3.1.2 CARBOHYDRATES Flashcards
explain the difference in the structure of a cellulose and starch molecule (2 marks):
- Starch formed from Alpha glucose, cellulose formed from Beta glucose
- Position of hydrogen and hydroxyl groups on carbon atom- inverted
Explain one way in which starch molecules are adapted for their function in plant cells (2 marks):
- Starch is insoluble- doesn’t affect water potential
- Helical structure- makes it compact
Explain how cellulose molecules are adapted for their function in plant cells (3 marks):
- Long and straight chained
- Linked together by many hydrogen bonds to form fibrils
- Provides strength to cell wall
examples of hexoses:
- A- glucose
- B- glucose
- Fructose
- Galactose
Examples of pentoses:
- ribose
- deoxyribose
Example of a triose:
Glyceraldehyde
Reducing sugars test:
- Benedict’s solution
- Heat in a water bath
- If present then will turn brick red
Monosaccharide constituents of sucrose:
A- glucose and A- fructose
Monosaccharide constituents of lactose:
A- glucose + B- galactose
Monosaccharide constituents of maltose:
A glucose + A glucose
- because it is made out of two A- glucose this makes it a reducing sugar
Condensation reaction process:
- New water molecule is released
- New covalent bond is formed
- Larger molecule is formed by bonding smaller molecules together
- The covalent bond that is formed is called a GLYCOSIDIC BOND
Hydrolosis reaction process:
- Requires water
- Breaks down larger biological molecules into their smaller components- adds a water molecule
Compare and contrast the structure of starch and the structure of cellulose (6 marks):
- Both glucose polymers
- Both contain glycosylic bonds
- Both contain carbon, hydrogen and oxygen only
- Both contain glucose
- Cellulose contains beta- glucose
- Starch is coiled/ cellulose is straight
What is starch?
The storage polysaccharide of plants
Where is starch stored?
Stored as granules in plastids (e.g. chloroplasts)
What is starch made out of?
Alpha-glucose and monosaccharides
What kind of bond does starch have?
]glycosidic bond
What kind of bond does starch have?
1,4 glycosidic bond
Does starch take more or less time to digest than glucose?
Takes longer due to the many monomers in a starch molecule
Does starch take more or less time to digest than glucose?
Takes longer due to the many monomers in a starch molecule
What are the two polysaccharides that starch is constructed from?
- Amylose
- Amylopectin
What type of structure and glycosidic bond is in amylose?
- 1,4 glycosidic bond between 2 a-glucose molecules
- helix shape- unbranded chain can be coupled tightly and is therefore more resistant to digestion
What structure and glycosidic bonds does amylopectin have?
- 1,4 glycosidic bonds between a-glucose molecules but ALSO, 1,6 glycosidic bonds form between glucose molecules.
- This creates a BRANCHED molecule
Advantages of a branched starch molecule:
May results in many terminal glucose molecules that can be easily hydrolysed for use during cellular respiration or added for storage
What is glycogen (and its structure)?
- the storage polysaccharide of animals and fungi
- highly branched, not coiled
Is glycogen more or less branched than amylopectin?
More branched, making it more compact, helps animals to store more
What is cellulose?
- a polysaccharide
What is a polysaccharide?
Macromolecules that are polymers formed by many monosaccharides joined together by glycosidic bonds in a condensation reaction to form chains
Is cellulose soluble or insoluble?
Insoluble because polysaccharides are insoluble in water
Structure of cellulose:
- polymer consisting of long chains of B- glucose joined together with 1,4 glycosidic bonds
How do the 1,4 glycosidic bonds between two B, glucose molecules form?
- Glucose molecules must be rotated to 180 degrees to each other
- Due to this inversion, many hydrogen bonds form between the long chains giving cellulose it’s strength
What is the function of cellulose?
Main structural component of cell walls due to its strength which is a result of the many hydrogen bonds found between the parallel chains of micro fibrils
