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A-level Biology > 2.1.5 ( Part 2 ) - Biological molecules > Flashcards

2.1.5 ( Part 2 ) - Biological molecules Flashcards

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1
Q

What are Lipids ?

A

They are large complex molecules known as macromolecules

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2
Q

Name examples of macromolecules ?

A
  • Triglycerides
  • Phospholipids
  • Sterols
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3
Q

What is a triglyceride ?

A

A triglyceride is made up of glycerol molecule and three fatty acid molecules

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4
Q

Draw a digram to display the structure of a triglyceride ?

A
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5
Q

What happens during a condensation reaction resulting in a triglyceride ?

A
  • During a condensation reaction, a hydroxyl group and a hydrogen atom is removed between the glycerol molecule and each fatty acid molecule
  • This leads to the formation of three ester bonds and elimination of three water molecules producing a triglyceride
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6
Q

Draw a diagram to represent the formation of a triglycerides from one glycerol molecule and three fatty acids ?

A
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7
Q

What happens during a hydrolysis reaction of a triglyceride ?

A
  • During a hydrolysis reaction, a water molecule is used to break an ester bond between a glycerol molecule and fatty acid molecule
  • When three water molecules are used to break the ester bonds, the triglyceride is broken down into one glycerol molecule and three fatty acids
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8
Q

What is the name of the bonds that form between glycerol molecules and fatty acid molecules ?

A

An ester bond

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9
Q

What are the two different types of fatty acids ?

A
  • Saturated ( contains only single C-C bonds )
  • Unsaturated ( Contains at leats one multiple C-C bond )
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10
Q

What are the features of unsaturated fatty acids due to their structure ?

A
  • Due to the presence of double bonds, this causes the molecule to kink/bend and means they cannot pack as closely together
  • This causes it to be liquid at room temperature rather than solid
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11
Q

What are phospholipids ?

A

A phospholipid is made up of one glycerol molecule, two fatty acids and a phosphate group

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12
Q

Explain the structure of phospholipids ?

A
  • Due to their length, they have non-polar tails which are repelled by water/ hydrophobic
  • The charged head is poler and therefore will interact with water/ is hydrophilic
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13
Q

What are the roles of lipids ?

A
  • Formation of cell membranes
  • Hormone production
  • Electrical insulation
  • Waterproofing
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14
Q

What is the function of triglycerides in particular ?

A
  • Thermal insulation to reduce heat loss ( penguins )
  • Cushioning of vital organs ( heart and kidneys )
  • Buoyancy for aquatic animals ( whales )
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15
Q

Explain how phospholipids are important in the formation of the cell membrane ?

A
  • Due to their structure, they can crate a phospholipid bilayer with the hydrophobic tails pointing inward creating a hydrophobic core while their hydrophilic heads point outward
  • This allows phospholipids to separate the cytoplasm in cells from aqueous environments
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16
Q

What are sterols ?

A

Sterols are complex alcohol molecules which have dual hydrophilic/ hydrophobic characteristics

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17
Q

Name an example of a sterol ?

A

Cholesterol

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18
Q

Explain how cholesterol is important in the formation of cell membranes ?

A
  • Cholesterol molecules are positioned between phospholipids and regulate the fluidity of the cell membrane
  • They keep membranes fluid at low temperatures and prevent them from becoming too fluid at higher temperatures
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19
Q

What is the test for the presence of lipids called ?

A

The emulsion test

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20
Q

Describe the test for the presence of lipids in a sample ?

A

1 ) sample is mixed with ethanol
2 ) Solution is mixed with water and shaken

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21
Q

What is a positive and negative result when testing for presence of lipids ?

A
  • If a white emulsion forms then lipids are present / positive
  • If there is no change then it is negative
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22
Q

What is a protein ?

A

One or more polypeptides arranged as a complex macromolecule

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23
Q

What does an amino acid contain ?

A

An amino acid contains a central carbon atom bonded to a hydrogen atom, an amine group, a carboxyl group and a R group

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24
Q

Draw a diagram to represent the structure of an amino acid ?

A
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25
Q

Explain what happens during a condensation reaction between two amino acids ?

A
  • During a condensation reaction, a hydroxyl group from the carboxyl group of one amino acid and a hydrogen atom from the amine group of another is removed
  • This leads to the formation of a peptide bond, elimination of a water molecules and production of a dipeptide
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26
Q

What is a polypeptide ?

A

A long-chain molecule made of three or more amino acids chemically joined together by peptide bonds

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27
Q

What is the name of the bond that forms between amino acids ?

A

a peptide bond

28
Q

Explain what happens during the hydrolysis reaction of a dipeptide ?

A
  • During a hydrolysis reaction, a water molecule is added to a dipeptide to break a peptide bond between the two amino acids
  • This results in two individual amino acids
29
Q

Draw a diagram to represent the formation of a dipeptide from two amino acids ?

A
30
Q

What are the different levels of protein structure ?

A
  • Primary structure
  • Secondary structure
  • Tertiary structure
  • Quaternary structure
31
Q

What is the primary structure of protein ?

A

It is the sequence ( and number ) of Amin acids in a polypeptide and associated peptide bonds

32
Q

What does the primary structure of a protein determine ?

A
  • It affect how the polypeptide folds to give the proteins final shape
  • It therefore affects the proteins shape and function
33
Q

What is the secondary structure of a protein ?

A

The formation of hydrogen bonds between the amine group of one amino acid and the carboxyl group of another pulling them into regular patterns

34
Q

What are the two main types of secondary structures of proteins ?

A
  • Alpha helix ( coiling )
  • Bet pleated sheets
35
Q

What is the tertiary structure of a protein ?

A

The folding of a protein into a specific 3D structure depending on the various interactions between R groups of amino acids

36
Q

What are the various interactions between R groups of amino acids in the tertiary and quaternary structure ?

A
  • Hydrophilic and hydrophobic interactions
  • Hydrogen bonds
  • Ionic bonds
  • Disulphide bonds/ bridges
37
Q

Where do hydrophilic and hydrophobic interactions occur in the tertiary structure ?

A

They are weak interactions between polar and non-polar R groups of amino acids

38
Q

Where do hydrogen bonds occur in the tertiary structure ?

A

They are the weakest bonds between two polar R groups of amino acids

39
Q

Where do ionic bonds occur in the tertiary structure ?

A

They form between oppositely charged/ ionised R groups of amino acids

40
Q

Where do disulphide bridges/ bonds occur in the tertiary structure ?

A

They are the strongest bonds formed between R groups of amino acids contains sulphur atoms

41
Q

What does the tertiary structure of a protein determine ?

A

the tertiary structure determines the 3D structure of the protein and therefore its function

42
Q

What is the quaternary structure of protein ?

A

The association of two or more proteins/ subunits to make a functioning protein

43
Q

What are the different types of proteins ?

A
  • Globular protiens
  • Conjugated proteins
  • Fibrous proteins
44
Q

What are the features of globular proteins ?

A
  • Coiled/ spherical- shaped
  • Soluble in water
45
Q

What are the functions of globular proteins ?

A

Regulate many processes such as chemical reactions, immunity and muscle contraction

46
Q

Name an example of a globular protein ?

A

Insulin

47
Q

Explain how Insulin’s structure as a globular protein helps aid its function ?

A
  • Insulin is a hormone involved in regulation of blood glucose concentration
  • Insulin needs to be soluble since hormones are transported via the blood stream
  • Insulin needs to have a precise shape since hormones have to fit into specific receptors on the cell membrane
48
Q

What is a conjugated protein ?

A

They are globular proteins that contain a non-protein component called a prosthetic group

49
Q

Name examples of conjugated proteins ?

A
  • Haemoglobin
  • Catalase
50
Q

Explain how haemoglobin’s structure as a conjugated protein aids its function ?

A
  • Haemoglobin is the red, oxygen-carrying pigment in red blood cells
  • It is made up of 4 polypeptides which each contain a heat group ( molecule contains Fe2+ )
  • Each Fe2+ ion can combine with an oxygen molecule to oxyhemoglobin and transport oxygen around the body
51
Q

Explain how catalase’s structure as a conjugated protein aids its function ?

A
  • Catalase is an enzyme which speeds up the breakdown of hydrogen peroxide ( common byproduct of metabolic reactions that is damaging to cells )
  • It contains 4 haem groups
  • Fe2+ ions allow catalase to interact with and increase the rate of the break down of hydrogen peroxide
52
Q

What are the features of fibrous proteins ?

A
  • Strands/ fibres
  • Insoluble in water
53
Q

Name examples of fibrous proteins ?

A
  • Keratin
  • Elastin
  • Collagen
54
Q

Explain how keratin’s structure as a fibrous protein aids its function ?

A
  • Keratin is a group of fibrous proteins present in hair, skin and nails
  • The degree of disulphide bonds determines the flexibility
55
Q

Explain how elastin’s structure as a fibrous protein aids its function ?

A
  • Elastin is a fibrous protein found in elastic fibres ( in walls of blood vessels / alveoli in lungs )
  • It allows structures flexibility and to expand/ return to normal size when needed
56
Q

Explain how collagen’s structure as a fibrous protein aids its function ?

A
  • Collagen is a fibrous protein which is connective tissue found in skin, tendons, ligaments and nervous system
  • Collagen has flexibility due to it being a fibrous protein
57
Q

Name the test for the presence of proteins in a sample ?

A

Biuret test

58
Q

Describe the test for the presence of proteins in a sample ?

A

1 ) Add equal volume of Biuret solution to sample
2 ) Note colour change

59
Q

What is the positive and negative test for the presence of proteins ?

A
  • If it changes from light blue to purple/ violet then proteins are present
  • If there is no change it is negative
60
Q

Explain why using Biuret solution tests for the presence of proteins ?

A
  • Peptide bonds forma violet precipitate with Cu2+ ions
  • Therefore, when proteins are present they forma violet precipitate with Biuret solution ( NaOH and hydrated CUSOv4 )
61
Q

What can be used to separate and identify the amino acids in a mixture ?

A

Thin layer chromatography

62
Q

What is the mobile and stationary phase in the TLC of amino acids ?

A
  • Stationarity phase = silica gel
  • Mobile phase = organic solvent
63
Q

What is the equation for Rf value ?

A

Rf = ( distance travelled by spot ) / ( distance travelled by solvent front )

64
Q

What are the key inorganic cations involved in biological processes ?

A
  • Ca2+
  • Na+
  • K+
  • H+
  • NHv4+
65
Q

What are the key inorganic anions involved in biological processes ?

A
  • NOv3-
  • POv4-3
  • OH-
  • Cl-
  • H-
  • HCOv3-

A-level Biology (30 decks)

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