AQA A LEVEL BIOLOGY - PAPER 3 (SYNOPTIC) QUESTIONS AND CORRECT DETAILED ANSWERS 2024/2025 BEST EXAM SOLUTION TOP RANKED TO SCORE A+ FOR SUCCESS
1.What are the useful properties of water and why ? - CORRECT ANSWERS 1) Water is a metabolite - in many metabolic reactions including condensation and hydrolysis 2) Water is a solvent - medium in which enzyme catalysed reactions take place (metabolic reactions ) and readily dissolves substances like inorganic ions ( as water is dipolar so totally surrounds the ions) , excretory products (urea/ammonia) , respiratory gases and small hydrophilic molecules ( amino acids , etc)
3) Water has a high latent heat of vaporisation (lots of energy required to break hydrogen bonds between water molecules so a lot of energy is used up when water evaporates ) so helps with temperature control as evaporation of sweat cools humans down 4) Water has a high specific heat capacity ( to separate the many hydrogen bonds requires a lot of energy) so acts as a buffer and resists temperature changes to maintain a constant internal body temperature 5) Water has large cohesive forces ( as hydrogen bonds stick together) so allows transportation of substances( water travelling in columns in xylem) and means water has a high surface tension when it comes into contact with air ( allowing pond skaters to walk on its surface)
Why is water dipolar ? - CORRECT ANSWERS As water is made up of two hydrogen atoms and one oxygen atom , the hydrogen atoms have a slightly positive pole and the oxygen atom has a slightly negative pole making water dipolar.
Hydrogen bonds - CORRECT ANSWERS Slightly negatively charged oxygen atom is attracted to the slightly positively charged hydrogen atom of other water molecules. The attraction between opposite charges is called hydrogen bonding, which are weak bonds but strong in large numbers. This makes water a major component in cells
Hydrolysis - CORRECT ANSWERS Breaks a bond between two molecules by the addition of a
molecule of water
Condensation - CORRECT ANSWERS Joins two molecules together with the formation of a bond by the removal of a molecule of water
Polymer - CORRECT ANSWERS A molecule ( carbohydrate, nucleotide or protein) made up of many monomers ( small repeating units) joined together by condensation reactions and broken down my hydrolysis AQA A LEVEL BIOLOGY - PAPER 3 (SYNOPTIC) QUESTIONS AND CORRECT DETAILED ANSWERS 2024/2025 BEST EXAM SOLUTION TOP RANKED TO SCORE A+ FOR SUCCESS
Monosaccharides - CORRECT ANSWERS Are the monomers from which larger carbohydrates are made and contain the elements C H and O. They are sweet and soluble and there are three types : fructose , glucose and galactose. Hexose sugars (glucose) have the formula C6H12O6
Glucose is the product of photosynthesis and a major substrate of respiration , draw the two structural isomers of glucose in long and short hand and state the difference between them -
CORRECT ANSWERS On carbon 1 in beta glucose the hydroxyl group (OH) points upwards and in alpha glucose the hydroxyl group points down on carbon 1
Sucrose - CORRECT ANSWERS Glucose and fructose
Maltose - CORRECT ANSWERS Glucose and glucose
Lactose - CORRECT ANSWERS Glucose and galactose
How do monosaccharides join together - CORRECT ANSWERS By condensation to form a glycosidic bond between two monosaccharides and a disaccharide and a molecule of water are formed
Disaccharide - CORRECT ANSWERS Two monosaccharides joined together by condensation forming a glycosidic bond. There are three types : maltose, sucrose and lactose. They have the chemical formula C12H22O11
Draw the hydrolysis of maltose in structural formula and short hand formula - CORRECT ANSWERS Test for starch - CORRECT ANSWERS Add iodine solution to the test sample , if starch is present colour changes from yellow to a blue-black colour.
Test for a reducing sugar - CORRECT ANSWERS Heat with Benedict's reagent ( blue) and if reducing sugar is present a brick red precipitate will form AQA A LEVEL BIOLOGY - PAPER 3 (SYNOPTIC) QUESTIONS AND CORRECT DETAILED ANSWERS 2024/2025 BEST EXAM SOLUTION TOP RANKED TO SCORE A+ FOR SUCCESS
Issues with the Benedict's test ? - CORRECT ANSWERS 1) It is non specific - doesn't tell which reducing sugar is present , a biosensor can be used to detect for specific sugars 2) It's qualitative so colour change is being measured so can't obtain concentration of reducing sugar but allows an estimate for how much is present in the strength of the colour
3) Is subjective
How to quantify results on the concentration of unknown glucose concentration? - CORRECT ANSWERS Use a colorimeter, as a serial dilution of known glucose concentrations can be measured producing a set of solutions with known concentrations . The Benedict's test can be performed with each of these and the colour intensity measured. A CALIBRATION
CURVE can be produced from the results and used to read iff the concentration of glucose in an unknown solution.
Test for a non-reducing sugar ? - CORRECT ANSWERS Heat the sample with Benedict's reagent and if there is no colour change a reducing sugar is not present but a non-reducing sugar could be.
Heat a fresh sample with dilute acid ( which will hydrolyse the non reducing sugar into its constituent monosaccharides).
Neutralise with alkali and carry out the Benedict's test again If the test is positive for a non-reducing sugar it will form a brick red precipitate
Polysaccharide - CORRECT ANSWERS Three main types - starch , glycogen and cellulose which are chains of many monomers of glucose formed in condensation reactions.
Starch - CORRECT ANSWERS Starch is used for energy storage in plants and is made from condensation of alpha glucose.
Amylose- compact helical chains so store lots of glucose in a small space Amylopectin - branched chains which allow many ends to be quickly hydrolysed by amylase enzymes to release glucose Insoluble and large so no osmotic effects , inert and cannot diffuse out of the cells which they are stored in . AQA A LEVEL BIOLOGY - PAPER 3 (SYNOPTIC) QUESTIONS AND CORRECT DETAILED ANSWERS 2024/2025 BEST EXAM SOLUTION TOP RANKED TO SCORE A+ FOR SUCCESS
Cellulose - CORRECT ANSWERS Major component of plant cell walls made up of beta glucose monomer in a condensation reaction.
Chains of beta glucose molecules form long straight unbranched chains.
These chains run parallel to each other and hydrogen bonds form cross-linkages between chains. These many hydrogen bonds provide high tensile strength which makes the cell wall rigid and prevents osmotic lysis
Hydrogen bonds also form strong fibres called microfibrils which are grouped into fibres which provide structural support.
Glycogen - CORRECT ANSWERS Energy storage molecule in animals found in liver cells and in muscle tissue and is made from the condensation of alpha glucose. Compact so store lots of glucose in a small space Is quickly hydrolysed to release soluble glucose as many ends for amylase enzymes to attack Large and insoluble so no osmotic effects , inert and cannot diffuse out of the cells which they are stored in .
Name the 4 inorganic ions and state their role - CORRECT ANSWERS Inorganic ions occur in solution in the cytoplasm and body fluids ( blood , tissue fluid) Hydrogen ions - affects pH levels, the higher the concentration of H+ ions the lower the pH( more acid ) Iron ions - important component of haemoglobin which carries oxygen around the body in the red blood cells Phosphate ions - component of DNA , ATP , RNA and phospholipids , bonds between phosphate groups store energy in ATP Sodium ions - involved in the absorption of glucose and amino acids in co transport in the small intestine
Amino acids - CORRECT ANSWERS Are the monomers from which polypeptides are made. Proteins are made up of one or more polypeptide chains. All amino acids contain the elements C H O and N and are made up of an amino group (NH2) , a carboxylic acid group (COOH) and a variable group (R)
What is a conjugated protein ? - CORRECT ANSWERS A protein with a non-protein chemical group attached
1.What are the useful properties of water and why ? - CORRECT ANSWERS 1) Water is a metabolite - in many metabolic reactions including condensation and hydrolysis 2) Water is a solvent - medium in which enzyme catalysed reactions take place (metabolic reactions ) and readily dissolves substances like inorganic ions ( as water is dipolar so totally surrounds the ions) , excretory products (urea/ammonia) , respiratory gases and small hydrophilic molecules ( amino acids , etc)
3) Water has a high latent heat of vaporisation (lots of energy required to break hydrogen bonds between water molecules so a lot of energy is used up when water evaporates ) so helps with temperature control as evaporation of sweat cools humans down 4) Water has a high specific heat capacity ( to separate the many hydrogen bonds requires a lot of energy) so acts as a buffer and resists temperature changes to maintain a constant internal body temperature 5) Water has large cohesive forces ( as hydrogen bonds stick together) so allows transportation of substances( water travelling in columns in xylem) and means water has a high surface tension when it comes into contact with air ( allowing pond skaters to walk on its surface)
Why is water dipolar ? - CORRECT ANSWERS As water is made up of two hydrogen atoms and one oxygen atom , the hydrogen atoms have a slightly positive pole and the oxygen atom has a slightly negative pole making water dipolar.
Hydrogen bonds - CORRECT ANSWERS Slightly negatively charged oxygen atom is attracted to the slightly positively charged hydrogen atom of other water molecules. The attraction between opposite charges is called hydrogen bonding, which are weak bonds but strong in large numbers. This makes water a major component in cells
Hydrolysis - CORRECT ANSWERS Breaks a bond between two molecules by the addition of a
molecule of water
Condensation - CORRECT ANSWERS Joins two molecules together with the formation of a bond by the removal of a molecule of water
Polymer - CORRECT ANSWERS A molecule ( carbohydrate, nucleotide or protein) made up of many monomers ( small repeating units) joined together by condensation reactions and broken down my hydrolysis AQA A LEVEL BIOLOGY - PAPER 3 (SYNOPTIC) QUESTIONS AND CORRECT DETAILED ANSWERS 2024/2025 BEST EXAM SOLUTION TOP RANKED TO SCORE A+ FOR SUCCESS
Monosaccharides - CORRECT ANSWERS Are the monomers from which larger carbohydrates are made and contain the elements C H and O. They are sweet and soluble and there are three types : fructose , glucose and galactose. Hexose sugars (glucose) have the formula C6H12O6
Glucose is the product of photosynthesis and a major substrate of respiration , draw the two structural isomers of glucose in long and short hand and state the difference between them -
CORRECT ANSWERS On carbon 1 in beta glucose the hydroxyl group (OH) points upwards and in alpha glucose the hydroxyl group points down on carbon 1
Sucrose - CORRECT ANSWERS Glucose and fructose
Maltose - CORRECT ANSWERS Glucose and glucose
Lactose - CORRECT ANSWERS Glucose and galactose
How do monosaccharides join together - CORRECT ANSWERS By condensation to form a glycosidic bond between two monosaccharides and a disaccharide and a molecule of water are formed
Disaccharide - CORRECT ANSWERS Two monosaccharides joined together by condensation forming a glycosidic bond. There are three types : maltose, sucrose and lactose. They have the chemical formula C12H22O11
Draw the hydrolysis of maltose in structural formula and short hand formula - CORRECT ANSWERS Test for starch - CORRECT ANSWERS Add iodine solution to the test sample , if starch is present colour changes from yellow to a blue-black colour.
Test for a reducing sugar - CORRECT ANSWERS Heat with Benedict's reagent ( blue) and if reducing sugar is present a brick red precipitate will form AQA A LEVEL BIOLOGY - PAPER 3 (SYNOPTIC) QUESTIONS AND CORRECT DETAILED ANSWERS 2024/2025 BEST EXAM SOLUTION TOP RANKED TO SCORE A+ FOR SUCCESS
Issues with the Benedict's test ? - CORRECT ANSWERS 1) It is non specific - doesn't tell which reducing sugar is present , a biosensor can be used to detect for specific sugars 2) It's qualitative so colour change is being measured so can't obtain concentration of reducing sugar but allows an estimate for how much is present in the strength of the colour
3) Is subjective
How to quantify results on the concentration of unknown glucose concentration? - CORRECT ANSWERS Use a colorimeter, as a serial dilution of known glucose concentrations can be measured producing a set of solutions with known concentrations . The Benedict's test can be performed with each of these and the colour intensity measured. A CALIBRATION
CURVE can be produced from the results and used to read iff the concentration of glucose in an unknown solution.
Test for a non-reducing sugar ? - CORRECT ANSWERS Heat the sample with Benedict's reagent and if there is no colour change a reducing sugar is not present but a non-reducing sugar could be.
Heat a fresh sample with dilute acid ( which will hydrolyse the non reducing sugar into its constituent monosaccharides).
Neutralise with alkali and carry out the Benedict's test again If the test is positive for a non-reducing sugar it will form a brick red precipitate
Polysaccharide - CORRECT ANSWERS Three main types - starch , glycogen and cellulose which are chains of many monomers of glucose formed in condensation reactions.
Starch - CORRECT ANSWERS Starch is used for energy storage in plants and is made from condensation of alpha glucose.
Amylose- compact helical chains so store lots of glucose in a small space Amylopectin - branched chains which allow many ends to be quickly hydrolysed by amylase enzymes to release glucose Insoluble and large so no osmotic effects , inert and cannot diffuse out of the cells which they are stored in . AQA A LEVEL BIOLOGY - PAPER 3 (SYNOPTIC) QUESTIONS AND CORRECT DETAILED ANSWERS 2024/2025 BEST EXAM SOLUTION TOP RANKED TO SCORE A+ FOR SUCCESS
Cellulose - CORRECT ANSWERS Major component of plant cell walls made up of beta glucose monomer in a condensation reaction.
Chains of beta glucose molecules form long straight unbranched chains.
These chains run parallel to each other and hydrogen bonds form cross-linkages between chains. These many hydrogen bonds provide high tensile strength which makes the cell wall rigid and prevents osmotic lysis
Hydrogen bonds also form strong fibres called microfibrils which are grouped into fibres which provide structural support.
Glycogen - CORRECT ANSWERS Energy storage molecule in animals found in liver cells and in muscle tissue and is made from the condensation of alpha glucose. Compact so store lots of glucose in a small space Is quickly hydrolysed to release soluble glucose as many ends for amylase enzymes to attack Large and insoluble so no osmotic effects , inert and cannot diffuse out of the cells which they are stored in .
Name the 4 inorganic ions and state their role - CORRECT ANSWERS Inorganic ions occur in solution in the cytoplasm and body fluids ( blood , tissue fluid) Hydrogen ions - affects pH levels, the higher the concentration of H+ ions the lower the pH( more acid ) Iron ions - important component of haemoglobin which carries oxygen around the body in the red blood cells Phosphate ions - component of DNA , ATP , RNA and phospholipids , bonds between phosphate groups store energy in ATP Sodium ions - involved in the absorption of glucose and amino acids in co transport in the small intestine
Amino acids - CORRECT ANSWERS Are the monomers from which polypeptides are made. Proteins are made up of one or more polypeptide chains. All amino acids contain the elements C H O and N and are made up of an amino group (NH2) , a carboxylic acid group (COOH) and a variable group (R)
What is a conjugated protein ? - CORRECT ANSWERS A protein with a non-protein chemical group attached
