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(1) Biological Molecules > 1.2 Carbohydrates > Flashcards

1.2 Carbohydrates Flashcards

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Organic Chemistry 101 flashcards
1
Q

What is a monosaccharide?

A

An individual sugar monomer from which carbohydrates are made (reducing).

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2
Q

Name 3 monosaccharides.

A
  • Galactose
  • Glucose
  • Fructose
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3
Q

What is a disaccharide?

A

A sugar formed from two monosaccharides
joined by a glycosidic bond
in a condensation
reaction.

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4
Q

Maltose?

A

α-glucose + α-glucose (reducing)

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5
Q

Lactose?

A

α-glucose + galactose (reducing)

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6
Q

Sucrose?

A

α-glucose + fructose (non-reducing)

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7
Q

Which type of covalent bond is found in carbohydrates?

A

Glycosidic Bond.

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8
Q

Name the two isomers of glucose.

A

α-glucose and β-glucose.

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9
Q

Where is the OH on C1 in α-glucose?

A

Below the ring.

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10
Q

Where is the OH on C1 in β-glucose?

A

Above the ring.

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11
Q

What method can be used to separate a mixture of monosaccharides and identify the individual components?

A

Chromatography.

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12
Q

Test for reducing sugars.

A
  1. Add Benedict’s Reagent to a sample solution in a test tube.
  2. Heat the test tube in water bath for 5 minutes.
    +ve result: coloured precipitate will form as copper (II) sulfate is reduced to copper (I) oxide which is insoluble in water (blue to green, yellow, orange, brick-red)
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13
Q

Test for non-reducing sugars.

A
  1. Add dilute hydrochloric acid to the sample and heat in a water bath that has been brought to boil
  2. Neutralise the solution with sodium hydrogen-carbonate (use litmus paper to check that it has been neutralised)
  3. Add Benedict’s Reagent to a sample solution in a test tube.
  4. Heat the test tube in water bath for 5 minutes.
    +ve result: coloured precipitate will form as copper (II) sulfate is reduced to copper (I) oxide which is insoluble in water (blue to orange, brick-red)
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14
Q

What is a polysaccharide?

A

Polysaccharides are polymers formed by many monosaccharides joined by glycosidic bonds in a condensation reaction to form chains.

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15
Q

Name 3 polysaccharides.

A
  • Cellulose
  • Starch
  • Glycogen
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16
Q

Properties of polysaccharides

A
  • very large
  • insoluble (suitable for storage)
  • some required for structural support
  • can be hydrolysed to release di/monosaccharides
17
Q

Why are starch and glycogen good storage molecules?

A
  • Branched (so compact + large amounts of energy can be stored in a small area)
  • Insoluble (so does not effect water potential/ no osmotic effect)
  • Polymers of α-glucose (so provides glucose for respiration)
  • Large (so can’t cross the cell membrane)
18
Q

What is glycogen?

A

Storage molecule in animals and fungi.

19
Q

Structure of glycogen.

A
  • very branched and compact so animals can store more
  • branching enables more free ends where glucose molecules can either be added or removed allowing for condensation and hydrolysis reactions to occur more rapidly – thus the storage or release of glucose can suit the demands of the cell
  • polysaccharide of α-glucose monomers
  • 1,4 AND 1,6 glycosidic
20
Q

What is starch?

A

Storage molecule in plants.

21
Q

What are the two types of starch?

A
  1. Amylose
  2. Amylopectin
22
Q

Amylose

A
  • long chain of alpha glucose
  • 1,4 glycosidic bonds
  • helix shape enables it to be more compact so it is more resistant to digestion & good for storage
23
Q

Amylopectin

A
  • long, branched chain of alpha glucose
  • 1-4 and 1-6 glycosidic bonds
  • branched: allow the enzymes that break down starch rapidly , meaning glucose can be released quickly
24
Q

Starch function

A
  • large: not going to diffuse through cell membrane
  • compact - can store lots in small place
  • can be hydrolysed: forms alpha glucose which is easily transported for use in respiration.
  • branched ends: large SA for hydrolysing enzymes
  • insoluble - doesn’t effect water potential or cause water to enter cell by osmosis
25
Q

What is cellulose?

A

Polysaccharide of β-glucose found in plant cell walls.

26
Q

Structure of cellulose.

A
  • Long, unbranched chains of β-glucose
    -1,4 glycosidic bonds
  • glucose molecules are rotated 180° to each other so glycosidic bond can form
  • long and straight chains become linked together by many hydrogen bonds to form fibrils so provides strength to cell wall
  • insoluble: permeable to molecules
27
Q

Function of cellulose.

A
  • Provides strength and structural support to plant cell walls
  • Strength of cellulose allows it to be stretched without breaking which makes it possible for cell walls to withstand turgor pressure
  • Source of fibre as few organisms have cellulase to hydrolyse it.
  • Stops cells from lysing- breaking down of the membrane
28
Q

What are microfibril?

A

Weak H bonds between beta glucose chains group together to form microfibril.

29
Q

Test for starch.

A
  1. Add Iodine Solution/ Potassium Iodide
    +ve result: (orange-brown to blue-black)
30
Q

What does the intensity of any colour change seen indicate? (In Benedict’s Test)

A

The concentration of reducing sugar present in the sample

31
Q

How do you set up standard solutions with known concentrations of a reducing sugar?

A

Serial dilution of an existing stock solution.

32
Q

Why should you use an excess of Benedict’s?

A

So that there is more than enough copper (II) sulfate present to react with any sugar present.

33
Q

How can you reduce subjectivity for colour change?

A

Use a colourimeter and compare against a calibration curve.

34
Q

General formula for glucose.

A

C6H12O6

35
Q

General formula for disaccharides.

A

C12H22O11

36
Q

Importance of Carbon

A
  • can form 4 chemical bonds
  • makes up all living things
  • found in organic molecules
  • can bond to carbon and other elements
37
Q

Carbohydrates formula

A

Cn(H2O)n
- subtract 1 H2O for every glycosidic bond

38
Q

Importance of Carbohydrates

A
  • respiration
  • photosynthesis
  • DNA
  • RNA
  • cellulose
  • starch
  • glycogen

(1) Biological Molecules (8 decks)

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