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2.1.2 Biological Molecules > Carbohydrates > Flashcards

Carbohydrates Flashcards

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Organic Chemistry 101 flashcards
1
Q

What is the general formula of monosaccharides?

A

(CH2O)n where n is either 3 (triose), 5 (pentose) or 6 (hexose)

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2
Q

What are some examples of pentose monosaccharides?

A
  • Ribose found in RNA and ATP
  • Deoxyribose in DNA
  • Ribulose 1,5 bisphosphate (RuBP) in photosynthesis
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3
Q

What are some examples of hexose monosaccharides?

A
  • Glucose
  • Fructose
  • Galactose
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4
Q

Draw alpha glucose

A

Answer on revision card

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5
Q

Draw beta glucose

A

Answer on revision card

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6
Q

All hexose are structural isomers. What is a structural isomer?

A

They all have the same chemical formula but a different molecular structure

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7
Q

What are some examples of disaccharides?

A
  • Maltose
  • Lactose
  • Sucrose
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8
Q

What is the structure, bonding and function of maltose? And draw it

A

Structure: two alpha glucose
Function: present in germinating seeds
Bonding: alpha 1,4 glycosidc bond

Drawing on revision card

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9
Q

What is the structure and function of sucrose?

A

Structure: composed of alpha glucose and fructose
Function: transport sugar in phloem plants

  • It is a non reducing sugar
  • Ir is also referred to as cane sugar or just sugar
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10
Q

What makes sucrose a non-reducing sugar?

A
  • It cannot reduce Cu2+ to Cu+
  • This is because the chemical group required for this reduction reaction is involved in the glycosidic bonds between the monosaccharides
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11
Q

What is the function, structure and bonding of lactose?

A

Function: found in milk/milk products
Structure: composed of glucose (alpha or beta) and beta galactose
Bonding: beta 1,4 glycosidic bond

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12
Q

What the reagent is used to test for sugars?

A

Benedict’s reagant, an alkaline solution of copper(II) sulfate

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13
Q

What is the procedure for the qualitative test for reducing sugars?

A
  • Place the sample to be tested in a boiling tube
  • If it is not in liquid form, grind it up or blend it in water
  • Add an equal amount of Benedict’s reagant
  • Heat the mixture gently in a boiling water bath for five minutes
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14
Q

What is the procedure for the qualitativ test for non-reducing sugars?

A
  • Place the sample to be tested in a boiling tube and add dilute hydrochloric acid
  • Heat the mixture gently in a boiling water bath for a few minutes
  • Neutralise the pH by adding sodium bicarbonate (NaHCO3)
  • Add an equal amount of Benedict’s reagant
  • Heat the mixture gently in a boiling water bath for five minutes
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15
Q

What is the procedure for the quantitative test for reducing sugars?

A
  • Set the colorimeter to the red filter
  • Place a cuvette containing distilled water into the colorimeter and set the colorimeter to zero
  • Place 2cm3 of each of the unknown glucose concentration samples in separate boiling tubes
  • Add 2cm3 of Benedict’s solution to all boiling tubes
  • Place boiling tubes in a boiling water bath for 5 minutes
  • Use tongs to take the boiling tubes out of the water bath, leave to cool and allow the supernatant to settle
  • Use a pipette to take 2cm3 of the solution left at the top from each boiling tube into seperate cuvettes
  • Place each cuvette in the colrimeter and measure the % transmission
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16
Q

What is the general formula for the polymerisation of glucose?

A

Answer on revision card

17
Q

What is the function of starch?

A

It is the storage carbohydrate in plants and is a source of glucose for respiration

18
Q

Where is starch found?

A
  • Found in chloroplasts and amyloplasts=> it is insoluble so does not affect the water potential
  • Found in grain => seed germination
  • Found in tubers (e.g. potato) => for asexual reproduction and can carry out respiration at night
19
Q

What are the two types of starch?

A

Amylose and amylopectin

20
Q

What is the bonding, structure, mass and composition of amylose?

A
  • 20% starch
  • The monomer is α glucose
  • The bond is an α 1,4 glycosidc bond
  • It is a helical molecule, it is a helix held together by intramolecular hydrogen bonds between -OH groups
  • Relative molecular mass ≈ 50,000 => there are about 300 glucose residues in a molecule of amylose (can’t go past that as it would be unstable)
21
Q

What is the bonding, structure, mass and composition of amylopectin?

A
  • 80% starch
  • The monomer is α glucose
  • The bond is an α 1,4 glycosidc bond between adjacent molecules AND α 1,6 glycosidc bonds between branching points
  • It has a branched structure
  • Relative molecular mass ≈ 500,000 => there are about 3000 glucose residues in a molecule of amylopectin
22
Q

What is the bonding, structure, mass and composition of glycogen?

A
  • The monomer is α glucose
  • The bond is an α 1,4 glycosidc bond between adjacent molecules AND α 1,6 glycosidc bonds between branching points
  • It has a highly branched structure
  • There are about up to 60,000 glucose residues in a molecule of glycogen
23
Q

What is the bonding, structure, mass and composition of cellulose?

A
  • The monomer is β glucose
  • The bond is an β 1,4 glycosidc bond between adjacent molecules
  • It has linear structure
  • There are about up to 10,000 glucose residues in a molecule of cellulose
24
Q

What occurs when iodine is mixed with amylose?

A
  • Iodine ions enter the helix (absorbs light of a different wavelength)
  • Turns starch/iodine complex blue-black
  • Heat breaks the hydrogen bonds and releases the iodine
  • This cause the blue-black colour to disappear
25
Q

What are the properties of glycogen and amylopectin that make them a good energy store?

A

Branched
- Meaning that => many glucose monomers are available at branch endings and glycogen is more highly branched than amylopectin
- Advantage => rapid release of glucose for respiration to provide energy for the cell
=> more glucose monomers are hydrolysed i.e. more rapid release of glucose for animals which are more metabollicaly active than plants

Compact
- Meaning that => many glucose monomers exist in a small volume
- Advantage => large quantities of energy can be store in the cell

Insoluble
- Meaning that => they do not affect the water potential
- Advantage => does not cause osmotic swell

26
Q

What is the function of cellulose?

A
  • Structural carbohydrate
  • Component of plant and algae cell walls
  • Homopolysaccharide (made of only one type of monomer)
27
Q

Why doesn’t a cellulose chain coil?

A
  • The chain does not coil because each beta glucose monomer is 180°/opposite orienation with respect to its neigbour
  • Each chain lies parallel to the next and can form intramolecular hydrogen bonds with it
28
Q

What do chains of cellulose molecules form?

A
  • Chains of cellulose molecules form microfibrils
  • A bundle of microfibrils makes macrofibrils
  • A bundle of macrofibrils makes cellulose fibres
29
Q

What are the properties of cellulose and what are their significance?

A
  • Linear => ß glucose monomers flip 180 degrees alternately giving rise
    to strands which are parallel to each other
  • Unbranched => Only ß 1,4 glycosidic bonds between the ß glucose monomers present, no 1,6 glycosidic bonds
  • Unreactive => Glucose monomers held in a chain (plus many H bonds between cellulose molecules) which are not easily hydrolysed to be available for respiration
  • High tensile strength => Many intermolecular H bonds between the individual cellulose molecules within the microfibrils hold the chains firmly together
  • Insoluble => Very large polymer with many H bonds keeping strands together so no access for water molecules to bond with polar OH groups

2.1.2 Biological Molecules (4 decks)

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