3.1.2 Carbohydrates
What is a pentose sugar?
- A monosaccharide - Contains 5 carbon atoms - 5 carbon ring
What is a hexose sugar?
- A monosaccharide - Formed from 6 carbon atoms - 6 carbon ring
How is sucrose formed?
- Formed from a glucose molecule and a fructose molecule - Joined together by an alpha 1-4 glycosidic bond
How is lactose formed?
- Formed from a glucose molecule and a galactose molecule - Joined together by a beta 1-4 glycosidic bond
How is maltose formed?
- Formed from two glucose molecules - Joined together by an alpha 1-4 glycosidic bond
How are cellulose molecules adapted for their function in plants?
- Hydrogen bonding between chains - Chains form microfibrils - Microfibrils layered - Cell walls ... Strengthens ... Prevents cells from bursting when they take in too much water
Glycogen is formed from...
- Many a-glucose molecules - B-glucose branches
1) Describe the iodine test 2) What substances are used on the starch? 3) Why does this happen?
1) - If you put iodine on starch, the solution will turn blue/black 2) Iodine/Potassium iodide 3) - When iodine molecules fit down the middle of the helical structure of amylose... - It forms a polyiodide starch complex
1) What is the difference between how an alpha 1-4 glycosidic bond looks to how a beta 1-4 glycosidic bond looks? 2) Why?
1) - On an alpha 1-4 glycosidic bond, the 'O' faces downward - Whereas on a beta 1-4 glycosidic bond, the 'O' faces upward 2) - As the -OH group on an alpha hexose faces downward - Whereas the -OH group on a beta hexose faces upward
1) How are the glucose molecules arranged in cellulose? 2) Why do they have to be arranged in this way?
1) - Every other glucose molecule upside down - So that the OH group matches the OH group 2) As only one side of the beta glucose monosaccharide has the OH group facing up rather than down
What are the two main structural isomers of glucose?
1) Alpha glucose (a-glucose) 2) Beta glucose (b-glucose)
Give two main components of starch
1) Amylose 2) Amylopectin
Which three elements do all carbohydrates contain?
1) Carbon 2) Hydrogen 3) Oxygen
1) What type of reaction are both disaccharides and polysaccharides formed by? 2) What are happens during this type of reaction?
1) Condensation reactions 2) H₂O molecule is lost
Amylopectin structure
1) Glucose - A-glucose molecules - Alpha 1-4 glycosidic bonds 2) Chains - Branching ... Alpha 1-6 bonds
Amylose structure
1) Glucose - A-glucose molecules - Alpha 1-4 glycosidic bonds 2) Chains - Unbranched - Helical
Cellulose structure
1) Glucose - B-glucose - Beta 1-4 glycosidic bonds - Alternate glucose molecule upside down 2) Chains - Unbranched - Straight 3) Microfibrils
Give 3 hexose monosaccharides
1) Glucose 2) Fructose 3) Galactose
Starch structure
1) Glucose - A-glucose - Alpha 1-4 glycosidic bonds - All glucose molecules face upwards 2) Chains - Branching ... alpha 1-6 - Helical
Give 1 feature of glucose Give 2 uses of glucose in the body as a result of this feature
1) Highly soluble 2) Respiration 3) Main form of transporting carbohydrates around the body
1) What is the opposite of a condensation reaction? 2) What is this reaction?
1) Hydrolysis reaction 2) When H₂O is put in to break up disaccharides
Give 3 ways in which starch molecules are adapted for their function in plants
1) Large molecule - Can't leave cell 2) Helical - Compact ... Carbohydrate storage molecule 3) Insoluble - Doesn't affect water potential
Give 3 disaccharides
1) Maltose (malt sugar) 2) Sucrose (table sugar) 3) Lactose (milk sugar)
1) Polysaccharides are made up of... 2) What are polysaccharides?
1) Many monosaccharide molecules 2) Polymers
What are the three categories of carbohydrates?
1) Monosaccharides 2) Disaccharides 3) Polysaccharides
1) Carbohydrate monomers are called... 2) Carbohydrate polymers are called...
1) Monosaccharides 2) Polysaccharides
Give 2 features of galactose
1) Not as soluble as glucose 2) Plays an important role in the production of glycolipids and glycoproteins
1) Monosaccharides are made up of... 2) What are monosaccharides? 3) What is the general formula for monosaccharides?
1) One monosaccharide molecule 2) Simple sugars 3) (CH₂O)n, where n can be 3-7
Give 2 structural isomers of pentose
1) Ribose 2) Deoxyribose
Give 3 features of fructose
1) Soluble 2) Sweeter than glucose 3) Main sugar in in fruits and nectar
Give 3 main polysaccharides
1) Starch - In plants and animals 2) Cellulose - In plants 3) Glycogen - In animals
1) Glucose exists in different forms of... 2) Which are...
1) Structural isomers 2) Molecules with the same atoms, but different arrangements of atoms
Give 3 main stages of forming glycosidic bonds
1) The hydroxyl groups bind 2) Condensation reaction - H₂O molecule is lost 3) A 1-4 glycosidic bond is formed
1) Disaccharides are made up of... 2) What are disaccharides?
1) Two monosaccharide molecules 2) Double sugars
Cellulose - Uses in plants
Cell walls
Amylose and amylopectin...
Coexist in the same chain
What is the general formula for all carbohydrates?
Cx(H₂O)y
What is the formula for glucose?
C₆H₁₂O₆
What type of bond is found in a disaccharide?
Glycosidic bond
What type of bond is found in polysaccharides?
Glycosidic bonds
3 hexose sugars... 2 pentose sugars...
Hexose: ... Glucose ... Fructose ... Galactose Pentose: ... Ribose ... Deoxyribose
Give one feature of both ribose and deoxyribose
Important constituents of RNA and DNA
Give one property of both amylose and amylopectin
Insoluble
What is the test to test for the presence of starch?
Iodine test
What is starch formed from?
Many a-glucose molecules
Cellulose is formed from...
Many b-glucose molecules
Starch - Uses in plants and animals
Plants 1) Carbodydrate storage molecule - Stored as plastids ... Which are intracellular starch grains in organelles eg) Green chloroplasts in leaves eg) Colourless amyloplasts in potatoes Animals 1) Broken down into glucose for respiration 2) Source of carbon for producing other molecules
What is the difference between ribose and deoxyribose?
RIBOSE - The carbon 2 group has a hydrogen facing upwards, and an OH facing downwards DEOXYRIBOSE - The carbon 2 group has a hydrogen facing upwards, and an H facing downwards ... Deoxyribose has one less oxygen atom than ribose
What is the main difference between starch and cellulose?
Starch - Weak Cellulose - Strong
Why are polysaccharides polymers?
They are molecules made up of many repeating monomers/subunits
