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

Topic 2.1.2 Biological Molecules Pt 1. Flashcards

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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
How do you test for a non-reducing sugar?
- 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
26
What is starch?
- energy store in plants - a long chain of hundreds of alpha glucose molecules joined by 1,4-glycosidic bonds formed by condensation reactions
27
What two types of cell store the polysaccharide starch?
- palisade mesophyll cells - spongy mesophyll cells
28
Starch is a mixture of which two polysaccharides?
- amylose - amylopectin
29
What is the structure of amylose?
- 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
30
What is the structure of amylopectin?
- base amylose structure - + 1,6-glycosidic bonds in a branched structure - less branched than glycogen
31
What is the test for starch?
iodine solution
32
What is the and why is there a colour change in the test for starch?
- yellow-brown --> blue/black - iodine molecules get trapped in the coils of amylose
33
What is Iodine Solution?
iodine dissolved in potassium iodide
34
What is glycogen?
- 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
35
What two types of cell store the polysaccharide glycogen?
- liver - muscle - stored as glycogen granules
36
What is the structure of glycogen?
- 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
37
Why are starch and glycogen ideal energy stores?
- 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)
38
What is cellulose?
- 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
39
What is the structure of cellulose?
- every second beta glucose molecule is rotated 180 degrees to the first - this forms a straight chain which is unbranched (unlike glycogen and amylopectin)
40
What are microfibrils?
bundles of cellulose molecules lined up close together
41
How many cellulose molecules in one microfibril?
70
42
How are cellulose molecules bonded in microfibrils?
cross linked by weak hydrogen bonds
43
What are macrofibrils?
larger bundles of microfibrils held together by H bonds
44
Why is cellulose an ideal structural polysaccharide?
- contains thousands of H bonds (weak when individual but strong when together) - insoluble and very strong
45
Water is a polar molecule. What does this mean?
the atoms within it have charges
46
Why is water a good solvent?
it's polarity makes it a good solvent for ions and polar compounds
47
Why is water a liquid at a range of temperatures?
weak H bonds between molecules are easy to overcome/ break down
48
Why is water a good transport medium?
- 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
What do H bonds in water do?
continually break and reform
50
What is the structure of ice?
- molecules are arranged in a lattice - this makes it less dense than water so it floats
51
How is ice insulating?
- floating ice insulates the water below - large bodies of water rarely freeze
52
What is cohesion?
- H bonds 'stick' water molecules together - used to draw water up the xylem during transpiration
53
What does cohesion create?
- surface tension - pond skaters 'walk on water'
54
How is water a reactant?
used in hydrolysis reactions
55
Water has a high latent heat of evaporation. True or False?
True
56
How is water a coolant?
when it evaporates it draws heat energy from its surroundings and cools surfaces e.g. evaporation of water when sweating cools skin
57
What does it mean for water to have a large specific heat capacity?
relatively large amounts of energy are needed to increase the temperature of water (by 1 degree c)
58
Oceans have a fairly constant temperature so they can ...?
provide a stable thermal environment
59
What are lipids?
a diverse group of chemicals
60
What elements make up lipids?
C, H and O (proportion of O is much lower than in carbohydrates)
61
Lipids are not polymers, but some contain what?
Subunits joined by condensation
62
What are lipids solubility like?
- all insoluble in water - dissolve in organic solvents (like ethanol)
63
What is the test for lipids?
the Emulsion test - forms a cloudy white emulsion/white precipitate if lipids are present
64
What are the three main groups of lipids?
- triglycerides (fats + oils) - phospholipids - cholesterol
65
What are triglycerides?
1 glycerol molecule + 3 fatty acid molecules
66
What is glycerol?
- an alcohol molecule - contains three OH groups
67
All triglycerides contain glycerol. True or False?
True
68
What is the structure of a glycerol backbone?
Structure: H I H - C - OH H - C - OH H - C - OH I H
69
What are fatty acids?
hydrocarbon chains (fatty groups) which end in a carboxylic acid group (COOH)
70
What determines the type of fatty acid?
- the length of the hydrocarbon chain - whether the hydrocarbon chain contains C=C (carbon double bonds) or not
71
Different triglycerides contain different fatty acids. True or false?
True
72
What are animal fats?
Triglycerides containing mainly saturated fatty acids
73
What are saturated fatty acids?
Fatty acids containing only C-C single bonds within the hydrocarbon chain
74
What does ‘saturated’ mean?
No more H atoms can be added to the chain
75
What state are animal fats at room temperature?
- solid - animal fats e.g. lard - stronger intermolecular bonding / forces
76
What are plant oils?
Triglycerides containing mainly unsaturated fatty acids
77
What are unsaturated fatty acids?
Fatty acids containing C=C double bonds within the hydrocarbon chain
78
What state are plant oils at room temperature?
- liquid - e.g. olive oil - double bond changes the entire structure of the fat
79
What is Esterification?
Triglyceride formation
80
How do Triglycerides form?
Glycerol and Fatty Acid join by condensation and form Ester bonds (covalent bond)
81
What is the structure of Monoglycerides?
Glycerol + 1 Fatty Acid
82
How does further condensation occur in Esterification?
Triglyceride formation - Glycerol + 3 Fatty Acids
83
How are Ester bonds broken?
Hydrolysis reaction (water added)
84
What is the highest possible ratio of saturated fatty acid?
CnH2n+2
85
Why are triglycerides such as fats and oils ideal energy stores?
- 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
What relevant properties relate to triglycerides' function of being energy stores?
- 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
How are triglycerides used for insulation?
- 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
What relevant property relates to triglycerides' function of insulation?
poor conductor of heat
89
How are triglycerides used for physical protection?
- fat cushions delicate organs (e.g. kidney) - protects them from mechanical damage
90
What relevant property relates to triglycerides' function of being used for physical protection?
shock absorbing
91
How are triglycerides used for waterproofing?
- mammals use oily secretions from sebaceous glands to water proof skin and fur - birds use oily secretion from preen glands to waterproof feathers
92
What relevant property relates to triglycerides' function of being used in waterproofing?
hydrophobic (repel water)
93
How are triglycerides involved in the release of metabolic water?
- water released by respiration of lipids is an essential water source for desert mammals - creating lipid ester bonds releases water
94
What relevant property relates to triglyceride's involvement in the release of metabolic water?
releases more water than carbohydrates when oxidised in respiration
95
What is the structure of phospholipids?
- similar to triglycerides - one of the three fatty acids is replaced with a phosphate group - phosphate head + two fatty acid tails
96
What components form the phosphate head of a phospholipid?
phosphate + glycerol
97
What is one of the main functions of phospholipids?
- components of cell membranes - form the bilayer within cell membranes
98
When do phospholipids form a bilayer?
when they are in contact with water
99
Is the phosphate head hydrophilic or hydrophobic?
hydrophilic
100
Are the fatty acid tails hydrophilic or hydrophobic?
hydrophobic
101
What sort of barrier do phospholipids form?
- partially permeable -
102
What is cholesterol?
- a small, narrow molecule formed from four carbon-based rings - a type of sterol
103
Is cholesterol hydrophilic or hydrophobic?
hydrophobic
104
Why can cholesterol slot between phospholipids in cell membranes?
- small size - narrow shape - hydrophobic nature
105
What is the purpose of cholesterol in cell membranes?
makes membranes stronger and less fluid
106
What is cholesterol used for?
- used to make Vitamin D - used to make steroid hormones
107
What are some examples of steroid hormones?
- testosterone - oestrogen
108
Why is excess cholesterol dangerous?
- causes gall stones - causes atherosclerosis
109
What is atherosclerosis?
cholesterol deposits in blood vessels
110
What is sterol?
- any naturally occurring unsaturated steroid alcohol
111
How does cholesterol's structure impact the cell membrane?
- stabilises the cell surface membrane - regulates cell surface fluidity
112
What test is used for lipids?
the Emulsion test
113
What are the steps of the emulsion test?
- 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
Why is the substance mixed with ethanol first in the emulsion test?
- if lipid is present it will dissolve in the ethanol
115
What is formed through the emulsion test as a positive result?
a cloudy white emulsion
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