Biological molecules

Question 1

What is a Monomer

Answer 1

molecules that can be linked to form long chains

Question 2

What is a Polymer

Answer 2

long chain of monomers formed by polymerisation

Question 3

What is a Macromolecule

Answer 3

• a large complex molecule e.g. nucleic acids, proteins, lipids.
• they have relatively large mass

Question 4

What is Hydrolysis

Answer 4

breaking down covalent bonds by inserting a H2O molecule across the bond

Question 5

What is Condensation

Answer 5

joining two molecules and the release of a H2O molecule

Question 6

Name 4 Monosaccharides

Answer 6

-Ribose (pentose sugar)
-Glucose
-Galactose
(glucose and galactose are isomers)
-Fructose

Question 7

Name 3 Disaccharides

Answer 7

Maltose - Glucose + Glucose (reducing sugar) C12H22C11
Sucrose - Glucose + Fructose (non - reducing sugar) C12H22C11
Lactose - Glucose + Galactose C12H22C11

Question 8

Name 3 Polysaccharides

Answer 8

• all contain glycosidic bonds
• starch (made from alpha glucose)
• glycogen (made from alpha glucose)
• cellulose (made from beta glucose)

Question 9

Test for reducing/non reducing sugars

Answer 9

Benedicts test
-add 2cm cubed of Benedict's reagent 
-add 2cm cubed of food sample
-heat in water bath for 5 minutes
Reducing sugar -> brick red
Non - reducing sugar -> No change, stays blue

Question 10

Test for starch

Answer 10

Add iodine to test solution

-if solution goes black, starch is present

Question 11

Structure/functions of lipids

Answer 11

• fats insulate organs
• create myelin sheath around neurons
• structural components of biological membranes
• waterproofing - prevents evaporation
• energy storage
• heat insulation

Question 12

What is the bond between glycerol and fatty acids in a triglyceride

Answer 12

ester bonds

Question 13

Whats the test for lipids

Answer 13

Emulsion test
-add ethanol to crushed sample
-add 2cm cubed of deionised water
If lipids present - layer of cloudy white suspension forms on top

Question 14

Saturated vs Unsaturated fatty acid chains

Answer 14

saturated - straight chains, solid at room temperature

unsaturated - double bods, oil at room temperature, common in plants

Question 15

What are the 3 groups that make up an amino acid

Answer 15

• amino group
• R group
• carboxyl group

Question 16

Outline Primary, Secondary, Tertiary and Quaternary structures

Answer 16

Primary - a sequence of a chain of amino acids

Secondary - first folding sequence of amino acids joined by hydrogen bonds (alpha helix/beta pleated sheets)

Tertiary - further folding of attractions between alpha helices and beta pleated sheets into a compact structure by using disulfide, ionic and hydrogen bonds

Quaternary - a protein consisting of four polypeptides

Question 17

Test for proteins

Answer 17

Biuret test
-add 1cm cubed of sodium hydroxide to 2cm cubed of sample, then mix
-add drops of 1% copper sulphate.
Proteins present - goes from blue to violet/purple

Question 18

What is enzyme activation energy

Answer 18

the minimum quantity of energy needed to activate a reaction

Question 19

Whats the structure of a enzyme (globular protein)

Answer 19

it has an active site made of amino acids, that is complementary to the substrate

Question 20

What is the induced fit theory and why is it better than the lock and key theory

Answer 20

• enzyme has general shape that alters in presence of substrate
• active site forms as enzyme and substrate interact
• better that lock and key theory as current observations see that enzyme activity changes when molecules bind to a site which isn’t the active site

Question 21

Factors effecting enzyme activity

Answer 21

temperature - more/less kinetic energy effect collisions
substrate concentration - more/less collisions
enzyme concentration - optimum rate of reaction to form enzyme substrate complexes

Question 22

Enzyme inhibitors

Competitive vs Non-competitive

Answer 22

Competitive inhibitor - bind to active side temporarily thus less enzyme active sites for substrates to bind to which slows the maximum rate of reaction

Non-competitive inhibitor - bind to enzyme at other position than active site thus changes the shape of the enzyme making it no longer functional

Question 23

What is end product inhibition

Answer 23

• regulation of enzyme activity in which the reactions product inhibits the enzymes activity
• its important as it controls synthesis of molecules being catalysed by enzymes

Question 24

What is the structure of Starch

Answer 24

• a polysaccharide found in plants
• long branched chains (large molecule) that cant diffuse out of cells
• made up of chains of alfa-glucose monosaccharides linked by glycosidic bonds formed by condensation
• it is insoluble thus has no effect on water potential so osmosis cant take place
• when hydrolysed the alpha-glucose is used for respiration

Question 25

What is the structure of Glycogen

Answer 25

• shorter chains that are highly branched that are found in animals and bacteria
• made up of chains of alfa-glucose monosaccharides linked by glycosidic bonds formed by condensation
• it is insoluble thus has no effect on water potential so osmosis cant take place
• a major carbohydrate storage product
• stored as small molecules mainly in the liver and muscles
• can be broken down more rapidly than starch, into glucose molecules, to meet the needs of a higher metabolic rate of animals

Question 26

What is the structure of Cellulose

Answer 26

• made up of beta-glucose molecules resulting in straight unbranched chains
• run parallel to one another allow for weak hydrogen bonds between chains making it stronger overall
• key component of the plant cell wall which provides rigidity and prevents cell from bursting during osmosis
• these molecules are grouped to form microfibrils which group to fibres which provide more strength

Question 27

how are proteins digested in the gut

Answer 27

• peptide bonds are broken down by hydrolysis
• endopeptidase break down the polypeptide chains into smaller peptide chains
• exopeptidase remove the terminal amino acids
• dipeptidase hydrolyse the dipeptides into amino acids