Biological molecule 2 (Proteins and Lipids)

Question 1

Elements in lipids

Answer 1

Carbon, hydrogen and oxygen but they have a high proportion of H

Question 2

Structure of triglycerides

Answer 2

One glycerol (alcohol) and three fatty acids

Question 3

Saturated

Answer 3

No double bonds between carbon atoms, most likely to be solid at room temperature

Question 4

Mono-unsaturated

Answer 4

One double bond between C atoms

Question 5

Polyunsaturated

Answer 5

More than 1 double bond between C atoms, they cause the molecule to bend and can not pack closely together making them liquid at room temperature

Question 6

Fatty acid tails

Answer 6

Made of hydrocarbons, they are hydrophobic making lipid insoluble in water

Question 7

Basic fatty acid structure

Answer 7

Long hydrocarbon tails containing a carboxylic acid at one end

Question 8

Forming a triglyceride

Answer 8

The hydroxyl groups interact leading to the formation of 3 water molecules and bonds between the fatty acid and glycerol molecule known as ester bonds in a process called esterification

Question 9

What type of reaction is esterification?

Answer 9

Condensation reaction

Question 10

What properties does the fatty acid tail give the triglyceride?

Answer 10

Density, melting point and sate at room temperature

Question 11

Phospholipid structure

Answer 11

Glycerol, 2 fatty acids and a phosphate group

Question 12

Is a phosphate group polar?

Answer 12

Yes

Question 13

What does the polar nature of the phosphate group cause?

Answer 13

The head of the phospholipid is attracted to water (hydrophilic)

Question 14

Non-polar fatty acid tail

Answer 14

Hydrophobic

Question 15

Define amphipathic

Answer 15

Both hydrophobic and hydrophilic regions

Question 16

Functions and properties of triglycerides

Answer 16

1. energy storage molecules in animals and plants
2. insoluble, they bundle into insoluble droplets with hydrophilic heads facing outwards
3. long hydrocarbon chains contain a lot of chemical energy (twice as much per g as carbohydrates)

Question 17

Phospholipid functions

Answer 17

cell membranes

Question 18

Cholesterol functions

Answer 18

Strengthen the cell membrane by interacting with the phospholipid bilayer, making it less fluid and more rigid

Question 19

Functions of lipids

Answer 19

1. Plasma membrane
2. energy store
3. absorption of fat soluble vitamins (A,E,D,K)
4. myelin sheath around axons
5. energy store, protection and buoyancy
6. source of water (respiration)
7. water proofing

Question 20

Test for lipids

Answer 20

Emulsion test - shake the substance with ethanol, shake, add to water and a milky colour will indicate a lipid

Question 21

Elements in proteins

Answer 21

Carbon, hydrogen, oxygen and smaller quantities of nitrogen and sulphur

Question 22

Protein monomers

Answer 22

Amino acids

Question 23

Functions of proteins

Answer 23

1. structural
2. catalytic
3. signalling
4. immunological

Question 24

General structure of proteins

Answer 24

Amino group, carboxylic acid group and ‘R group’

Question 25

Carboxyl group

Answer 25

COOH

Question 26

Amino group

Answer 26

NH2

Question 27

R group

Answer 27

Can be variable, simple as a H to a more complex ring structure

Question 28

Protein synthesis

Answer 28

Long chains of amino acids joined together in a condensation reaction to from peptide bonds between individual amino acid monomers

Question 29

Peptide bond (C-N)

Answer 29

Covalent bond between the C (from the carboxylic acid) and the N (from the amino group)

Question 30

4 structural levels of protein

Answer 30

1. Primary 2. secondary 3. tertiary 4. quaternary

Question 31

Primary structure

Answer 31

1. The sequence of amino acids in the polypeptide chain 2. no IM bonds or interactions 3. different proteins have different sequences

Question 32

Secondary structure

Answer 32

1. Hydrogen bonds form between near by amino acids in the chain 2. this causes them to coil into an alpha helix or beta pleated sheet 3. thus they are no longer flat

Question 33

Tertiary structure

Answer 33

1. The coiled chain is coiled further 2. more bonds form between different parts of the polypeptide chain 3. forms the final 3D structure (for proteins made of one chain)

Question 34

Bonding in the tertiary structure

Answer 34

1. hydrophobic/hydrophilic interactions 2. hydrogen bonds 3. ionic bonds 4. disulphide bridges

Question 35

Quaternary structure

Answer 35

1. The way in which the polypeptide chains are assembled together 2. more than 1 polypeptide chain for subunit 3. NOT all proteins have a quaternary structure 4. influenced by all bonds above 5. prosthetic group

Question 36

What causes denaturation of proteins?

Answer 36

Changes in temperature, PH or salt concentration

Question 37

Fibrous protein shapes

Answer 37

Long unbranched, parallel chains

Question 38

Fibrous protein function

Answer 38

Support and structural

Question 39

Fibrous protein sequence of amino acids

Answer 39

Repetitive and regular

Question 40

Fibrous protein stability / sensitivity to temperature

Answer 40

Stable

Question 41

Fibrous protein examples

Answer 41

Collagen, keratin

Question 42

Globular protein shape

Answer 42

Spherical (chains folded)

Question 43

Globular protein fucntions

Answer 43

Metabolic (enzymes)

Question 44

Globular protein solubility in water

Answer 44

Soluble

Question 45

Fibrous protein solubility in water

Answer 45

Insoluble

Question 46

Globular protein sequence of amino acids

Answer 46

Irregular

Question 47

Globular protein stability / sensitivity to temperature

Answer 47

Unstable

Question 48

Globular protein exmaples

Answer 48

All enzymes, some hormones (e.g insulin) and haemoglobin

Question 49

Haemoglobin

Answer 49

1. Carries O2 around the body in red blood cells 2. conjugated protein (a non-protein group attached) 3. non-protein part is called a prosthetic group = Heam group containing iron

Question 50

Insulin

Answer 50

1. Hormone secreted by the pancreas 2. regulates the blood glucose levels 3. soluble meaning it can be easily transported in the blood

Question 51

Insulin structure

Answer 51

Two polypeptide chains, held together by disulphide bridges

Question 52

Amylase

Answer 52

1. enzyme - breakdown of starch | 2. single chain of amino acids

Question 53

Collagen

Answer 53

1. found in animal connective tissues 2. mineral bind to increase rigidity 3. strong

Question 54

Keratin

Answer 54

Found in external structures of animals (hair, nails and skin, feathers and horns)

Question 55

Elastin

Answer 55

Found in elastic connective tissue such as skin, large blood vessels and some ligaments

Question 56

Biuret test for proteins

Answer 56

1. add a few drops of sodium hydroxide to turn the solution alkaline 2. then add a few drops of copper (II) sulphate solution 3.

Question 57

Positive Biuret test result

Answer 57

Purple

Question 58

Negative Biuret test

Answer 58

Remain blue (due to copper ions)