Title: For humans , starch constitutes a digestible carbohydrate , while cellulose is one of the indigestible carbohydrates that form a large part of the fiber , bulk , or roughage of our diets .Grass , leaves , and other plant material all of which are indiges
19. Carbohydrates Chapter 16
2CARBOHYDRATES
- Contain C, H, O only
- CXH2YOY CX(H2O)Y
- i.e hydrates of carbon
- most common names end in '-----ose'
3CarbohydratesGeneral Structural Features
- Usually 5/6 membered rings with C and one O
- Many -OH groups ? water soluble
(simple ones ) - ? easily broken down for energy
- (already partly
'oxidized')
4From Monosaccharides to Polysaccharides
- The root sacchar- comes from the Latin saccharum,
"sugar".
A monosaccharide is the smallest molecular unit
of a carbohydrate. Glucose, the prototypical
monosaccharide, is the most abundant organic
molecule on earth.
5- A disaccharide is a molecule formed from a
combination of two monosaccharides, eg. sucrose - A polysaccharide is a molecular chain (maybe
branched) of hundreds / thousands of mono-
saccharides, eg. cellulose
6Common Carbohydrates
Formula
Carbohydrate
Monosaccharides, C6(H2O)6 Glucose (blood sugar,
grape sugar, dextrose) C6H12O6
Fructose ( levulose )
C6H12O6 Galactose C6H12O6
Disaccharides, C12(H2O)11 Sucrose (table
sugar,beet sugar, cane sugar)
C12H22O11 Maltose (malt sugar)
C12H22O11 Cellobiose
C12H22O11 Lactose (milk sugar )
C12H22O11 Polysaccharides,
Cx(H2O)y Starch Cellulose
7Glucose a 2,3,4,5,6-pentahydroxy hexanal
C6H12O6 a(aldo)hexose
open chain
cyclic (6 mem. ring
pyran)
8Glucose single then soluble
9Polysaccharides the Glycosidic Linkage
glycosidic linkage
monosaccharides
starch 1,4 linkages cellulose
10STARCHES
- Plant
- ?Amylose -straight chain (200 ?-D glucose
units) - ? Amylopectin - branched every 25 units
(1000 ?-D glucose units) - ? Dextrins -partial breakdown of amylopectin
(food additives , paste , fabric finishes ) - Animal
- ? Glycogen
- -branches every12 units
- -short-term energy in body (liver muscle).
11More Branching Faster Breakdown
Amylopectin Glycogen
12Amylose Helical Structure
- Left hand helix (partial)
13Iodine test for Starch
- Helical structure of amylose holds the I3- ion
linear cellulose does not
14Carbohydrates The Most Common Energy Source
- Chemical Breakdown / Reaction Digestion
-
- Complex ? Dextrins ? Simple ? Mono-
-
-
- ? acetate(2C) CO2 H2O Energy
- NB. can be reversed, ie. glucose ? ? glycogen
H2O
H2O
H2O
(glucose)
(starch)
O2
15Starch Breakdown / Digestion
Complex Dextrins Small
Mono-
16Energy Sources Instant Blood
sugar(glucose) 1g/L or 20Cal or
30mins. Short Term Liver/Muscles(glycogen)
325g or 6 hrs. the more muscle,
the more glycogen any excess is converted into
fat Long Term Fat(adipose tissue) 20kg
or 35 days
17Nutritional / Dietary Carbohydrates Starch -
the digestible carbohydrate(for humans)
Simple - mono-/disaccharides, eg. sugars
Complex -seeds/roots of plants,
eg. grains(pasta), corn, potatoes, rice
Recommended - at least 55 of our Caloric
intake (10
sugar 45 complex) N A average - 20
sugar 25 complex!
18Cellulose - indigestible carbohydrate for
humans Soluble(pectins/gums) -
fruits(apples), grain husks
(oat
bran) Insoluble(fiber/bulk/roughage) - potato
skins, apple
peels, celery, lettuce Recommende
d - 30g/day NA average - 15g/day
19What is Dextrose?
- Dextrose (Blood sugar) is the form of glucose
that rotates the plane of polarized light in a
clockwise direction.
20What is invert sugar?
- Hydrolysis of ()sucrose (table sugar) produces
equal amounts of ()glucose and (-) fructose
(levulose). - But, fructose optical rotation is larger
(negatively) than glucose rotation is positively.
Hence, the resulting solution is levorotatory
(-). - Thus, start with only () then get (-) after
hydrolysis-so the net result of hydrolysis is
inversion of the direction of the optical
rotation - Honey is mostly invert sugar ie an equal mixture
of glucose and fructose
21Sucrose -gt Glucose Fructose (Invert)
sucrose(66)
sucrase (invertase)
D-glucose(52) (dextrose)
D-fructose(-92) (levulose)
22Maltose the basic unit of Starch
?(down) - linkage
requires maltase (humans gt yes)
23Cellobiose the basic unit of Cellulose
?(up) - linkage
requires cellobiase (humans gt no)
24Why Dietary Fibre? It's Indigestible!
- Beneficial statistical correlations for colon
cancer, obesity, diabetes, heart disease. - Acts as a sponge for water and other substances
- Functions as a physical 'cleaner'
- Soluble - can help lower cholesterol levels
- reduces rate of glucose absorption
- Insoluble - fills you up ?eat less fat
- 'cleans' folds in intestinal walls
- no physical damage to intestinal
walls - adsorbs/removes many 'nasties'
25Human Exploitation of Cellulose
Cellulose is a major component of grass, leaves,
wood, cotton(produced by photosynthesis). World
Biomass Production 1011 tons annually Present
Humans benefit indirectly by allowing
ruminants(cows, sheep) to digest cellulose
and convert it into protein which we eat.
26Enzyme Substrate like a Lock Key
Enzymes are huge protein molecules with intricate
but well-defined shapes. They are the catalysts
that bring about all the chemical reactions in
our bodies. For effective reactivity the molecule
must fit into the convolutions of the shape of
the enzyme. Much like a key must fit the tumblers
of a lock.
27Lactose Intolerance
Lactase is the enzyme that specifically breaks
the ?-1,4- linkage of lactose to produce
D-galactose and D-glucose. Infants have a highly
active form but 70 of adults have some lactase
deficiency. If lactose is not cleaved in small
intestine it passes to the colon and 1) absorbs
water or 2) is degraded by bacteria, resulting in
cramps, diarrhea, etc. About 10 of NA adults
permanently lose their lactase compared to 3 of
Danes and 97 of Thais.
28Lactose (milk sugar) a disaccharide
lactase H2O
D-galactose
D-glucose
4-O-(?-D-galactopyranosyl)-D-glucopyranose
29Solving the problem
30Sweetness Index
Substance Relative
Sweet Taste
Lactose
0.16 Maltose
0.33 Glucose
0.74 Sucrose
1.00 Fructose
1.73
(NB. Glucose Fructose Honey or Invert Sugar)
Aspartame
180 Saccharin
300
31Sucrose lots of OHs high water solubility
?-D-glucopyranosyl-? -D-fructofuranoside
32Refined Sugar
NA sugar consumption 1kg
(1750) (annually/person)
50 kg(1990) Per day 50,
000/365 136 grams per person/day
world-wide production gt80 million tons
(60 from cane 40 from beets)
Dangers
dumps too much
glucose into blood too quickly all other
nutrients(vitamins, minerals) are removed
33Everybodys Comfort Food !
Wow !
34An Informative Label ?! ..Not Likely
35Refined Sugar in some Processed Foods
Food
Sugar
Jello
83 Coffeemate
65 ShakeN Bake
50 Salad Dressing
30 Ketchup
29 Ice cream
21 Peaches(in syrup)
18 Peanut butter
9 Coca Cola
9
36Sugar in human blood
- Blood sugar is glucose (dextrose)
- It is the only fuel for the brain and the Central
nervous system (CNS) and supplies the E for basal
metabolism - For continuous supply, a concentration of 0.06 to
0.11 weight is maintained
37Control of Blood Sugar (normal 100mg/dL)
Too Low
(lt75mg/dL) hypoglycemia(fainting)
Too High
(gt150mg/dL) hyperglycemia/diabetes
38Urine test for diabetes
- Above 0.16 weight in blood , glucose seeps
through the kidneys into the urine
39Diabetes Mellitus
Type I (insulin dependent) 10 of all diabetics
(juvenile onset)
Type II (non-insulin dependent insulin receptors
in
cells have become inactivated by excess use of
sugar) 90 of all diabetics (formerly called
adult onset but now found in 10-12 year
olds!)
NB. Diabetes is
1) second only to trauma for leg amputation
2) leading cause of blindness in adults over 20
3) leading cause of kidney failure
4) almost triples risk of heart attack or
stroke
40Type 1 Diabetes
- Body produces virtually no insulin
- Thus insulin needed for treatment
- Absence of insulin causes uncontrolled lipolysis
of fat and severe wasting of body tissues,
eventually resulting in death
41Living with Type 2 Diabetes
- Body makes too little insulin or its effect is
resisted - In some cases insulin is needed
- sometimes controlled with a reduced sugar diet
- Loss of weight will cause an increase in the
number of insulin receptors, hence improved
condition
42Canadians Discover Insulin (1921)
- Frederick Banting and his assistant Charles Best
isolated insulin from the pancreas of dogs
(canine insulin) and administered it to Type 1
patients - Nobel Prize awarded to Banting and McLeod for
this work
43Structural Differences
- Porcine canine insulin are identical and have
50/51 amino acids in common with human insulin - Bovine insulin and human insulin have 48/51 amino
acids in common - Thus porcine insulin most often used
44Source of Human Insulin
- Patients who are allergic to these can now get
cloned Insulin marketed as the Drug Humulin
45Synthesis of Human Insulin
- Saran Narang (NRC Ottawa) 1930-2007
- Synthesised the proinsulin gene
- Enabled mass production of Humulin
- Via recombinant DNA
- Insulin is a protein
- 51 amino acids
- DNAgtRNAgtprotein
46Other molecules with sugar type structures
47Fake Fats
Simplesse - from egg white or milk proteins
Emulsified starch - in
Hellmans light mayonaisse
Emulsified protein - gelatin water
Olestra (200 million, by ProctorGamble) -
may cause cramps/diarrhea(?dehydration)
reduces absorption of vit. A, D, E, K (fat-
soluble
vitamins) into body
not digested available in USA since 1996 must
carry warning label not legal in Canada
48Olestra Sucrose Octa Palmitate
Not OH but OR (R OC-C16 (sat.
palmitate)
NB. At least 6OHs esterified to be non-metabolized
49Olestra Indigestible !
Olestra
a Triglyceride
50Chitin (an exoskeleton polymer)
?(D)-glucosamine
51Glucosamine
- A simple amino sugar C6H13NO5.
- Produced commercially by hydrolysis of crustacean
exoskeletons - Used in treatment of osteoarthritis
- Sold as a salt-either HCl or sulfate
- Typical dose up to 1.5gr/day
52 Glucosamine (3-aminoglucose)
53Blood Typing by Glycoprotein Antigens
Type A
acetylgalactosamine-galactose-acetylglucosamine-PR
O
fucose
Type B lactose-galactose-acetylglucosamine-PRO
fucose
Type O galactose-acetylglucosamine-PRO
fucose
54Chocolate - Covered Cherries
Cherries are first coated with sugar
paste(sucrose) sucrase(enzyme). After hardening
they are dipped in chocolate and stored. After
1-2 weeks the sucrose is hydrolyzed/split by the
sucrase into glucose fructose which dissolves
easily in the cherry juice.
Chemistry is Everywhere !
553 Cherry Blossom Questions
- One ingredient is called invertase .What is
another name for this? - Another ingredient is soy lecithin. What function
does it serve? - Another ingredient is modified vegetable oil
How has it been modified?
56Problem set 3
- Chapt 13 1
- Chapt 151,8,9,10,11,25,29
- Chapt 161,9,11,12,18