Edexcel A level biology B Biochemistry Questions
With Complete Answers
What are carbohydrates made out of?
carbon, hydrogen and oxygen
What is a monosaccharide (with examples of 3)?
Carbohydrates with a single sugar unit, such a glucose, fructose and ribose
What is a disaccharide (with 3 examples)?
A carbohydrate with two sugar units, including maltose, sucrose or lactose.
What is a polysaccharide (with three examples)?
A long chain of sugars that has been made through condensation polymerisation,
these include glycogen, starch and amylose. It contains 11+ sugar units. It doesn't
have the sweet taste of many mono and disaccharides.
What is the monosaccharide equation
(CH2O)n
How many carbons do monosaccharides have and what do we call each
monosaccharide (with examples)?
Between 3 and 6.
3 carbons - triose sugar (C3H6O3) In respiration, glucose is broken down into triose
sugar
5 carbons - pentose sugar (C5H10O5), ribose and deoxyribose are both pentose
sugars and make up genetic material.
6 carbons - hexose suagr (C6H12O6), often tastes sweet and include glucose,
galactose and fructose.
Why are carbohydrates important?
They store energy in plant, fungi and bacterial cells. They also make up an important
part of the cell wall. The best known carbohydrates are sugars and starch. Sucrose
is a white crystalline sugar, glucose supplies energy in sports drinks, starch is found
in flour and potatoes. They can come in the form of monosaccharides,
disaccharides, oligosaccharides and polysaccharides.
What is a dissacharide? Give an example.
, A molecule formed from the combination of two monosaccharides through a
condensation reaction where water is lost. A covalent bond called a glycosidic bond
forms between the two molecules. The reaction can be reversed by adding in water (
hydrolysis ). Sucrose is table sugar and is formed by alpha glucose joining to a
fructose.
What are the monosaccharides of sucrose?
monosaccharides = alpha glucose + fructose
What are the monosaccharides of lactose?
monosaccharides = glucose + galactose
What are the monosaccharides of maltose
monosaccharides - 2 alpha glucose molecules
How do we test for reducing sugars? How can we make a non- reducing sugar
test positive?
We use a solution called Benedict's solution. It is bright blue and contains copper (II)
ions. When heated gently, the Benedict's copper (II) ions are reduced to copper (I)
ions. A precipitate is formed, turning the solution from bright blue to orange. All
monosaccharides are a reducing sugar and some disaccharides are too.
With non-reducing sugars, you can add a few drops of hydrochloric acid to hydrolyse
the glycosidic bonds. Allow to cool then neutralise with sodium hydrogen carbonate
which will now give a positive result as the sugar has been broken down into its
monosaccharide units.
What is an isomer?
compounds with the same molecular formula but different structural formulas
Draw alpha glucose and beta glucose
Draw a ribose molecule
What is an oligosaccharide?
a carbohydrate with 3-10 monosaccharide units
Why do polysaccharides form good storage molecules?
- Can form very compact molecules meaning a cell can store a large number of
them.
- Glycosidic bonds can be easily broken, allowing from the quick release of
monosaccharide units for cellular respiration.
- Not very soluble in water meaning they have little effect on water potential within a
cell and causes no osmotic water movements.
With Complete Answers
What are carbohydrates made out of?
carbon, hydrogen and oxygen
What is a monosaccharide (with examples of 3)?
Carbohydrates with a single sugar unit, such a glucose, fructose and ribose
What is a disaccharide (with 3 examples)?
A carbohydrate with two sugar units, including maltose, sucrose or lactose.
What is a polysaccharide (with three examples)?
A long chain of sugars that has been made through condensation polymerisation,
these include glycogen, starch and amylose. It contains 11+ sugar units. It doesn't
have the sweet taste of many mono and disaccharides.
What is the monosaccharide equation
(CH2O)n
How many carbons do monosaccharides have and what do we call each
monosaccharide (with examples)?
Between 3 and 6.
3 carbons - triose sugar (C3H6O3) In respiration, glucose is broken down into triose
sugar
5 carbons - pentose sugar (C5H10O5), ribose and deoxyribose are both pentose
sugars and make up genetic material.
6 carbons - hexose suagr (C6H12O6), often tastes sweet and include glucose,
galactose and fructose.
Why are carbohydrates important?
They store energy in plant, fungi and bacterial cells. They also make up an important
part of the cell wall. The best known carbohydrates are sugars and starch. Sucrose
is a white crystalline sugar, glucose supplies energy in sports drinks, starch is found
in flour and potatoes. They can come in the form of monosaccharides,
disaccharides, oligosaccharides and polysaccharides.
What is a dissacharide? Give an example.
, A molecule formed from the combination of two monosaccharides through a
condensation reaction where water is lost. A covalent bond called a glycosidic bond
forms between the two molecules. The reaction can be reversed by adding in water (
hydrolysis ). Sucrose is table sugar and is formed by alpha glucose joining to a
fructose.
What are the monosaccharides of sucrose?
monosaccharides = alpha glucose + fructose
What are the monosaccharides of lactose?
monosaccharides = glucose + galactose
What are the monosaccharides of maltose
monosaccharides - 2 alpha glucose molecules
How do we test for reducing sugars? How can we make a non- reducing sugar
test positive?
We use a solution called Benedict's solution. It is bright blue and contains copper (II)
ions. When heated gently, the Benedict's copper (II) ions are reduced to copper (I)
ions. A precipitate is formed, turning the solution from bright blue to orange. All
monosaccharides are a reducing sugar and some disaccharides are too.
With non-reducing sugars, you can add a few drops of hydrochloric acid to hydrolyse
the glycosidic bonds. Allow to cool then neutralise with sodium hydrogen carbonate
which will now give a positive result as the sugar has been broken down into its
monosaccharide units.
What is an isomer?
compounds with the same molecular formula but different structural formulas
Draw alpha glucose and beta glucose
Draw a ribose molecule
What is an oligosaccharide?
a carbohydrate with 3-10 monosaccharide units
Why do polysaccharides form good storage molecules?
- Can form very compact molecules meaning a cell can store a large number of
them.
- Glycosidic bonds can be easily broken, allowing from the quick release of
monosaccharide units for cellular respiration.
- Not very soluble in water meaning they have little effect on water potential within a
cell and causes no osmotic water movements.
