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AS Level Biology > Topic 2.1.2 Biological Molecules Pt 1. > Flashcards

Topic 2.1.2 Biological Molecules Pt 1. Flashcards

1
Q

What elements make up carbohydrates?

A

Carbon, Hydrogen, Oxygen

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2
Q

What are the main functions of carbohydrates?

A
  • energy source (ATP during respiration)
  • energy store (starch in plants, gylcogen in animals)
  • structural (cellulose in plant cell walls)
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3
Q

What are the three main types of carbohydrates?

A
  • monosaccharides (single, simple)
  • disaccharides (two single sugars)
  • polysaccharides (many single sugars)
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4
Q

What are the three main types of monosaccharide?

A
  • Trioses (3 carbons - C3H6O3)
  • Pentoses (5 carbons - C5H10O5)
  • Hexoses (6 carbons - C6H12O6)
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5
Q

what is a polymer?

A

a long chain (e.g. polysaccharides)

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6
Q

Name three properties of monosaccharides.

A
  • soluble in water
  • sweet tasting
  • crystalline
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7
Q

Monosaccharides contain C, H and O in what ratio?

A

C : H : O
1 : 2 : 1

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8
Q

Name some examples of hexose sugars

A
  • glucose
  • fructose
  • galactose
  • mannose
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9
Q

What is a condensation reaction?

A

forming bonds through the removal of water

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10
Q

What is a hydrolysis reaction?

A

splitting bonds by adding water

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11
Q

What is Alpha Glucose?

A
  • C6H12O6
  • ABBA ( Alpha Below Beta Above)
  • the OH group is on the bottom of the first carbon
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12
Q

What are two alpha glucose joined to make?

A
  • maltose
  • the covalent bond formed by condensation is a 1,4-glycosidic bond ( C1 - O - C4)
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13
Q

what are hundreds of alpha glucose joined to make?

A
  • starch (polysaccharide)
    -glycogen (polysaccharide)
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14
Q

What is Beta Glucose?

A
  • C6H12O6
  • ABBA ( Alpha Below Beta Above)
  • the OH group is above the first carbon
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15
Q

what are thousands of beta glucose joined to make?

A
  • cellulose (structural polysaccharide)
  • thousands of beta glucose join together through condensation forming 1,4-glycosidic bonds
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16
Q

What is an ion?

A

an atom that contains a different number of protons and electrons (not equal)

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17
Q

What is a cation?

A

A positively charged ion - contains more protons than electrons

  • The ‘cat’ is doing your ‘ioning’ - what a ‘positive’!
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18
Q

What is an anion?

A

a negatively charged ion - contains more electrons than protons

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19
Q

What is metabolism?

A

the sum total of chemical reactions in an organism

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20
Q

what is anabolism?

A

building up reactions

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21
Q

what is catabolism?

A

breaking down reactions

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22
Q

Name an example of a reducing sugar

A
  • glucose
  • fructose
  • maltose
  • lactose
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23
Q

Name an example of a non-reducing sugar

A
  • sucrose
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24
Q

How do you test for a reducing sugar?

A
  • pale blue Benedict’s Solution (more than half of how much solution being tested)
    • heat
  • green, orange or brick red precipitate formed depending on % of reducing sugar
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25
Q

How do you test for a non-reducing sugar?

A
  • e.g. sucrose
  • boil with hydrochloric acid (HCL) to break the covalent bond known as the 1,4-glycosidic bond
  • neutralise with sodium hydrogen carbonate
  • the hydrolysed (broken down with the addition of water) sample will consist of glucose and fructose
  • pale blue Benedict’s Solution
    • heat
  • green, orange or brick red precipitate formed depending on % of reducing sugar
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26
Q

What is starch?

A
  • energy store in plants
  • a long chain of hundreds of alpha glucose molecules joined by 1,4-glycosidic bonds formed by condensation reactions
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27
Q

What two types of cell store the polysaccharide starch?

A
  • palisade mesophyll cells
  • spongy mesophyll cells
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28
Q

Starch is a mixture of which two polysaccharides?

A
  • amylose
  • amylopectin
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29
Q

What is the structure of amylose?

A
  • chains of amylose coil into a compact helix
  • all the OH on the bottom of the first carbon of alpha glucose forms a helix shape
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30
Q

What is the structure of amylopectin?

A
  • base amylose structure
    • 1,6-glycosidic bonds in a branched structure
  • less branched than glycogen
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31
Q

What is the test for starch?

A

iodine solution

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32
Q

What is the and why is there a colour change in the test for starch?

A
  • yellow-brown –> blue/black
  • iodine molecules get trapped in the coils of amylose
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33
Q

What is Iodine Solution?

A

iodine dissolved in potassium iodide

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34
Q

What is glycogen?

A
  • an energy store in animals
  • a polysaccharide (many single sugars) polymer (a long chain) of hundreds of alpha glucose molecules joined together by 1,4-glycosidic bonds formed by condensation
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35
Q

What two types of cell store the polysaccharide glycogen?

A
  • liver
  • muscle
  • stored as glycogen granules
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36
Q

What is the structure of glycogen?

A
  • much branched (makes it even more compact)
  • branches formed by 1,6-glycosidic bonds between alpha glucose molecules
  • many glucose can be hydrolysed from glycogen
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37
Q

Why are starch and glycogen ideal energy stores?

A
  • compact (lots can be stored in a small space)
  • insoluble (don’t effect the water potential water potential of cells)
  • unreactive (stable stores of glucose)
  • easily hydrolysed by enzymes ( can release glucose from the ends quickly by splitting the glycosidic bonds)
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38
Q

What is cellulose?

A
  • a structural polysaccharide in plant cell walls
  • a polymer (long chain) of thousands of beta glucose molecules joined by 1,4-glycosidic bonds formed by condensation
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39
Q

What is the structure of cellulose?

A
  • every second beta glucose molecule is rotated 180 degrees to the first
  • this forms a straight chain which is unbranched (unlike glycogen and amylopectin)
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40
Q

What are microfibrils?

A

bundles of cellulose molecules lined up close together

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41
Q

How many cellulose molecules in one microfibril?

A

70

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42
Q

How are cellulose molecules bonded in microfibrils?

A

cross linked by weak hydrogen bonds

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43
Q

What are macrofibrils?

A

larger bundles of microfibrils held together by H bonds

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44
Q

Why is cellulose an ideal structural polysaccharide?

A
  • contains thousands of H bonds (weak when individual but strong when together)
  • insoluble and very strong
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45
Q

Water is a polar molecule. What does this mean?

A

the atoms within it have charges

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46
Q

Why is water a good solvent?

A

it’s polarity makes it a good solvent for ions and polar compounds

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47
Q

Why is water a liquid at a range of temperatures?

A

weak H bonds between molecules are easy to overcome/ break down

48
Q

Why is water a good transport medium?

A
  • flows as a body
  • can carry dissolved substances with it
  • e.g. magnesium and nitrates in a river or body of water to aid plant life
49
Q

What do H bonds in water do?

A

continually break and reform

50
Q

What is the structure of ice?

A
  • molecules are arranged in a lattice
  • this makes it less dense than water so it floats
51
Q

How is ice insulating?

A
  • floating ice insulates the water below
  • large bodies of water rarely freeze
52
Q

What is cohesion?

A
  • H bonds ‘stick’ water molecules together
  • used to draw water up the xylem during transpiration
53
Q

What does cohesion create?

A
  • surface tension
  • pond skaters ‘walk on water’
54
Q

How is water a reactant?

A

used in hydrolysis reactions

55
Q

Water has a high latent heat of evaporation. True or False?

56
Q

How is water a coolant?

A

when it evaporates it draws heat energy from its surroundings and cools surfaces e.g. evaporation of water when sweating cools skin

57
Q

What does it mean for water to have a large specific heat capacity?

A

relatively large amounts of energy are needed to increase the temperature of water (by 1 degree c)

58
Q

Oceans have a fairly constant temperature so they can …?

A

provide a stable thermal environment

59
Q

What are lipids?

A

a diverse group of chemicals

60
Q

What elements make up lipids?

A

C, H and O (proportion of O is much lower than in carbohydrates)

61
Q

Lipids are not polymers, but some contain what?

A

Subunits joined by condensation

62
Q

What are lipids solubility like?

A
  • all insoluble in water
  • dissolve in organic solvents (like ethanol)
63
Q

What is the test for lipids?

A

the Emulsion test - forms a cloudy white emulsion/white precipitate if lipids are present

64
Q

What are the three main groups of lipids?

A
  • triglycerides (fats + oils)
  • phospholipids
  • cholesterol
65
Q

What are triglycerides?

A

1 glycerol molecule + 3 fatty acid molecules

66
Q

What is glycerol?

A
  • an alcohol molecule
  • contains three OH groups
67
Q

All triglycerides contain glycerol. True or False?

68
Q

What is the structure of a glycerol backbone?

A

Structure:

  H 
   I   H - C - OH H - C - OH H - C - OH 
   I
  H
69
Q

What are fatty acids?

A

hydrocarbon chains (fatty groups) which end in a carboxylic acid group (COOH)

70
Q

What determines the type of fatty acid?

A
  • the length of the hydrocarbon chain
  • whether the hydrocarbon chain contains C=C (carbon double bonds) or not
71
Q

Different triglycerides contain different fatty acids. True or false?

72
Q

What are animal fats?

A

Triglycerides containing mainly saturated fatty acids

73
Q

What are saturated fatty acids?

A

Fatty acids containing only C-C single bonds within the hydrocarbon chain

74
Q

What does ‘saturated’ mean?

A

No more H atoms can be added to the chain

75
Q

What state are animal fats at room temperature?

A
  • solid
  • animal fats e.g. lard
  • stronger intermolecular bonding / forces
76
Q

What are plant oils?

A

Triglycerides containing mainly unsaturated fatty acids

77
Q

What are unsaturated fatty acids?

A

Fatty acids containing C=C double bonds within the hydrocarbon chain

78
Q

What state are plant oils at room temperature?

A
  • liquid
  • e.g. olive oil
  • double bond changes the entire structure of the fat
79
Q

What is Esterification?

A

Triglyceride formation

80
Q

How do Triglycerides form?

A

Glycerol and Fatty Acid join by condensation and form Ester bonds (covalent bond)

81
Q

What is the structure of Monoglycerides?

A

Glycerol + 1 Fatty Acid

82
Q

How does further condensation occur in Esterification?

A

Triglyceride formation - Glycerol + 3 Fatty Acids

83
Q

How are Ester bonds broken?

A

Hydrolysis reaction (water added)

84
Q

What is the highest possible ratio of saturated fatty acid?

85
Q

Why are triglycerides such as fats and oils ideal energy stores?

A
  • don’t effect the cell they’re in
  • useful when storage mass has to be kept to a minimum (e.g. seeds for dispersal)
86
Q

What relevant properties relate to triglycerides’ function of being energy stores?

A
  • Insoluble in water: don’t cause a cell to take in water by osmosis
  • High energy content per gram: 2x higher than carbohydrates
  • Metabolically inert until hydrolysed
87
Q

How are triglycerides used for insulation?

A
  • fats (known as subcutaneous fats) stored in adipose tissue just beneath the skin of mammals helps the body retain heat
  • aquatic mammals (e.g. whales and seals) - this layer of fat is very thick and called blubber - buoyancy
88
Q

What relevant property relates to triglycerides’ function of insulation?

A

poor conductor of heat

89
Q

How are triglycerides used for physical protection?

A
  • fat cushions delicate organs (e.g. kidney)
  • protects them from mechanical damage
90
Q

What relevant property relates to triglycerides’ function of being used for physical protection?

A

shock absorbing

91
Q

How are triglycerides used for waterproofing?

A
  • mammals use oily secretions from sebaceous glands to water proof skin and fur
  • birds use oily secretion from preen glands to waterproof feathers
92
Q

What relevant property relates to triglycerides’ function of being used in waterproofing?

A

hydrophobic (repel water)

93
Q

How are triglycerides involved in the release of metabolic water?

A
  • water released by respiration of lipids is an essential water source for desert mammals
  • creating lipid ester bonds releases water
94
Q

What relevant property relates to triglyceride’s involvement in the release of metabolic water?

A

releases more water than carbohydrates when oxidised in respiration

95
Q

What is the structure of phospholipids?

A
  • similar to triglycerides
  • one of the three fatty acids is replaced with a phosphate group
  • phosphate head + two fatty acid tails
96
Q

What components form the phosphate head of a phospholipid?

A

phosphate + glycerol

97
Q

What is one of the main functions of phospholipids?

A
  • components of cell membranes
  • form the bilayer within cell membranes
98
Q

When do phospholipids form a bilayer?

A

when they are in contact with water

99
Q

Is the phosphate head hydrophilic or hydrophobic?

A

hydrophilic

100
Q

Are the fatty acid tails hydrophilic or hydrophobic?

A

hydrophobic

101
Q

What sort of barrier do phospholipids form?

A
  • ## partially permeable
102
Q

What is cholesterol?

A
  • a small, narrow molecule formed from four carbon-based rings
  • a type of sterol
103
Q

Is cholesterol hydrophilic or hydrophobic?

A

hydrophobic

104
Q

Why can cholesterol slot between phospholipids in cell membranes?

A
  • small size
  • narrow shape
  • hydrophobic nature
105
Q

What is the purpose of cholesterol in cell membranes?

A

makes membranes stronger and less fluid

106
Q

What is cholesterol used for?

A
  • used to make Vitamin D
  • used to make steroid hormones
107
Q

What are some examples of steroid hormones?

A
  • testosterone
  • oestrogen
108
Q

Why is excess cholesterol dangerous?

A
  • causes gall stones
  • causes atherosclerosis
109
Q

What is atherosclerosis?

A

cholesterol deposits in blood vessels

110
Q

What is sterol?

A
  • any naturally occurring unsaturated steroid alcohol
111
Q

How does cholesterol’s structure impact the cell membrane?

A
  • stabilises the cell surface membrane
  • regulates cell surface fluidity
112
Q

What test is used for lipids?

A

the Emulsion test

113
Q

What are the steps of the emulsion test?

A
  • mix substance with ethanol
  • pour the ethanol mixed with the substance into a tube containing water
  • if the ethanol contains a lipid it will come out of the solution as tiny droplets
114
Q

Why is the substance mixed with ethanol first in the emulsion test?

A
  • if lipid is present it will dissolve in the ethanol
115
Q

What is formed through the emulsion test as a positive result?

A

a cloudy white emulsion

AS Level Biology (15 decks)

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