1: Biological molecules

Question 1

What process forms polymers from monomers

Answer 1

Polymerisation

Question 2

Condensation reaction

Answer 2

Reactions that produce water. (giving out of water in reactions)

Question 3

Hydrolysis

Answer 3

Breaks down the chemical bond between two molecules with the addition of water. (taking in water to split molecules in reaction)

Question 4

Molar solution

Answer 4

A solution that contains one mole of solute in each litre of solution

Question 5

Whats a monosaccharide, formula and example

Answer 5

The monomers from which larger carbohydrates are made. (CH2O)n. Glucose, galactose and fructose.

Question 6

Glucose two isomers

Answer 6

• Alpha glucose
• Beta glucose

Question 7

What is the chemical reaction of reduction

Answer 7

Gain of electrons or hydrogen

Question 8

Test for reducing sugar (donates electrons to another chemical)

Answer 8

Benedicts test.
Alkaline blue cooper sulfate. Copper oxide not soluble in water so forms a brick-red precipitate.
Heated in water bath, turns brown/brick-red if present

Question 9

Disaccharide

Answer 9

Monosaccharides formed in pairs. Examples:
glucose + glucose= maltose
glucose + fructose= sucrose
glucose + galactose= lactose

Question 10

When monosaccharides join, is it a condensation or hydrolysis? And whats the bond called thats formed?

Answer 10

A molecule of waters removed so a condensation reaction. The bond formed is a glycosidic bond

Question 11

What happens when waters added to a disaccharide?

Answer 11

Hydrolysis. It breaks the glycosidic bond releasing the monosaccharides.

Question 12

Test for non reducing sugars

Answer 12

Must undergo hydrolyisis into monosaccharide components.
2) liquid form (ground up w water)
3) 2cm food sample + 2cm benedicts reagent
4) water bath 5 mins, if no colour change no reducing sugar present
5) add 2cm food sample again + 2cm dilute hydrochloric acid in boiling water bath 5 mins (hydrolysis)
6) slowly add sodium hydrogencarbondate solution to neutralise acid. Test w pH paper that solution is alkaline
7) Re-test by heating with benedicts reagent in gently boiling water bath 5 mins
8) turns orange-brown

Question 13

Polysaccharides characteristics

Answer 13

many monosacchrides combined joined by glycosidic bonds that were formed by condensation reactions.
They are very large molecules, and insoluble. features make the suitable for storage. An example of polysaccharides is cellulose, structural support for plant cells.

Question 14

Test for starch

Answer 14

(Starch is polysaccharide)
1) two drops of yellow iodine solution added to test solution
2) if starch is present it turns the iodine a blue-black colour

Question 15

Starch structure

Answer 15

• made of chains of alpha glucose monosaccharides linked by glycosidc bonds formed by condensation reactions
• chains may be branched or unbranched
• unbranched chain is wound into tight coil = compact molecule
• OH groups point inwards + form hydrogen bonds that hold helix in place

Question 16

Role of starch:

Answer 16

• insoluble (doesnt affect water potential so waters not drawn into cells by osmosis)
• large (cant diffuse out of cells)
• compact (stored in small space)
• when hydrolysed, forms alpha glucose (easily transported and used in respiration)
• highly brached (acted on by enzymes, glucose released rapidly)
  Never found in animal cells, instead glycogen

Question 17

Glycogen

Answer 17

• similar to starch, shorter chains and more highly branched
• major carb storage product
• stored in small granules in muscles and liver
• mass is small

Question 18

How does glycogens structure make it good for storage?

Answer 18

• insoluble
• compact
• more highly branched than starch so has more ends that can be acted on simultaneously by enzymes - so more rapidly broken down
  (important for animals as they have higher metabolic rate than plants)

Question 19

Cellulose

Answer 19

• major component of plant cell walls + provide rigidity
• beta glucose
• cellulose molecular chains run parallel and cross linked by H bonds
• cellulose molecules grouped together to form microfibils which form parrallel fibre groups
• prevents cell from bursting (osmosis) by exerting inward pressure. makes plant cells turgid

Question 20

Lipids

Answer 20

• contain C, H and O
• insoluble in water
• soluble in organic solvents like alcohols and acetone
  The main groups of lipids are triglycerides (fats and oils) and phospholipids

Question 21

Roles of lipids

Answer 21

• flexibility of cell membranes
• big source of energy when oxidised
• waterproof - insoluble. Waxy lipid cuticles
• insulation - fats
• protection of organs

Question 22

Triglycerides

Answer 22

• three fatty acids combined with glycerol
• each fatty acid forms an ester bond with glycerol in condensation reaction

Question 23

Fatty acids

Answer 23

Variation comes from the fatty acids, all have carboxyl (–COOH) group with a hydrocarbon chain attached
- Saturated = no double bonds between carbon atoms
- Monosaturated = one double bond between carbon atoms
- Polyunsaturated = more than one double bond between carbon atoms

Question 24

Structure of triglycerides related to properties

Answer 24

• high ratio to energy storing carbon hydrogen bonds to carbon atoms and so gd source energy
• low mass to energy ratio
• large so insoluble, so doesnt affect osmosis or wp
• high rate of H to O atoms, so release water when oxidised

Question 25

Phospholipids

Answer 25

- like lipids but one fatty acid molecule is replaced by a phosphate molecule - phosphate attract water, fatty acid repel water SO phospholipid made of hydrophillic head and hydrophobic tail.

Question 26

Structure of phospholipids related to their properties

Answer 26

- polar molecules, hydrophillic phosphate head and hydrophobic tail of two fatty acids. in water forms a bilayer in membranes - strucutre allows to form glycolipids by combining with carbs in membrane

Question 27

Test for lipids

Answer 27

emulsion test - 2cm of sample in test tube - 5cm ethanol - shake to dissolve lipid - add 5cm water shake gently

Question 28

Amino acid structure

Answer 28

A chain of amino acids form a polypeptide chain, which is a protein. - carboxyl group (COOH) - r group (R) - amino group (NHH) - hydrogen atom (H)

Question 29

The formation of a peptide bond

Answer 29

forms dipeptides by condesation reaction (removal of water molecule), from the OH of the carboxyl group and the H from amino group. the two amino acids then link by peptide bond. Can be broken down by hydrolysis

Question 30

Primary structure of amino acid

Answer 30

- through condensation reactions - amino acids joined together by polymerisation - creates a chain of amino acids called a polypeptide chain

Question 31

Secondary structure of amino acid

Answer 31

- Hydrogen bonds - polypeptides are coiled - 3D shape - alpha helix and beta sheet

Question 32

Tertiary structure of amino acid

Answer 32

- A helix twist even more for complex 3D structure, max stability - Disulfide bridges (strong) - Ionic bonds (weak, broken by pH change) - Hydrogen bonds (numerous+weak)

Question 33

Quaternary structure of amino acid

Answer 33

- consist of two or more chains of polypeptides - to make a large protein molecule - may be a non protein group (such as haem group)

Question 34

Test for proteins

Answer 34

Biuret test - detects peptide bonds 1) sample in solution in test tube 2) add sodium hydroxide 3) add dilute copper sulfate and mix 4) turns purple if peptide bonds present, remiains blue if not

Question 35

Induced fit model of enzyme action

Answer 35

active site forms as enzyme and substrate interact. the enzyme has a general shape but molds when in presence of substrate

Question 36

what 4 factors effect enzyme action

Answer 36

- temperature (increases kinetic energy, denatures at 60C) - pH (measure of its hydrogen ion conc) - enzyme concentration - substrate concentration

Question 37

difference between competitive and noncompetitive inhibitors

Answer 37

- competitive; bind to active site of enzyme - bind to enzyme at position other than the active site