monomer and polymer

What is a monomer?

A small molecule that can join with others to form a larger molecule.

What is a polymer?

A large molecule made from many repeating monomers.

What is a condensation reaction?

A reaction that joins molecules together and releases water.

What is hydrolysis?

A reaction that breaks a bond using water.

What elements are carbohydrates made from?

Carbon, hydrogen and oxygen.

What is a monosaccharide?

A single sugar unit.

What is a disaccharide?

A carbohydrate made from two monosaccharides joined together.

What is a polysaccharide?

A carbohydrate made from many monosaccharides joined together.

What bond joins monosaccharides together?

A glycosidic bond.

What are the three common monosaccharides?

Glucose, galactose and fructose.

What are the two forms of glucose?

Alpha-glucose and beta-glucose.

What is maltose made from?

Two glucose molecules.

What is sucrose made from?

Glucose and fructose.

What is lactose made from?

Glucose and galactose.

What type of reaction forms a glycosidic bond?

A condensation reaction.

What type of reaction breaks a glycosidic bond?

Hydrolysis.

What is the main animal storage polysaccharide?

Glycogen.

What is the main plant storage polysaccharide?

Starch.

What is cellulose used for?

Providing strength to plant cell walls.

What is glycogen made from?

Alpha-glucose molecules.

What type of bonds are found in glycogen?

1,4 and 1,6 glycosidic bonds.

Why is glycogen highly branched?

Branching allows glucose to be released quickly.

Why is glycogen compact?

Its branching and coiling allow a lot of glucose to be stored in a small space.

Why is glycogen insoluble?

It does not affect water potential and does not easily diffuse out of cells.

What is starch made from?

Alpha-glucose molecules.

What are the two components of starch?

Amylose and amylopectin.

What is amylose?

An unbranched chain of alpha-glucose molecules joined by 1,4 glycosidic bonds.

What shape does amylose form?

It coils into a compact structure.

What is amylopectin?

A branched chain of alpha-glucose molecules.

What bonds are found in amylopectin?

1,4 and 1,6 glycosidic bonds.

Why is starch suitable for storage?

It is compact and insoluble.

What is cellulose made from?

Beta-glucose molecules.

How are cellulose glucose molecules arranged?

They form long, straight, unbranched chains.

What holds cellulose chains together?

Hydrogen bonds.

What are microfibrils?

Bundles of cellulose chains held together by hydrogen bonds.

Why is cellulose strong?

Hydrogen bonds between chains give the cell wall high tensile strength.

Why can't humans digest cellulose?

Humans do not have the enzyme needed to break its beta-glycosidic bonds.

What is a reducing sugar?

A sugar that can reduce Benedict's reagent.

What test is used for reducing sugars?

Benedict's test.

What reagent is used to test for reducing sugars?

Benedict's solution.

How do you test for a reducing sugar?

Add Benedict's solution and heat the mixture in a water bath.

What is a positive Benedict's test?

A colour change from blue towards orange/brick-red, depending on the amount of reducing sugar.

What does a blue Benedict's result indicate?

No detectable reducing sugar.

How can a non-reducing sugar be tested?

Hydrolyse it with hydrochloric acid, neutralise with sodium hydrogencarbonate, then repeat Benedict's test.

Why is hydrochloric acid used in the non-reducing sugar test?

It hydrolyses the glycosidic bonds.

Why is sodium hydrogencarbonate added after hydrochloric acid?

To neutralise the acid before carrying out Benedict's test.

What test is used for starch?

The iodine test.

What reagent is used to test for starch?

Iodine solution, usually iodine dissolved in potassium iodide.

What colour indicates starch is present?

Blue-black.

What colour is a negative iodine test?

Yellow-brown/orange-brown.

What elements are lipids mainly made from?

Carbon, hydrogen and oxygen.

Are lipids soluble in water?

No, they are insoluble in water.

What are lipids soluble in?

Organic solvents.

What is a triglyceride?

A lipid made from one glycerol molecule and three fatty acid molecules.

What bond joins glycerol and fatty acids?

An ester bond.

What reaction forms ester bonds in triglycerides?

A condensation reaction.

How many fatty acids are joined to one glycerol in a triglyceride?

Three.

What is a saturated fatty acid?

A fatty acid with no carbon-carbon double bonds.

What is an unsaturated fatty acid?

A fatty acid containing one or more carbon-carbon double bonds.

Why are unsaturated fats often liquid at room temperature?

Double bonds create bends in the fatty acid chains, preventing tight packing.

Why are triglycerides good energy stores?

They contain many energy-rich bonds and have a high energy-to-mass ratio.

Why are triglycerides insoluble?

They do not affect the water potential of cells.

What happens when triglycerides are oxidised?

Energy is released and water is produced.

What is a phospholipid?

A lipid in which one fatty acid of a triglyceride is replaced by a phosphate-containing group.

What are the two parts of a phospholipid?

A hydrophilic phosphate head and hydrophobic fatty acid tails.

What does hydrophilic mean?

Attracted to water.

What does hydrophobic mean?

Repelled by water.

How do phospholipids behave in water?

They arrange themselves with hydrophilic heads facing water and hydrophobic tails away from it.

What is a phospholipid bilayer?

Two layers of phospholipids arranged with their heads facing the water and tails facing inward.

What is a micelle?

A spherical arrangement of phospholipids with hydrophilic heads outside and hydrophobic tails inside.

What are glycolipids involved in?

Cell recognition.

How do you carry out the emulsion test for lipids?

Add ethanol to the sample, shake, then add water.

What indicates a positive emulsion test?

A cloudy or milky white emulsion forms.

What does a clear solution indicate in the emulsion test?

No detectable lipid.

What is the purpose of using ethanol in the emulsion test?

Lipids dissolve in ethanol.

Why is water added in the emulsion test?

Lipids are insoluble in water, so they form a cloudy emulsion.

What are proteins made from?

Amino acids.

How many different amino acids are commonly used to make proteins?

20.

What are the three main parts of an amino acid?

An amino group, a carboxyl group and an R group.

What determines the properties of an amino acid?

Its R group.

What bond joins amino acids?

A peptide bond.

What reaction forms a peptide bond?

A condensation reaction.

What is a dipeptide?

Two amino acids joined by a peptide bond.

What is a polypeptide?

A chain of three or more amino acids joined by peptide bonds.

What is the primary structure of a protein?

The specific sequence of amino acids in a polypeptide.

What is the secondary structure of a protein?

The folding of the polypeptide into structures such as alpha helices and beta-pleated sheets.

What holds secondary protein structure together?

Hydrogen bonds.

What is an alpha helix?

A coiled form of a polypeptide chain held by hydrogen bonds.

What is a beta-pleated sheet?

A folded sheet-like structure formed by parts of a polypeptide chain.

What is the tertiary structure of a protein?

The overall three-dimensional shape of a polypeptide.

What bonds/interactions help maintain tertiary structure?

Disulfide bridges, ionic bonds and hydrogen bonds.

What is a disulfide bridge?

A strong bond formed between sulfur-containing groups in amino acid side chains.

What are ionic bonds in proteins?

Attractions between charged R groups.

What are globular proteins?

Compact, roughly spherical proteins with important roles such as enzymes.

What are fibrous proteins?

Long, strong proteins that often provide structural support.

What is the Biuret test used for?

Testing for proteins.

What reagents are used in the Biuret test?

Sodium hydroxide and dilute copper sulfate.

What colour is a positive Biuret test?

Purple/lilac.

What colour is a negative Biuret test?

Blue.

Why is sodium hydroxide used in the Biuret test?

It provides alkaline conditions for the reaction.