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Human Nutrition

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Human Nutrition WJEC Additional Science Module 2 – PowerPoint PPT presentation

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Title: Human Nutrition


1
Human Nutrition
  • WJEC Additional Science
  • Module 2

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?

3
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.

4
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.

5
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

6
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.

7
Main Nutrients
Nutrient Elements present Use in body Good food sources
Carbohydrate Carbon, hydrogen, oxygen Source of energy Rice, potato, bread
Fats and oils Carbon, hydrogen, oxygen Source of energy Insulation Butter, milk, cheese, egg yolk
Protein Carbon, hydrogen, oxygen, nitrogen Growth and tissue repair Meat, fish, eggs, soya, milk
8
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

9
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

10
Fats
  • Fats are made up of three fatty acids and a
    glycerol

11
Proteins
  • Proteins are made up of long chains of amino acids

12
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?

13
Carbohydrates
  • Carbohydrates give us energy.
  • Chemical elements C, H and O.
  • Starch is made from simple sugars.

14
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

15
Testing For Starch
  • Put a few drops of starch solution on a spotting
    tile.
  • Add a few drops of iodine.

16
Proteins
  • Proteins are needed for growth and repair.
  • Proteins are made from amino acids
  • Chemical elements C, H, O, N (and S)

17
Testing for Proteins
  1. Put 2 ml of protein solution in a test tube
  2. Add 2ml of Biurets reagent

18
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.

19
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.

20
Mystery Foods
  • Test the three mystery food samples
  • Which food substances are present in each one?

21
Pupil activity
  • Design a mind map to summarise the information on
    basic nutrition

22
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23
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

24
What happens to the food we eat?
Ingestion Digestion Absorption Egestion
25
The gut as a production line
26
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

27
  • 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

28
  • 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.

29
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.

30
Salivary glands
mouth
oesophagus
tongue
trachea
liver
stomach
Gall bladder
pancreas
Small intestine
Duodenum
colon
Large intestine
ileum
rectum
appendix
anus
31
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

32
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.

33
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.

34
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

35
Peristalsis in the gullet
36
Digestion of Starch
  • Take 10ml of 1 starch solution
  • Test for starch
  • Test for sugars

37
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

38
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

39
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.

40
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

41
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

42
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

43
Summary digestive enzymes
Enzyme Site of action substrate End products
Amylase Mouth, duodenum Starch Maltose Glucose
Protease Stomach, duodenum Protein Amino acids
lipase duodenum fat Fatty acids glycerol
44
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)

45
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.

46
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

47
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

48
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

49
Protein Digestion
  • Add 2ml of protein solution to three test tubes.
  • Number the test tubes 1, 2 and 3
  • Add 1ml HCl
  • Add 1ml Water
  • Add 1ml HCl
  • Do not add the trypsin until last
  • Add 0.5ml water
  • Add 0.5ml trypsin
  • Add 0.5ml trypsin

50
Protein digestion
  • Leave for 10 minutes
  • Test each of the test tubes for the presence of
    protein using Biurets reagent.
  • Explain your results.

51
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.

52
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 3 ml 3ml 3ml 3ml
Bile 0 0.5ml 1 ml 1ml
Water 1ml 0.5ml 0 0
53
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.

54
Learning Outcomes
  • define enzymes as proteins that function as
    biological catalysts
  • describe the effect of changes in temperature and
    pH on enzyme activity

55
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

56
Graph effect of temperature on the rate of
enzyme activity
57
Effect of pH on enzymes
  • pH of a solution is how acid or alkaline it is
  • Most enzymes have optimum pH 7
  • Exceptions
  • Pepsin pH2.0 stomach
  • Salivary amylase pH 6.8 mouth
  • Catalase pH 7.6 plants
  • Pancreatic amylase pH 9.0 duodenum

58
Effect of pH on enzymes
  • An extreme pH can denature enzymes permanently
    altering the active site

59
Graph - Effect of pH on enzyme activity
60
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

61
What happens next?
62
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)

63
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

64
Absorption in the Villi
65
The Model Gut
  • A model of absorption

66
the model gut
67
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
68
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

69
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.

70
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.

71
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.

72
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