Metabolic reactions are the chemical processes that occur within cells to maintain life, such as breaking down nutrients and building cellular components.

Water is the medium in which all reactions take place in cells and in which all substances are around the body.

Water is the medium in which all metabolic reactions take place in cells and in which all substances are transported around the body.

What is a covalent bond ?

A covalent bond is a chemical bond formed when two atoms share pairs of electrons.

True or False? Water is a polar molecule because the electrons are evenly shared between oxygen and hydrogen atoms.

False. Water is a polar molecule because the electrons are unevenly shared between the oxygen and hydrogen atoms, creating partial charges.

A hydrogen bond is a weak attraction between the positive region of one polar molecule and the negative region of another, such as between water molecules.

When a molecule has one end that is negatively charged and one end that is positively charged, it is said to be a molecule.

When a molecule has one end that is negatively charged and one end that is positively charged, it is said to be a polar molecule.

What is cohesion in the context of water molecules?

Cohesion is the attraction of water molecules to each other due to hydrogen bonding.

How does water act as a solvent in living organisms?

Water acts as a solvent because its polar molecules surround charged particles and allow them to dissolve, which enables chemical reactions and the transport of metabolites in cells.

A carbohydrate is a carbon-based compound found in living organisms, containing the elements carbon (C) , hydrogen (H) and oxygen (O) .

Why are carbon atoms so important for the structure of organic compounds?

Carbon atoms are important because each carbon atom can form covalent bonds , making the compounds very stable and able to form straight chains, branched chains, or rings.

The monomers of carbohydrates are simple sugars called .

The monomers of carbohydrates are simple sugars called monosaccharides.

What are the three types of carbohydrates found in living organisms?

The three types of carbohydrates are monosaccharides , disaccharides and polysaccharides .

A monosaccharide is a simple sugar molecule, such as glucose , that consists of a single sugar unit and acts as a basic building block of carbohydrates.

Glucose is a sugar with a ring structure made up of carbons.

Glucose is a hexose sugar with a ring structure made up of six carbons.

What is the main function of monosaccharides in cells?

The main function of monosaccharides is to store energy within their bonds , which is released during respiration.

Alpha glucose has the hydrogen carbon 1 and the OH group .

Alpha glucose has the hydrogen above carbon 1 and the OH group below .

True or False? Disaccharides are insoluble in water.

False. Disaccharides are easily soluble in water due to their many hydroxyl groups forming hydrogen bonds with water.

A glycosidic bond is a covalent bond that joins two monosaccharide molecules together in a carbohydrate.

Starch is made of two polysaccharides: (an unbranched helix) and (a branched molecule).

Starch is made of two polysaccharides: amylose (an unbranched helix) and amylopectin (a branched molecule).

Why is glycogen an effective storage polysaccharide in animals?

Glycogen is highly branched and compact , allowing quick release or storage of glucose and fitting large amounts in a small space.

A reducing sugar is a sugar that can donate electrons to another molecule, and is detected by its ability to reduce copper (II) sulfate to copper (I) oxide in Benedict’s test.

What does Benedict’s test detect in a sample?

Benedict’s test detects the presence of reducing sugars , which reduce copper (II) sulfate to copper (I) oxide, forming a coloured precipitate.

Benedict’s reagent contains (CuSO₄) ions and is initially .

Benedict’s reagent contains copper (II) sulfate (CuSO₄) ions and is initially blue .

True or False? A brick-red precipitate in Benedict’s test indicates a low concentration of reducing sugar.

False. A brick-red precipitate indicates a high concentration of reducing sugar in the sample.

A non-reducing sugar is a sugar that cannot donate electrons to another molecule and does not react with Benedict’s reagent unless broken down into monosaccharides first.

What must be done to test for non-reducing sugars using Benedict’s reagent?

The sample must be hydrolysed by adding dilute hydrochloric acid , heated, then neutralised with sodium hydrogencarbonate , before repeating Benedict’s test.

In a semi-quantitative Benedict’s test, the of the colour change is used to estimate the of reducing sugar.

In a semi-quantitative Benedict’s test, the intensity of the colour change is used to estimate the concentration of reducing sugar.

How does a colorimeter help make Benedict’s test more quantitative?

A colorimeter measures the absorbance of light passing through the sample, providing a quantitative value that can be compared to a calibration curve to determine the concentration of reducing sugar.

A is made by taking a series of dilutions from a stock solution so that the decreases by the same amount each time.

A serial dilution is made by taking a series of dilutions from a stock solution so that the concentration decreases by the same amount each time.

Iodine test for starch

The iodine test for starch is a chemical test in which iodine solution is added to a sample. If starch is present, the sample turns blue-black .

What colour change indicates a positive result in the iodine test for starch?

A positive result in the iodine test for starch is indicated by a blue-black colour forming when iodine solution is added to the sample.

In a semi-quantitative iodine test, the of the colour change relates to the of starch in the sample.

In a semi-quantitative iodine test, the intensity of the colour change relates to the concentration of starch in the sample.

True or False? A colourimeter can be used to measure the intensity of colour in the iodine-starch test to estimate starch concentration.

True. A colourimeter measures the absorbance or transmission of light through the solution, allowing a calibration curve to estimate the concentration of starch .

Condensation reaction

A condensation reaction joins two molecules together as a chemical bond (glycosidic, peptide or ester) forms and a molecule of water is released.

Polysaccharides are so have less influence on the process of osmosis.

Polysaccharides are insoluble so have less influence on the process of osmosis.

What is the name of the bond formed between two monosaccharides during a condensation reaction?

The bond formed between two monosaccharides during a condensation reaction is called a glycosidic bond .

A 1,4 glycosidic bond forms when the OH groups are located on carbon 1 of one monosaccharide and of the other.

A 1,4 glycosidic bond forms when the OH groups are located on carbon 1 of one monosaccharide and carbon 4 of the other.

A hydrolysis reaction is a chemical process that breaks a glycosidic bond by adding a water molecule .

True or False? A hydrolysis reaction forms a glycosidic bond between monosaccharides.

False. A hydrolysis reaction breaks a glycosidic bond by adding water; glycosidic bonds are formed by condensation reactions .

When two glucose molecules join by a glycosidic bond, the resulting disaccharide is .

When two glucose molecules join by a glycosidic bond, the resulting disaccharide is maltose .

Which monosaccharides join together to form lactose ?

Lactose is formed when glucose joins with galactose .

Which monosaccharides join together to form sucrose ?

Sucrose is formed when glucose joins with fructose .

A lipid is a macromolecule containing carbon, hydrogen and oxygen , with a lower proportion of oxygen than carbohydrates. Lipids are non-polar and hydrophobic .

A triglyceride is a type of lipid that consists of one glycerol molecule joined to three fatty acids . It is the main component of fats and oils.

Lipids are and , meaning they are insoluble in water.

Lipids are non-polar and hydrophobic , meaning they are insoluble in water.

What are the building blocks that make up a triglyceride ?

The building blocks that make up a triglyceride are glycerol and fatty acids .

What is the chemical formula for a fatty acid ?

The shorthand chemical formula for a fatty acid is RCOOH .

A triglyceride is formed by joining fatty acid molecules to glycerol molecule(s).

A triglyceride is formed by joining three fatty acid molecules to one glycerol molecule.

True or False? The formation of a triglyceride from glycerol and fatty acids is a condensation reaction.

True. Triglycerides are formed by esterification , which is a condensation reaction that releases water.

The bond formed between a glycerol and a fatty acid is called an .

The bond formed between a glycerol and a fatty acid is called an ester bond .

A fatty acid is a molecule containing a methyl group at one end of a hydrocarbon chain (R group) and a carboxyl group at the other end.

International A Level (IAL)BiologyEdexcelFlashcards1. Molecules, Transport & HealthBiological Molecules

Biological Molecules (Edexcel International A Level (IAL) Biology): Flashcards

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FrontThe Importance of Water
Metabolic reactions

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Cards in this collection (54)

Metabolic reactions
Metabolic reactions are the chemical processes that occur within cells to maintain life, such as breaking down nutrients and building cellular components.
Water is the medium in which all reactions take place in cells and in which all substances are around the body.
Water is the medium in which all metabolic reactions take place in cells and in which all substances are transported around the body.
What is a covalent bond?
A covalent bond is a chemical bond formed when two atoms share pairs of electrons.
True or False?
Water is a polar molecule because the electrons are evenly shared between oxygen and hydrogen atoms.
False.
Water is a polar molecule because the electrons are unevenly shared between the oxygen and hydrogen atoms, creating partial charges.
Hydrogen bond
A hydrogen bond is a weak attraction between the positive region of one polar molecule and the negative region of another, such as between water molecules.
When a molecule has one end that is negatively charged and one end that is positively charged, it is said to be a molecule.
When a molecule has one end that is negatively charged and one end that is positively charged, it is said to be a polar molecule.
What is cohesion in the context of water molecules?
Cohesion is the attraction of water molecules to each other due to hydrogen bonding.
How does water act as a solvent in living organisms?
Water acts as a solvent because its polar molecules surround charged particles and allow them to dissolve, which enables chemical reactions and the transport of metabolites in cells.
Carbohydrate
A carbohydrate is a carbon-based compound found in living organisms, containing the elements carbon (C), hydrogen (H) and oxygen (O).
Why are carbon atoms so important for the structure of organic compounds?
Carbon atoms are important because each carbon atom can form covalent bonds, making the compounds very stable and able to form straight chains, branched chains, or rings.
The monomers of carbohydrates are simple sugars called .
The monomers of carbohydrates are simple sugars called monosaccharides.
What are the three types of carbohydrates found in living organisms?
The three types of carbohydrates are monosaccharides, disaccharides and polysaccharides.
Monosaccharide
A monosaccharide is a simple sugar molecule, such as glucose, that consists of a single sugar unit and acts as a basic building block of carbohydrates.
Glucose is a sugar with a ring structure made up of carbons.
Glucose is a hexose sugar with a ring structure made up of six carbons.
What is the main function of monosaccharides in cells?
The main function of monosaccharides is to store energy within their bonds, which is released during respiration.
Alpha glucose has the hydrogen carbon 1 and the OH group .
Alpha glucose has the hydrogen above carbon 1 and the OH group below.
True or False?
Disaccharides are insoluble in water.
False.
Disaccharides are easily soluble in water due to their many hydroxyl groups forming hydrogen bonds with water.
Glycosidic bond
A glycosidic bond is a covalent bond that joins two monosaccharide molecules together in a carbohydrate.
Starch is made of two polysaccharides: (an unbranched helix) and (a branched molecule).
Starch is made of two polysaccharides: amylose (an unbranched helix) and amylopectin (a branched molecule).
Why is glycogen an effective storage polysaccharide in animals?
Glycogen is highly branched and compact, allowing quick release or storage of glucose and fitting large amounts in a small space.
Reducing sugar
A reducing sugar is a sugar that can donate electrons to another molecule, and is detected by its ability to reduce copper (II) sulfate to copper (I) oxide in Benedict’s test.
What does Benedict’s test detect in a sample?
Benedict’s test detects the presence of reducing sugars, which reduce copper (II) sulfate to copper (I) oxide, forming a coloured precipitate.
Benedict’s reagent contains (CuSO₄) ions and is initially .
Benedict’s reagent contains copper (II) sulfate (CuSO₄) ions and is initially blue.
True or False?
A brick-red precipitate in Benedict’s test indicates a low concentration of reducing sugar.
False.
A brick-red precipitate indicates a high concentration of reducing sugar in the sample.
Non-reducing sugar
A non-reducing sugar is a sugar that cannot donate electrons to another molecule and does not react with Benedict’s reagent unless broken down into monosaccharides first.
What must be done to test for non-reducing sugars using Benedict’s reagent?
The sample must be hydrolysed by adding dilute hydrochloric acid, heated, then neutralised with sodium hydrogencarbonate, before repeating Benedict’s test.
In a semi-quantitative Benedict’s test, the of the colour change is used to estimate the of reducing sugar.
In a semi-quantitative Benedict’s test, the intensity of the colour change is used to estimate the concentration of reducing sugar.
How does a colorimeter help make Benedict’s test more quantitative?
A colorimeter measures the absorbance of light passing through the sample, providing a quantitative value that can be compared to a calibration curve to determine the concentration of reducing sugar.
A is made by taking a series of dilutions from a stock solution so that the decreases by the same amount each time.
A serial dilution is made by taking a series of dilutions from a stock solution so that the concentration decreases by the same amount each time.
Iodine test for starch
The iodine test for starch is a chemical test in which iodine solution is added to a sample. If starch is present, the sample turns blue-black.
What colour change indicates a positive result in the iodine test for starch?
A positive result in the iodine test for starch is indicated by a blue-black colour forming when iodine solution is added to the sample.
In a semi-quantitative iodine test, the of the colour change relates to the of starch in the sample.
In a semi-quantitative iodine test, the intensity of the colour change relates to the concentration of starch in the sample.
True or False?
A colourimeter can be used to measure the intensity of colour in the iodine-starch test to estimate starch concentration.
True.
A colourimeter measures the absorbance or transmission of light through the solution, allowing a calibration curve to estimate the concentration of starch.
Condensation reaction
A condensation reaction joins two molecules together as a chemical bond (glycosidic, peptide or ester) forms and a molecule of water is released.
Polysaccharides are so have less influence on the process of osmosis.
Polysaccharides are insoluble so have less influence on the process of osmosis.
What is the name of the bond formed between two monosaccharides during a condensation reaction?
The bond formed between two monosaccharides during a condensation reaction is called a glycosidic bond.
A 1,4 glycosidic bond forms when the OH groups are located on carbon 1 of one monosaccharide and of the other.
A 1,4 glycosidic bond forms when the OH groups are located on carbon 1 of one monosaccharide and carbon 4 of the other.
Hydrolysis reaction
A hydrolysis reaction is a chemical process that breaks a glycosidic bond by adding a water molecule.
True or False?
A hydrolysis reaction forms a glycosidic bond between monosaccharides.
False.
A hydrolysis reaction breaks a glycosidic bond by adding water; glycosidic bonds are formed by condensation reactions.
When two glucose molecules join by a glycosidic bond, the resulting disaccharide is .
When two glucose molecules join by a glycosidic bond, the resulting disaccharide is maltose.
Which monosaccharides join together to form lactose?
Lactose is formed when glucose joins with galactose.
Which monosaccharides join together to form sucrose?
Sucrose is formed when glucose joins with fructose.
Lipid
A lipid is a macromolecule containing carbon, hydrogen and oxygen, with a lower proportion of oxygen than carbohydrates. Lipids are non-polar and hydrophobic.
Triglyceride
A triglyceride is a type of lipid that consists of one glycerol molecule joined to three fatty acids. It is the main component of fats and oils.
Lipids are and , meaning they are insoluble in water.
Lipids are non-polar and hydrophobic, meaning they are insoluble in water.
What are the building blocks that make up a triglyceride?
The building blocks that make up a triglyceride are glycerol and fatty acids.
What is the chemical formula for a fatty acid?
The shorthand chemical formula for a fatty acid is RCOOH.
A triglyceride is formed by joining fatty acid molecules to glycerol molecule(s).
A triglyceride is formed by joining three fatty acid molecules to one glycerol molecule.
True or False?
The formation of a triglyceride from glycerol and fatty acids is a condensation reaction.
True.
Triglycerides are formed by esterification, which is a condensation reaction that releases water.
The bond formed between a glycerol and a fatty acid is called an .
The bond formed between a glycerol and a fatty acid is called an ester bond.
Fatty acid
A fatty acid is a molecule containing a methyl group at one end of a hydrocarbon chain (R group) and a carboxyl group at the other end.
The shorthand chemical formula for a fatty acid is .
The shorthand chemical formula for a fatty acid is RCOOH.
True or False?
Saturated fatty acids contain carbon-carbon double bonds.
False.
Saturated fatty acids contain no carbon-carbon double bonds, meaning the hydrocarbon chain is saturated with hydrogen atoms.
What is the difference between cis- and trans-unsaturated fatty acids?
In cis-unsaturated fatty acids, hydrogen atoms are on the same side of the double bond, allowing enzymes to metabolise them. In trans-unsaturated fatty acids, hydrogens are on opposite sides, so they cannot be metabolised and are linked to coronary heart disease.

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