2.2 BIOLOGICAL MOLECULES

Question 1

What is biochemistry?

Answer 1

Biochemistry is chemical reactions involving biological molecules

Question 2

What are most abundant bio moles?

Answer 2

The most abundant bio moles are carbon, oxygen, nitrogen, sulfur and phosphorus.

Question 3

What are monomers?

Answer 3

Monomers are single, small molecules capable of joining together to form a polymer

Question 4

What are polymers?

Answer 4

Polymers are large molecules made up of many identical monomers

Question 5

What is are condensation and hydrolysis reactions?

Answer 5

Condensation reactions covalently bond monomers together to form polymers are release monomers. Hydrolysis reactions add water to break those bonds

Question 6

What is an ion?

Answer 6

An ion is an atom or group of atoms that carry a positive (cations) or negative (anions) charge.

Question 7

What are cations necessary for?

Answer 7

Cations are necessary for:
Ca2+ = nerve impulse transmission muscle contraction
Na+ = nerve impulse transmission kidney function
K+ = nerve impulse transmission stomata openings
H+ = catalysis of reactions pH determination
NH4+ = production of nitrate ions by bacteria

Question 8

What are anions necessary for?

Answer 8

Anions are necessary for:
NO3- = nitrogen supply to plants
HCO3- = maintenance of blood pH
Cl- = balance positive charge of Na and K ions
PO4- = cell membrane, nucleic acid and ATP formation
OH- = catalysis of reactions pH determination

Question 9

Why does water contain hydrogen bonds?

Answer 9

Water contains hydrogen bonds as water is polar. Oxygen is slightly more delta negative than hydrogen and so the negative charge is pulled closer to oxygens nucleus

Question 10

What are the properties of water?

Answer 10

The properties of water are:
- cohesive (attraction of other molecules of the same kind)
- adhesive (attraction of other molecules of a different kind, xylem function)
- high specific heat capacity (preventing temperature fluctuations, absorb large amounts of heat)
- high latent heat of vaporisation (water removes heat as it evaporates, moderates earths climate and prevents organisms overheating)
- density (ice less dense than liquid = floats)
- solvent (dissolves other substances)
- transparency (light can pass through)

Question 11

What are monosaccharides?

Answer 11

Monosaccharides are any of the class of sugars that cannot be hydrolysed to give a simple sugar.
- general formula (CH2O)n
- same number C and O atoms
- white crystalline solides
- dissolve in water to form sweet tasting solutions

Question 12

What are isomers?

Answer 12

Isomers are molecules that have the same chemical formula but different structural formulae

Question 13

What are the properties of glucose?

Answer 13

The properties of glucose are:
- polar and soluble in water
- number of polar OH groups attached to carbons
- hydrogen bonds can form between OH groups (causes glucose to dissolve)
- soluble in cytosol of cells

Question 14

What are discaccharides?

Answer 14

Disaccharides are molecules formed from two monosaccharides joined together by a glycosidic bond
- general formula C12H22O11
-crystalline water

Question 15

What is a polysaccharide?

Answer 15

Polysaccharides are large molecules made of many smaller monosaccharides joined together by glycosidic bonds
- general formula Cx(H20)y
- can be linear or branched
- function in organisms is often storage or structure related
- often insoluble molecules

Question 16

Why are polysaccharides formed?

Answer 16

Polysaccharides are formed as glucose must be stored appropriately in cells as it is soluble- meaning it would effect the osmotic properties of the cells, so it is stored as polysaccharides which are insoluble. Glucose needs to be stored as when it breaks down in respiration it releases ATP. Animals only have the enzymes to break down alpha glucose, not beta glucose

Question 17

Amylose and amylopectin structure and function.

Answer 17

Amylose is an alpha-glucose molecule, in the shape of an alpha helix with 1-4 glycosidic bonds. It is found in plant cells and is used as an energy store in plants.
Amylopectin is also an alpha-glucose molecule, but is highly branched and contains 1-4 and 1-6 glycosidic bonds

Question 18

Cellulose structure and function.

Answer 18

Cellulose is a beta-glucose molecule with 1-4 glycosidic bonds in a long chain. It contains fibres/fibrils and is found in plant cells. Cellulose forms the plant cell wall

Question 19

Glycogen structure and function.

Answer 19

Glycogen is a alpha-glucose molecule with 1-4 and 1-6 glycosidic bonds. It is highly branched and found in animal cells. It is used as an energy store.

Question 20

What are the uses of lipids?

Answer 20

The uses of lipids are:
- energy storage
- membrane component
- insulation (thermal and mechanical)
- waterproofing
- hormones
- source of energy

Question 21

What are lipids?

Answer 21

Lipids are a group of macromolecules that are not polymers. They include triglycerides and are non-polar. They include phospholipids and steroids, e.g cholesterol waxes

Question 22

What are triglycerides?

Answer 22

Triglycerides are made from 3 fatty acids and a glycerol, joined together by ester bonds. They are a triester of glycerol.
They are formed by a condensation reaction between the carboxyl group of the fatty acid and hydroxyl group of glycerol

Question 23

Saturated and unsaturated fatty acids.

Answer 23

Saturated fatty acids do not contain a double bond, unsaturated do.

Question 24

What are phospholipids?

Answer 24

Phospholipids are similar to triglycerides but are 2 fatty acids bonded to the glycerol, with a phosphate group covalently bonded to the 3rd.
- have a hydrophobic region (head)
- have a hyrophillic region (tail)

Question 25

What is cholesterol?

Answer 25

Cholesterol are complex alcohol molecules with a hydroxyl group at one end (OH).
- have hydrophobic and hydrophillic ends
- can fit between phospholipids and help regulate fluidity in membranes
- stops membrane being flimsy and gives membrane rigidity

Question 26

Facts about proteins.

Answer 26

Proteins are:
- CHONS
- broken down by protease
- made from long chained amino acids (polymers)
- form over 50% cells dry mass
- consist of one or more polypeptides arranged as complex macromolecules and have specific biological functions

Question 27

What is the amino acid structure?

Answer 27

Amino acid structure:
hydrogen
amine - C - carboxyl
R-group

Question 28

Peptide-dipeptide formation.

Answer 28

Peptide-dipeptide formation:
- condensation and hydrolysis happens in the same way as in polysaccharide formation (peptide bond formed in process)
- all peptides will have an amino acid end and carboxyl end

Question 29

What are polypeptides?

Answer 29

Polypeptides are:
- lots of amino acids joined together
- polymers and macromolecules
- formation of peptide bonds takes place at ribosomes and is catalysed by enzyme peptidyltransferase

Question 30

Protein structure.

Answer 30

Levels of protein structure:
1. primary - sequence of amino acids
2. secondary - O, H and N atoms of amino acids interact and form hydrogen bonds and leads to formation of alpha helix (chain of amino acids coiled due to hydrogen bonding with attractions forming between O in -CO on an amino acid or H in -NH on an amino acid 4 places ahead) or beta pleated sheets (polypeptide chains that lie parallel to one another joined by hydrogen bonds)
3. tertiary structure - coils and pleats start to fold, held together by; hydrogen bonds, hydrophobic and hydrophillic between polar and non-polar R-groups, disulphide bridge
- denatured by heating
4. quaternary - interaction of two or more individual proteins (polypeptide chains) called subunits

Question 31

Protein bonding.

Answer 31

Protein bonding:
- hydrophobic parts of the R-groups move to the centre of the polypeptide to avoid water, whereas hydrophillic parts move towards the water
- causes the twisting of amino acid chain which changes shape to form globular proteins
- makes protein water soluble as water molecules can easily cluster around them

Question 32

Fibrous proteins.

Answer 32

Fibrous proteins:
- long, insoluble molecules
- high proportion of amino acids with hydrophobic R-groups
- primary structure is repetitive
e.g collagen- consists of 3 polypeptide chains crosslinked by numerous hydrogen bonds and wrapped in triple helix
- hydrogen bonds form staggered ends between adjacent collagen molecules (allow for attachment of proteins and each end- forming tropocollagen)
- many collagen molecules form a fibril which link to form fibres
- contains high proportions of amino acids
- found in skin, tendons, ligaments and other tissues
e.g keratin- rich in cysteine so lots of disulfide bridges making keratin strong, inflexible and insoluble
- provides mechanical protection
- waterproof
- found in fingernails, hair, horns, scales, fur, feathers
e.g elastin- cross-linking and coiling make structure strong and flexible
- found in lungs, bladder, skin, lining blood vessels

Question 33

Globular proteins.

Answer 33

Globular proteins:
- almost spherical in shape
- soluble in water groups
- compact
e.g insulin- made of two polypeptide chains
- hormone un regulating blood glucose levels
- needs to be soluble to be transported in the blood
e.g conjugated proteins- contain non-protein element (prosthetic group)
e.g haemoglobin- quaternary structure
- made up of 2 alpha-globin and 2 beta-globin polypeptide chains
- a haem group in each subunit (molecule of O can bind to each haem group)
e.g catalase- quaternary protein with 4 haem prosthetic groups
- allows catalase to interact with hydrogen peroxide to speed up its breakdown