Transcript Intro_Carbohydrates

5 Animal Nutrients
The Body Owner’s
Handbook by Nick Arnold
Topic Outline
1. Biochemistry
a. Macromolecules
2. Carbohydrates
a. Definition
b. Classification
c. Formation of glycosidic bond
d. Test for reducing, non-reducing sugars and
starch
e. Principle source and dietary importance of
carbohydrates and fibre
3.
4.
5.
6.
7.
8.
9.
Proteins
Fats
Role of the liver in the metabolism of glucose and amino acids
Vitamins C and D
Minerals (calcium and iron)
Balanced diet
World food supply problems
Internet sites
1)http://www.biologylessons.sdsu.edu/classes/l
ab6/lab6.html - general overview of
chemicals of life
2)http://web.mit.edu/esgbio/www/lm/lmdir.html
- structure and function of chemicals of life
3)http://www.pbs.org/wgbh/pages/frontline/sho
ws/meat/safe/foodborne.html - Food-borne
diseases
THE NEED FOR FOOD
1. For growth
- synthesis of new protoplasm, cells and tissues
2. For repair or replacement of worn and damaged tissues
- replace red blood cells, skin
- repair wounds
3. As a source of energy
- Energy store in food is called potential chemical energy
- Released and used for:
chemical reactions that build complex molecules
activities, eg movement (kinetic energy), heartbeat
maintenance of body temperature (mammals, birds)
4. To maintain health and prevent deficiency diseases
Taking in useful substances = feeding or nutrition
A FOOD CHAIN
Nasty Nature by Nick Arnold
THE WAY PLANTS FEED:
Simple inorganic substances (CO2, H2O, minerals)
taken in by plants
Built up to complex organic materials (sugars)
AUTOTROPHIC NUTRITION = plants can make their
own food via photosynthesis
THE WAY ANIMALS FEED:
They feed on organic substances originally made by
plants.
This is called HETEROTROPHIC NUTRITION
CONDENSATION –
process whereby simpler substances built up to form a more
complex substance by the removal of a water molecule.
HYDROLYSIS – process whereby complex substance is broken
down into simpler substances by the addition of a water molecule.
COMPONENTS OF FOOD
3 main components: nutrients, fibre, water
NUTRIENTS: chemical substances in food that nourish the
body, i.e. provide energy and materials required
5 groups of nutrients:
- Carbohydrates, fats, proteins
required in large quantities
supply energy and materials to make new protoplasm
- Minerals, vitamins
required in smaller quantities
maintain normal metabolism, no energy value
BIOCHEMISTRY
(The study of chemicals in living organisms)
Biochemicals
Water
1. small MW
2. molecules interact with hydrogen bonds
Carbohydrates
Polymers
1. large MW
2. units of monomers
3. condensation rxn
Proteins
Lipids
Nucleic acids
Macromolecules
§ Giant molecules made from many repeating units
§ Polymers made up of basic units called monomers
Four types of macromolecules/ polymers:
1) Polysaccharides - made up of monosaccharides
2) Fats - made up of fatty acids and glycerol
3) Proteins - made up of amino acids
4) Nucleic acids - made up of nucleotides
2. Carbohydrates
http://opbs.okstate.edu/~Blair/Bioch2344/Chapter10/Ch
apter10.htm#Anchor-D-Fructose
a. Definition
- Substances that contain the elements
carbon, hydrogen and oxygen.
- General formulae: CnH2nOn
- The ratio of hydrogen to oxygen is 2:1
- Carbohydrates are made up of
monosaccharides.
b. Classification
 Carbohydrates are classified into
monosaccharides, disaccharides and
polysaccharides.
Monosaccharides
 Greek monos means single and sacchar
means sugars
 Common simple sugars have six carbon
atoms
 glucose - found in all animals
 fructose - found in plants but uncommon in
animals
 galactose - formed when milk sugar is
digested
galactose
Disaccharides
§ Complex sugars
§ Made up of two molecules of simple sugars
(monsaccharides)
§ Formed by condensation reaction and
involved the loss of a single water molecule
§ Resultant bond formed between the two
simple sugars is called glycosidic bond
§ Hydrolysis is the reverse of condensation
where water is added to break a disaccharide
into its constituent monosaccharides.
 Sucrose- made up of glucose and fructose
 Found in cane sugar, sugar beet and carrots
 Maltose - made up of two molecules of glucose
 Found in malted cereals, barley grains, and
sprouted grains
 Formed in the partial digestion of starch
 Lactose - made up of glucose and galactose
 Found in milk
Polysaccharides
 Macromolecule; polymers made up of several
hundred to several thousand monosaccharides
linked by glycosidic bonds.
 Process of joining the monosaccharides is called
polymerisation
 Two classes of polysaccharides:
 Storage polysaccharides (starch and glycogen) when hydrolysed/ broken down, supply sugars to
cells for energy production
 Structural polysaccharides (cellulose) - building
materials for structures that protect cells or even
whole organisms.
Starch
§ Made up of up to 200 glucose
molecules condensed together
§ Found in cereals, potato, tapioca
§ Not formed and stored in animals but in
plants
§ When starch is hydrolysed by amylase,
maltose is formed. Maltose is
hydrolysed by maltase to form glucose.
Glycogen
§ Made up of glucose molecules condensed
together and are highly branched
§ Storage form of carbohydrate in animals,
stored in liver and muscle cells of mammals
 When glucose is needed, glycogen is
converted to glucose by hormones
(glucagons)
unbranched
extensively
branched
Biology by Campbell, Reece & Mitchell
branched
Starch and glycogen are ideal storage
materials:
- They are insoluble in water, so does not
change the osmotic pressure in the cell.
- They are large molecules, so cannot
diffuse through cell membrane.
- They can be hydrolysed to glucose.
- They have compact shapes, so occupy
less space.
Cellulose
§ Made up of glucose molecules
condensed together
§ Main component of plant cell wall to
prevent the bursting of plant cells and
keep the cells turgid
§ Inert and few animals can digest it
Used to make cotton goods and a
constituent of paper.
STRUCTURAL FUNCTION
Parallel
arrangement of
unbranched
cellulose molecules
Biology by Campbell, Reece & Mitchell
Since both starch and cellulose are made of glucose
units joined together, why then only starch can be
digested in our bodies but not cellulose?
CELLULOSE
STARCH
Biology: Principles and Processes by
Roberts, Reiss & Monger
c. Formation of glycosidic bond
 A condensation reaction which involved
the loss of a water molecule
Glucose + Fructose
Condensation
(water lost)
Hydrolysis
(water added)
Sucrose
Test for reducing sugars
Name of test: Benedict’s solution Test
Benedict’s solution = copper (II) sulphate
in an alkaline solution
(blue)
Method:
1. Add 2cm3 of reducing sugar into a test
tube.
2. Add an equal volume of Benedict’s solution.
3. Shake and boil in a boiling water bath for
2 - 3 minutes.
Test for reducing sugars
Precautions to take when comparing samples
1) Same volume of Benedict's reagent
2) Same duration of heating time (3 mins) and
3) Same volume of sample used.
4) Place tubes into water bath only after the water in water bath
has boiled
NB:
Water level in water
bath must always be
above the solutions in
the test tubes
Results:
A brick-red precipitate will be formed.
Soluble blue copper (II) sulphate is
reduced by reducing sugar to form
insoluble copper (I) oxide which is a
brick-red precipitate
Principle of the test
Glucose is a reducing sugar. Cu2+ ions (blue) are
reduced to brick-red (Cu2O) precipitate.
The colours obtained can therefore range from
blue
green
Yellow
orange
increasing concentration
of reducing sugars
brick-red
Colour and amount of precipitate gives a rough
estimate of amount of reducing sugars present
It is a semi-quantitative test.
Control
Blue,
clear
Brick-red
opaque
Orange,
opaque
Green,
opaque
Blue,
clear
Increasing concentration of reducing sugars
Control
Remained
clear, blue
Red,
cloudy
Qty of RS: 4>2>5>1,3
Remained
clear, blue
Dark red,
opaque
Green, cloudy
Sensitivity of
Benedict’s Test
(Different amounts of glucose)
0.001% - Remained clear, blue
0.01% - Slightly cloudy, blue
0.1% - Slightly cloudy, red ppt
in blue solution,
1%
- Opaque, orange-red
10% - Opaque, reddish brown
Test for non-reducing sugars
Name of test: Non-reducing sugar Test
§ Not a specific test for non-reducing sugars.
§ Based on inability to give a positive result in
Benedict’s solution test.
§ The non-reducing is then hydrolysed by boiling with
dilute hydrochloric acid to break down the nonreducing sugars into its monosaccharides.
§ The mixture is then neutralized/ made alkaline before
performing the Benedict’s solution test.
Thus a non-reducing sugar is said to be present when
it shows a negative Benedict’s solution test and a
positive test after hydrolysis.
Method:
1. Add 2cm3 of non-reducing sugar into a test tube
2. Add 1cm3 of dilute hydrochloric acid.
3. Boil the mixture for 1 minute.
4. Cool
5. Carefully neutralize with sodium hydrogen
carbonate (check with ph paper) – be careful
because vigorous effervescence may occur
6. Carry out Benedict’s solution test.
Results:
A brick-red precipitate will be formed.
Non-reducing sugars (eg, sucrose)
Note that in Tube 3,
sucrose did not reduce
the copper ions in the
Benedict's solution. It
remained blue and
clear.
Test for starch
Name of test: Iodine starch Test
§ Iodine solution or iodine in potassium iodide
solution
Method:
1. Add 2cm3 of 1% starch solution into a test
tube
2. Add a few drops of iodine/ KI solution
3. Or add a few drops of iodine/ KI solution to
the solid form of starch
Results:
A blue-black colouration is formed.
Starch granules
Potato stained with I/KI
X 100
Potato stained
with I/KI X 200
The same test when done with onion epidermis.
100x
magnification
Onion stained with I/KI X 100 - The nuclei of these
cells are light brown in this photograph. The numerous
starch granules seen in potatoes are absent.
Principle source and dietary importance of
carbohydrates and fibre
 http://www.nutramed.com/nutrition/carbohydrates.htm - detailed descriptions
of carbohydrates and fibre in diet
 http://www.americanheart.org/presenter.jhtml?identifier=4471
 Principle source of carbohydrates and fibre
 Carbohydrate intake should come mainly from
complex carbohydrates - vegetables, fruits and
grains - rather than the simple carbohydrates found
in sugars. Complex carbohydrates add more fiber,
vitamins and minerals to the diet than foods high in
refined sugars. Foods high in complex
carbohydrates are usually lower in calories,
saturated fat and cholesterol. The American Heart
Association recommends 25-30 grams of fiber per
day.
Balanced Food pyramid
 Which foods are sources
of complex
carbohydrates?
 Starches - Flour, bread,
rice, corn, oats, barley,
potatoes, legumes, fruits
and vegetables
 Fiber - Insoluble: wholewheat breads and cereals,
wheat bran, cabbage,
beets, carrots, Brussels
sprouts, turnips, cauliflower
and apple skin (pectin)
 Fiber - Soluble: oat bran,
oats, legumes, citrus fruits,
strawberries, apple pulp,
psyllium, rice bran and
barley
 Which foods are sources of simple carbohydrates?
 Sucrose - Table sugar, brown sugar, confectioners sugar, raw
sugar and turbinado
 Glucose - Dextrose, corn syrup and glucose syrup
 Fructose - Fruits, vegetables and honey
 High fructose corn syrup - Liquid sweetener that contains 4290 percent fructose
 Honey - Made up of glucose, fructose and water
 Sugar alcohols - Sorbitol, mannitol, xybitol
 Lactose - milk and milk products
 Maltose, dextrose - cereals and some baked goods
 Dietary importance of carbohydrates
– Main source of energy
– To form supporting structures eg cellulose
cell walls in plants
– To be converted to other organic
compounds such as amino acids and fats
– For the formation of nucleic acids (DNA)
– To synthesize lubricants eg mucus which
consists of a carbohydrate and a protein
– To produce the nectar in some flowers.
DIETARY FIBRE (ROUGHAGE)
- Cell walls of plants consist mainly of cellulose
- No enzymes to digest cellulose
- Cellulose is not absorbed into the bloodstream
- Reaches the large intestine (colon)
- Undigested part of diet = fibre or roughage
- Egested in the faeces
Functions of fibre
1. Fibre prevents constipation.
Fibre + bacteria add bulk to contents of colon
Help it to retain water
Softens the faeces
Reduces time for undigested residues to pass out
2. Fibre helps peristalsis.
Peristalsis moves food along digestive tract
Harder, indigestible food stimulates muscles to
contract more than soft food
Sources: fruits, vegetables, bran, wholemeal bread
In short…..
Biology by
Jones & Jones