biological molecules

Question 1

What is a polymer?

Answer 1

Molecule made of large number of monomers joined together

Question 2

What are monomers?

Answer 2

single units that join to form polymers

Question 3

What are the monomers in carbohydrates called?

Answer 3

Monosaccharides

(e.g. glucose, fructose, galactose)

Question 4

Draw the skeletal structure for α-glucose

Answer 4

H on top
OH on bottom

Question 5

Draw the skeletal structure for β-glucose

Answer 5

H OH

HO H

Question 6

What is a condensation reaction?

Answer 6

Joining together of molecules with a chemical bond & the elimination of a water molecule (it’s released)

Question 7

What type of bond is formed between the 2 monosaccharides as a molecule of water is released?

Answer 7

A glycosidic bond

Question 8

What is formed when 2 monosaccharides join together?

Answer 8

A disaccharide

Question 9

How is sucrose formed?

Answer 9

α-glucose molecule and fructose molecule

Question 10

What is lactose formed from?

Answer 10

From glucose molecule & galactose molecule

Question 11

What is maltose formed from?

Answer 11

2 α-glucose molecules

Question 12

What is hydrolysis?

Answer 12

Breaking of the chemical bond between monomers using a water molecule

Question 13

What are polysaccharides?

Answer 13

When more than 2 monosaccharides are joined together by condensation reactions

Question 14

What is the purpose of starch?

Answer 14

Plants store excess glucose as starch

Question 15

How are glycogen and starch produced?

Answer 15

the condensation of α-glucose.

Question 16

what is the structure of starch?

Answer 16

long unbranched coiled or long branched chain

Question 17

Describe glycogen’s structure

Answer 17

similar to starch but more side branches coming off it + shorter chains

Question 18

features of starch and glycogen that make it a good storage molecule

Answer 18

insoluble in water so it doesn’t affect water potential
branched so makes molecule compact
polymer of α-glucose so provides glucose for respiration
large so cant cross cell membrane
highly branched also means more enzyme action

Question 19

Describe the test for starch

Answer 19

1. Add iodine solution to test sample

2.If starch present = sample changes from browny-orange to blue-black colour

Question 20

Describe the structure of cellulose

Answer 20

Long, unbranched chains made up of β-glucose
Straight chains run parallel to each other in cell walls which allows hydrogen bonds to form cross-linkages between chains
formation of micro fibrils which then join together with hydrogen bonds to make fibrils

Question 21

function of cellulose

Answer 21

used for cell walls bc it adds rigidity and structural support

Question 22

Describe Benedict’s test for reducing sugars

Answer 22

Add Benedict’s reagent (blue) to sample & heat it in water bath that’s been brought to a boil (for 5 mins)
Test’s positive is orange/red precipitate
Higher the concentration of reducing sugar, further the colour change goes

Question 23

What’s a more accurate way of comparing the amount of reducing sugar in different solutions (than colour change)?

Answer 23

Filter solution & weigh precipitate

Question 24

Describe the test for non-reducing sugars

Answer 24

1.Boil (new test sample) with dilute hydrochloric acid (in water bath)

2. neutralise it with 5cm3 sodium hydrogencarbonate

3.Carry out Benedict’s test as you would for a reducing sugar

If test’s positive = orange/red precipitate
If test’s negative = solution remains blue = no sugar present

Question 25

In the test for non-reducing sugars, why is dilute hydrochloric acid added?

Answer 25

To hydrolyse, break down, the non-reducing sugar (disaccharide) into monosaccharides

Question 26

Name 4 roles of lipids

Answer 26

Energy source-provide more than twice energy as carbs Protection-stored around delicate organs Insulation-slow conductors of heat Waterproofing-insoluble in water

Question 27

How are triglycerides are formed

Answer 27

condensation of one molecule of glycerol and three molecules of fatty acid. each fatty acid forms an ester bond with glycerol

Question 28

how is the structure of triglycerides related to their properties?(4)

Answer 28

high ratio of energy-storing carbon-hydrogen bonds to carbon atoms so good source of energy low mass to energy ratio so good storage as lots of energy stored in small volume insoluble and large so doesn't affect water potential high ratio of hydrogen to oxygen atoms means water is released when oxidised

Question 29

Describe the structure of a phospholipid

Answer 29

One molecule of glycerol with 2 fatty acids + a phosphate group attached to it

Question 30

what are the two parts of a phospholipid?

Answer 30

hydrophilic head hydrophobic tail

Question 31

Describe how a phospholipid's structure relates to its function(3)

Answer 31

Phospholipids make up the bilayer of cell membranes Heads are hydrophilic & tails are hydrophobic which forms double layer with their heads facing out towards the water on either side structure allows them to form glycolipids with carbohydrates which is important for cell recognition

Question 32

Describe the emulsion test for lipids

Answer 32

1. add 2cm3 of sample to dry test tube 2. add 5cm3 of ethanol 3. shake and add 5cm3 water 4. shake thoroughly to mix if there is milky emulsion, lipid is present

Question 33

what is the general structure of an amino acid?(4)

Answer 33

R group central carbon COOH group amine group

Question 34

what bond is formed in the condensation of 2 amino acids?

Answer 34

peptide bond

Question 35

What is the primary structure in proteins?

Answer 35

Sequence of amino acids in polypeptide chain

Question 36

What is the secondary structure in proteins?

Answer 36

Hydrogen bonds form between amino acids in chain making it coil into alpha helix or fold into beta pleated sheet

Question 37

What is the tertiary structure in proteins?

Answer 37

Further folding of whole polypeptide chain to create 3d structure formation of: Hydrogen bonds Ionic bonds Disulfide bonds

Question 38

What is the quaternary structure in proteins?

Answer 38

Arrangement of more than 1 polypeptide chain in a protein

Question 39

Describe the biuret test for proteins

Answer 39

1. add equal volumes of sodium hydroxide and sample into test tube 2. add biuret solution colour change from blue to purple indicates protein

Question 40

what is an enzyme?

Answer 40

a globular protein that acts as a biological catalyst by lowering activation energy

Question 41

what is the induced fit model?

Answer 41

the enzyme is flexible and moulds around the substrate. as it changes shape, this puts a strain on the substrate and lowers activation energy

Question 42

what are competitive inhibitors?

Answer 42

an enzyme inhibitor that binds to the active site of the enzyme as it has a complementary shape to the tertiary structure of the active site.

Question 43

what is a non competitive inhibitor?(2)

Answer 43

inhibitors that attach themselves to the enzyme at a binding site other than the active site this alters the shape of the enzyme so that the substrates are no longer complementary and so can not bind