Biological Molecules

Question 1

How does hydrogen bonding occur?

Answer 1

There is an uneven distribution of electrons in the O-H covalent bond due to differing electronegativites. Hydrogen bonds are the electrostatic forces of attraction between delta positive H atoms and the lone pair on the delta negative O- atom’s lone pair.

Question 2

What is a monomer?

Answer 2

The smaller unit or units from which larger molecules (polymer) are made.

Question 3

What is a polymer?

Answer 3

A molecule made from a large number of monomers joined together.

Question 4

What is condensation?

Answer 4

A reaction that creates a chemical bond between two molecules and eliminates a water molecule.

Question 5

What is hydrolysis?

Answer 5

A reaction that breaks a chemical bond between two molecules and uses a water molecule.

Question 6

What is a carbohydrate?

Answer 6

An organic compound containing hydrogen and oxygen atoms in a ratio of 2:1.

Question 7

What is a monosaccharide?

Answer 7

A single sugar unit, the monomer from which larger polysaccharides are made.

Question 8

What two monosaccharides is sucrose made of?

Answer 8

Fructose and glucose

Question 9

What are three most common monosaccharides?

Answer 9

Glucose, galactose and fructose

Question 10

What two monosaccharides is lactose made from?

Answer 10

Glucose and galactose

Question 11

What two monosaccharides is maltose made from?

Answer 11

Glucose and glucose

Question 12

What are the two polysaccharide molecules known as starch?

Answer 12

Amylopectin and Amylose

Question 13

Describe the structure of amylose.

Answer 13

Amylose consists of alpha glucose molecules bonded by only 1,4 glycosidic bonds, twisting to form an alpha helix.

Question 14

Describe the structure of amylopectin.

Answer 14

Amylopectin consists of alpha glucose molecules with long chains bonded by 1,4 glycosidic bonds and branches linked by 1,6 glycosidic bonds.

Question 15

Describe the structure of cellulose.

Answer 15

Unbranched chains formed by beta glucose monomers, joined together only by 1,4 glycosidic bonds. Adjacent monomers are in alternation orientations. There are H bonds between neighbouring chains to form microfibrils, macrofibrils and fibre.

Question 16

What is a triglyceride?

Answer 16

Glycerol and three fatty acid chains (hydrophobic hydrocarbon chains)

Question 17

Even though both carbohydrates and lipids are made of the same elements: C,H and O, what is the difference?

Question 18

State the bonds formed when a fatty acid combines with glycerol and the name of this reaction.

Answer 18

• Ester
• Esterification / Condensation

Question 19

What is a saturated fatty acid?

Answer 19

A fatty acid with no double bonds between carbon atoms.

Question 20

What is a (poly)unsaturated fatty acid?

Answer 20

A fatty acid with one or more doble bonds between carbon atoms. These cause kinks.

Question 21

What is the structure of a phospholipid?

Answer 21

A phospholipid is a molecule with two fatty acids and a phosphate group bonded to one molecule of glycerol formed by condensation reactions.

Question 22

What five elements make proteins?

Answer 22

Carbon, Hydrogen, Oxygen, Nitrogen and Sulphur

Question 23

What is a peptide bond?

Answer 23

A covalent bond between two amino acids formed by a condensation reactions.

Question 24

What is a protein’s primary structure?

Answer 24

The order of amino acids

Question 25

What is a conjugated protein?

Answer 25

A protein that contains non-protein prosthetic groups, attached by covalent, hydrogen or ionic bonds.

Question 26

What is the chemical test for reducing and non-reducing sugars?

Answer 26

Benedict's test Blue - Green - Yellow - Orange - Brick Red depending on sugar concentration

Question 27

What is the function of nucleic acids?

Answer 27

The storage and transfer of genetic information and synthesis of proteins.

Question 28

Describe the structure of a nucleotide.

Answer 28

A nucleotide molecule (can be DNA or RNA) consist of a pentose sugar, a nitrogen containing base and a phosphate group.

Question 29

What are some properties of water that are useful?

Answer 29

- High SHC: Water acts as a buffer against rapid temperature changes e.g functions as an aquatic habitat - Ice is less dense than water: Habitat + Insulates water below, prevents aquatic life from freezing - High LHV: High energy to evaporate water, Cooling without much water loss, transfer of heat energy - Solvent: Carry O2 for transport in the blood so that organisms can respire, Dissolve mineral ions - Cohesive: Forms H bonds between water molecules, allows for the transpiration stream to occur - High Surface Tension: Acts as a habitat - Adhesion: Binds to xylem walls to allow water to move up through capillary action

Question 30

How is the structure of starch relate to its function?

Answer 30

- Insoluble in water, no effect on wo - Polymers, too large to diffuse through csm - Compact - Branched, more exposed free ends for enzymes to act on and hydrolyse, glucose molecules are released faster

Question 31

What is the difference between alpha glucose and beta glucose?

Answer 31

The hydroxyl group is in the downwards position for alpha glucose and the upwards position for beta glucose on C1

Question 32

What are the 4 types of bonding in the tertiary structure?

Answer 32

- Hydrogen bonding (easily broken by temperature or pH) - Hydrophobic and hydrophilic interactions (often found in the centre) - Ionic (Charged R groups on amino acids and broken by changes in pH) - Disulfide bridges (Cysteine R group and contains an S atom forms a covalent bond which is relatively strong)

Question 33

Globular Proteins:

Answer 33

- Hydrophilic R groups on external surface, form H bonds, soluble in water - Spherical - Tertiary structure - Specific - Temperature sensitive

Question 34

Fibrous:

Answer 34

- Insoluble - Flexible - Elongated Ropes

Question 35

How are triglycerides adapted for their function?

Answer 35

- Storage of energy content (2x than carbohydrates because of tails) - Insoluble so do not affect water potential or release contents in water

Question 36

What is a conjugated protein?

Answer 36

A globular protein containing a non-protein group called a prosthetic group

Question 37

Describe haemoglobin.

Answer 37

A globular protein made of 4 polypeptide chains (2 alpha and 2 beta) with an iron ion (prosthetic haem group) attached that can bind to O2 reversibly

Question 38

Describe catalase.

Answer 38

A globular protein that catalyses the breakdown of H2O2 into oxygen and water