Sunday, March 15, 2015
CARBOHYDRATES
Includes
- sugars
- glycogen
- starches
- cellulose
- Large diverse group of organic compounds.
- Represent only 2 - 3 % of total body mass.
MAIN FUNCTION
1. As a source of chemical energy for generating ATP needed to drive metabolic reactions.
2. A few are used for building structural units.
eg. deoxyribose
- a type of sugar that is a building block of DNA.
ELEMENTS FOUND IN CARBOHYDRATES
CARBON
HYDROGEN
OXYGEN
The ratio of hydrogen to oxygen atom is usually 2 : 1
the same as in water.
THE NAME CARBOHYDRATES
- WATERED CARBON
Carbohydrates generally contain 1 water molecule for each carbon atom.
3 MAJOR GROUPS OF CARBOHYDRATES
1. MONOSACCHARIDES
2. DISACCHARIDES
3. POLYSACCHARIDES
Monosaccharides and disaccharides are simple sugars.
1. MONOSACCHARIDES
mono = one
sacchar = sugar
- Simple sugars
- Contain 3 -7 carbon atoms.
- Designated by names ending in - ose
- with a prefix that indicates the number of carbon atoms.
eg
Trioses - monosaccharides with 3 carbon atoms.
Tetroses - monosaccharides with 4 carbon atoms.
COMMON MONOSACCHARIDES
1. Glucose - The main blood sugar
2. Fructose - Found in fruits.
3. Galactose- In milk sugar
4. Deoxyribose - In DNA
5. Ribose - In RNA.
2. DISACCHARIDES
di = 2
-molecule formed from combination of 2 monosaccharides by dehydration synthesis.
A. SUCROSE / TABLE SUGAR
- molecules of monosaccharides glucose and fructose combine to form a molecule of disaccharide sucrose.
C12 H22 O11
not C12 H24 O12
- Because a molecule of water is removed when 2 disaccharides combine.
B. LACTOSE/ MILK SUGAR
- Glucose + Galactose.
3. MALTOSE
- Glucose + Glucose.
Disaccharides can also be split into smaller simple molecules
-by hydrolysis
eg. A molecule of sucrose may be hydrolysed into glucose and fructose by the addition of water.
ARTIFICIAL SWEETENERS
-Much sweeter than sucrose.
- Have fewer calories.
- Do not cause tooth decay.
3. POLYSACCHARIDES
Tens or hundreds of monosaccharides join through dehydration synthesis reactions.
- usually insoluble in water.
- Do not taste sweet.
eg .
1. Glycogen
3. Galactose- In milk sugar
4. Deoxyribose - In DNA
5. Ribose - In RNA.
2. DISACCHARIDES
di = 2
-molecule formed from combination of 2 monosaccharides by dehydration synthesis.
A. SUCROSE / TABLE SUGAR
- molecules of monosaccharides glucose and fructose combine to form a molecule of disaccharide sucrose.
C12 H22 O11
not C12 H24 O12
- Because a molecule of water is removed when 2 disaccharides combine.
B. LACTOSE/ MILK SUGAR
- Glucose + Galactose.
3. MALTOSE
- Glucose + Glucose.
Disaccharides can also be split into smaller simple molecules
-by hydrolysis
eg. A molecule of sucrose may be hydrolysed into glucose and fructose by the addition of water.
ARTIFICIAL SWEETENERS
-Much sweeter than sucrose.
- Have fewer calories.
- Do not cause tooth decay.
3. POLYSACCHARIDES
Tens or hundreds of monosaccharides join through dehydration synthesis reactions.
- usually insoluble in water.
- Do not taste sweet.
eg .
1. Glycogen
- Made entirely of glucose monomers linked to 1 another in branching chains.
- A limited amount of carbohydrates is stored as glycogen in liver and skeletal muscles.
2. Starches
- Formed from glucose by plants.
- Are found in food such as pasta, potatoes.
- Are the major carbohydrate in the diet.
3. Cellulose
- Formed from glucose by plants.
- Cannot be digested by humans.
- But does provide movement of food through intestine.
- Provide bulk to help eliminate feces.
Like disaccharides, polysaccharides such as glycogen and starch can be broken down in to monosaccharides through hydrolysis reaction.
eg.
When blood glucose level falls
Liver cells break down glycogen into glucose
Release it into blood
Making it available to body cells.
Which breaks it down to synthesis ATP.
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