DIGESTION

1
DIGESTION

• ENZYMES
• DIET

2
ENZYMES

• Enzymes are proteins
• They are biological catalysts
• Catalysts are substances which speed up the rate
  of a chemical rxn without being used up. Hence
  they will be available for other rxns.

3

• Human saliva contains an enzyme called amylase.
  This enzyme helps to turn starch into a sugar
  called maltose.
• When you swallow a mouthful of food, the amylase
  stops working because it is much too acid in the
  stomach (pH 2).
• Amylase works best in neutral or slightly
  alkaline conditions, i.e. at about pH 7.
• When your food gets into the small intestine,
  more amylase is made by the pancreas and this
  turns the remaining starch into maltose.
• Another enzyme (maltase) turns all this maltose
  into glucose. Glucose is then absorbed into the
  blood.

4
TYPES OF ENZYMES
amylase
5

• Digestive enzymes are enzymes that break down
  food into usable material. The major different
  types of digestive enzymes are
• Amylase breaks down carbohydrates, starches,
  and sugars which are prevalent in potatoes,
  fruits, vegetables, and many snack foods
• lactase breaks down lactose (milk sugars)
• sucrase digests complex sugars and starches
• maltase digests disaccharides to
  monosaccharides (malt sugars)

6

• Protease breaks down proteins found in meats,
  nuts, eggs, and cheese
• pepsin breaks down proteins into peptides
• peptidase breaks down small peptide proteins to
  amino acids
• trypsin derived from animal pancreas, breaks
  down proteins
• Lipase breaks down fats found in most dairy
  products, nuts, oils, and meat

7
Some enzymes that digest food in the
gut(substances in bold are end products that can
be absorbed into the blood)
8
HOW ENZYMES WORK

• Enzymes have an active site. This is part of the
  molecule that has just the right shape and
  functional groups to bind to one of the reacting
  molecules.
• The reacting molecule that binds to the enzyme is
  called the substrate.
• An enzyme-catalysed reaction takes a different
  'route'. The enzyme and substrate form a reaction
  intermediate.
• Its formation has a lower activation energy than
  the reaction between reactants without a
  catalyst.

9

• A simplified equation
• Route A reactant 1 reactant 2  
  product    
• Route B
• reactant 1 enzyme     intermediate
   
• intermediate reactant 2     product
  enzyme
• So the enzyme is used to form a reaction
  intermediate, but when this reacts with another
  reactant the enzyme reforms.

10

• Animation http//www.bbc.co.uk/schools/gcsebitesi
  ze/science/add_aqa/enzymes/enzymes1.shtml
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__how_enzymes_work.
  html

11
Reaction profiles uncatalysed and
enzyme-catalysed
Uncatalysed reaction
Enzyme-catalysed reaction
Intermediate formed between enzyme and one or
more reactant molecules
reactants
exergonic reaction
products
Course of reaction
12
no enzyme present
enzyme present
Intermediate enzyme/reactant 1
reactant 2
reactant 1 reactant 2
enzyme
products
enzyme
Course of reaction
13
FACTORS AFFECTING ENZYME ACTIVITY

• TEMPERATURE
• As the temperature rises, reacting molecules of
  substrate enzyme have more and more kinetic
  energy. This increases the chances of a
  successful collision and so the rate increases.
• There is a certain temperature at which an
  enzyme's catalytic activity is at its greatest.
  This optimal temperature is usually around human
  body temperature (37.5 oC) for the enzymes in
  human cells.
• Above this temperature (usually over 40 oC)the
  enzyme structure begins to break down/lose their
  shape (denature) since at higher temperatures
  intra- and intermolecular bonds are broken as the
  enzyme molecules gain even more kinetic energy.

14

• This can be seen when an egg is boiled.
• Egg white is protein, turns from a clear runny
  liquid into a white solid as the heat denatures
  the protein.
• NB Some bacteria may have an optimum temperature
  of 10 oC or 75 oC (those in hot springs)
• Enzymes from plants have optimum temperatures
  around 28 30 oC

15
Graph showing the Effect of temperature on enzyme
activity
16
(No Transcript)
17

• pH
• Each enzyme works within quite a small pH range.
  There is a pH at which its activity is greatest
  (the optimal pH).
• Most human enzymes are their correct shape pH
  of 7
• This is because changes in pH can make and break
  intra- and intermolecular bonds, changing the
  shape of the enzyme thus the active site can no
  longer fit the substrate and, therefore, its
  effectiveness.

18

• Pepsin has an optimum pH of 2 since it works best
  in acidic conditions of the stomach.

19

• SUBSTRATE CONCENTRATION
• The rate of an enzyme-catalysed reaction depends
  on the concentrations of enzyme and substrate. As
  the concentration of either is increased the rate
  of reaction increases (see graphs).
• For a given enzyme concentration, the rate of
  reaction increases with increasing substrate
  concentration up to a point, above which any
  further increase in substrate concentration
  produces no significant change in reaction rate.

20

• This is because the active sites of the enzyme
  molecules at any given moment are virtually
  saturated with substrate. The enzyme/substrate
  complex has to dissociate before the active sites
  are free to accommodate more substrate. (See
  graph)
• Provided that the substrate concentration is high
  and that temperature and pH are kept constant,
  the rate of reaction is proportional to the
  enzyme concentration. (See graph)

21
(No Transcript)
22
DIET

• Animals are heterotrophic i.e. they depend on
  other organisms for food.
• Term diet refers to food an animal eats daily.
• What is a balanced diet?
• One that contains carbohydrates, lipids,
  proteins, vitamins, mineral salts, fibre/roughage
  and water in the correct amounts and proportions.

23
VITAMINS MINERALS

• Vitamins organic substances which help control
  metabolism
• A few are produced by our bodies whereas the rest
  come from the food we eat.
• Some (like Vitamin K) are produced by bacteria in
  our intestines. Vitamin K helps blood to clot.
• Some minerals are important for growth repair
  of our bodies, others control metabolism.

24

• We need small amounts of minerals from our food
  for good health.
• Calcium is an important mineral. It is needed for
  strong bones teeth for blood to clot.
• An adult needs about 1.1g of Ca a day.
• An adult needs 16mg of iron a day.
• See tables on pages 64 66 Atwaroo and pages
  72 73 in Chinnery
• (NB Vitamins are organic substances made by
  plants animals while minerals are inorganic
  elements that come from soil water are
  absorbed by plants animals e.g. calcium)

25
WATER

• Our body has about ? (70) water.
• Why is it important?
• It is important for chemical rxns (solvent).
• It is the solvent in which waste matter is
  transported passed out of the body in solution.
• Water in blood and lymph fluids is used to
  transport materials around our bodies.
• It keeps the body cool.

26

• We need 2 ½ litres of water daily.
• If we dont get enough water we become dehydrated
  and cellular processes cant occur.
• How do we gain lose water?
• We can only survive a few days w/o water.

27
FIBRE

• What is the source of fibre?
• Fibre in our diets come from plants.
• Soluble fibre dissolves in water
• Insoluble fibre does not dissolve but holds water
  swells up with water.
• Soluble fibre comes from fruit pulp, vegetables,
  oat bran dried beans
• Insoluble water comes from cellulose of plant
  cell walls husks that cover wheat, rice other
  grains.

28

• Insoluble fibre adds to the bulk of undigested
  food passing through intestines maintains
  peristalsis by giving muscles something to push
  against.
• Fibre can also reduce the amount of fat absorbed
  from food this in turn reduces the risk of
  bowel cancers.
• A lack of fibre causes constipation which can
  lead to bowel cancer in the long term.

29
MEET YOUR FAMILY
30
How much food do we need in a balanced diet?

• Every day, a person uses energy (E).
• The amount used depends on age, gender, where you
  live and activities done.
• Food supplies us with energy.
• The amount of E in food is measured in kilojoules
  (kJ).
• Men need more E than women.
• Kids young adults need a lot of E. Why?

31

• People who exercise or are active need more than
  those with sedentary lifestyles.
• People who live in cold climates burn more E and
  thus eat more than those in warmer climates. Why?
• See charts on page 67 Atwaroo and pages 70 71
  (Table 5.1) in Chinnery

32
The 5 food groups recommended daily intake of
each
33
The average daily energy requirements are 2000
kcal for women and 2500 kcal for men
34
Effects of an unbalanced diet

• Malnutrition means bad nourishment.
• It results from an unbalanced unhealthy diet.
• Who are malnourished? What does it mean?
• When dont get enough food, or not getting enough
  variety of food or eating too much food.

35
Gout is a condition characterized by an abnormal
metabolism of uric acid. People with gout either
produce too much uric acid, or more commonly,
their bodies have a problem in removing it.
36
Vegetarian diets

• Eat mainly foods from plants.
• This diet is chosen for many reasons against
  cruelty to animals, religion, think it is
  healthier.
• Must ensure that they have a balanced diet. Why?
• This diet has more fibre, less saturated fat
  cholesterol less high-energy food.
• Less likely to be overweight
• Have lower risk of heart disease, diabetes and
  some types of cancers

37

• Vegans dont eat any food derived from animals
  including honey.
• Special care should be taken if children are
  being brought up on a vegetarian diet. Why?
• Parents must ensure that the child has a wide
  range of foods in the diet with plenty of
  protein, minerals and vitamins.

38
DIGESTION

• Absorption small molecules are absorbed into
  the blood.
• Digestion break down of large molecules into
  smaller ones
• Ingestion food is taken into the alimentary
  canal
• Egestion food could not be digested or absorbed
  is removed from the body.

39
(No Transcript)
40

• Mechanical vs. chemical digestion
• Mechanical large pieces are broken up by teeth
  into smaller bits and by churning of alimentary
  canal.
• Chemical once the food is broken up, the large
  molecules are further broken up into small ones
  i.e. there is a chemical change from one molecule
  to the next. Enzymes are involved in this process.

41
ROLE OF TEETH

• Read sections on teeth in Atwaroo and Chinnery.
• Learn different types of teeth their functions.
• Draw diagram of tooth and annotate parts of
  teeth.
• Summarise role of teeth in notebook.
• Learn importance of dental hygiene.

42
THE DIGESTIVE SYSTEM

• Name the parts of the digestive system.
• Do you know what they do?
• Where does digestion begin?
• Where does it end?

43
THE DIGESTIVE SYSTEM

• The alimentary canal is a long muscular tube
  which runs from the mouth to the anus.
• This along with the liver and pancreas makes up
  the digestive system.
• The wall of the alimentary canal contains muscles
  which contract relax to make food move along.
• This movement along the canal peristalsis.

44

• The alimentary canal contains special muscles
  which hold food in one part of the canal until it
  is ready to move to another part of the canal.
  These muscles are called sphincter muscles.
• Movement along the canal is aided by the
  secretion of mucus which are made by goblet
  cells.

45
(No Transcript)
46
IN THE MOUTH

• Digestion begins in the mouth
• After the food is broken up by the teeth, the
  food is mixed with saliva formed into a
  bolus/ball.
• The saliva contains water, mucus amylase
  enzyme.
• The water dissolved the food allowing us to taste
  it.
• The mucus binds the chewed food together helps
  it to slide easily down the oesophagus

47

• Amylase begins to digest starch to maltose.
  Hence, this is the first area for carbohydrate
  digestion.
• The tongue helps roll the bolus which exits the
  mouth into the oesophagus via swallowing.

48
(No Transcript)
49
(No Transcript)
50

• Draw diagram of digestive system and annotate
  parts.
• IMPORTANT Take note of any enzymes in each organ
  and their functions in your annotations.
• Note functions of liver in both books (pg 78 79
  Atwaroo 83, 148, 149 in Chinnery) and write
  summary in notebook.

51

• Digestion animation http//www.bing.com/videos/wa
  tch/video/once-upon-a-time-life-the-digestion-2-of
  -3/11636c0441ecd26b9baa11636c0441ecd26b9baa-257804
  009974?qanimation20with20digestionFROMLKVR5G
  T1LKVR5FORMLKVR8
• Check this site on digestion http//www.bbc.co.uk
  /schools/ks3bitesize/science/organisms_behaviour_h
  ealth/diet_drugs/revise1.shtml

52
REFERENCES

• http//kvhs.nbed.nb.ca/gallant/biology/human_diges
  tive_system.jpg
• http//wgu.educommons.net/liberal-arts/nutrition-n
  uc1/a44.html/digestion-map
• http//sun.menloschool.org/dspence/biology/chapte
  r29/chapt29_4.html
• http//www.eatologies.com/wp-content/uploads/2009/
  02/baby_blues1.gif
• Enzyme animation http//highered.mcgraw-hill.com/s
  ites/0072495855/student_view0/chapter2/animation__
  how_enzymes_work.html
• http//www.rsc.org/education/teachers/learnnet/cfb
  /enzymes.htm
• http//www.enzymestuff.com/basicswhichenzyme.htm
• http//click4biology.info/c4b/6/hum6.1.htm
• http//www.courseworkbank.co.uk/GCSE/Biology_Cours
  ework/Enzymes/
• Experiments http//www.biotopics.co.uk/nutrition/a
  mylex.html
• http//users.rcn.com/jkimball.ma.ultranet/BiologyP
  ages/E/Enzymes.html
• http//www.fhs.d211.org/departments/science/bgraba
  /AP20Handouts/AP20BIO20CHEM20UNIT/Bio44920Enz
  ymeExper.BWG.pdf
• http//www.purchon.com/biology/enzymes.htm
• http//www.besthealth.com/besthealth/bodyguide/r
  eftext/html/dige_sys_fin.html
• http//users.rcn.com/jkimball.ma.ultranet/BiologyP
  ages/G/GITract.html
• http//www.guam.net/pub/sshs/depart/science/mancus
  o/apbiolecture/32_DigestionNut/DigestionNutrition.
  htm

53

• http//library.thinkquest.org/J0112390/digestive_s
  ystem.htm
• http//www.bing.com/videos/watch/video/once-upon-a
  -time-life-the-digestion-2-of-3/11636c0441ecd26b9b
  aa11636c0441ecd26b9baa-257804009974?qanimation20
  with20digestionFROMLKVR5GT1LKVR5FORMLKVR8
• http//www.cchs.net/health/health-info/docs/1600/1
  699.asp?index7041
• http//digestive.niddk.nih.gov/ddiseases/pubs/yrdd
  /
• http//library.thinkquest.org/J0112390/digestive_s
  ystem.htm
• http//www.bbc.co.uk/schools/gcsebitesize/science/
  add_aqa/enzymes/enzymes_and_digestion1.shtml
• http//www.bbc.co.uk/schools/ks3bitesize/science/o
  rganisms_behaviour_health/diet_drugs/revise1.shtml
  
• Vitamins minerals http//kidshealth.org/teen/foo
  d_fitness/nutrition/vitamins_minerals.html