A LEVEL BIOLOGY 7402 PAPER 3 2026 EXAM
PREP STUDY GUIDE COMPREHENSIVE REVIEW
◉ Beta Glucose Answer:
◉ Alpha glucose Answer:
◉ Glucose formula Answer: C₆H₁₂O₆
◉ Name of the bond between monosaccharides? Answer: Glycosidic
bond.
◉ What is sucrose made from? Answer: Glucose and fructose.
◉ What is lactose made from? Answer: Glucose and galactose.
◉ What is maltose made from? Answer: Two alpha glucose.
◉ Testing for reducing sugars? Answer: Add Benedict's reagent
(blue) and heat in a water bath. If present: Green → yellow → orange
→ brick red
,◉ Test for non-reducing sugars? Answer: Add dilute hydrochloric
acid and boil, neutralise with Sodium Hydrogencarbonate. Then do
the Benedict's test - add Benedicts reagent and heat.
◉ What is the scientific name for the polymer of carbohydrates?
Answer: Polysaccharides.
◉ What is starch made of? Answer: Starch is a mixture of two
polysaccharides of alpha glucose: Amylose and amylopectin.
◉ What is amylose? Answer: A long, unbranched alpha glucose
chain, joined by alpha 1,4 glycosidic bonds. It has a coiled shape
which makes it compact and effective for storage.
◉ What is amylopectin? Answer: A long, branched alpha glucose
chain alpha 1,4 and alpha 1,6 glycosidic bonds. The side branches
mean that enzymes can get to and hydrolyse glycosidic bonds faster
so glucose can be released quickly.
◉ What is glycogen? Answer: A polysaccharide of alpha glucose with
a similar structure to starch except it is more branched (alpha 1,4
and alpha 1,6 glycosidic bonds), allowing even faster energy release.
It is also very compact.
,◉ What is cellulose? Answer: it is made of long, straight chains of
beta glucose joined by beta 1,4 glycosidic bonds. The chains are
linked by hydrogen bonds to form microfibrils, a strong fibre. The
strong fibres allow it to provide structural support in cells as cell
walls.
◉ How to test for starch. Answer: Add iodine. Positive result: Turns
blue-black. Negative result: stays browny-orange.
◉ Which of proteins, polysaccharides and lipids are not a polymer.
Answer: Lipids.
◉ What are triglycerides made of? Answer: Glycerol and fatty acids.
◉ What causes lipids to be insoluble in water? Answer: The
hydrophobic fatty acid tails.
◉ What is the structure of a fatty acid? Answer:
◉ What do double bonds cause in fatty acids? Answer: A kink in the
chain.
◉ Triglyceride formation? Answer:
, ◉ What are phospholipids? Answer: Similar to triglycerides, but one
of the fatty acid tails is replaced by a phosphate group head.
◉ Which part of a phospholipid is hydrophilic and which part is
hydrophobic? Answer: The phosphate group is hydrophilic and the
fatty acid tail is hydrophobic.
◉ What are triglycerides mainly used for? Answer: To store energy,
they are effective at this as the hydrocarbon tails contain a lot of
energy. They are also insoluble so do not affect the water potential of
cells, preventing swelling.
◉ How much energy do lipids contain compared to carbohydrates?
Answer: Twice as much energy per gram.
◉ Why do triglycerides bundle together in water? Answer: The fatty
acid tails are hydrophobic so face inwards, so are shielded by the
glycerol heads.
◉ What role do phospholipids perform? Answer: They make up the
bilayer in cell membranes.
◉ Test for lipids? Answer: The emulsion test: Shake substance with
ethanol and pour into water. A white emulsion forms if it is present.
PREP STUDY GUIDE COMPREHENSIVE REVIEW
◉ Beta Glucose Answer:
◉ Alpha glucose Answer:
◉ Glucose formula Answer: C₆H₁₂O₆
◉ Name of the bond between monosaccharides? Answer: Glycosidic
bond.
◉ What is sucrose made from? Answer: Glucose and fructose.
◉ What is lactose made from? Answer: Glucose and galactose.
◉ What is maltose made from? Answer: Two alpha glucose.
◉ Testing for reducing sugars? Answer: Add Benedict's reagent
(blue) and heat in a water bath. If present: Green → yellow → orange
→ brick red
,◉ Test for non-reducing sugars? Answer: Add dilute hydrochloric
acid and boil, neutralise with Sodium Hydrogencarbonate. Then do
the Benedict's test - add Benedicts reagent and heat.
◉ What is the scientific name for the polymer of carbohydrates?
Answer: Polysaccharides.
◉ What is starch made of? Answer: Starch is a mixture of two
polysaccharides of alpha glucose: Amylose and amylopectin.
◉ What is amylose? Answer: A long, unbranched alpha glucose
chain, joined by alpha 1,4 glycosidic bonds. It has a coiled shape
which makes it compact and effective for storage.
◉ What is amylopectin? Answer: A long, branched alpha glucose
chain alpha 1,4 and alpha 1,6 glycosidic bonds. The side branches
mean that enzymes can get to and hydrolyse glycosidic bonds faster
so glucose can be released quickly.
◉ What is glycogen? Answer: A polysaccharide of alpha glucose with
a similar structure to starch except it is more branched (alpha 1,4
and alpha 1,6 glycosidic bonds), allowing even faster energy release.
It is also very compact.
,◉ What is cellulose? Answer: it is made of long, straight chains of
beta glucose joined by beta 1,4 glycosidic bonds. The chains are
linked by hydrogen bonds to form microfibrils, a strong fibre. The
strong fibres allow it to provide structural support in cells as cell
walls.
◉ How to test for starch. Answer: Add iodine. Positive result: Turns
blue-black. Negative result: stays browny-orange.
◉ Which of proteins, polysaccharides and lipids are not a polymer.
Answer: Lipids.
◉ What are triglycerides made of? Answer: Glycerol and fatty acids.
◉ What causes lipids to be insoluble in water? Answer: The
hydrophobic fatty acid tails.
◉ What is the structure of a fatty acid? Answer:
◉ What do double bonds cause in fatty acids? Answer: A kink in the
chain.
◉ Triglyceride formation? Answer:
, ◉ What are phospholipids? Answer: Similar to triglycerides, but one
of the fatty acid tails is replaced by a phosphate group head.
◉ Which part of a phospholipid is hydrophilic and which part is
hydrophobic? Answer: The phosphate group is hydrophilic and the
fatty acid tail is hydrophobic.
◉ What are triglycerides mainly used for? Answer: To store energy,
they are effective at this as the hydrocarbon tails contain a lot of
energy. They are also insoluble so do not affect the water potential of
cells, preventing swelling.
◉ How much energy do lipids contain compared to carbohydrates?
Answer: Twice as much energy per gram.
◉ Why do triglycerides bundle together in water? Answer: The fatty
acid tails are hydrophobic so face inwards, so are shielded by the
glycerol heads.
◉ What role do phospholipids perform? Answer: They make up the
bilayer in cell membranes.
◉ Test for lipids? Answer: The emulsion test: Shake substance with
ethanol and pour into water. A white emulsion forms if it is present.
