biological molecules (lipids + proteins)

Question 1

describe the functions of triglycerides

Answer 1

• energy storage molecules
• insulation

Question 2

describe the functions of phospholipids

Answer 2

• found in cell membranes of eukaryotic and prokaryotic cells making up the phospholipid bilayer controlling what enters and leaves the cell

Question 3

describe the functions of cholestrol

Answer 3

• in eukaryotic cells it helps strengthen the cell membrane by interacting with the phospholipid bilayer
• helps make up steroid hormones (e.g. testosterone
• regulates fluidity of the cell membrane

Question 4

describe the structure of triglycerides

Answer 4

• 1 glycerol
• 3 fatty acid tails (can be saturated/unsaturated)
• bonded by ester bonds
• insoluble

Question 5

describe the structure of phospholipids

Answer 5

• 1 glycerol
• 1 phosphate group (hydrophilic)
• 2 fatty acid tails (hydrophobic)
• connected by ester bonds

Question 6

describe the structure of cholesterol

Answer 6

• polar hydroxyl group
• hydrocarbon rings
• hydrocarbon tail
• connected by ester bonds
• small size
• flattened shape

Question 7

how does the structure of triglyceride aid its function

Answer 7

• good storage molecule : long hydrocarbon tails of the fatty acids contain a lot of chemical energy which is released when they are broken down into ATP for aerobic respiration
• insoluble : water can’t enter the cells by osmosis so the cells don’t swell

Question 8

how does the structure of phospholipids aid its function

Answer 8

• the centre of the bilayer is hydrophobic so water substances can’t easily pass through it allowing the membrane to act as a barrier to those substances
• the more unsaturated the fatty acids, the higher the fluidity of the membrane

Question 9

how does the structure of cholesterol aid its function

Answer 9

• small, flattened shape : can fit inbetween phospholipid molecules in the membrane
• it can bind to the hydrophobic tails allowing it to be packed more closely together helping the membrane become more rigid and less fluid
• however in excess it can cause gall stones, stoke or atherosclerosis

Question 10

what is esterification

Answer 10

• a condensation reaction

Question 11

describe the structure of a unsaturated fatty acid

Answer 11

• double bonds between carbona
• less saturated with oxygen
• causes kink in structure so can’t be packed as tightly together

Question 12

describe the structure of a saturated fatty acid

Answer 12

• only single bonds (no double bond)
• more saturated with hydrogen
• long and straight chain so can fit closer to other fatty acids

Question 13

describe the primary structure of a protein

Answer 13

• number and sequence of amino acids in a polypeptide chain
• encoded by DNA and mRNA

Question 14

describe the function of primary proteins

Answer 14

• determines the structure of the polypeptide and the 3D shape of proteins and their active sites

Question 15

describe the secondary structure of a protein

Answer 15

• hydrogen bonds form between some amino acids causing them to either pleat, twist or coil
• hydrogen bonds provide it with stability
• it forms either beta-pleated sheets or alpha helices

Question 16

describe the function of a secondary protein

Answer 16

• beta-pleated sheets are structured like silk
• alpha helices make up DNA binding and transmembrane proteins

Question 17

describe the tertiary structure of a protein

Answer 17

• the final 3D specific shape of a polypeptide held in place by ionic, disulfide and hydrogen bonds between R-groups
• also determined by hydrophobic and hydrophilic interactions

Question 18

describe the quaternary structure of a protein

Answer 18

• seperate twisted or folded polypeptides linked together
• non-protein, prosthetic groups may be associated with proteins having this structure

Question 19

what are examples of quaternary protein structures

Answer 19

• globular proteins (haemoglobin, insulin, amylase)
• fibrous proteins (collagen, keratin, elastin)

Question 20

describe the structure and function of haemoglobin

Answer 20

• protein that carries oxygen
• conjugated, globular protein
• made up of 4 polypeptide chains and 4 haem prosthetic groups containing iron

Question 21

describe the structure and function of insulin

Answer 21

• protein invloved in controlling blood glucose levels
• made up of 2 polypeptide chains joined by disulfide bonds
• globular protein

Question 22

describe the structure and function of amylase

Question 23

describe the structure and function of collagen

Answer 23

• fibrous protein
• found in bones and tendons allowing them to withstand large pulling forces
• found in atery walls allowing them to withstand high pressure

Question 24

describe the structure of a globular protein

Answer 24

• spherical shape
• invloved in metabolic processes
• water soluble (hydrophilic R-group on the outside)

Question 25

describe the structure of a fibrous protein

Answer 25

- made of long polypeptide chains forming fibres - insoluble (hydrophobic R-group amino acids) - very strong - flexible

Question 26

describe the function and structure of keratin

Answer 26

- strong molecule - large number of cysteine amino acids and therefore disulfide bonds - found in hooves, hair, finger nails and horns - fibrous protein

Question 27

describe the function and structure of elastin

Answer 27

- elastic fibrous protein - found in walls of blood vessels the lungs and bladder

Question 28

describe the structure of an amino acid

Answer 28

- NH2 - amine group - COOH - carboxyl group - R - side chain (R-group 30 different possibilities)

Question 29

describe the formation of dipeptides

Answer 29

- condensation of 2 amino acids - releases water - forms peptide bond

Question 30

whats the equation for rf value

Answer 30

distance travelled by component divided by distance travelled by solvent