Carbohydrates Flashcards
(24 cards)
What elements do carbohydrates contain?
Carbon, hydrogen and oxygen
What are the main functions of carbohydrates in living organisms?
- energy supply
- energy storage
- structural component
- cellular recognition
- building blocks for biological molecules
What are pentose sugars?
Sugars containing 5 carbon atoms (e.g ribose and deoxyribose)
What are hexose sugars?
Sugars containing 6 carbon atoms (e.g glucose, fructose and galactose)
What is the formula of glucose?
C6 H12 O6
What is the difference between alpha and beta glucose?
Alpha glucose = OH group is on bottom of carbon 1
Beta glucose = OH group is on top of carbon 1
What features help glucose function as an energy source?
Soluble = hydroxyl groups can form H bonds with H2O so can be transported around organisms
Bonds store lots of energy = energy released when the bonds are broken
What is maltose made up of?
Glucose and glucose
What is sucrose made up of?
Glucose and fructose
What is lactose made up of?
Glucose and galactose
How are glucose polysaccharides formed via condensation reaction?
When 2 monosaccharides join a hydroxyl group (OH) of 1 monosaccharide reacts with a hydroxyl group (OH) of another monosaccharide
a glycosidic bond (usually between C1 and C4) is formed and a H2O is released
How are glucose polysaccharides broken down via hydrolysis reaction?
When a H2O molecule is added to a disaccharide the glycosidic bond is broken to release the 2 monosaccharides
What are polysaccharides and give an example?
Complex carbohydrates made up of monosaccharides joined via glycosidic bonds
e.g starch, glycogen and cellulose
What is starch and what is it’s function in plants?
Polysaccharide used by plants to store excess glucose so can be hydrolysed back into glucose when plants require energy
starch chains are made up of amylose and amylopectin
What is amylose?
Long unbranched chain of alpha-glucose joined by 1-4 glycosidic bonds
angles of bonds cause the chain to coil into a helix to make a compact structure for storage
What is amylopectin?
Long branched chain of alpha-glucose joined by both 1-4 and 1-6 glycosidic bonds
side branches allow enzymes to hydrolyse alpha-glucose monomers easily to provide energy rapidly
What features of starch allow it to function as an energy store and how?
Insoluble = doesn’t affect water potential (doesn’t cause osmosis in cells)
Large = can’t diffuse out of cell
Side branches = allow rapid hydrolysation of glycosidic bonds releasing glucose rapidly
Coiled = lot’s of glucose can be stored in a small space
Easy hydrolysis = glycosidic bonds are easily hydrolysed to release a-glucose monomers for respiration
What is glycogen?
Polysaccharide used by animals to store excess glucose so can be hydrolysed back into glucose when animals require energy
made up of many alpha-glucose monomers joined via 1-4 and 1-6 glycosidic bonds to form highly branched chains
What features of glycogen allow it to function as an energy store and how?
Insoluble = doesn’t affect water potential (doesn’t cause osmosis in cells)
Compact = lot’s of glucose can be stored in a small space
Highly branched = enzymes can easily hydrolyse the glycosidic bonds to rapidly release glucose
Large = can’t diffuse out of cells
Easy hydrolysis = glycosidic bonds are easily hydrolysed to release a-glucose monomers for respiration
What is cellulose?
Polysaccharide formed from b-glucose where every other b-glucose molecule is inverted by 180°
primarily provides structural support for plant cell walls
Why is every other b-glucose in cellulose rotated 180°?
if 2 beta-glucose monomers line up next to each other the OH groups on carbon 1 and 4 are too far from each other to react
flipping every other b-glucose brings the OH groups close enough together to react
How are b-glucose chains arranged in cellulose?
When many b-glucose monomers join together they form long, straight, unbranched chains
alternating inversion of the b-glucose molecules allows for H+ bonds to form between individual chains (huge number of H bonds provides great strength)
What are cellulose microfibrils?
Multiple cellulose chains become tightly cross linked via hydrogen bonds to form bundles called microfibrils
microfibrils join together to make macrofibrils which combine to make strong cellulose fibres in the plant cell wall
What are the adaptions of cellulose for it’s role?
Long unbranched chains = provide rigidity to cell wall
H bonds = cross link chains to add collective tensile strength
Microfibrils = provide additional strength
