AQA A level Biology
Monomer - Answer A small, basic unit that can form a polymer. E.g. monosaccharides,
amino acids and nucleotides.
Polymers - Answer Long complex molecules consisting of chain of identical monomers.
Condensation Reactions - Answer Forming a chemical bond between monomers and
releasing a molecule of water.
Hydrolysis - Answer Breaking down polymers into monomers with the addition of water
Sugars - Answer All carbohydrates contain Carbon, Hydrogen and oxygen.
The monomers for carbohydrates are monosaccharides e.g. glucose, fructose and
galactose (reducing sugars).
Glucose - Answer Is a hexose sugar with six carbons in each molecule. There are two
types: alpha and beta glucose. These are isomers which means the same chemical
formula, but a different molecular arrangement.
Disaccharides - Answer A disaccharide forms when two monosaccharides join together
through a condensation reaction. This forms a glycosidic bond.
Glucose + Glucose = maltose
Glucose + Fructose = sucrose
Glucose + Galactose = lactose.
Benedict's Test for Reducing Sugars - Answer 1.Add Benedict's reagent
2.Bring to Boil
3.Forms a brick red precipitate if positive.
To find how much sugar there is, filter the solution and weigh the precipitate
Non Reducing Sugars Benedict's Test - Answer 1. Initial Benedict's Test - negative.
2. With a new sample, add dilute HCl to the sample and boil.
3. Neutralise with sodium hydrogen carbonate.
4. Repeat Benedict's
Polysaccharides - Answer Carbohydrates that are made up of more than two
monosaccharides. Polysaccharides are joined by 1-4 glycosidic bonds can be broken
down to monosaccharides by hydrolysis.
Starch - Answer Insoluble in water and therefore doesn't affect the water potential
gradient.
Has no impact on Osmosis.
Good for storage.
Not Sweet
Large molecule so cannot leave the cell and is always available.
, AQA A level Biology
Branched and unbranched.
Starch is the long term energy store in plant cells, found as starch grains in the
cytoplasm.
Amylose (25%) - Answer - Long unbranched chain of alpha glucose, linked by a 1-4
glycosidic bond.
- Hydrogen bonds give it a coiled, spiral structure so it is therefore very compact.
-Hydroxyl groups project into the middle. They form hydrogen bonds with each other
which stabilises the spiral.
Iodine detects this as it gets stuck inside the spiral and forms an iodine starch complex.
Amylopectin (75%) - Answer - Long, branched chain of alpha glucose
-Side branches allow the enzymes to break down the molecule to get at the glycosidic
bonds easily. This means glucose can be released quickly.
-The molecule is branches at 1-4 glycosidic bonds and 1-6 glycosidic bonds.
-Highly branched means it can be easily digested by enzymes to produce glucose for
respiration for ATP production due to the large surface area.
Glycogen - Answer -Iodine does not detect this as it only detects amylose and glycogen
only has a branched structure.
-It is a monomer of alpha glucose with 1,4 and 1,6 glycosidic bonds.
-Animal cells store their excess glucose from carbohydrate as glycogen in muscles and
the liver. This is large and insoluble and therefore has no effect on osmosis.
-The branched points occur more often. Therefore they are less dense and more
soluble. Enzymes can hydrolyse glycosidic bonds of glycogen into glucose for
respiration and the consequent ATP production. Glucose can be produced more
quickly.
-Indicates the higher metabolic requirements for animals compared with plants as
animals need muscle contractions, homeostasis, temperature regulation).
-Compact so it is good for storage.
Cellulose - Answer -Long, unbranched chains of beta glucose. When beta molecules
bond, every other molecule is inverted 180 degrees, forming straight cellulose chains,
linked by 1,2 glycosidic bonds.
-Chains become linked together by many hydrogen bonds to form microfibrils (many
hydrogen bonds provides strength and stability). These stack to form fibrils.
-Used in the cell wall of plants.
-Provides strength and rigidity to cell wall as it can resist turgid pressure from water,
stopping the cell from bursting.
Starch Test - Answer Add iodine dissolved in potassium iodide solution to the sample. If
the starch is present, the sample will turn from orange to blue/black.
Lipids - Answer These are not polymers as they are not made of identical repeated units
and contain ester bonds not glycosidic.
They are made form hydrocarbons, glycerol, phosphates and fatty acids.
Monomer - Answer A small, basic unit that can form a polymer. E.g. monosaccharides,
amino acids and nucleotides.
Polymers - Answer Long complex molecules consisting of chain of identical monomers.
Condensation Reactions - Answer Forming a chemical bond between monomers and
releasing a molecule of water.
Hydrolysis - Answer Breaking down polymers into monomers with the addition of water
Sugars - Answer All carbohydrates contain Carbon, Hydrogen and oxygen.
The monomers for carbohydrates are monosaccharides e.g. glucose, fructose and
galactose (reducing sugars).
Glucose - Answer Is a hexose sugar with six carbons in each molecule. There are two
types: alpha and beta glucose. These are isomers which means the same chemical
formula, but a different molecular arrangement.
Disaccharides - Answer A disaccharide forms when two monosaccharides join together
through a condensation reaction. This forms a glycosidic bond.
Glucose + Glucose = maltose
Glucose + Fructose = sucrose
Glucose + Galactose = lactose.
Benedict's Test for Reducing Sugars - Answer 1.Add Benedict's reagent
2.Bring to Boil
3.Forms a brick red precipitate if positive.
To find how much sugar there is, filter the solution and weigh the precipitate
Non Reducing Sugars Benedict's Test - Answer 1. Initial Benedict's Test - negative.
2. With a new sample, add dilute HCl to the sample and boil.
3. Neutralise with sodium hydrogen carbonate.
4. Repeat Benedict's
Polysaccharides - Answer Carbohydrates that are made up of more than two
monosaccharides. Polysaccharides are joined by 1-4 glycosidic bonds can be broken
down to monosaccharides by hydrolysis.
Starch - Answer Insoluble in water and therefore doesn't affect the water potential
gradient.
Has no impact on Osmosis.
Good for storage.
Not Sweet
Large molecule so cannot leave the cell and is always available.
, AQA A level Biology
Branched and unbranched.
Starch is the long term energy store in plant cells, found as starch grains in the
cytoplasm.
Amylose (25%) - Answer - Long unbranched chain of alpha glucose, linked by a 1-4
glycosidic bond.
- Hydrogen bonds give it a coiled, spiral structure so it is therefore very compact.
-Hydroxyl groups project into the middle. They form hydrogen bonds with each other
which stabilises the spiral.
Iodine detects this as it gets stuck inside the spiral and forms an iodine starch complex.
Amylopectin (75%) - Answer - Long, branched chain of alpha glucose
-Side branches allow the enzymes to break down the molecule to get at the glycosidic
bonds easily. This means glucose can be released quickly.
-The molecule is branches at 1-4 glycosidic bonds and 1-6 glycosidic bonds.
-Highly branched means it can be easily digested by enzymes to produce glucose for
respiration for ATP production due to the large surface area.
Glycogen - Answer -Iodine does not detect this as it only detects amylose and glycogen
only has a branched structure.
-It is a monomer of alpha glucose with 1,4 and 1,6 glycosidic bonds.
-Animal cells store their excess glucose from carbohydrate as glycogen in muscles and
the liver. This is large and insoluble and therefore has no effect on osmosis.
-The branched points occur more often. Therefore they are less dense and more
soluble. Enzymes can hydrolyse glycosidic bonds of glycogen into glucose for
respiration and the consequent ATP production. Glucose can be produced more
quickly.
-Indicates the higher metabolic requirements for animals compared with plants as
animals need muscle contractions, homeostasis, temperature regulation).
-Compact so it is good for storage.
Cellulose - Answer -Long, unbranched chains of beta glucose. When beta molecules
bond, every other molecule is inverted 180 degrees, forming straight cellulose chains,
linked by 1,2 glycosidic bonds.
-Chains become linked together by many hydrogen bonds to form microfibrils (many
hydrogen bonds provides strength and stability). These stack to form fibrils.
-Used in the cell wall of plants.
-Provides strength and rigidity to cell wall as it can resist turgid pressure from water,
stopping the cell from bursting.
Starch Test - Answer Add iodine dissolved in potassium iodide solution to the sample. If
the starch is present, the sample will turn from orange to blue/black.
Lipids - Answer These are not polymers as they are not made of identical repeated units
and contain ester bonds not glycosidic.
They are made form hydrocarbons, glycerol, phosphates and fatty acids.
