2.1.2 biological molecules

Question 1

why is collagen described as having a quaternary structure rather than tertiary?

Answer 1

it has 3 polypeptide chains in each molecule so forms a triple helix structure

Question 2

what chemical elements make up carbohydrates?

Answer 2

carbon, hydrogen , oxygen

Question 3

what chemical elements make up lipids?

Answer 3

carbon, hydrogen , oxygen.

Question 4

what chemical elements make up proteins?

Answer 4

carbon , hydrogen, oxygen ,nitrogen, sulphur

Question 5

what chemical elements make up nucleic acids?

Answer 5

carbon , hydrogen, oxygen, nitrogen, phosphorus

Question 6

• give 3 examples of fibrous proteins. ( beginning with k,c and e)
• where are they found?

Answer 6

• keratin (found in hair and nails)
• collagen (found in skin and tendons)
  -elastin ( found in connective tissue and skin)

Question 7

how do you calculate the Rf value for chromatography?

Answer 7

distance moved by solute / distance moved by solvent

Question 8

describe is the test for proteins?
what will you see for a positive test?

Answer 8

• biuret test
• add your testing sample to a test tube.
  -add an equal amount of sodium hydroxide.
  -then add a few drops of copper surface and mix.
  -if positive, the solution will turn purple
  -if negative solution will stay blue

Question 9

what is the test for non-reducing and reducing sugars?
what will you see for a positive result?

Answer 9

• benedict’s test
• add benedict’s reagent to a test tube.
• add your test sample
• put in a water bath of 70°c for 30 minutes
• if positive, it will be a brick red colour.
  -if negative it will stay blue

Question 10

what is the test for lipids?
what will you see if it’s a positive test?

Answer 10

• emulsion test
• add 2cm3 of test sample to a test tube
• add 5cm3 of cold ethanol to test tube and mix
• add 5cm3 of distilled water
• if positive, the solution will turn cloudy
• if negative the solution will stay clear

Question 11

what is the test for starch?
what will you see if it’s a positive result?

Answer 11

• iodine test
• add your sample to a spotting tile
• add a few drops of iodine to the sample
• if positive, the sample will turn blue-black
• if negative it will remain orange-brown

Question 12

what is the functions of fibrous proteins?

Question 13

what properties do fibrous proteins possess?

Question 14

what’s the general structure of an amino acid?

Question 15

what’s the function of collagen?

Answer 15

• provide mechanical strength

Question 16

what’s the function of elastin?

Answer 16

-

Question 17

what’s the function of keratin? (2)

Answer 17

• provides mechanical protection
• provides an impermeable barrier to infection and water-borne pollutants

Question 18

what ions has the symbol NO3-?

Answer 18

nitrate

Question 19

what ion has the symbol Ca²+?

Answer 19

calcium ions

Question 20

what ion has the symbol Na+?

Answer 20

sodium ion

Question 21

what ion has the symbol OH-?

Answer 21

hydroxide ion

Question 22

what is the symbol for phosphate ion?

Answer 22

PO43-

Question 23

what ion has the symbol H+?

Answer 23

hydrogen ions

Question 24

what ion has the symbol NH4+?

Answer 24

ammonium ion

Question 25

what ion has the symbol HCO3-?

Answer 25

hydrogen carbonate ion

Question 26

what ion has the symbol K+?

Answer 26

potassium ion

Question 27

what ion has the symbol Cl-?

Answer 27

chloride ion

Question 28

what is the primary structure of proteins?

Answer 28

the sequence of amino acids in a chain bonded by peptide bonds

Question 29

what determines the primary structure of a protein?

Answer 29

it’s dna

Question 30

what is the secondary structure of a protein?

Question 31

what is the tertiary structure of a protein?

Answer 31

further folding of the protein forming additional bonds between the R groups

Question 32

what are the 4 additional bonds in the tertiary structure and where do they take place?

Answer 32

• hydrogen bonding between R groups
• disulphide bonds between cysteine amino acids
• ionic bonds between charged R groups
• hydrophobic interactions between non-polar R groups

Question 33

what does the tertiary structure of a protein determine?

Answer 33

it’s function

Question 34

what is the quaternary structure of a protein?

Answer 34

more than one polypeptide chain working together

Question 35

what is the difference between a hexose and pentose sugar?

Answer 35

hexose sugars have 6 carbon atoms, whereas pentose sugars have 5 carbon atoms

Question 36

where are inorganic ions found?

Answer 36

in the cytoplasm and in bodily fluids

Question 37

name properties of water (4)

Answer 37

• dipole
• has a high specific heat capacity
• has a high latent heat of vaporisation
• is cohesive

Question 38

how does having a high latent heat of vaporisation give water a function?

Question 39

how does the dipole nature of water give it a function?

Answer 39

• since it is dipole, other charged molecules can dissolve in water, allowing it to be a great solvent

Question 40

how does the cohesive nature of water give it a function? (2)

Answer 40

• there’s cohesion between the water molecules, enabling effective transport of water in the xylem of a plant
• there is also high surface tension at the water air boundary