Carbohydrates Flashcards
What are monosaccharides and what are they the building blocks for?
- They are small organic molecules
- They are building blocks for larger carbohydrates.
What general formula do monosaccharides have?
(CH20)n
What is a sugar called that has
A) three carbon atoms
B) five carbon atoms
C) six carbon atoms + type of sugar it is
A) triose
B) pentose
C) hexose which is a glucose sugar
What is the general formula of hexose sugars?
C6H12O6
What do all hexose sugars differ in?
Molecular structure
What occurs when monosaccharides are dissolved in water and how can they alter their binding?
The carbon atoms of the monosaccharides make a ring.
They can alter their binding to make straight chains, with the rigs and chains in equilibrium.
Name the two isomers of glucose and state what they are based on.
α-glucose and β-glucose and they are based on the positions of an (OH) and (H) of the molecule.
What do the different forms of glucose result in and give example(s).
They result in biological differences when they form polymers, such as starch and cellulose.
What is a monosaccharide (simple).
An individual sugar molecule.
Monosaccharides have four main functions.
Describe them and give examples where possible.
- A source of energy in respiration.
Carbon-hydrogen and carbon-carbon bonds are broken to release energy, which is transferred to make ATP.
- Building blocks for larger molecules.
E.g. Glucose is used to make the polysaccharides starch, glycogen and cellulose.
- Intermediates in reactions.
E.g. Trioses, are intermediates in the reactions of respiration and photosynthesis.
- Constituents of nucleotides.
E.g. Deoxyribose in DNA, and ribose in RNA, ATP and ADP.
What are disaccharides and described their formation.
- Disaccharides are composed of two monosaccharide units.
- They are bonded together with the formation of a condensation reaction.
Describe (or draw) the formation of a glycosidic bond between two glucose molecules, making maltose.
α-glucose + α-glucose = maltose
- This is a condensation reaction.
- Water is being removed between C4 of one glucose molecule and C1 of the other.
- The bond formed between glucose molecules is a glucosidic bond.
- It is between C1 and C4, so it is called a 1, 4-glucosidic bond.
- Because the disaccharide molecule is straight and not twisted, the bond is an α-1, 4-glycosidic bond.
Name three disaccharides, their component monosaccharides and their biological role.
Maltose:
glucose + glucose
germinating seeds
Sucrose:
glucose + fructose
transport in phloem of flowering plants
Lactose:
glucose + galactose
in mammalian milk
What do reducing sugars include?
All monosaccharides and some disaccharides, e.g. Maltose.
What are polysaccharides (detail).
They are large, complex polymers.
They are formed from dry large numbers of monosaccharide units, which are their monomers, linked by glucosidic bonds.
What is glucose the main source for?
Energy in cells.
Describe glucose when placed in water and a problem that occurs.
Also, how is this problem avoided?
It is soluble in water and the problem is, it would increase the concentration of the cell contents, and consequently draw water in by osmosis.
This problem is avoided by converting the glucose into a storage product, a polysaccharide, starch.
Why is starch a useful storage form of glucose? (4 points)
- It is insoluble so it has no osmotic effect.
- It cannot diffuse out of the cell.
- It is a compact molecule and can be stored in a small space.
- It carries a lot of energy in its C-H and C-C bonds.
What is starch and what is it made of?
What are the two different forms?
Starch is the main store of glucose for plants.
Starch grains are found in high concentrations in seeds and storage organs such as potato tubers.
Starch is made of α-glucose molecules in two different ways, found in two polymers:
- amylose
- amylopectin
Describe the structure of amylose and state what is formed when the chain coils.
It is a linear, unbranded molecule with α-1, 4-glycosidic bonds forming between the first carbon atom (C1) on one glucose monomer and the fourth carbon atom (C4) on the adjacent one.
This is repeated, forming a chain, which coils into an α-helix.
Describe the structure of amylopectin.
It has chains of glucose monomers joined with α-1, 4-glycosidic bonds.
They are cross-linked with α-1,6-glycosidic bonds and fit inside the amylose.
When a glycosidic bond forms between the C1 atom of one glucose molecule and the C6 atom on another, a side branch is seen.
α-1,4-glycosidic bonds continue on from the start of the branch.
What are carbohydrates (in detail).
- Carbohydrates are organic compounds containing carbon, hydrogen and oxygen.
- The basic unit is a monosaccharide.
- Two basic units combine to from a disaccharide.
- And many basic units combine to form a polysaccharide.
What is glycogen?
The main storage product in animals.
What used to be called ‘animal starch’ and why?
Because it’s very similar to amylopectin.
