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OCR A-level Biology > Biological molecule 2 (Proteins and Lipids) > Flashcards

Biological molecule 2 (Proteins and Lipids) Flashcards

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1
Q

Elements in lipids

A

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

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2
Q

Structure of triglycerides

A

One glycerol (alcohol) and three fatty acids

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3
Q

Saturated

A

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

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4
Q

Mono-unsaturated

A

One double bond between C atoms

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5
Q

Polyunsaturated

A

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

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6
Q

Fatty acid tails

A

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

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7
Q

Basic fatty acid structure

A

Long hydrocarbon tails containing a carboxylic acid at one end

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8
Q

Forming a triglyceride

A

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

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9
Q

What type of reaction is esterification?

A

Condensation reaction

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10
Q

What properties does the fatty acid tail give the triglyceride?

A

Density, melting point and sate at room temperature

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11
Q

Phospholipid structure

A

Glycerol, 2 fatty acids and a phosphate group

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12
Q

Is a phosphate group polar?

A

Yes

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13
Q

What does the polar nature of the phosphate group cause?

A

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

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14
Q

Non-polar fatty acid tail

A

Hydrophobic

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15
Q

Define amphipathic

A

Both hydrophobic and hydrophilic regions

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16
Q

Functions and properties of triglycerides

A
  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)
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17
Q

Phospholipid functions

A

cell membranes

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18
Q

Cholesterol functions

A

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

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19
Q

Functions of lipids

A
  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
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20
Q

Test for lipids

A

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

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21
Q

Elements in proteins

A

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

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22
Q

Protein monomers

A

Amino acids

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23
Q

Functions of proteins

A
  1. structural
  2. catalytic
  3. signalling
  4. immunological
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24
Q

General structure of proteins

A

Amino group, carboxylic acid group and ‘R group’

25
Q

Carboxyl group

A

COOH

26
Q

Amino group

A

NH2

27
Q

R group

A

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

28
Q

Protein synthesis

A

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

29
Q

Peptide bond (C-N)

A

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

30
Q

4 structural levels of protein

A
  1. Primary
  2. secondary
  3. tertiary
  4. quaternary
31
Q

Primary structure

A
  1. The sequence of amino acids in the polypeptide chain
  2. no IM bonds or interactions
  3. different proteins have different sequences
32
Q

Secondary structure

A
  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
33
Q

Tertiary structure

A
  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)
34
Q

Bonding in the tertiary structure

A
  1. hydrophobic/hydrophilic interactions
  2. hydrogen bonds
  3. ionic bonds
  4. disulphide bridges
35
Q

Quaternary structure

A
  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
36
Q

What causes denaturation of proteins?

A

Changes in temperature, PH or salt concentration

37
Q

Fibrous protein shapes

A

Long unbranched, parallel chains

38
Q

Fibrous protein function

A

Support and structural

39
Q

Fibrous protein sequence of amino acids

A

Repetitive and regular

40
Q

Fibrous protein stability / sensitivity to temperature

A

Stable

41
Q

Fibrous protein examples

A

Collagen, keratin

42
Q

Globular protein shape

A

Spherical (chains folded)

43
Q

Globular protein fucntions

A

Metabolic (enzymes)

44
Q

Globular protein solubility in water

A

Soluble

45
Q

Fibrous protein solubility in water

A

Insoluble

46
Q

Globular protein sequence of amino acids

A

Irregular

47
Q

Globular protein stability / sensitivity to temperature

A

Unstable

48
Q

Globular protein exmaples

A

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

49
Q

Haemoglobin

A
  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
50
Q

Insulin

A
  1. Hormone secreted by the pancreas
  2. regulates the blood glucose levels
  3. soluble meaning it can be easily transported in the blood
51
Q

Insulin structure

A

Two polypeptide chains, held together by disulphide bridges

52
Q

Amylase

A
  1. enzyme - breakdown of starch

2. single chain of amino acids

53
Q

Collagen

A
  1. found in animal connective tissues
  2. mineral bind to increase rigidity
  3. strong
54
Q

Keratin

A

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

55
Q

Elastin

A

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

56
Q

Biuret test for proteins

A
  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.
57
Q

Positive Biuret test result

A

Purple

58
Q

Negative Biuret test

A

Remain blue (due to copper ions)

OCR A-level Biology (2 decks)

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