Absorption: Villi
The fatty acids and glycerol go into one of these lymphatic vessels in the villus.
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.
Absorption of carbohydrates
• Glucose is the product of carbohydrate digestion and it is absorbed by diffusion, assisted by active transport (using a carrier molecule)
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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)
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Absorption of fats
Fatty acid-Bile Complex
FATTY ACIDS 1 FATTY ACIDS +BILE SALTS
LIPID DROPLETS BILE SALTS GLYCEROL 2 GLYCEROL
Columnar Epithelium LACTEAL
Glycerol Active transport across
cell
Fatty acids and glycerol, are absorbed as follows:• Fatty acids combines with bile salts to form a fatty acid-
bile salts complex so that they can diffuse through the epithelium into the lacteal.
• Glycerol is soluble and is actively absorbed into the lacteal.
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Hepatic Portal System
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Liver Functions
1. DEAMINATION OF EXCESS AMINO ACIDS Amino acids not used for the synthesis of proteins are deaminated
2. SECRETES BILE
4. LIVER FORMS AND STORES FAT
5. LIVER DETOXIFIES (MAKES HARMLESS) HARMFUL SUBSTANCES
6. STORAGE ORGAN FOR THE VITAMINS A, D AND B12
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Control of Blood Glucose
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Normal level of blood glucose Normal level of blood glucose
CORRECTIVE MECHANISM
NEGATIVE FEEDBACK MECHANISM
Blood glucose level rises
Blood glucose level drops
CORRECTIVE MECHANISM
NEGATIVE FEEDBACK MECHANISM
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.
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
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Digestion Products:• Proteins
• Carbo-hydrates
• 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
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Balanced Diet: Carbohydrate
67% Carbohydrates (sugar, sweets, bread, cakes)
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Protein
33% Protein (eggs, milk,
meat, poultry, fish)
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Fat
33% Fats (dairy products, oil)
• 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.
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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)
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• 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)
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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 grams of Protein
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BALANCED DIET• CARBOHYDRATES: 2/3 = 403 g• FATS: 1/6 = 86g• PROTEINS: 1/6 = 194 g
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2436 kJ in a big Mac Hamburger (of the 10 122 an athlete of 50kg needs)
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3/80 = 3.75%1/78 = 1.282%24/343 = 6.99%
235/10122 = 2.32%
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Obesity
This man is digging his own grave with his teeth
Malnutrition
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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.
Malnutrition
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MARASMUS• This is due to a general
lack of energy foods.• SYMPTOMS are:• Monkey-like face with
sunken eyes, thin body, tight skin, lethargy.
Malnutrition
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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.
Malnutrition
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BulimiaMalnutrition
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
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Effect of Saliva on Starch
An experiment will containThe factor being measured (SALIVARY AMYLASE)
No starch after 1 hour, all hydrolysed by amylase.IODINE STAYS BROWN
No hydrolysis. Starch remains. IODINE TURNS BLUE-BLACK
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– 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)
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