Topic one

Question 1

What forms maltose?

Answer 1

A condensation reaction between two glucose molecules

Question 2

What forms sucrose?

Answer 2

A condensation reaction between a glucose molecule and a fructose molecule

Question 3

What forms lactose?

Answer 3

A condensation reaction between a glucose molecule and a galactose molecule

Question 4

Describe the structure of starch

Answer 4

-Two alpha glucose polysaccharides
-Amylose-long, unbranched chain, angle of glycosidic bonds causes it to coil
-Amylopectin-long, branched chain

Question 5

Describe the function of starch in relation to its structure, in plant cells

Answer 5

-Coiled amylose-makes it compact, good for storing large amounts in small spaces
-Branched amylopectin-allows the enzymes to hydrolyse glycosidic bonds quicker, faster release of energy
-Insoluble in water and doesn’t affect water potential-won’t cause water to enter cell by osmosis, preventing swelling, making it good for storage

Question 6

Describe the structure of glycogen

Answer 6

-Alpha glucose chain
-Similar structure to amylopectin, but with many more side branches

Question 7

Describe the function of glycogen in relation to its structure, in animal cells

Answer 7

-Compact molecule-good for storage
-Branched-easy to hydrolyse bonds for a quick release of energy

Question 8

Describe the structure of cellulose

Answer 8

-Long, unbranched chain of beta glucose molecules, each rotated 180º to allow for glycosidic bonds
-Cellulose chains linked by hydrogen bonds to form strong fibres-myofibrils

Question 9

Describe the function of cellulose in relation to its structure

Answer 9

Strong fibres provide structural support for plant cell walls

Question 10

Describe the test for reducing sugars

Answer 10

-Add benedict’s reagent
-Heat in a water bath that has boiled
-If reducing sugars are present, a brick-red precipitate will form

Question 11

Describe the test for non-reducing sugars

Answer 11

-Add HCl to test sample and heat in a water bath
-Add NaOH to neutralise
-Add benedict’s reagent and heat
-If non-reducing sugars are present, a brick-red precipitate will form

Question 12

Describe the test for starch

Answer 12

-Add iodine/potassium iodide to test solution
-If starch is present, solution will change from an orange/brown colour to blue/black

Question 13

Describe the formation of an ester bond

Answer 13

-RCOOH
-Condensation reaction between glycerol and fatty acid

Question 14

Describe the structure of a saturated fatty acid

Answer 14

-No double bonds between carbon atoms
-Chain is ‘saturated’ with hydrogen

Question 15

Describe the structure of a non-saturated fatty acid

Answer 15

Some double bonds between carbon atoms, which can cause the chain to kink

Question 16

Describe the properties of a triglyceride in relation to its structure

Answer 16

-Long hydrocarbon tail-storage molecule, release lots of energy when broken down
-Insoluble in water-don’t affect the water potential of the cell, preventing osmosis/swelling
-Hydrophobic tails-bundle together as insoluble droplets, glycerol heads ‘protect’ tails

Question 17

Describe the properties of a phospholipid in relation to its structure

Answer 17

-Hydrophilic heads with hydrophobic tails
-Can form a double layer membrane with tails facing inward
-Hydrophobic centre, so water-soluble molecules can’t easily pass through, acting as a barrier

Question 18

Describe the test for lipids

Answer 18

-Add ethanol to test solution
-Shake for one minute
-Pour into water
-Any lipids present will show up as a milky emulsion

Question 19

Primary structure

Answer 19

Sequence of amino acids in a polypeptide chain

Question 20

Secondary structure

Answer 20

-H bonds automatically form in the polypeptide chain, causing it to fold
-Forms either an alpha helix or beta pleated sheet

Question 21

Tertiary structure

Answer 21

-Chain folds further by more bonds
-Hydrogen bonds
-Ionic bonds between opposite charges on parts of the molecule
-Disulfide bridges between two cysteine molecules (amino acid that contains sulfur)

Question 22

Quaternary structure

Answer 22

Proteins made from more than one polypeptide chain bonded together, such as haemoglobin

Question 23

Describe the test for proteins

Answer 23

-Add a few drops of NaOH to make the solution alkali
-Add copper (II) sulfate solution
-If a protein is present, the solution will go from blue to purple

Question 24

Described the induced fit enzyme model

Answer 24

As the substrate binds to the active site, it adjusts its shape to fit the substrate, allowing an enzyme-substrate complex to form

Question 25

Competitive enzyme inhibitors

Answer 25

-Have a similar shape to the enzyme's substrate -Bind to the active site, but no reaction takes place, so they just block the substrate from forming an enzyme-substrate complex

Question 26

How to increase rate of reaction when competitive inhibitors are present

Answer 26

Add more of the substrate, so it has more chance of binding to the enzyme than the inhibitor

Question 27

Non-competitive enzyme inhibitors

Answer 27

Bind away from the active site of the enzyme, in a way that alters the shape of the active site so the substrate can no longer bind

Question 28

Describe an ATP molecule

Answer 28

A nucleotide derivative, formed by a molecule of adenine, a molecule of ribose and three phosphate groups

Question 29

Describe hydrolysis of ATP

Answer 29

-To release energy from the cell -Catalysed by ATP hydrolase -Produces Adenosine diphosphate and an inorganic phosphate group

Question 30

Used of ATP hydrolysis

Answer 30

-Can be 'coupled' with another reaction in the cell, releasing the energy directly to the reaction -Phosphorylation-Pi can be added to another molecule to make it more reactive

Question 31

Describe resynthesis of ATP

Answer 31

-Can happen in respiration and photosynthesis -Catalysed by ATP synthase -Condensation reaction between ADP and Pi

Question 32

Water is a metabolite...

Answer 32

...in many metabolic processes, including condensation and hydrolysis reactions

Question 33

Water is an important solvent...

Answer 33

...in which many metabolic reactions can occur

Question 34

Water has a relatively high heat capacity...

Answer 34

...buffering changes in temperature

Question 35

Water has a relatively large latent heat of vaporisation...

Answer 35

...providing a cooling effect with little loss of water through evaporation

Question 36

Water has strong cohesion between water molecules...

Answer 36

...this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air

Question 37

Importance of hydrogen ions (H+)

Answer 37

-pH is calculated based on the amount of H+ present in a solution -The more H+ present, the lower the pH, so a solution is more acidic

Question 38

Importance of iron ions (Fe2+)

Answer 38

-Important for haemoglobin -Each polypeptide chain has an Fe2+ in the centre, which binds to the oxygen and temporarily becomes Fe3+ until the O unloads

Question 39

Importance of sodium ions (Na+)

Answer 39

-Co-transport -A glucose molecule or amino acid can cross a cell membrane alongside a Na+

Question 40

Importance of phosphate ions (Po₄³⁻)

Answer 40

-In DNA, RNA, and ATP -When a Po₄³⁻ attaches to another molecule it is a phosphate group -The phosphate group in RNA and DNA allows the nucleotides to join up

Question 41

Where are inorganic ions found?

Answer 41

-in solution in the cytoplasm and body fluids of organisms -Some in high concentrations and others in very low concentrations.