AQA A LEVEL BIOLOGY PAPER 1 FULLY SOLVED
TEST PAPER GRADED A+
◉ what are monomers
Answer: small repeating units that make up polymer
◉ what is a condensation reaction?
Answer: the formation of a bond via the release of a water molecule
◉ What is a glycosidic bond?
Answer: A bond between two monosaccharides formed in a
condensation reaction.
◉ How is sucrose formed?
Answer: glucose + fructose
◉ How is maltose formed?
Answer: alpha glucose + alpha glucose
◉ How is lactose formed?
Answer: glucose + galactose
,◉ What is a hydrolysis reaction?
Answer: a reaction in which a chemical bond is broken by the
addition of a water molecule
◉ describe benedicts test for reducing sugars
Answer: 1. Add an equal volume of Benedict's reagent to a sample.
2. Heat the mixture in an electric water bath at 100℃ for 5 mins.
3. Positive result: colour change from blue to green to yellow to
orange to brick-red (depending on concentration) precipitate forms.
- the higher the concentration of reducing sugar the further the color
change
◉ Describe the Benedict's test for non-reducing sugars.
Answer: 1. add dilute HCL and heat in a water bath thats been
brough to a boil
2. neutralise the sample using sodium hydrogencarbonate
3. Add an equal volume of Benedict's reagent to a sample.
4. Heat the mixture in an electric water bath at 100℃ for 5 mins.
5. Positive result: colour change from blue to green to yellow
◉ Structure of alpha glucose
Answer: OH on bottom
,◉ Structure of beta glucose
Answer: OH on top
◉ structure of fructose
Answer: pentagon
◉ structure of galactose
Answer: both OH on top
◉ What is starch used for?
Answer: Plants store excess glucose as starch
◉ Structure of starch
Answer: - It is found in small grains, and is a major source of energy.
- It is made of chains of alpha glucose monosaccharides linked by
glycosidic bonds which can be branched or unbranched. The
unbranched chain (Amylose) is rolled into a tight coil which makes
the molecule very compact.
- the other polysaccharide in starch is amylopectin, and it is
branched, its side branches allow the enzymes that break down
glucose to access it more easily.
- starch is insoluble in water, so it doesn't affect water potential
, ◉ What is the iodine test?
Answer: Test for starch
add iodine dissolved in potassium iodide solution to sample
positive result = change from brown to dark blue-black
◉ Structure of glycogen
Answer: - animals store excess glucose as glycogen
- similar structure to amylopectin but a lot more branched, so easy
access for enzymes
- compact molecule, so good for storage
◉ Structure of cellulose
Answer: - Long, unbranched chains of beta-glucose which run
parallel to each other.
- Hydrogen bonds form cross linkages between adjacent chains. This
allows cellulose to group together to form microfibrils which
provides strength to molecule.
◉ Structure of a triglycerides
Answer: - 1 glycerol and 3 fatty acids
- have long tails made of hydrocarbons
- tails are hydrophobic, so lipids are insoluble in water
TEST PAPER GRADED A+
◉ what are monomers
Answer: small repeating units that make up polymer
◉ what is a condensation reaction?
Answer: the formation of a bond via the release of a water molecule
◉ What is a glycosidic bond?
Answer: A bond between two monosaccharides formed in a
condensation reaction.
◉ How is sucrose formed?
Answer: glucose + fructose
◉ How is maltose formed?
Answer: alpha glucose + alpha glucose
◉ How is lactose formed?
Answer: glucose + galactose
,◉ What is a hydrolysis reaction?
Answer: a reaction in which a chemical bond is broken by the
addition of a water molecule
◉ describe benedicts test for reducing sugars
Answer: 1. Add an equal volume of Benedict's reagent to a sample.
2. Heat the mixture in an electric water bath at 100℃ for 5 mins.
3. Positive result: colour change from blue to green to yellow to
orange to brick-red (depending on concentration) precipitate forms.
- the higher the concentration of reducing sugar the further the color
change
◉ Describe the Benedict's test for non-reducing sugars.
Answer: 1. add dilute HCL and heat in a water bath thats been
brough to a boil
2. neutralise the sample using sodium hydrogencarbonate
3. Add an equal volume of Benedict's reagent to a sample.
4. Heat the mixture in an electric water bath at 100℃ for 5 mins.
5. Positive result: colour change from blue to green to yellow
◉ Structure of alpha glucose
Answer: OH on bottom
,◉ Structure of beta glucose
Answer: OH on top
◉ structure of fructose
Answer: pentagon
◉ structure of galactose
Answer: both OH on top
◉ What is starch used for?
Answer: Plants store excess glucose as starch
◉ Structure of starch
Answer: - It is found in small grains, and is a major source of energy.
- It is made of chains of alpha glucose monosaccharides linked by
glycosidic bonds which can be branched or unbranched. The
unbranched chain (Amylose) is rolled into a tight coil which makes
the molecule very compact.
- the other polysaccharide in starch is amylopectin, and it is
branched, its side branches allow the enzymes that break down
glucose to access it more easily.
- starch is insoluble in water, so it doesn't affect water potential
, ◉ What is the iodine test?
Answer: Test for starch
add iodine dissolved in potassium iodide solution to sample
positive result = change from brown to dark blue-black
◉ Structure of glycogen
Answer: - animals store excess glucose as glycogen
- similar structure to amylopectin but a lot more branched, so easy
access for enzymes
- compact molecule, so good for storage
◉ Structure of cellulose
Answer: - Long, unbranched chains of beta-glucose which run
parallel to each other.
- Hydrogen bonds form cross linkages between adjacent chains. This
allows cellulose to group together to form microfibrils which
provides strength to molecule.
◉ Structure of a triglycerides
Answer: - 1 glycerol and 3 fatty acids
- have long tails made of hydrocarbons
- tails are hydrophobic, so lipids are insoluble in water
