Biological molecules

Question 1

what is the bond between two monosaccharides

Answer 1

glycosidic bond

Question 2

maltose-
sucrose-
lactose-

Answer 2

maltose- two glucose
sucrose- glucose and fructose
fructose- galactose and glucose

Question 3

Structure and role of glycogen

Answer 3

contains many alpha glucose with the 1,4 and 1,6 glycosidic bonds
- energy storage in animals
- large and compact
- insoluble so doesn’t affect water potential

Question 4

structure and role of starch

Answer 4

contains the alpha glucose amylose and amylopectin
- amylose- 1,4 and 1,6 glycosidic bond and is unbranched. Coiled so compact to store energy
- amylopectin- 1,6 glycosidic bond, branched
- energy storage in plants
- doesn’t effect water potential

Question 5

Benedict’s test

Answer 5

• food in liquid form
• Benedict’s reagent
• heat mixture gently in water bath
• brick red means reducing sugar
• if blue add HCl to hydrolyse the non reducing sugar
• add NaOH to neutralise it
  then add Benedict’s again and the colour should change to brick red

Question 6

Triglycerides

Answer 6

• formed by the condensation of one molecule of glycerol and three fatty acids
• large and non polar
• does not affect water potential of cells when stored
• important water source for organisms in dry places

Question 7

Phospholipids

Answer 7

• one fatty acids of a triglycerides is substituted by a phosphate containing group
• polar so bilayer can form
• hydrophilic head
• structure important for cell recognition

Question 8

Emulsion test

Answer 8

• liquid food sample
• ethanol and shake
• add water
  cloudy = lipid

Question 9

Primary structure

Answer 9

the order of amino acids

Question 10

secondary structure

Answer 10

mainly arranged as alpha helix or beta pleated

Question 11

tertiary structure

Answer 11

secondary but more folded and has 3D structure and contains 3 different bonds

Question 12

disulphide bridges

Answer 12

not easily broken

Question 13

hydrogen bonds

Answer 13

numerous and easily broken

Question 14

ionic bonds

Answer 14

between the carboxyl group and amino group that are not involved in peptide bond, easily broken by pH change

Question 15

Biuret test

Answer 15

• sample in test tube
• add NaOH
• few drops of very dilute copper sulfate solution and mix gently
• purple means there is peptide bond

Question 16

induced fit model of an enzyme

Answer 16

When the enzyme and substrate bind they form an enzyme substrate complex, and the structure of the enzyme is altered so that the active site of the enzyme fits around the substrate. This is called the induced fit model.

Question 17

what are ribosomes formed from

Answer 17

RNA and proteins

Question 18

RNA and DNA contains

Answer 18

ribose, phosphate group, nitrogen containing base

Question 19

bonds between bases

Answer 19

hydrogen bonds

Question 20

bonds between nucleotides

Answer 20

phosphodiester bond

Question 21

DNA

Answer 21

• double helix
• two poly nucleotide chains
• stable due to phosphodiester backbone that protects more chemically reactive nitrogen

Question 22

semi conservative replication

Answer 22

• unwinding of double helix
• hydrogen bonds between bases break by DNA helicase
• new DNA nucleotides attracted to exposed bases on template strand and complementary base pairing occurs
• DNA polymerase involved in the condensation reaction that joins adjacent nucleotides

Question 23

ATP

Answer 23

adenine, ribose and three phosphate molecules

Question 24

properties of water

Answer 24

• metabolite in many metabolic reactions
• important solvent in which reactions ca occur
• high heat capacity so acts as a buffer in changes of temperatures
• high latent heat of vaporisation provides a cooling effect when it evaporates
• strong cohesion supports column of water in transport of water through cells and produces reface tension where water meets air

Question 25

structure and role of cellulose

Answer 25

contains many beta glucose
- prevents cells from bursting from high osmotic pressure and is tough and rigid