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(1) Biological Molecules > 1.2 Carbohydrates > Flashcards

1.2 Carbohydrates 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 and *heat**
  4. +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 (so can move around body)
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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.
Found in liver a muscle cells.

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-IMPORTANT as animals have high rate of respiration
  • polysaccharide of α-glucose monomers
  • 1,4 AND 1,6 glycosidic
20
Q

What is starch?

A

Storage molecule in plants
Starch is broken down to release glucose when cells need energy

21
Q

What are the two types of starch?

A
  1. Amylose
  2. Amylopectin
22
Q

Amylose

A
  • long unbranched chain of alpha glucose
  • 1,4 glycosidic bonds
  • helix shape /coiled structure 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
What is cellulose?
Polysaccharide of β-glucose found in plant cell walls.
26
Structure of cellulose.
- **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 -Stops cells from lysing
27
Function of cellulose.
- 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
What are microfibril?
**Weak H bonds** between **beta glucose** chains group together to form microfibril.
29
Test for starch.
1. Add Iodine Solution/ Potassium Iodide +ve result: (orange-brown to blue-black)
30
What does the intensity of any colour change seen indicate? (In Benedict’s Test)
The concentration of reducing sugar present in the sample
31
How do you set up standard solutions with known concentrations of a reducing sugar?
Serial dilution of an existing stock solution.
32
Why should you use an excess of Benedict’s?
So that there is more than enough copper (II) sulfate present to react with any sugar present.
33
How can you reduce subjectivity for colour change?
Use a colourimeter and compare against a calibration curve.
34
General formula for glucose.
C6H12O6
35
General formula for disaccharides.
C12H22O11
36
Importance of Carbon
- can form 4 chemical bonds - RNA, DNA, cellulose, glycogen, starch - respiration, photosynthesis - found in organic molecules - can bond to carbon and other elements
37
Carbohydrates formula
Cn(H2O)n - subtract 1 H2O for every glycosidic bond
38
Importance of Carbohydrates
- respiration - photosynthesis - DNA - RNA - cellulose - starch - glycogen
39
The enzymes that hydrolyse 1. Maltose 2. Sucrose 3. Lactose
1. Maltase 2. Sucrase 3. Lactase
40
Amylopectin function
Branched → allows enzymes to break down starch rapidly to release glucose

(1) Biological Molecules (8 decks)

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