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A-levle Biology > 2.1.2 - Biologial Molecules (set B - Carbohydrates) > Flashcards

2.1.2 - Biologial Molecules (set B - Carbohydrates) Flashcards

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1
Q

Explain what a carbohydrate is?

A

molecules that only contains the elements carbon,hydrogen and oxygen- they are known as saccharides or sugars

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2
Q

Give the general formula of carbohydrates, where n is the number of carbons in the molecule?

A

(CH ₂O) ₙ

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3
Q

Define a monosaccharide?

A

Single sugar unit, eg glucose, fructose and ribose

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4
Q

Define a disaccharide?

A

formed when two monosaccharides are joined together by a glycosidic bond, happens in a condensation reaction which involves the removal of a molecule of water, eg maltose or sucrose

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5
Q

Give three examples of monosaccharides?

A
  • glucose
  • fructose
  • ribose
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6
Q

Give three examples of disaccharides?

A
  • lactose
  • maltose
  • sucrose
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7
Q

Define a polysaccharide?

A

A long chain of monosaccharides which are linked together by glycosidic bonds, eg glycogen, cellulose and starch

  • multiple monomers
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8
Q

Give three examples of polysaccharides?

A
  • glycogen
  • cellulose
  • starch
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9
Q

What is glucose?give its formula and both its structural variations?

A

Glucose is a monosaccharide with the molecular formula of C ₆H ₁₂O ₆ it is important for providing energy to cells - excess glucose is stored as glycogen

  • 2 structural variations of glucose molecules, alpha and beta - main difference is the hydroxyl groups are opposite
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10
Q

What are the two structural variations of glucose?

A

Alpha and beta glucose molecules

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11
Q

Why are glucose molecules soluble in water?significance?

A

The reason glucose dissolves readily in water is because it has lots of polar hydroxyl groups which can form hydrogen-bonds with water molecules

  • important as it allows glucose to pass through the cell membrane of cells
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12
Q

Explain what a condensation reaction is?

A

a reaction in which two molecules combine to form a single molecule - a small molecule, often water is usually removed during the reaction

  • involved in the formation of a disaccharide
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13
Q

Explain how a disaccharide is formed with reference to the bond formed?

A

Formed when two monosaccharides are joined together by a glycosidic bond in a condensation reaction which also involves the removal of a water molecule

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14
Q

Explain how the disaccharide maltose if formed?

A

During condensation reaction, bond is formed between carbon 1 of one alpha glucose molecule and carbon 4 of the other alpha glucose molecule (called 1-4 glycosidic bond) - water also formed as product

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15
Q

Explain 3 factors of the polysaccharide cellulose?

A
  • polymer of long unbranched chains of beta glucose - orientated alternately upwards and downwards
  • condensation reaction links carbon atom 1 to carbon atom 4 on the next beta glucose molecule
  • cellulose molecule is a straight chain
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16
Q

Give the structure of cellulose?

A
  • cellulose chains are linked together by hydrogen bonds which form cellulose microfibrils which join together to make macrofibrils which combine to produce fibres
  • tensile strength of cellulose provides structural support for the cell
17
Q

How is cellulose strong?why is it important?

A

Cellulose chains are linked together by hydrogen bonds which form cellulose microfibrils - gives it high tensile strength and allows it to support cells and prevents them from bursting

18
Q

Explain 2 factors of the polysaccharide cellulose?

A
  • Energy store for plants, where excess glucose is stored as starch, so it can be broken down to release energy when needed
  • mixture of the two polysaccharides of alpha glucose (amylase and amylopectin)
19
Q

Explain and describe the structure of amylose?

A

Long unbranched chain of alpha glucose - due to the angle of the glycosidic bond it has a coiled cylinder structure, allows for efficient storage

20
Q

Explain and describe the structure of amylopectin?

A

Long branched chain with 1-4 glycosidic bonds between alpha glucose molecules (some glycosidic bonds between carbon 1 and carbon 6 on two glucose molecules) has side branches which allows enzymes to easily break down and access the glycosidic bond - so glucose can be released quickly

21
Q

Explain 3 factors of the structure of the polysaccharide starch?

A
  • condensation reaction links carbon atom 1 via a glycosidic bond to carbon atom 4 on the next alpha glucose molecule
  • glucose molecules ordinated in the same way - as opposed to alternately up and down like cellulose
  • starch molecule is curved and the size if not fixed
22
Q

Explain 2 factors of the polysaccharide glycogen?

A
  • main energy storage material in animals and fungi - excess glucose stored as glycogen in the liver and muscles of humans
  • polymer of repeating alpha glucose sub-units, similar structure to amylopectin but has more side branches so more energy can be released
23
Q

Explain 2 factors of the structure of the polysaccharide glycogen?

A
  • glycogen is very compact - makes it a good energy store
  • glycogen does not affect the osmosis balance of cells
24
Q

Explain how cell walls are made,reference starch and fibres?

A

Cellulose molecules make hydrogen bonds with each other forming microfibrils which join together to form macro fibrils which then combine to produce fibres

  • these fibres are strong and insoluble and are used to make the cell wall
25
Q

Explain the significance of glycogen having more branches then amylopectin?

A
  • more compact, so it requires less space to be stored - due to coiling of the polymer chain
  • more free ends on the branches - so glucose molecules can be added or removed efficiently
26
Q

What are the two monosaccharides which are condensed to form maltose?

A

Condensation of two alpha glucose molecules

27
Q

What are the two monosaccharides which are condensed to form sucrose?

A

Condensation of a glucose molecule and fructose

28
Q

What are the two monosaccharides which are condensed to form lactose?

A

Condensation of a glucose molecule and a galactose molecule

29
Q

What is the difference between a hexose monosaccharide and a pentose monosaccharide?

A

Pentose is a five-carbon monosaccharide, whereas hexose contains six carbon atoms

30
Q

Give an example of a hexose monosaccharides?

A
  • glucose
31
Q

Give an example of a pentose monosaccharide?

A
  • ribose
32
Q

Explain what a hydrolysis reaction is?

A

Reverse of condensation reaction, a larger molecule forms two smaller molecules with a water molecule being consumed in order to break a chemical bond between 2 molecules

  • eg ester bonds between fatty acids and glycerol in lipids
33
Q

Explain how glucose is released from starch or glucose, reference hydrolysis reactions?

A

To release glucose for respiration, starch or glycogen undergo hydrolysis reactions, and require the addition of water molecules

  • reaction is catalysed by enzymes
34
Q

Define what a monomer is and give some examples?

A

Smaller units that join together to form large molecules - for example monosaccharides (glucose,fructose and ribose) amino acids and nucleotides

35
Q

Define what a polymer is and give some examples?

A

Molecules formed when many monomers join together - for example polysaccharides, proteins and DNA/RNA

36
Q

Describe the properties of alpha glucose - give 3?

A
  • small and water soluble - easily transported in bloodstream
  • complementary shape to antiport for co-transport for absorption in gut
  • complementary shape to enzymes for glycolysis - respiratory substrate
37
Q

Name 3 disaccharides, describe how they form?

A

Condensation reaction forms glycosidic bond between 2 monosaccharides

  • maltose : glucose + glucose
  • sucrose : glucose + fructose
  • lactose : glucose + galactose
38
Q

Explain what type of bonds cellulose,glycogen and starch have?

A
  • Starch - alpha 1-4 glycosidic bonds
  • glycogen - alpha 1-4, 1-6 glycosidic bonds
  • cellulose - beta 1-4 glycosidic bonds

A-levle Biology (43 decks)

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