Transcript Animal Nutrition

Human Nutrition
WJEC Additional Science
Module 2
Animal Nutrition
• Learning Objectives (the big picture)
• By the end of this topic, you should be
able to answer the questions
– Why is digestion needed?
– How does the digestive system work?
– What happens to the end products?
Learning outcomes
• know that fats, made up of fatty acids and
glycerol, proteins, made up of amino acids,
and starch (a carbohydrate), made up of a
chain of glucose, in our food are insoluble.
They are broken down during digestion into
soluble substances so that they can be
absorbed through the wall of the small
intestine into the bloodstream.
• Consider the use of visking tubing as a
model gut and the limitations of the model.
Learning outcomes
• recognise and label on a given
diagram of the human digestive
system and associated structures: the
mouth, oesophagus/gullet, stomach,
pancreas, small intestine, large
intestine, anus and understand the role
of the following organs in digestion:
mouth, stomach, pancreas, small
intestine.
Learning outcomes
• know that during digestion, the breakdown
of large molecules into smaller molecules is
carried out by enzymes which are specific
for each type of molecule.
• know that the body cells need the digested
products of fats and carbohydrates to
provide energy whilst amino acids are
needed to build proteins in the body
Quick Revision
• A balanced diet must contain all the
essential nutrients in the correct amounts
and proportions.
• The nutrients needed are
–
–
–
–
–
–
–
Carbohydrate
Fat
Protein
Vitamins
Minerals
Fibre
Water.
Main Nutrients
Nutrient
Elements
present
Use in
body
Good food
sources
Carbohydrate Carbon,
Source of
energy
Rice, potato,
bread
Fats and oils Carbon,
Source of
energy
Insulation
Butter, milk,
cheese, egg
yolk
hydrogen,
oxygen
hydrogen,
oxygen
Protein
Carbon,
hydrogen,
oxygen,
nitrogen
Growth and Meat, fish,
tissue repair eggs, soya,
milk
What you really need to
remember!!
• Carbohydrates, fats and proteins are
all made up of the elements carbon,
hydrogen and oxygen
• Proteins always contain nitrogen and
sometimes sulphur
• One way to remember this is
– Carb O Hydrate
Carbohydrates
• Large carbohydrate molecules such as
starch and glycogen are made up of
long chains of smaller units, e.g.
glucose, which are held together by
chemical bonds
Fats
• Fats are made up of three fatty acids
and a glycerol
Proteins
• Proteins are made up of long chains of
amino acids
Food Tests
• What is the test for starch?
• What is the test for glucose?
• What is the test for protein?
• What is the test for fats?
• What does a positive result look like?
Carbohydrates
• Carbohydrates give us energy.
• Chemical elements – C, H and
O.
• Starch is made from simple
sugars.
Testing for glucose
1. Pour some glucose solution into a
test tube
2. Add a few drops of benedict's
solution
3. Heat in a water bath
Testing For Starch
• Put a few drops of
starch solution on a
spotting tile.
• Add a few drops of
iodine.
Proteins
• Proteins are needed for growth
and repair.
• Proteins are made from amino
acids
• Chemical elements – C, H, O,
N (and S)
Testing for Proteins
1. Put 2 ml of protein
solution in a test tube
2. Add 2ml of Biurets
reagent
Fats
• Fats are an energy store,
protecting vital organs and
providing insulation.
• Fats contain C, H and O
• Fats are made from a glycerol
molecule and three fatty
acids.
Testing for fat (the emulsion
test)
• Add a few drops of cooking oil into a
test tube
• Add 2cm3 ethanol and shake
• Add 2cm3 water and shake again.
Mystery Foods
• Test the three “mystery food” samples
– Which food substances are present in
each one?
Pupil activity
• Design a mind map to summarise the
information on basic nutrition
Main
Nutrients
fibre
vitamins
Nutrients
water
minerals
Learning Outcomes
• identify the gross structure of the
alimentary canal and associated
organs (mouth, oesophagus, stomach,
small intestine: duodenum and ileum,
large intestine: colon and rectum,
anus, pancreas, liver)
• define ingestion, digestion,
absorption, assimilation and egestion
What happens to the food
we eat?
The gut as a production line
What happens to the food we
eat?
• Ingestion
– Intake of food into the mouth
• Digestion
– Breaking down large, insoluble food
molecules into smaller soluble ones using
enzymes
• Absorption
– Digested food molecules pass across the
wall of the small intestine into the blood or
the lymph
• Assimilation
– Uptake of food molecules by cells
• Egestion
– Passing out of undigested food, in the
form of faeces, from the anus
• Deamination
– Removal of nitrogen containing part of an
amino acid as urea.
Pupil Activity
• Label the diagram of the digestive
system.
– Use the textbook supplied to help if
needed
– Design a table to link the structure and
function of different parts of the digestive
system.
mouth
tongue
Salivary glands
oesophagus
trachea
liver
stomach
Gall bladder
Small
Duodenum
intestine ileum
appendix
pancreas
colon
Large
rectum intestine
anus
Learning Outcomes
• define ingestion, digestion,
absorption, assimilation and egestion
• describe the functions of the
alimentary canal's various parts in
relation to ingestion, digestion,
absorption, assimilation and egestion
of food
Digestion
• Digestion is the breakdown
of large, insoluble food
molecules into small, soluble
food molecules so that they
can be absorbed into the
blood stream.
Digestion of Food
• The digestion of food can either be
mechanical or chemical.
• Mechanical digestion includes
– Chewing
– Action of muscles in oesophagus, stomach and small
intestine
• In chemical digestion enzymes catalyse the
breakdown of larger food molecules into
smaller food molecules.
Digestion in the mouth and
oesophagus
• Chewed food is mixed with saliva in the
mouth
• Saliva contains
– Amylase is an enzyme which starts to digest
starch into sugars (maltose)
– Mucus helps soften the food making it easier to
swallow
• The bolus travels down the oesophagus with
the aid of peristalsis
Peristalsis in the gullet
Digestion of Starch
• Take 10ml of 1% starch solution
– Test for starch
– Test for sugars
Action of amylase on starch
• Put a drop of iodine solution into all the wells
on a white spotting tile
• Add 10ml 1% starch solution and 10ml 1%
amylase solution to a test tube.
• Every minute, test the contents of the test
tube for starch.
• After 15 minutes – test the solution for the
presence of sugars
• Write a conclusion on your results
Learning Outcomes
• The significance of producing small,
soluble molecules
• describe:
– digestion in the alimentary canal
– the functions of a typical amylase,
protease and lipase, listing the substrate
and end-products
Digestion
• Digestion is the breakdown
of large, insoluble food
molecules into small, soluble
food molecules by enzymes,
so that they can be absorbed
into the blood stream.
Digestion
• Physical Digestion
– Increases the surface area of food
• Chewing in the mouth
• Churning food in stomach and small intestine
• Bile emulsifies fats – turns them into smaller
droplets with a larger surface area
Digestion
• Chemical Digestion
– Breakdown of large insoluble molecules
into smaller soluble ones
– Enzymes act as biological catalysts – they
speed up the process
– They work efficiently at body temperature
(37OC) and at a suitable pH
Digestive enzymes
• There are different types of digestive
enzyme
– Proteases break down proteins into amino
acids
– Lipases break down fats into fatty acids
and glycerol
– Amylase breaks down starch into maltose
(sugar)
• Maltose is then broken down by maltase to
form glucose
Summary – digestive enzymes
Enzyme
Site of action substrate End products
Amylase
Mouth,
duodenum
Starch
Maltose
Glucose
Protease
Stomach,
duodenum
Protein
Amino acids
fat
Fatty acids
glycerol
lipase
duodenum
Chemical Digestion
• Hydrogen carbonate ions
– Secreted by pancreas
– Neutralises acid, enabling enzymes in small
intestine to work
• Bile
– Produced by liver, stored in gall bladder, secreted
into small intestine
– Emulsifies fats (Larger surface area for enzymes
to work on)
Prep
• Surface area and digestion
– Read the information
– Answer questions 1- 3
– Answer question Ho2
• A snake swallowed a mouse whole. Explain
why it took several days to digest it.
Learning Outcomes
• define the term catalyst
• define enzymes as proteins that
function as biological catalysts
• describe the effect of changes in
temperature and pH on enzyme
activity
Enzymes Revision
• Are proteins
• Are produced by cells
• Change chemical substances into new
products
• Are “specific” to one substance
• Work best at their “optimum temperature”
(around 30 – 40oC)
• Work best at an optimum pH
Protein Digestion
• Protein digestion occurs in the stomach and
small intestine.
• Protease enzymes are produced by the
gastric pits in the stomach lining or by the
pancreas.
• In the stomach, hydrochloric acid is also
produced which provides the optimum pH
for trypsin to work
Protein Digestion
• Add 2ml of protein solution to three
test tubes.
• Number the test tubes 1, 2 and 3
1. Add 1ml HCl
2. Add 1ml Water
3. Add 1ml HCl
• Do not add the trypsin until last
1. Add 0.5ml water
2. Add 0.5ml trypsin
3. Add 0.5ml trypsin
Protein digestion
• Leave for 10 minutes
• Test each of the test tubes for the
presence of protein using Biurets
reagent.
• Explain your results.
Fat Digestion
• Milk does not dissolve in water, in the
digestive system, bile produce by the liver
(stored in the gall bladder) emulsifies fats to
give a larger surface area for enzymes to
work on.
• You are going to use phenolphthalein to
investigate the effect of bile on the
digestion of fat.
Fat Digestion
• Take 4 test tubes and number them 1,
2, 3 and 4.
• set up the test tubes as shown in the
table below.
Test tube
1
2
3
4
Milk
Bile
3 ml
0
3ml
0.5ml
3ml
1 ml
3ml
1ml
Water
1ml
0.5ml
0
0
Fat Digestion
• Add 5 drops of phenolphthalein to each test
tube
• Add sodium carbonate to each test tube
until the solution goes pink.
• Add 0.5ml of lipase to test tubes 1, 2 and 3.
• Add 0.5 ml water to test tubes 4.
• Observe your results. Try to explain what you
are observing.
Learning Outcomes
• define enzymes as proteins that
function as biological catalysts
• describe the effect of changes in
temperature and pH on enzyme
activity
Effect of temperature on
enzymes
• The optimum temperature for enzyme
controlled reactions is around 37oC
– Above optimum
• Slows reaction down
• Enzyme becomes denatured – enzyme loses it shape,
deforming the active site so that the substrate no
longer fits.
– Below optimum
• Slower reaction – lack of energy in molecules
Graph – effect of temperature
on the rate of enzyme activity
Effect of pH on enzymes
• pH of a solution is how acid or alkaline it is
• Most enzymes have optimum pH 7
• Exceptions
–
–
–
–
Pepsin
Salivary amylase
Catalase
Pancreatic amylase
pH2.0
pH 6.8
pH 7.6
pH 9.0
stomach
mouth
plants
duodenum
Effect of pH on enzymes
• An extreme pH can denature enzymes
– permanently altering the active site
Graph - Effect of pH on enzyme
activity
Learning Outcomes
• identify the small intestine as the region
for the absorption of digested food
• describe the significance of villi in
increasing the internal surface area
• describe the structure of a villus,
including the role of capillaries and
lacteals
What happens next?
Absorption in the ileum
• The small intestine is well designed for
absorption, it has
– Thin lining
– A good blood supply
– A very large surface area (about 9m2)
Villi
• Increase the surface area for absorption
• Each villus contains
– Blood capillaries that absorb glucose and amino
acids
– Lacteals which absorb fatty acids and glycerol
• Absorption is by
– Diffusion – thin lining only 1 cell thick
– Active transport – epithelial cells contain
mitochondria to provide energy
Absorption in the Villi
The Model Gut
A model of absorption
“the model gut”
Making a model gut
• Wash a 12cm length of visking
tubing (A) in warm water.
• Tie a knot in one end
• Fill the tubing with 10cm3 of
starch and amylase solution(B).
• Wash the outside of the tubing.
• Put it into a boiling tube
containing DI water (C)
– holding it in place with a rubber
band
C
B
A
Model Gut Results
• After 40 minutes
– Take a sample of the water in the boiling
tube
• Test the water for glucose
• Test the water for starch
Conclusions of the
experiment
• Draw conclusions from the experiment,
explaining what the results were, and
how the model gut represents the real
situation
• E.g. what does the water represent,
what does the Visking tubing
represent, etc.
Large intestine and the
elimination of waste.
• A watery mix of enzymes and
undigested food (mainly fibre) moves
into the colon.
• Water is absorbed back into the blood
stream.
• Faeces are compacted in the rectum
and egested through the anus.
Pupil Activity - Diagrams
• Use your notes and your textbooks to
help you label the diagrams.
• Complete for prep.
• There are key words and phrases in the
boxes beside the diagrams to help
you.
The end
What do
they think
they are
looking at?