Lesson 7 - Carbohydrates Flashcards
Elements in carbohydrates:
Carbon, Oxygen, Hydrogen
Meaning of ‘carbohydrates’:
Hydrated carbon
General formula of carbohydrates:
Cx(H2O)y
Monomer of carbohydrates:
Monosaccharide
Examples of monosaccharides:
- Glucose
- Fructose
- Ribose
Two monosaccharides bonded together:
Disaccharide
Examples of disaccharides:
- Lactose
- Sucrose
Polymer of carbohydrates:
Polysaccharides
Examples of polysaccharides:
- Cellulose
- Starch
- Glycogen
Other words for carbohydrates:
- Saccharides
- Sugars
Chemical formula of glucose:
C6H12O6
As Glucose is conformed of 6 carbons, it is called a …
hexose monosaccharide (hexose sugar)
Different types of glucose:
α-glucose
β-glucose
Difference between α-glucose and β-glucose?
Hydroxyl group on carbon 1 are in opposite positions.
Properties of glucose?
Soluble in water and polar
How are glucose molecules soluble in water and polar?
They have hydrogen bonds that form between hydroxyl groups and water.
Why is the solubility of glucose important?
Glucose is dissolved in the cytosol of the cell.
How condensation reactions occur between glucose?
When two alpha-glucose molecules are side by side, the two hydroxyl groups interact. When this happens bonds are broken and new bonds form in different places producing new molecules.
Condensation reaction in glucose?
Two hydrogen atoms and an oxygen atom are removed from glucose monomers and join to form a water molecule. A bond forms between carbons 1 and 4 on the glucose molecules, which are now joined.
This bond is called a glycosidic bond and is formed between 2 glucose molecules. This is a condensation reaction, as water is formed as one of the products of the reaction.
1,4 Glycosidic bond:
Carbon 1 of one glucose molecule is joined to carbon 4 of the other glucose molecule.
New molecule formed in condensation of glucose?
Maltose
Hexose monosaccharides:
- Glucose
- Fructose
- Galactose
Fructose
Naturally occurs in fruits, often in a combination with glucose to form disaccharide sucrose (cane sugar or just sugar)
Can sugar
Disaccharide sucrose
- Fructose + Glucose
Disaccharide lactose:
Galactose + Glucose
Commonly found in milk and milk products
Order of sweetness of Glucose, Fructose, and Galactose
- Fructose
- Glucose
- Galactose
Sugars that contain 5 carbon atoms:
Pentose monosaccharides
Ribose and deoxyribose:
Two pentose monosaccharides
Ribose present:
RNA nucleotides
Deoxyribose present:
DNA nucleotides
Starch made up of:
Alpha glucose molecules joined by glycosidic bonds to form two slightly different polysaccharides collectively known as Starch.
How is starch a chemical store:
Glucose made by photosynthesis in plant cells is stored as starch.
What is amylose?
One of the polysaccharides in starch
Structure of amylose?
Formed by alpha glucose molecules joined together by only 1,4 glycosidic bonds. Angle of the bond means that the long chain of glucose twists into a helix structure. The helix structure is stabilised by hydrogen bonding within the molecule. This makes the polysaccharide more compact, much less soluble, than the glucose molecules used to make it.
Amylopectin:
Another starch polysaccharide.
Formed from 1,4 polycosidic bonds in glucose and bonds between carbon 1 and 6 atoms in glucose.
Results of carbon 1 and 6 bonds in amylopectin:
Amylopectin has a branched structure. with 1,6 branching points occurring approximately 1 in every 25 glucose subunits.
Functionally equivalent energy store to starch (plants) to animals and fungi is …
glycogen
Structure of glycogen:
Has more branches than amylopectin, so is more compact and less space is needed for storage.
Why is glycogen’s compact structure important?
Animals (unlike plants) are mobile.
- Branching makes it extremely compact, ideal for storage.
- There are lots of ends glucose can be added and removed from. This speeds up process of storing or releasing glucose molecules required by the cell.
Key properties of amylopectin and glycogen:
- Compact
- Branched
- Insoluble
How is glucose released from starch/glycogen for respiration?
Hydrolysis reactions.
- Requires addition of water molecules
- Enzymes catalyse reaction
- Reverse condensation reactions that form glycosidic bonds.
Beta glucose reactions:
Beta glucose molecules are unable to join together in the same way as alpha molecules. Carbon 1,4 are too far away.
Alternate beta molecules are turned upside down.
Unable to coil or form branches, so a straight chain molecule is formed called cellulose.
Cellulose:
Form hydrogen bonds with each other to form microfibrils.
Microfibrils join together to form macrofibrils.
Macrofibrils join together to form fibres.
Fibres are strong and insoluble. They join together to form the cell wall.
Importance of cellulose:
Important for diet. Hard to break down into monomers so forms to ‘fibres’ and ‘roughage’ important for a healthy digestive system.
