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AS-Level Biology Unit 1 > Carbohydrates > Flashcards

Carbohydrates Flashcards

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1
Q

Elements Contained

A

Hydrogen (H)
Oxygen (O)
Carbon (C)

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2
Q

Carbohydrates

A

Organic molecules used as source of energy in all organisms and as structural materials in cell walls

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3
Q

The General Formula for a carbohydrate

A

Cn(H2O)n

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4
Q

The 3 main groups of carbohydrates

A

Monosaccharides - Mono=1
Disaccharides - Di=2
Polysaccharides - Poly=Many

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5
Q

Monosaccharides

A

Monosaccharides are single sugar units that form the building blocks for the larger carbohydrates.

They are classified according to the number of carbons:

Trioses=3C eg glyceraldehyde

Pentoses=5C eg ribose, deoxyribose (in RNA/DNA)

Hexoses=6C eg alpha and beta glucose, fructose and galactose

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6
Q

Glucose

A
  • Is the most common monosaccharide
  • Is a Hexose sugar with the formula C6H12O6
  • exists in both straight chain and ringed form (rings form when glucose is dissolved in water)
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7
Q

Isomer

A

Same chemical formulae but different structural formulae

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8
Q

2 isomers of glucose

A

1) Alpha-Glucose

2) Beta-Glucose

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9
Q

Disaccharides

A

Sugars formed when 2 monosaccharides join during condensation reaction.
The 3 we need to know are:

Glucose+Glucose=Maltose+Water

Glucose+Fructose=Sucrose+Water

Glucose+Galactose=Lactose+Water

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10
Q

Chemical formula Disaccharide

A

C6H12O6=C12H22O11 + H2O

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11
Q

Reducing sugars

A

All the monosaccharides and many of the disaccharides are reducing sugars

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12
Q

Biochemical Test for Reducing Sugars

A
  • Add Benedicts Reagent to a solution with water
  • Heat
  • Blue to Brick-Red colour
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13
Q

Biochemical test for non-reducing sugar

A
  • Hydrolyse/heat with acid (acid hydrolysis)
  • Neutralise, with alkali/sodium hydrogen carbonate
  • Add Benedicts Reagent
  • Heat-Blue to Brick-Red colour
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14
Q

Polysaccharides

A 
Polysaccharides are all:
-Polymers of glucose
-Macromolecules
-Insoluble
The 4 polysaccharides we need to know are:
-Starch
-Glycogen
-Cellulose
-Chitin
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15
Q

Starch

A

Starch is a polymer of Alpha-Glucose and made up of 2 chains-Amylose and Amylopectin

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16
Q

Amylose

A

Amylose is formed by a series of condensation reactions that bond alpha glucose molecules together into a long chain forming many glyosidic bonds

17
Q

Amylopectin

A

Amylopectin consists of a straight chain of alpha glucose units with branch points occurring at approx. every twelfth glucose units the straight chain. The branch points form when carbon 6 of a glucose molecule positioned above the chain forms a glyosidic bond with carbon 1 of a glucose molecule positioned above the chain.

18
Q

Starch Biological Importance

A

Starch is only stored in plants as an energy store. Animals store glycogen. Starch is hydrolysed by the enzyme amylase

19
Q

Starch Structure

A
  • Polymer of alpha-glucose
  • made up of amylose and/or amylopectin
  • so it has 2 polysaccharides
  • glyosidic bonds/ 1-4 and 1-6 linkages
  • amylose coil/starch coiled/amylopectin branched; not compact
  • glucose all same way up
  • consists of single chains
20
Q

Starches Function and Properties

A

Function:
-Energy store in plant cells only
Properties:
-Insoluble so doesn’t affect osmotic potential in cell
-Can’t diffuse out of cell
-Coiled making it compact so stored lots in small space
-Starch as few free ends for enzyme hydrolysis so it is an excellent long term storage molecule - not broken down quickly

21
Q

Biochemical test for starch

A
  • Add iodine

- Turns from orange-brown to blue-black colour

22
Q

Glycogen

A

Its a polymer of a alpha-glucose and it is an energy store in animal cells mainly in the liver and skeletal muscles. Glycogen has a similar structure as amylopectin but there is significantly more branching

23
Q

Glycogen function and properties

A

Function:
-Energy store in animal cells only
Properties:
-Has many more branches so it can hydrolyse rapidly to meet the higher energy demands of animals

24
Q

Cellulose

A

Its a polymer of Beta-Glucose and it has structural role in plant cell walls

25
Q

Cellulose Structure

A
  • Polymer of Beta-Glucose
  • With 1-4 glyosidic bonds
  • Adjacent glucose molecules are rotated by 180’/head up and head down
  • Hydrogen bonds form between OH groups adjacent parallel chains/reference to cross linking
  • Forming microfibrils
  • Straight chain only/no branches; not parallel
  • Cellulose (cross linked) in straight chains
  • Linked with hydrogen bonds
26
Q

Cellulose functions and properties

A

Function:
-Structural role in plant cell walls
Properties:
-Strength or stability-long chains cross linked by hydrogen bonds
-Freely permeable due to spaces between fibres so water can pass to cell membrane

27
Q

Chitin Structure

A
  • Polymer of beta-glucose

- It has some - OH groups replaced by nitrogen-containing acteylamine groups

28
Q

Chitin function and properties

A

Function:
-Structural role in forming the exoskeleton of many invertebrates and cell walls in fungi eg yeast
Properties:
-Strong-long chains cross linked by hydrogen bonds
-Waterproof
-Lightweight

AS-Level Biology Unit 1 (19 decks)

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