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OCR Biology AS H020 > Biological Molecules > Flashcards

Flashcards in Biological Molecules Deck (119):
1

What is a polar molecule?

A molecule that contains unsymmetrical bonds where there is a difference in electronegativity leading to dipoles with positive and negative charges.

2

Water is a ______ molecule and forms ______ bonds...

Polar, hydrogen.

3

What is the bonding angle in water?

104.5

4

Why does water have a unusually large BP?

The hydrogen bonds require large amounts of energy to break.

5

Why is ice less dense than water?

The molecules spread out forming 4 hydrogen bonds creating a giant, rigid but open structure.

6

Water has cohesive/adhesive properties, explain what this means...

Cohesion - the sticking together of particles of the same substance.
Adhesion - the action or process of adhering to a surface or object.

7

Give an example of waters cohesive properties...

In the xylem.

8

What property of water allows pond skaters' to walk on it's surface?

Surface tension.

9

State 2 ways that water is useful as a solvent...

Transport medium, reaction medium.

10

The effects of cohesion and adhesion means water can exhibit the property of _____ ?

Capillary action.

11

What is capillary action?

Water can rise up a narrow tube against the force of gravity.

12

What term describes water 'buffering temperature changes'?

Coolant.

13

Why is it important that water has a high SHC?

Maintains a stable constant environment.

14

When water freezes it forms an insulating layer above, why is this important?

It prevents further freezing and insulates life below.

15

What is a monosaccharide?

A single sugar unit.

16

What is a carbohydrate?

Molecules that only contain the elements carbon, hydrogen and oxygen, the literal meaning is 'hydrated carbon'.

17

What is the general formula of a carbohydrate?

Cx(H20)y

18

Name 4 monosaccharides...

Glucose, fructose, ribose, galactose.

19

Name 2 disaccharides...

Lactose, sucrose.

20

Name 3 polysaccharides...

Glycogen, cellulose, starch.

21

What is the molecular formula of glucose?

C6H12O6.

22

Why is glucose considered a hexose monosaccharide?

It is a single sugar unit with 6 carbons in it's structure.

23

How are carbons numbered in carbohydrates?

Clockwise beginning with the carbon to the right of the oxygen in the ring.

24

Where is the OH (hydroxyl) group in alpha glucose?

Below.

25

Where is the OH (hydroxyl) group in beta glucose?

Above.

26

In a glucose molecule, from carbon 2 onwards, what is the placement of OH groups?

BAB.

27

In a glucose molecule what is the extra group?

CH2OH.

28

Glucose + Fructose =

Sucrose + H20

29

Galactose + Glucose =

Lactose + H20

30

What type of bond is formed between two monosaccharides?

Glycosidic bond.

31

What type of bond is formed between two glucose monomers?

1,4 glycosidic bond.

32

What type of reaction takes place when two monosaccharides join?

Condensation reaction producing water.

33

Glucose + Glucose =

Maltose.

34

Place the following sugars in order of sweetness (glucose, galactose, fructose)...

Fructose, glucose, galactose.

35

Give 2 examples of pentose monosaccharides...

Ribose, deoxyribose.

36

What is starch made up of?

Alpha glucose monomers.

37

What are the two forms of starch?

Amylose and amylopectin.

38

How is amylose formed?

A condensation reaction between alpha glucose molecules forming 1,4 glycosidic bonds ONLY.

39

Describe the structure of amylose...

The chain twists to forma helix which is stabilised by hydrogen bonds, it is unbranched.

40

Name two properties of glucose molecules and why they are important...

Polar and soluble in water, can be dissolved in the cytosol of cells.

41

Explain the properties of amylose...

The helix makes the polymer more compact and less soluble.

42

How is amylopectin formed?

A condensation reaction between alpha glucose molecules forming 1,4 glycosidic bonds and branched 1,6 glycosidic bonds every 25 subunits.

43

What are the properties of amylopectin?

Amylopectin is branched, insoluable and compact. Glucose can be stored or released quickly by hydrolysis due to an abundance of free ends.

44

How are carbohydrates broken down?

Hydrolysis.

45

What is the equivalent energy store to starch in animals and fungi?

Glycogen.

46

What is the difference between amylopectin and glycogen?

Glycogen has more branches so is more compact wich is important and animals are mobile.

47

How is cellulose formed?

Alternate beta glucose molecules turned upside down form 1,4 glycosidic bonds.

48

Why is hydrolysis of carbohydrates important?

Respiratory demands.

49

Describe the structure of cellulose...

Straight chain, unbranched.

50

What is formed when cellulose molecules form hydrogen bonds with one another?

Microfibrils.

51

Microfibrils form _____ ?

Macrofibrils.

52

Macrofibrils form _____ ?

Fibres.

53

What are the properties of cellulose fibres?

Strong and insoluable.

54

What are cellulose fibres used for?

Making cell walls.

55

In our diet, what does cellulose fibre do?

Form roughage necessary for a healthy digestive system.

56

What is a reducing sugar?

A monosaccharide (sometimes di) that donate electrons/reduce molecules.

57

What is Benedict's reagent?

Alkaline aq solution of Copper (II) Sulfate.

58

Describe Benedict's test for reducing sugars...

Grind up sample and blend with water in not liquid. Add an equal volume of BR. Heat the mixture gently in a water bath for 5 minutes.

59

What happens in a +ve Benedict's test?

Blue Cu2+ ions are reduced to brick red Cu+ ions forming a precipitate.

60

Describe the colour changes and how they represent the % of reducing sugar during Benedict's test... (qualitativity)

Blue - None
Green - Very low
Yellow - Low
Orange - Medium
Red - High

61

How can a non-reducing sugar show a +ve result in Benedict's test?

Boil it with HCl (hydrolyse it) first.

62

What is the iodine test?

Used to detect the presence of starch. Iodine dissolved in potassium iodide is mixed with a sample. A colour change from yellow/brown to purple/black indicate the presence of starch.

63

What are reagent strips used for?

Test for the presence of reducing sugars, they use a colour coded chart to measure the concentration.

64

What elements do lipids contains?

Carbon, hydrogen, oxygen and phosphorus.

65

Fats are ____ and oils are ____ at RTP?

Solid, liquid.

66

Lipids are large complex molecules known as?

Macromolecules.

67

What are the properties of lipids?

Non polar and insoluble in water.

68

What is a triglyceride made up of?

1 glycerol (alcohol) molecule and 3 fatty acids (carboxylic acids).

69

What us the functional group of a carboxylic acid?

-COOH

70

How are triglycerides formed?

3 OH groups from the glycerol molecule react with the COOH groups from 3 carboxylic acids forming 3 ester bonds and 3 water molecules during esterification.

71

Esterification is an example of what type of reaction?

Condensation.

72

What is a saturated fatty acid?

No C=C double bonds present.

73

What is an unsaturated fatty acid?

A fatty acid that contains one (monounsaturated) or more (polyunsaturated) C=C double bonds in it's chain.

74

What effect does a C=C double bond have on a fatty acid chain?

It causes a kink in the chain so they cannot pack as closely together leading to the fatty acid being liquid at RTP (oil not fat).

75

What are phospholipids?

Modified triglycerides containing a phosphate group (PO4 3-) instead of a fatty acid.

76

Explain the charges on a phospholipid...

A -ve charged head and a non charged tail.

77

Why are phospholipids are hydrophobic?

Their non-polar tails are repelled by water.

78

Why are phospholipids hydrophilic?

The charged heads interact and are attracted to water.

79

Name 2 structures phospholipids can form...

Bilayers and monolayers.

80

Why are phospholipids described as surfactants (surface active agents?

They form monolayers with their hydrophilic heads in the water and hydrophobic tails out of the water.

81

Sterols are also known as?

Steroid alcohols.

82

Explain a property of sterols...

Dual hydrophobic/philic characteristics. OH group is polar hence hydrophilic and the rest of the molecule is hydrophobic.

83

What structure are sterols based on?

4 carbon ring structure with a OH group at one end.

84

Name a sterol...

Cholesterol.

85

Where is cholesterol primarily manufactured?

Liver and intestines.

86

What role does cholesterol play in cell membranes?

Adds stability and regulates their fluidity.

87

Give 3 things manufactured using cholesterol...

Bile, vitamin D and steroid hormones.

88

What are the 8 biological roles of lipids?

Membrane formation, hormone production, electrical insulation, waterproofing, thermal insulation, cushioning, buoyancy and energy stores.

89

How does the emulsion test work?

The sample is mixed with ethanol then water and shaken. If a white emulsion forms a lipid is present.

90

Describe the 3 groups coming off a carbon atom in an amino acid.

Hydrogen, carboxyl group, amine group, R group.

91

What are peptides?

Polymers made up of amino acid molecules.

92

What are proteins?

One or more polypeptides arranged as complex macromolecules.

93

What elements do proteins contain?

CHON

94

How many amino acids are there?

20

95

How many essential amino acids are there?

9

96

How many non-essential amino acids are there?

5

97

How many conditionally essential amino acids are there?

6

98

How do amino acids join to form a dipeptide?

A peptide bond is formed between the carboxyl (OH) and amine groups (H) producing water.

99

What type of reaction is the formation of a dipeptide?

Condensation.

100

What is the primary structure?

The amino acid sequence.

101

What bonds are involved in the primary sequence?

Peptide bonds.

102

What determines the primary sequence?

DNA

103

What bonds are involved in the secondary structure?

Hydrogen bonds

104

What structures can be formed in the secondary structure?

Alpha helix and beta pleated sheet.

105

What bonds are involved in the tertiary structure?

Hydrophobic/philic interactions between polar/non-polar R groups. Hydrogen bonds. Ionic bonds, Disulfide bridges.

106

What is the quaternary structure?

The association of individual proteins (subunits)

107

Give 3 examples of quaternary proteins...

Haemoglobin, insulin, enzymes.

108

Describe globular proteins...

Compact, water soluble, spherical proteins with hydrophobic groups on the inside.

109

Give an example of a globular protein...

Insulin, a blood glucose concentration hormone, it is transported in the bloodstream and has a specific shape that fits receptors on cell surface membranes.

110

What are conjugated proteins?

Globular proteins with prosthetic groups (cofactors).

111

What is an example of a prosthetic group?

Haem (Fe2+) in haemoglobin and catalase.

112

Elaborate on the structure of haemoglobin and how it relates to it's function.

Made of 4 subunits, 2 alpha, 2 beta. There are 4 haem groups which enable O2 to be picked up.

113

State 2 conjugated proteins...

Haemoglobin and catalase.

114

Elaborate on the structure of catalase...

A quaternary protein with 4 haem groups allowing it to interact with H2O2 and speed up it's breakdown as it is a toxic by product of metabolism.

115

What are the properties of fibrous proteins?

Formed from long, insoluble molecules as many R groups are hydrophobic. They contain a limited range of R groups which are usually small, the amino acid sequence is repetitive, they are strong,

116

Name 3 fibrous proteins...

Keratin, elastin and collagen.

117

Describe the fibrous protein keratin...

High sulphur (cyestine) content forming strong disulfide bridges resulting in strong, inflexible, insoluble molecules. The degree of bridges determines the flexability.

118

Describe the fibrous protein elastin...

Quaternary protein made from stretchy tropoelastin molecules, they are present in elastic fires.

119

Describe the fibrous protein collagen...

A connective tissue found in skin, tendons, ligaments and the nervous system. Made up of 3 polypeptides wound like a rope giving it flexibility.