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A-level Biology > 2.1.2 - Biological molecules > Flashcards

2.1.2 - Biological molecules Flashcards

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1
Q

Define the term ‘polymer’ ?

A

Polymer - A long chain molecule composed of a large number of individual units called monomers bonded together in a repeating pattern

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2
Q

Define the term ‘monomer’ ?

A

Monomer - Individual molecules that make up a polymer

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3
Q

Define the term ‘condensation reaction’ ?

A

Condensation reaction - A reaction between two molecules resulting in the formation of a larger molecule and the release of a water molecule

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4
Q

Define the term ‘hydrolysis reaction’ ?

A

Hydrolysis reaction - The breakdown of a larger molecule into two smaller molecules requiring the addition of a water molecule

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5
Q

What elements are carbohydrates made of ?

A

C, H and O

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6
Q

What elements are lipids made of ?

A

C, H and O

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7
Q

What elements are proteins made of ?

A

C, H, N, O and S

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8
Q

What elements are nucleic acids made of ?

A

C, H, N, O and P

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9
Q

What are the properties of water ?

A
  • Water is a metabolite
  • Water is an important solvent
  • Water has a high boiling point/ specific heat capacity
  • Water has a high latent heat of vaporisation
  • Water has a strong cohesion/ surface tension
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10
Q

Explain how water is a metabolite ?

A

Water is a metabolite in many chemical reactions such as condensation and hydrolysis reactions

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11
Q

Explain how water is a solvent ?

A
  • Water is a solvent in which metabolic reactions occur
  • It readily dissolves numerous substances and allows for effective transport of substances
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12
Q

Explain why water has a high boiling point/ specific heat capacity ?

A
  • Due to hydrogen binds, more energy is required to raise the temperature of water
  • This allows water to act as a buffer against drastic temperature change
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13
Q

Name examples where water acts as a buffer to drastic temperature change ?

A
  • Majority of organisms are mostly made up of water buffering them against drastic temperature change
  • Aquatic environments are temperature-stable as water acts as a buffer against drastic temperature change
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14
Q

Explain how water has a high specific latent heat of vaporisation ?

A
  • Due to hydrogen bonds, more energy is required to overcome bonds between water molecules and change the state of water
  • This allows water to act as a coolant
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15
Q

Name an example where water acts a coolant ?

A

When we sweat, more heat is used from our body to evaporate the sweat off our skin providing a cooling effect

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16
Q

Explain how water has a strong cohesion/ surface tension ?

A
  • This supports columns of water in xylem of plant setting up a transpiration stream
  • This provides surface tension when water meets air ( ie. allows water to act as a habitant and support small organisms such as pond skaters )
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17
Q

Define the term ‘monosaccharide’ ?

A

Monosaccharide - A single sugar molecule

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18
Q

Name examples of monosaccharides ?

A
  • Glucose ( alpha and beta )
  • Fructose
  • Galactose
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19
Q

Define the term ‘polysaccharide’ ?

A

Polysaccharide - A long-chain polymer made up of a large number of sugar monomers / monosaccharides chemically joined together

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20
Q

What is a hexose monosaccharide ?

A

A monosaccharide composed of six carbon toms

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21
Q

Name examples of hexose monosaccharides ?

A
  • Alpha glucose
  • Beta glucose
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22
Q

Draw the displayed formula of Alpha and Beta Glucose ?

A
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23
Q

What is a pentose monosaccharide ?

A

A monosaccharide composed of five carbon atoms

24
Q

Name examples of pentose monosaccharides ?

A
  • Ribose
25
Q

Define the term ‘disaccharide’ ?

A

Disaccharide - A molecule composed of two monosaccharides joined together by a glycosidic bond

26
Q

Name examples of disaccharides ?

A
  • Sucrose
  • Maltose
  • Lactose
27
Q

Name the monosaccharides that the disaccharides sucrose, lactose and maltose are composed of ?

A
  • Sucrose = fructose + glucose
  • Lactose = galactose + glucose
  • Maltose = glucose + glucose
28
Q

Explain what happens during a condensation reaction between two monosaccharides ?

A
  • During a condensation reaction, a hydroxyl group from one monosaccharide and a hydrogen atom from another monosaccharide is removed
  • This leads to the elimination of a water molecule and the formation of a glycosidic bond
29
Q

What is the name of the bon that forms between monosaccharides ?

A

A glycosidic bond

30
Q

Explain what happens during the hydrolysis of a disaccharides ?

A
  • During a hydrolysis reaction, a single water molecule is added to a disaccharide to break the glycosidic bond between the monosaccharides
  • This results in two individual monosaccharides
31
Q

Draw a diagram to represent the formation of a disaccharide and glycosidic bond ?

A
32
Q

What is starch ?

A

A polymer of alpha glucose which is an energy store in plants

33
Q

What are the two types of starch ?

A
  • Amylose
  • Amylopectin
34
Q

Explain the structure of amylose ?

A
  • Amylose is formed by alpha glucose molecules joining together only by 1-4 glycosidic bonds
  • This forms a helix shape ( making it compact and less soluble than glucose )
35
Q

Explain the structure of amylopectin ?

A
  • Same as amylose and additionally some glycosidic bonds form between carbon 1 and 6 on two glucose molecules
  • This results in a more branched structure ( which can be hydrolysed to release more glucose molecules )
36
Q

Explain the effect of the helix shape of starch/ glycogen ?

A

The helix-shaped structure causes it to be more compact so more glucose can be stored in a smaller volume

37
Q

Explain the effect of starch/ glycogen being branched ?

A

Each end can be hydrolysed to release glucose for respiration/ transport

38
Q

Explain the effect of starch/ glycogen being insoluble ?

A
  • Too large to leave the cell
  • Does not affect the water potential of the cell/ cause cell lysis
39
Q

Explain the effect of glycogen being more highly branched than starch ?

A
  • This means it has more ends which can be hydrolysed to release more glucose at a faster rate
  • This allows glycogen to combat animals higher metabolic rate which requires more glucose due to being mobile unlike plants
40
Q

What is glycogen ?

A

A polymer of alpha glucose which is an energy store in animals

41
Q

Explain the structure of glycogen ?

A
  • It is helix shaped
  • It is insoluble
  • It is more highly branched than starch ( both amylose/ amylopectin )
42
Q

What is cellulose ?

A

A polymer of beta glucose resulting in straight, unbranched chains

43
Q

Explain the structure of cellulose ?

A
  • Cellulose is a polymer of beta glucose resulting in straight, unbranched chains
  • Each cellulose polymer cab form hydrogen bonds with parallel molecules
  • Cellulose molecules are bundled into microfibrils which are grouped into fibres
44
Q

Explain how the structure of cellulose aids it function ?

A

This results in the rigidity of the cell wall, providing mechanical strength which prevents cell lysis

45
Q

What are the two different types of sugars ?

A
  • Reducing sugars
  • Non-reducing sugars
46
Q

What are reducing sugars ?

A
  • Sugars that can reduce another molecule/ donate electrons
  • All monosaccharides and some disaccharides are reducing sugars
47
Q

What are non-reducing sugars ?

A
  • Sugars that cannot reduce another molecule/ donate electrons
48
Q

Name the test used to identify reducing sugars in a sample ?

A

Testing using Benedict’s Reagent

49
Q

What is Benedict’s Reagent ?

A

Copper ( II ) Sulphate

50
Q

Describe the test for reducing sugars ?

A

1 ) Place sample in a boiling tube
2 ) Add an equal volume of Benedict’s Regent into the boiling tube
3 ) Heat the mixture gently in a electric water bath for five minutes

51
Q

Explain how Benedict’s Reagent helps identify reducing sugars in a sample ?

A
  • Reducing sugars react with Benedict’s Reagent causing Cu2+ ions to be reduced to Cu+ ions
  • This causes a brick-red precipitate to form/ CuO
52
Q

Explain how testing for reducing sugars is a quantitive test ?

A
  • The more reducing sugars present, the more precipitate forms as more Cu2+ ions are reduced to Cu+ ions
  • Therefore, colour seen will depend on concentration of reducing sugars present
53
Q

Explain why non-reducing sugars will no produce a positive result when tested with Benedict’s Reagent ?

A

Non-reducing sugars don’t react with Benedict’s Reagent and therefore will produce a negative result

54
Q

Describe how to test for non-reducing sugars ?

A
  • Boil non-reducing sugars/ sample with dilute hydrochloric acid ( this will cause non-reducing sugars to be hydrolysed and break down into its monosaccharides/ reducing sugars )
  • Test for presence of reducing sugars using Benedict’s Reagent
55
Q

Describe the test for the presence of starch ?

A
  • Add a few drops of iodine solution ( iodine dissolve in potassium iodide ) to the sample
  • Mix it with the sample
56
Q

What is a positive and negative result when testing for the presence of starch ?

A
  • If it changes form yellow/brown to blue/black it is positive
  • If it does not change it is negative

A-level Biology (30 decks)

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