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Biology > 3.1.2 Carbohydrates > Flashcards

3.1.2 Carbohydrates Flashcards

1
Q

What are monosaccharides?

A

Monomers from which larger carbohydrates are made. They are soluble

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2
Q

What are three examples of monosaccharides?

A

Glucose, galactose, fructose

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3
Q

How is a glycosidic bond formed?

A

Through a condensation reaction between two monosaccharides

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4
Q

What are disaccharides?

A

Formed by the condensation of two monosaccharides

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5
Q

What is maltose?

A

A disaccharide formed by condensation of two glucose molccules

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6
Q

What is sucrose?

A

A disaccharide formed by condensation of a glucose molecule and a fructose molecule

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7
Q

What is lactose?

A

A disaccharide formed by condensation of a glucose molecule and a galactose molecule

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8
Q

What are the two glucose isomers?

A

α-glucose, β-glucose

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9
Q

How does α-glucose and β-glucose differ?

A

α-glucose - H above, OH below
β-glucose - H below, OH above

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10
Q

What are polysaccharides?

A

Formed by the condensation of many glucose units. They are insoluble

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11
Q

Which polysaccharides are formed by the condensation of α-glucose?

A

Glycogen, starch

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12
Q

Which polysaccharides are formed by the condensation of β-glucose

A

Cellulose

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13
Q

Why is dilute hydrochloric acid added into food sample of non-reducing sugar?

A

It will hydrolyse any disaccharide present into its constituent monosaccharides by breaking its glycosidic bonds

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14
Q

Why is sodium hydrogen carbonate solution (NaHCO3) added to hydrochloric acid (HCl)?

A

Benedict’s reagent will not work in acidic conditions - needs to be neutralised

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15
Q

What is the test for reducing sugar?

A

1.Combine equal quantities of test solution and Benedict’s reagent in a test tube
2. Heat in water bath at 80°C
3. Observe change in colour and opacity of solution - indicates concentration of reducing sugar: Green(least), Yellow, Orange, Brick Red(most)

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16
Q

Why is non-reducing sugar not detected by Benedict’s reagent?

A

They do not change colour of Benedict’s reagent as they have a lack of reducing parts - used in making glycosidic bond

17
Q

How to detect non-reducing sugars?

A

It must be hydrolysed into its monosaccharide components (reducing sugar) by hydrolysis as they do not change the colour of Benedict’s reagent

18
Q

When do you do a non-reducing sugar test?

A

When results for Benedict’s reagent is negative

19
Q

What is the test for non-reducing sugar?

A
  1. Hydrolyse the glycosidic bond with warm dilute hydrochloric acid
  2. Neutralise with sodium hydrogen carbonate
  3. Perform a Benedict’s test again
20
Q

What is the structure of amylose?

A

A straight chain, unbranched polymer of glucose units bound by (α1-4) glycosidic bond

21
Q

What are the main two components of starch?

A

Amylose and amylopectin

22
Q

Which type of glucose is amylose and amylopectin made of?

A

α-glucose

23
Q

What secondary structure does amylose form?

A

α-helices

24
Q

What is the structure of amylopectin?

A

A branched chain polymer with α1-4 glycosidic bonds, and occasional α1-6 bonds in order to create branches

25
Q

Why is the rate of hydrolysis of amylopectin faster?

A

It has branches which increases surface area

26
Q

What is the test for starch?

A
  1. Add iodine/ potassium iodide
  2. Observe change in colour: Yellow to Blue/Black
27
Q

How does iodine indicate the presence of starch?

A

Iodine passes through the helix structure of amylose, which change the chemical properties of the helix, causing a different colour of light to reflect

28
Q

What is the structure of glycogen?

A

It is a macro molecule with 1-4 and 1-6 glycosidic bonds from α-glucose

29
Q

What is the difference in structure between starch and glycogen?

A

Glycogen has more frequent branching than starch - more surface area as demand in energy is more in animals for movement

30
Q

What is the structure of cellulose?

A

It is a straight chain polymer of β-glucose monomers

31
Q

How does fibres formed from cellulose give plant cell wall its strength

A

Cellulose molecules join to make microfibres through hydrogen bonds
Microfibres group into fibres
The arrangement of OH group of β-glucose on either side of chain allows for hydrogen bonds to form between adjacent chains above and below
All the hydrogen bonds have collective strength

32
Q

How does cellulose make plant cell walls permeable?

A

Fibres are laid down in layers which are arranged at 90°to form sheet-like structure - cross-hatches which they are holes between chains

Biology (19 decks)

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