SECTION 1

What type of sugar is glucose?

Hexose

a-glucose and b-glucose are isomers, what are isomers?

Molecules with the same molecular formula as each other, but with the atoms connected in a different way

What is a condensation reaction?

A condensation reaction is when 2 molecules join together with the formation of a new chemical bond and a water molecule is released.

What is the bond between 2 monosaccharide?

Glycosidic bond

State the 3 monosaccharides

Glucose / Galactose / Fructose

State the 3 disaccharides

Maltose / Sucrose / Lactose

What is a hydrolysis reaction?

A hydrolysis reaction breaks the chemical bond between monomers using a water molecule.

What is the colour of (unreacted) benedict’s reagent?

Blue

Test for reducing sugar

Add benedict’s reagent to a sample and heat it in a water bath

What counts as a reducing sugar?

All monosaccharides + maltose and lactose

Test for non-reducing sugars

Add dilute HCl and heat gently in a water bath. Then neutralise with sodium hydrogen-carbonate. Then carry out the test for reducing sugars as usual.

Test for starch

Add iodine dissolved in potassium iodide solution.

What are the 2 polysaccharides in starch?

Amylose and Amylopectin

Describe the structure for amylose and explain its benefits

Long, unbranched chain of a-glucose / coiled structure. This makes it compact

Describe the structure for amylopectin

Long, branched chain of a-glucose / have lots of side branches.

Why is amylopectin being branched, beneficial for active organisms?

This allows enzymes to reach and break down the glycosidic bonds. Therefore glucose can be released quickly

State the solubility of starch

Starch is insoluble in water

Why is starch being insoluble, good for storage?

Doesn’t affect water potential, so it doesn’t cause water to enter cells by osmosis, which would make them swell.

Details for cellulose

Long, unbranched chains of b-glucose. Forms straight cellulose chains. These chains are linked by hydrogen bonds forming microfibrils, providing structural support.

Fatty acids with double bonds are…

Unsaturated

Fatty acids without double bonds are…

Saturated

Why are triglycerides good for energy storage?

Long hydrocarbon tails of fatty acids contain lots of chemical energy and lots of energy is released when broken down.

Solubility of triglycerides

Insoluble therefore doesn’t affect water potential.

Describe the emulsion test (don’t include results)

Shake the test substance with ethanol, then pour the solution into water.

What are the 3 main groups of a peptide molecule

Carboxyl group (COOH) / Amine group (NH2) / R group

Primary structure

This is the sequence of amino acids in the polypeptide chain.

Secondary structure

Hydrogen bonds forms between the amino acid in the chain. Causing the chain to coil into an alpha helix or fold into a beta pleated sheets.

Tertiary structure

Coil / folding further due to hydrogen / ionic / disulphide bonds forming a 3D structure

Quaternary structure

Proteins made from several different polypeptide chains

Name the 4 different types of protein

Enzyme / Antibodies / Transport protein / Structural proteins

Biuret test (state the chemicals used)

Add a few drops of sodium hydroxide solution, then add copper(II) sulphate solution. Solution will turn from blue to purple.

What do enzymes do?

Enzymes speed up chemical reactions by acting as biological catalysts

What is a catalyst?

A catalyst is substance that speeds up a chemical reaction without being used up in the reaction itself.

What does the enzyme (active site) from with a substrate?

Enzyme-substrate complex

Competitive inhibitor

Competitive inhibitors have a similar shape to the substrate, therefore can bind to the active site and block / prevent substrate from binding.

Non-competitive inhibitor

Non-competitive inhibitors binds to the allosteric site, causing the enzyme (/active site) to change shape and therefore no longer complementary to the substrate.

Function of DNA

To store genetic information

Name the 3 biological molecules in DNA

Deoxyribose sugar / A phosphate group / A nitrogen-containing base (A/T/G/C)

Name the 3 biological molecules in RNA

Ribose sugar / A phosphate group / A nitrogen-containing base (A/U/G/C)

Name of the sugar and phosphate chain in a polynucleotide

Sugar-phosphate backbone

How many hydrogen bonds are between A and T

2 hydrogen bonds

How many hydrogen bonds are between C and G

3 hydrogen bonds

What does antiparallel mean?

Running in opposite direactions

What is the key term for ‘specific base pairing’?

Complementary base pairing

DNA replicates by…

Semi-conservative replication

Step 1 of semi-conservative replication

DNA helicase breaks H-bonds between bases of the 2 polynucleotide. This makes the helix unwind

Step 2 of semi-conservative replication

Original strand acts as a template for a new strand. Complementary base pairing means that free-floating DNA molecules are attracted to their complementary exposed bases

Step 3 of semi-conservative replication

Condensation reaction joins the nucleotides of the new strand together, this is catalysed by DNA polymerase. Hydrogen bonds also form between the bases.

Step 4 of semi-conservative replication

Each new DNA molecule contains one original strand and a new strand of DNA.

Who are the 2 people that discovered / determined the structure of DNA?

Watson and Crick

Who are the 2 people that came up with the theory of semi-conservative replication?

Watson and Crick

Who are the 2 people that provided evidence / validated the theory of semi-conservative replication?

Meselson and Stahl

What did Watson and Crick do?

Determine the structure of DNA and came up with the theory of semi-conservative replication

What did Meselson and Stahl do?

Provided evidence / validated the theory of semi-conservative replication

Name the 5 useful properties of water

Important metabolite / High latent heat of vaporisation / Buffer temperature change / Good solvent / Cohesive

How is water an important metabolite

Many metabolic reactions involved a condensation or hydrolysis reaction

How does water have a high latent heat of vaporisation?

Takes lots of energy (heat) to break hydrogen bonds between water molecules.

Why is water having high latent heat of vaporisation useful?

Lots of energy (heat) is used up when water evaporates which provides a cooling affect for living organism, without losing too much water

How does water buffer temperature change?

The hydrogen bonds between water molecules can absorb a lot of energy.

Why is water being able to buffer temperature useful?

Provide stable habitat for organisms under water / the water inside organisms can maintain a stable temperature (also help maintain a constant body temperature)

What enzyme is used for the condensation of ATP?

ATP synthase

What enzyme is used for the hydrolysis of ATP?

ATP hydrolase

What are the products of hydrolysis of ATP

ADP and inorganic phosphate (Pi)

What is the (MAIN) use of inorganic phosphate (from the hydrolysis of ATP)

Phosphorylation, when the Pi is added to another compound, making the compound more reactive

Name the 4 inorganic ions

Iron / Hydrogen / Sodium / Phosphate (ions)

What is an inorganic ion?

Ion that does not contain carbon

What is a monomer?

Small repeating unit from which larger molecules such as polymers are made

What is NOT an example of a polymer?

Triglycerides / Phospholipids

Describe test for non-reducing sugars (3 marks)

Heat with acid and neutralise / Heat with benedict’s reagent / positive result = brick red ppt

Suggest a method to measure the quantity of a ppt in a solution

Filter and dry the ppt / find mass by weighing

Using colorimeter would improve the repeatability of a colour changing experiment. Explain why? (3)

Quantitative / colour change is subjective / standardises the method

State 3 features of starch that make it a good storage molecule

Insoluble / coiled

Explain why starch being insoluble is good for storage?

Does not affect water potiential

hy starch being coiled is good for storage?

So its compact

State the test for starch

Iodine / potassium iodide test

Describe the structure of glycogen (2)

Polysaccharide of a-glucose joined by glycosidic bonds / Branched structure

Describe the induced-fit model of enzymes

Substrate bind to the active site / which changes shape to be complementary to the substrate

How does an enzyme act as a catalyst?

It reduces the active energy

What are the 2 substrates needed for ATP synthase enzyme?

ADP / Pi (inorganic phosphate)

How do you stop enzyme controlled reactions (IN GENERAL) ?

Make the conditions not optimal

State ways to stop enzyme controlled reactions (4)

Boil / Freeze / add acid / add alkali

How does a competitive inhibitor decrease rate of enzyme-controlled reaction? (3)

Inhibitor similar shape to substrate / binds to active site / reduce enzyme-substrate complexes forming

Formation of an enzyme-substrate complex increases the rate of reaction Explain how?

Reduce activation energy / Due to bending bonds

Why can 2 proteins have the same number and type of amino acids but different tertiary structures?

Different sequence of amino acids / form ionic, hydrogen, disulphide bonds in different places

Describe how the secondary structure of a polypeptide is produced by bonds between amino acids

H-bonds / between amine group of one amino acid and carboxyl group of another

Name the protein associated with DNA in a chromosome

Histone

Describe how the separation of DNA strands occur?

DNA helicase / Breaks H-bonds between complementary base pairs

What is the function of DNA helicase?

Unwinding DNA and breaking h-bonds between chains / bases / strands

What is the function of DNA polymerase?

Join adjacent nucleotides to form phosphodiester bonds (sugar-phosphate backbone)

Name the group represented by COOH

Carboxyl group

Describe the test for lipids

Add enthanol and shake solution / add water / positive result shows milky emulsion

Describe how ATP is resynthesized in cells

From ADP and Pi / by ATP synthase / during respiration

Explain the process of phosphorylation

Adding phosphate to other substances, making them more reactive / change their shape

State 5 properties that make water important for organisms

Metabolite / solvent / high specific heat capacity / large latent heat of vaporisation / cohesion

Explain how water having large latent heat of vaporisation is important?

Provides a cooling effect through evaporation

Explain how water having high specific heat capacity is important?

Can gain or lose a lot of energy without changing temperatures (buffers)

Explain how water having cohesion is important?

Can support columns of water in plant / can produce surface tension supporting small organisms

State 2 properties of water that are important in the cytoplasm of cells

Polar molecule / Reactive

How is water being a polar molecules, biologically important in cells?

Acts as a universal solvent

How is water being a reactive molecule, biologically important in cells?

Can take place in hydrolysis / condensation reactions