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OCR A level Biology > 2.2 Biological molecules > Flashcards

2.2 Biological molecules Flashcards

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1
Q

What is a covalent bond?

A

when 2 atoms share a pair of electrons

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2
Q

What is an ion?

A

an atom/molecule in which the total number of electrons is not equal to the total number of protons

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3
Q

What is an ion that has a net positive charge and has lost electrons called?

A

a cation

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4
Q

What is an ion that has a net negative charge and has gained electrons?

A

an anion

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5
Q

What is Ca2+ necessary for?

A

nerve impulse transmission and muscle contraction

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6
Q

What is HCO3- necessary for?

A

maintenance of blood pH

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7
Q

Define polarity

A

When the electrons shared in a covalent bond are not shared equally between the 2 atoms in the bond

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8
Q

Is the atom in a covalent bond with the greater share of electrons delta positive or delta negative?

A

delta negative

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9
Q

What bonds form between polar molecules?

A

Hydrogen bonds

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10
Q

Name 3 characteristics of water

A
  • unusually high boiling point
  • ice is less dense than water
  • has cohesive and adhesive properties
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11
Q

Name 4 properties of water that make it critical in sustaining life

A
  • water acts as a solvent
  • water is an effective transport medium due to cohesive/adhesive properties
  • water acts as a coolant
  • water is stable
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12
Q

What is the general formula of carbohydrates?

A

Cx(H2O)y

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13
Q

Name 3 types of carbohydrate

A
  • monosaccharide
  • disaccharide
  • polysaccharide
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14
Q

Name 3 examples of monosaccharides

A
  • glucose (hexose)
  • fructose (hexose)
  • ribose (pentose)
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15
Q

Name 2 examples of disaccharides

A
  • lactose

- sucrose

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16
Q

Name 3 examples of polysaccharides

A
  • glycogen
  • cellulose
  • starch
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17
Q

What is the chemical formula of glucose?

A

C6H12O6

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18
Q

What is a condensation reaction?

A

when 2 OH groups react and a covalent bond is formed and a water molecule is formed

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19
Q

How is starch formed?

A

When many alpha-glucose molecules join by glycosidic bonds to form 2 different polysaccharides (amylose and amylopectin) collectively known as starch

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20
Q

What is the difference between amylose and amylopectin?

A

amylose is formed of alpha-glucose molecules joined only by 1,4-glycosidic bonds and is a straight chain whereas amylopectin also has 1,6-glycosidic bonds and is branched

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21
Q

What is glycogen?

A

The functionally equivalent energy storage molecules to starch in animals and fungi

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22
Q

How does glycogen differ from amylopectin?

A

Glycogen forms more branches so is more compact - important as animals are mobile

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23
Q

Key properties of amylopectin and glycogen that make them suitable for storage

A
  • insoluble
  • branched
  • compact
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24
Q

What is a hydrolysis reaction?

A

the addition of H2O to break covalent bonds

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25
Q

How is cellulose formed?

A

beta-glucose molecules join with each alternate molecule being turned upside down, forming a straight chain

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26
Q

How are microfibrils formed?

A

Cellulose molecules make H-bonds with each other forming microfibrils

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27
Q

How are macrofibrils formed?

A

microfibrils join together to form macrofibrils

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28
Q

How are cellulose fibres formed?

A

Macrofibrils joining together

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29
Q

What properties make cellulose good for forming cell walls?

A

cellulose fibres are insoluble and strong

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30
Q

What is the test for reducing sugars?

A

Benedict’s test

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31
Q

What colour indicates a positive result in Benedict’s test for reducing sugars?

A

brick red, depending on the concentration - negative result is blue

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32
Q

What is the iodine test used for?

A

to detect the presence of starch

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33
Q

How can carbohydrate concentration be quantitatively determined?

A

using a colorimeter

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34
Q

What are lipids more commonly known as?

A

fats or oils

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35
Q

Are lipids polar or non-polar?

A

non-polar

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36
Q

How is a triglyceride made?

A

combining 1 glycerol molecule with 3 fatty acids

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37
Q

What is a fatty acid?

A

Carboxylic acids with a hydrocarbon chain attached

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38
Q

What is the name of the reaction that forms triglycerides?

A

esterification which is a type of condensation reaction

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39
Q

What does saturated mean?

A

all the carbon atoms in the hydrocarbon chain form the maximum number of bonds with hydrogen atoms

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40
Q

What are phospholipids?

A

modified triglycerides with a phosphate group replacing one of the fatty acid groups

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41
Q

How is a phospholipid bilayer formed?

A

the hydrophilic head of the phospholipids will be attracted to the water and the hydrophobic tails will point towards the centre of the sheet

42
Q

What are sterols?

A

steroid alcohols based on a 4-C ring structure with an OH group at one end

43
Q

Name one example of a sterol

A

cholesterol

44
Q

What is the function of cholesterol?

A

plays an important role in the formation of cell membranes

45
Q

Name 5 biological roles of lipids

A
  • membrane formation
  • hormone production
  • electrical insulation
  • waterproofing
  • buoyancy
46
Q

How are lipids identified?

A

emulsion test

47
Q

What are peptides?

A

polymers made up of amino acid molecules

48
Q

What do proteins consist of?

A

one or more polypeptides arranged as complex macromolecules

49
Q

How many essential amino acids are there that can only be obtained from diet?

A

9

50
Q

How are peptides synthesised?

A

condensation reaction of amino acids to form peptide bonds

51
Q

What catalyses the reaction that forms polypeptides?

A

Peptidyl transferase

52
Q

What technique is used to separate different amino acids?

A

Thin layer chromatography

53
Q

What are the 4 levels of protein structure?

A

primary, secondary, tertiary and quaternary

54
Q

What is the primary structure of a protein?

A

the sequence of amino acids

55
Q

What is the secondary structure of a protein?

A

The interaction of the O, H and N atoms in the basic repeating structure of the amino acids (not R groups) forming alpha helices and beta pleated sheets

56
Q

What is the tertiary structure of a protein?

A

the folding of the protein into its final shape involving a number of different interactions

57
Q

What are the interactions involved in the tertiary structure of a protein?

A
  • Hydrophobic and hydrophilic interactions
  • Hydrogen bonds
  • Ionic bonds
  • Disulphide bonds/bridges
58
Q

What reaction is responsible for the breakdown of proteins?

A

Hydrolysis

59
Q

How are proteins identified?

A

Biuret test - purple result is positive, blue result is negative

60
Q

What are the 2 different types of proteins?

A

globular and fibrous

61
Q

What are 3 properties of globular proteins?

A
  • Compact
  • Water soluble
  • Roughly spherical in shape
62
Q

What is an example of a globular protein?

A

Insulin

63
Q

What is a conjugated protein?

A

A type of globular protein that contains a prosthetic group

64
Q

What is a prosthetic group?

A

a non protein component

65
Q

What are the 2 types of prosthetic groups?

A
  • Lipids/carbohydrates forming lipoproteins/glycoproteins

- Metal ions/molecules derived from vitamins forming cofactors

66
Q

What is are 2 examples of conjugated proteins?

A

Haemoglobin and catalase

67
Q

What does catalase do?

A

catalyses the breakdown of hydrogen peroxide

68
Q

What are 3 properties of fibrous proteins?

A
  • long
  • insoluble
  • strong and stable
69
Q

What are 3 examples of fibrous proteins?

A
  • Keratin
  • Collagen
  • Elastin
70
Q

Where is keratin found in the body?

A

hair, skin and nails

71
Q

What makes keratin so strong?

A

presence of many disulphide bonds

72
Q

Where is elastin found in the body?

A

walls of blood vessels and alveoli

73
Q

What is elastin made up of?

A

lots of molecules of tropoelastin

74
Q

Why can elastin stretch?

A

The tropoelastin molecules contain alternate hydrophobic and lysine-rich areas and get are able to stretch and recoil without breaking

75
Q

What is collagen?

A

a connective tissue found in skin, tendons, ligaments and the nervous system

76
Q

Describe the structure of collagen

A

3 polypeptides wound together in a long, strong rope-like structure in a triple helix. It is flexible. It is strong due to tropocollagen fibrils cross-linking to produce strong fibres.

77
Q

What are nucleic acids?

A

large polymers formed from nucleotides

two types - DNA and RNA

78
Q

What are the 3 components of a nucleotide?

A
  • a pentose sugar
  • a phosphate group
  • a nitrogenous base
79
Q

What is the name of the bond between the phosphate group of one pentose sugar and the hydroxyl group on another pentose sugar?

A

Phosphodiester bond

80
Q

What are the 4 possible bases on a DNA nucleotide?

A
  • Cytosine
  • Guanine
  • Adenine
  • Thymine
81
Q

What are the 2 groups that the DNA bases can be classed as?

A
  • Pyrimidines

- Purines

82
Q

What is complementary base pairing?

A

A and T can form 2 H-bonds and always join with each other and C and G can form 3 H-bonds so also join with each other

83
Q

What is RNA?

A

Ribonucleic acid

84
Q

What essential role does RNA play?

A
  • transfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body
85
Q

How does RNA differ from DNA?

A
  • ribose sugar

- uracil instead of thymine

86
Q

Why is RNA required?

A

DNA is too large to leave the nucleus so a gene is transcribed to a mRNA molecule which is small enough to leave the nucleus

87
Q

What is semi-conservative replication?

A

Double helix unwinds and separates into 2 strands and free DNA nucleotides then pair with their complementary bases via H-bonds. The new nucleotides join to their adjacent nucleotides with phosphodiester bonds. Each new molecule of DNA consists of 1 new strand and 1 old strand.

88
Q

What are the 2 enzymes involved in replication?

A
  • DNA helicase unwinds DNA double helix

- DNA polymerase catalyses the formation of phosphodiester bonds

89
Q

What is continuous replication?

A

The strand that is unzipped from the 3’ end can be continuously replicated as the strands unzip.

90
Q

What is discontinuous replication?

A

The other strand that is unzipped from the 5’ end so DNA polymerase has to wait until a section of the strand has unzipped and then work back along the strand producing Okazaki fragments

91
Q

What is the genetic code?

A

DNA carries ‘instructions’ needed to synthesise the many different proteins required by organisms. These proteins are made up of a sequence of amino acids, folded into complex structure, therefore DNA must code for a sequence of amino acids

92
Q

What is a codon?

A

a sequence of 3 bases that code for an amino acid

93
Q

How many different base codons are possible?

A

64

94
Q

How many stop codons are there and how many amino acids do they code for?

A
  • 3 stop codons that do not code for any amino acids and signal the end of the sequence
95
Q

What does degenerate code mean?

A

There are only 2o different amino acids that regularly occur in biological proteins and there are a lot more codons, therefore many amino acids can be coded for by more than one codon which makes the code degenerate.

96
Q

What is transcription?

A

The copying of the base sequences of genes and transporting them to the ribosome.

97
Q

What is translation?

A

The decoding of the mRNA into a sequence of amino acids

98
Q

What are the 3 main types of activity that cells require energy for?

A
  • Synthesis
  • Transport
  • Movement
99
Q

What is ATP made up of?

A
  • a nitrogenous base - always adenine
  • a pentose sugar - always ribose
  • 3 phosphate groups
100
Q

How much energy is released by ATP?

A

30.6 kJ/mol

101
Q

How does ATP release energy?

A

hydrolysis to form ADP and Pi

102
Q

What are the properties of ATP that make it ideally suited to carry out its function in energy transfer?

A
  • small
  • water soluble
  • contains bonds between phosphates with intermediate energy
  • releases energy in small packets
  • easily regenerated by phosphorylation of ADP

OCR A level Biology (8 decks)

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