3.3 Carbohydrates Flashcards
What elements do carbohydrates contain?
C, H, O
What’s another term for a carbohydrate?
Saccharide (sugar)
What is a single sugar unit called?
Monosaccharide
State the names of the 3 common monosaccharides.
Glucose, fructose, ribose
What do 2 linked monosaccharides form?
Disaccharide
State the names of the 2 common disaccharides.
Lactose and sucrose
What do 2 or more linked monosaccharides form?
Polysaccharides - (Polymer made up of many sugar monomers/monosaccharides)
State the names of the 3 common polysaccharides.
Glycogen, cellulose and starch
What is the formula for glucose?
C6H12O6
What name would you give glucose in the context of its structure?
6-C hexose monosaccharide
How are carbons labelled in molecular structure
diagrams?
Clockwise from the oxygen atom
What is the property of glucose? Why is this?
Polar + soluble in water - due to H bonds that form between hydroxyl groups + water molecules
Why is the solubility of glucose important?
So glucose can be dissolved in the cell cytoplasm
What happens when 2 alpha glucose are next to each other?
- 2 hydroxyl groups react w/ each other
- 2 H atoms and 1 O is removed in total from both glucoses and join to form water
- Glycosidic bond forms between carbon 1 of one glucose and carbon 4 of the second glucose, forming 1-4 glycosydic bond
Why is the reaction between 2 alpha glucoses a condensation reaction?
Water is produced as a product of the reaction
What disaccharide forms when 2 alpha glucose react?
Maltose
Give examples of 2 other hexose monosaccharide sugars.
Fructose and galactose
Where is fructose naturally found?
Fruit + often with glucose to form sucrose - cane sugar
What do you produce when you combine glucose and fructose?
Sucrose, disaccharide
What do you produce when you combine glucose and galactose?
Lactose
What is lactose? Where is it commonly found?
Lactose is the product of galactose and glucose, commonly found in milk.
Compare the sweetness between fructose, glucose and galactose.
Fructose is sweeter than glucose.
Glucose is sweeter than galactose.
What are pentose monosaccharides?
5-C sugars
State 2 examples of pentose monosaccharides.
Ribose, deoxyribose
What’s the name of the sugar in RNA nucleotides?
Ribose
What’s the name of the sugar in DNA nucleotides?
Deoxyribose
What is starch?
A polysaccharide formed from alpha glucose molecules joined together
In plants, what is glucose stored as?
Starch
What is one of the polysaccharides in starch called?
Amylose
How is amylose formed?
Amylose is formed by alpha glucose molecules joined together by 1-4 glycosidic bonds
What does the angle of the 1-4 glycosidic bond joining amylose mean?
The long glucose chain twists to form a helix, which is further stabilised by H bonding within the molecule
Why is the polysaccharide starch less soluble than the glucose molecules used to make it?
The long glucose chain [making up amylose] twists to form a helix, which is further stabilised by H bonding.
This makes the molecule more compact, so it’s less soluble than glucose.
What is the second polysaccharide making up starch, with 1-6 bonds?
Amylopectin
What are the 2 polysaccharides that make up starch?
Amylose + amylopectin
How is amylopectin formed?
Amylopectin is formed by 1-4 glycosidic bonds between alpha glucose molecules + 1-6 glycosidic bonds (formed by condensation reactions between carbon 1 + carbon 6 of 2 glucose molecules)
Why does amylopectin have a branched structure?
Due to 1-6 glycosidic bonds - 1-6 branching points occur every 25 glucose subunits
In animals and fungi, what form is glucose stored in?
Glycogen
What is glycogen?
A branched polysaccharide formed from alpha glucose molecules + a chemical energy store in animals
What’s the difference between glycogen and amylopectin?
Glycogen is more branched = more compact + less space needed for it to be stored
Besides compaction for storage, what other adaptation is there for the branching of glycogen?
Due to the branching, there are many free ends where glucose can be added or removed - this speeds up the storage/release of glucose
What are the key properties of amylopectin and glycogen?
They’re insoluble, branched and compact
What must happen to glycogen and starch for them to release glucose?
Hydrolysis reactions - the addition of water molecules
Why can’t beta join together in the same way as alpha?
Hydroxyl/OH groups on carbon 1 and carbon 4 are too far from each other to react
What must happen for beta molecules to react?
Second beta must be flipped upside down
What polysaccharide is formed when 2 beta join? Describe its structure.
Cellulose - Straight chain, unable to coil or form branches
What is formed when cellulose forms H bonds with each other?
Microfibrils
What is formed when microfibrils join?
Macrofibrils
What is formed when macrofibrils join?
Fibres
Describe the properties of the fibres produced when macrofibrils combine, and state what they’re used to form?
Strong and insoluble. Used to form cell walls.
What type of sugar are glucose, fructose, ribose?
Monosaccharide
What kind of sugar are lactose and sucrose?
Disaccharide
What type of sugar are glycogen, cellulose and starch?
Polysaccharide
