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2.1.2 Biological Molecules > Carbohydrates > Flashcards

Carbohydrates Flashcards

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1
Q

What are three types of carbohydrates?

A
  • Monosaccharide
  • Disaccharide
  • Polysaccharide
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2
Q

What is the general formula for monosaccharides?

A

(CH₂O)n

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3
Q

What is an example of a pentose (type of monosaccharide)?

A
  • Ribose -> found in ATP and RNA
  • Formula: C₅H₁₀O₅
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4
Q

What is an example of a hexose (type of monosaccharide)?

A
  • Glucose -> alpha or beta (animal transport sugar)
  • Fructose -> found in plant transport sugar (sucrose)
  • Galactose (in milk)
  • Formula: C₆H₁₂O₆
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5
Q

What is the difference between alpha (α) glucose and beta (β) glucose?

A
  • In α-glucose, the OH group on carbon 1 is below the plane of the ring
  • In β-glucose, the OH group on carbon 1 is above the plane of the ring
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6
Q

What are disaccharides?

A
  • 2 monosaccharides joined together in a condensation reaction
  • Joined by a glycosidic bond
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7
Q

What is maltose (disaccharide) made up of?

A

α-glucose + α-glucose

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8
Q

What is sucrose (disaccharide) made of?

A

α-glucose + fructose

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9
Q

What is lactose (disaccharide) made of?

A

Glucose + galactose

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10
Q

What are polysaccharides?

A

Long chain of monosaccharides, joined in condensation reactions

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11
Q

What are the two polysaccharides of starch?

A
  • Amylose
  • Amylopectin
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12
Q

What is the structure/bonding of amylose (plants)

A
  • α-glucose monomers
  • α 1,4 glycosidic bonds
  • Helical structure (held together by intermolecular hydrogen bonds
  • 20% of starch
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13
Q

What is the structure/bonding of amylopectin (plants)?

A
  • α-glucose monomers
  • α 1,4 and 1,6 glycosidic bonds
  • Branched structure
  • 80% of starch
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14
Q

What is the structure/bonding of glycogen (animals)?

A
  • α-glucose monomers
  • α 1,4 and 1,6 glycosidic bonds
  • Highly branched structure
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15
Q

What is the structure/bonding of cellulose?

A
  • β-glucose monomers
  • β 1,4 glycosidic bonds
  • Linear structure-> every other monomer is flipped, so unable to coil
  • Chains of cellulose molecules lie parallel -> joined by hydrogen bonds to form microfibrils.
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16
Q

Amylopectin and glycogen are both compact. Why does this property make them good storage molecules?

A

As it means many glucose monomers can be packed in a small space -> lots of energy can be stored in cell

17
Q

Amylopectin and glycogen are both insoluble. Why does this property make them good storage molecules?

A

Because it does not affect the water potential of the cell -> so no swelling due to osmosis

18
Q

Amylopectin and glycogen are both branched. Why does this property make them good storage molecules?

A

Many glucose monomers at branched endings -> are rapidly released for respiration (faster in glycogen as it is more branched so animals are more metabolically active)

19
Q

What makes cellulose insoluble and unreactive?

A

Intermolecular hydrogen bonds prevent water bonding with and hydrolysing polar –OH groups

20
Q

What makes cellulose flexible?

A

Microfibrils can slide over each other

21
Q

What makes cellulose have high tensile strength?

A

The intermolecular hydrogen bonds

22
Q

What makes cellulose have an unbranded structure?

A

Only has β 1,4 glycosidic bonds (no 1,6 bonds)

23
Q

What makes cellulose linear?

A

Every other monomer is flipped 180° so forms parallel strands

24
Q

What is a reducing sugar and an example?

A
  • A saccharide (sugar) that donates electrons which results in the reduction (gain of electrons) of other molecules
  • Glucose
25
Q

What is the qualitative test for reducing sugars?

A
  • Benedict’s solution is added to solution being tested and heated
  • Colour change: from blue- green- yellow- orange- brick red (colour depends on conc. of sugar in solution)
  • The more sugar that is present, the more blue Cu²⁺ ions in benedict’s solution are reduced to red Cu⁺ ions in CuO precipitate
26
Q

What is the qualitative test for non-reducing sugars (e.g sucrose)?

A
  • Heat with HCl to hydrolyse solution into reducing monosaccharides
  • Neutralise with an alkaline solution (sodium hydrogencarbonate)
  • Heat with Benedict’s solution
27
Q

What is the quantitative test for reducing sugars?

A
  • Carry out the test for reducing sugars
  • Filter the solution to remove the precipitate formed because it may obstruct the transmission of light through the solution
  • Calibrate a colorimeter using distilled water for the transmission of red light
  • Add a sample of the solution to the cuvette and place it in the colorimeter to measure the transmission of red light through it
  • Repeat with different concentrations and plot a calibration curve.
28
Q

How do you test for starch?

A
  • Use iodine solution
  • Colour change: yellow/orange to blue/black
  • Because the iodine molecules enter the helical amylose structure, forming blue-black starch-iodine complex
  • When heated, the iodine is released as intramolecular hydrogen bonds in the helix break, turning yellow again
29
Q

Which molecule consists of many alpha glucose molecules joined together by alpha (1-4) glycosidic bonds and alpha (1-6) glycosidic bonds to form a branched polysaccharide that is the storage carbohydrate in animals?

A

Glycogen

30
Q

Which molecule consists of many alpha glucose molecules joined together by alpha (1-4) glycosidic bonds and alpha (1-6) glycosidic bonds to form a branched polysaccharide that is one component of starch?

A

Amylopectin

31
Q

Which elements are found in carbohydrates?

A

Carbon, hydrogen and oxygen

32
Q

What is the transport carbohydrate in animals?

A

Glucose

33
Q

Which disaccharide is the transport carbohydrate in plants?

A

Sucrose

2.1.2 Biological Molecules (5 decks)

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