Biomolecules: Carbohydrates Flashcards
Main elements in Carbohydrates
Carbon, Hydrogen, Oxygen 1:2:1 ratio
Carbohydrate means hydrate (water of) carbon aqueous Reflects the 2:1 ratio of hydrogen to oxygen
Examples of carbohydrate
sugars, starches, glycogen, cellulose, chitin
Function of sugars and starches
Sugars and starches are energy sources for cells
Function of cellulose and chitin
indigestible and act as structural component
Importance of carbohydrates
- Constitute the structure. of cells and tissues
- Participate and regulate metabolic reactions
- Transmit info
- Provide energy
Glucose
One sugar unit - Monosaccharides e.g. glucose for metabolic fuel
C6H12O6
Most abundant, a hexose sugar
Oxidised by the cell in cellular respiration
Used as a compound in the synthesis of other compounds such as amino acids and fatty acids
Mechanisms have evolved to keep it at a relatively constant level in the blood
Diabetes is a breakdown of the mechanism
Glycosidic Bond- Joins the sugars together
Monosaccharides can join together to create polymers of Disaccharides and Polysaccharides
Common Disaccharides
Sucrose, Lactose, Maltose
Sucrose
Glucose alpha (1-2) fructose. From cane or beet and hydrolysed by the enzyme Invertase an equimolar mixture of glucose(1 mole) and fructose(1 mole)
Lactose
Galactose Beta (1-4) glucose. Occurs in milk and hydrolysed by lactase or Beta Galactosidase. Lactose intolerance is nausea pain, cramps, diarrhoea due to the osmotic effects when lactose is built up in the ileum.
Maltose
Glucose alpha (1-4) glucose. Homodimer of glucose units. Occurs as a by- product of starch hydrolysis. Degraded to glucose by Maltase.
Polysaccharides
Means ‘many sugars’
1000s of mono rings joined by glycosidic linkages usually glucoses
Most abundant carbs in nature
E.g. starches, glycogen, cellulose, chitin
Long chained or branched
Enzymatic or acid hydrolysis during digestion will release mono
Homopolysaccharides many of the same monosaccharide e.g. Glucans Mannans
Storage Polysaccharides
Plants - starch two forms of starch alpha amylose and amylopectin
Animals - Glycogen
Deposited as granules in the cytoplasm
Starch
Homopolymer of alpha Glucose units joined by glycosidic bonds
Alpha Amylose
- a long unbranched chain of glucose units linked by alpha (1-4) bonds
- Not water soluble but forms hydrated micelles *
- In the micelles the polymer from a helical coil
Amylopectin
- highly branched polymer,
- branch length 24-30 glucose residues,
- backbone linkages = alpha (1-4)
- branch points = alpha(1-6)