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(OCR A) - A-level Biology > 2.1.2 Biological molecules > Flashcards

2.1.2 Biological molecules Flashcards

1
Q

How is water a solvent?

A

Dissolves polar molecules

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2
Q

How is water a transport medium?

A

Capillary action due to cohesion and adhesion

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3
Q

What is cohesion between?

A

Water molecules

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4
Q

What is adhesion between?

A

Water molecules and vessel wall

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5
Q

What makes water a coolent?

A

High latent heat of evaporation (high boiling point)

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6
Q

Why is ice less dense than water?

A

Due to hydrogen bonding

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7
Q

What molecules do carbohydrates contain?

A

C, H, O

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8
Q

Examples of monosaccharides?

A
  • Glucose
  • Fructose
  • Galactose
  • Ribose
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9
Q

Examples of polysaccharides?

A
  • Glycogen
  • Cellulose
  • Starch
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10
Q

What units make up the disaccharide sucrose and which bond is involved?

A
  • Fructose + glucose
  • 1,6-glycosidic
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11
Q

What units make up the disaccharide lactose and which bond is involved?

A
  • Galactose + glucose
  • 1,4-glycosidic bond
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12
Q

Where is the OH in α-glucose?

A

Below carbon-1

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13
Q

Where is the OH in β-glucose

A

Above carbon-1

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14
Q

Why is glucose soluble in water?

A

Polar molecule due to hydrogen bonds that form between OH and water

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15
Q

What reaction MAKES glycosidic bonds

A

Condensation reaction (removal of water)

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16
Q

What units make up the disaccharide maltose and which bond is involved?

A
  • α-glucose + α-glucose
  • 1,4-glycosidic bond
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17
Q

What % of amylose is present in starch?

A

20-30%

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18
Q

What % of amylopectin is present in starch?

A

70-80%

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19
Q

What is the structure of amylose?

A

Linear chain of glucose units joined by α-1,4-glycosidic bonds

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20
Q

What is the structure of amylopectin?

A

Branched chain of glucose units joined by α-1,6-glycosidic bonds and α-1,4-glycosidic bonds

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21
Q

Why is it important for amylose and amylopectin to be able to coil into a spiral shape?

A

Makes it compact and less soluble

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22
Q

What is the structure of glycogen?

A

Branched chain of glucose units joined by α-1,6-glycosidic bonds and α-1,4-glycosidic bonds (more than amylopectin)

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23
Q

Where is glycogen normally found?

A

Liver and muscle cells

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24
Q

What reaction BREAKS glycosidic bonds?

A

Hydrolysis reaction (addition of water)

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25
Q

What is the structure of cellulose?

A

Straight chain containing repeating units of β-glucose that alternate so OH groups are next to each other. Forms 1,4-glycosidic bonds

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26
Q

What makes cellulose suitable to be the cell wall of plants?

A

High tensile strength
Insoluble
Flexible

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27
Q

What molecules do lipids contain?

A

C, H, O

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28
Q

Why are lipids insoluble in water?

A

Non polar and hydrophobic fatty acids

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29
Q

What are triglycerides made up of?

A

Glycerol + 3 fatty acids

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30
Q

What bond forms between glycerol and fatty acids?

A

Ester bond (condensation reaction)

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31
Q

What state are saturated fats normally?

A

Solids

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32
Q

What state are unsaturated fats normally?

A

Liquids (oils)

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33
Q

What do phospholipids contain?

A

Hydrophilic phosphate head (PO43-)
Hydrophobic fatty acid tails

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34
Q

Which parts of a phospholipid are hydrophobic and hydrophilic?

A
  • Hydrophobic - fatty acid tail
  • Hydrophilic - phosphate head
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35
Q

Functions of phospholipids when interacting with water?

A
  • Surfactant
  • Cell membrane bilayer
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36
Q

What are sterols?

A

Complex alcohol molecule with hydrophobic and hydrophilic properties

37
Q

What is cholesterol?

A

A sterol which adds stability and regulates fluidity in between the phospholipids of a cell membrane

38
Q

What can be manufactured using cholesterol?

A

Vitamin D, steroid hormones and bile

39
Q

Differences between peptide hormones and steroid hormones?

A

Peptide hormone
- Polar
- Cannot pass through cell membrane
- Attach to receptor

Steroid hormone
- Non polar
- Lipid soluble
- Pass through cell membrane

40
Q

Roles of lipids?

A
  • Membrane formation
  • Hormone production
  • Myelin sheath for electrical insulation
  • Thermal insulation
  • Cushioning
41
Q

What molecules do proteins contain?

A

C, H, O, N

42
Q

What functional groups does an amino acid contain?

A

Amine group
Carboxyl group

43
Q

What bond forms between amino acids?

A

Peptide bond (condensation reaction)

44
Q

What is the primary structure in proteins?

A

Sequence in which amino acids are joined

45
Q

What bonds are involved in the primary structure of proteins?

A

Peptide bonds

46
Q

What is the secondary structure in proteins?

A

Amino acids pulled into either alpha helix or beta pleated sheet

47
Q

What bonds are involved in the secondary structure of proteins?

A

Hydrogen bonds

48
Q

What is the tertiary structure of proteins?

A

R-groups interact to fold protein into final shape

49
Q

What bonds are involved in the tertiary structure of proteins?

A
  • Hydrogen bonds
  • Hydrophilic and hydrophobic
  • Ionic bonds
  • Disulphide bonds
50
Q

What is the quaternary structure of proteins?

A

Two or more proteins interact

51
Q

What bonding is involved in quaternary structure of proteins?

A
  • Hydrogen bonds
  • Hydrophilic and hydrophobic
  • Ionic bonds
  • Disulphide bonds
52
Q

What is inulin’s quaternary structure?

A

Two identical subunits, disulphide bonding involved due to the presence of sulphur

53
Q

What is haemoglobin’s quaternary structure?

A

Two different subunits (four in total): 2 alpha chains, 2 beta chains and haem group (Fe)

54
Q

What are globular proteins?

A

Molecules which have a chemical function in living organisms and take part in specific reactions

55
Q

What is the structure of globular proteins?

A

Rough spherical structure - hydrophilic groups outside and hydrophobic groups inside

56
Q

What are the key features of globular proteins?

A
  • Soluble in water
  • Compact
57
Q

What is an example of a globular protein?

58
Q

What are conjugated proteins?

A

A globular protein that contains a prosthetic group

59
Q

What is a prosthetic group?

A

Non protein component e.g. haem

60
Q

What are examples of conjugated proteins?

A

Haemoglobin
Catalase

61
Q

What are fibrous proteins?

A

Molecules which have a structural role

62
Q

What are the key features of fibrous proteins?

A
  • Insoluble in water
  • Strong
  • Flexible (except in keratin)
63
Q

What are examples of fibrous proteins?

A

Keratin
Elastin
Collagen

64
Q

What are nitrate ions, NO3- necessary for?

A

Amino acid and protein formation

65
Q

What are hydrogen carbonate ions, HCO3- necessary for?

A

Maintenance of blood pH

66
Q

What are chloride ions, Cl- necessary for?

A

Cofactor for amylase

67
Q

What are phosphate ions, PO43- necessary for?

A
  • Cell membrane formation
  • Nucleic acid and ATP formation
68
Q

What are hydroxide ions, OH- necessary for?

A

pH determination

69
Q

What are calcium ions, Ca2+ necessary for?

A
  • Nerve impulse transmission
  • Muscle contraction
70
Q

What are sodium ions, Na+ necessary for?

A
  • Nerve impulse transmission
  • Kidney function
71
Q

What are potassium ions, K+ necessary for?

A
  • Nerve impulse transmission
  • Stomatal opening
72
Q

What are hydrogen ions, H+ necessary for?

A

pH determination

73
Q

What are ammonium ions, NH4+ necessary for?

A

Production of nitrate ions by bacteria in the nitrogen cycle

74
Q

What is the test for reducing sugars?

A

Benedict’s test - add copper II sulphate and heat

75
Q

What are reducing sugars?

A

All monosaccharides and some disaccharides (maltose and lactose)

76
Q

What is the positive result for a Benedict’s test?

A

Brick red precipitate

77
Q

What is the negative result for a Benedict’s test?

78
Q

What type of sugar is sucrose? (Non reducing or reducing)

A

Non reducing

79
Q

What does a reagent strip show in the Benedict’s test to identify concentration of reducing sugars?

A

More reducing sugar = more precipitate so darker colour
- Green - low concentration
- Yellow - medium concentration
- Red - high concentration

80
Q

What is the test for starch?

A

Iodine test

81
Q

What is the positive result for an iodine test?

A

Solution changes colour from yellow/brown to blue/black

82
Q

What is the negative result for iodine test?

A

Solution remains yellow/brown

83
Q

What is the test for lipids?

A

Emulsion test - mixing with ethanol and distilled water

84
Q

What is the positive result for emulsion test?

A

White emulsion layer forms

85
Q

What is the negative result for emulsion test?

A

Solution remains clear

86
Q

What is the test for proteins?

A

Biuret test - copper ions in alkaline solution

87
Q

What is the positive result for Biuret test?

A

Solution turn purple

88
Q

What is the negative result for Biuret test?

A

Solution remains blue

89
Q

What are the quantitive methods to determine concentration of a chemical substance in a solution?

A

Colorimeter
Biosensors

(OCR A) - A-level Biology (26 decks)

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