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A-level Biology Year 1 > Monomers, Polymers and Carbohydrates > Flashcards

Monomers, Polymers and Carbohydrates Flashcards

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1
Q

What are monomers?

A

Small identical or similar molecules, which can be joined together to make larger molecules called polymers.

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2
Q

What are polymers?

A

Large molecules made from joining many identical or similar monomers together

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3
Q

How are monomers joined to form polymers?

A

They are joined by condensation reactions. This joins two monomer units together with the removal of one water molecule.

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4
Q

How are polymers broken down into monomers?

A

They are broken down by hydrolysis reactions. This hydrolyses a polymer into monomers with the addition of one water molecule.

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5
Q

What elements are found in carbohydrates? What is the formula?

A

Carbon, hydrogen & oxygen
CnH2nOn

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6
Q

What are carbohydrate monomers called?

A

Monosaccharides

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7
Q

Monosaccharides go through condensation reactions to form …

A

Dissacharides and polysaccharides.

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8
Q

What bonds are carbohydrate monomers joined together with?

A

Glycosidic bonds

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9
Q

What is the chemical formula of glucose?

A

C6H12O6

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10
Q

What is the difference between alpha and beta glucose?

A

The H and OH are switched on carbon 1.
H is Above in Alpha glucose
H is Below in Beta glucose

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11
Q

______ + _______ = maltose

A

Glucose + glucose

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12
Q

______ + _______ = lactose

A

Glucose + galactose

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13
Q

______ + _______ = sucrose

A

Glucose + fructose

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14
Q

Monosaccharides and disaccharides are ….

A

Small, sweet and soluble

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15
Q

What are the three polysaccharides we study?

A
  • Starch
  • Cellulose
  • Glycogen
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16
Q

What is the function of starch?

A

Is a glucose storage in plants.

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17
Q

What is the function of cellulose?

A

Is used for structure in plants.

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18
Q

What is the function of glycogen?

A

Is a glucose storage molecule in animals.

19
Q

What is the structure of starch?

A
  • Amylose = an unbranched chain of alpha glucose which is wound into a tight coil, it has C1-C4 bonds.
  • Amylopectin = branched chains of alpha glucose, it has C1-C4 & C1-C6 bonds.
20
Q

What is the structure of cellulose?

A

Long, straight unbranched chains of alternating beta glucose with C1-C4 bonds. Chains joined by hydrogen bonds to form microfibrils.

21
Q

What is the structure of glycogen?

A

Shorter, highly branched chains of alpha glucose with C1-C4 and C1-C6 bonds.

22
Q

How is structure of starch related to its function?

A
  • Amylose is coiled so is compact
  • Amylopectin is branched so has large surface area so glucose easily hydrolysed for respiration
  • Large so cannot leave cells
  • Polymer of glucose which can be hydrolysed and used in respiration
23
Q

How is structure of cellulose related to its function?

A
  • Straight so can form layers to form microfibrils
  • Many hydrogen bonds for strength, to prevent tearing of cells due to osmosial pressures
24
Q

How is structure of glycogen related to its function?

A
  • Branched so has large surface area so glucose easily hydrolysed for respiration
  • Insoluble so doesn’t affect W.P.
  • Polymer of glucose which can be hydrolysed and used in respiration
25
Q

How do you test for reducing sugars?

A
  1. Add 3cm^3 of food solution into a boiling tube.
  2. Add an equal amount of blue Benedict’s solution.
  3. Place boiling tube in hot water bath at 95C for 5 minutes.
  4. If red precipitate forms, reducing sugars are present.
26
Q

How do you test for non-reducing sugars?

A
  1. Test for reducing sugars using a Benedict’s test.
  2. Add 3cm^3 of food solution into a fresh boiling tube.
  3. Add 3cm^3 of dilute hydrochloric acid to hydrolyse the non-reducing sugars.
  4. Place boiling tube in hot water bath at 95C for 5 minutes.
  5. Add 3cm^3 of dilute alkali e.g. sodium hydroxide, then use pH paper to check that the solution is alkaline.
  6. Complete a second Benedict’s test, if a red precipitate forms, non-reducing sugars are present.
27
Q

How do you test for starch?

A
  1. Add solution into a spotting tile.
  2. Add two drops of iodine solution.
  3. A positive result changes from orange to blue-black
28
Q

Q1. Glucose is a monosaccharide. Two glucose molecules join together to form a disaccharide.
i) Name the products of this reaction. (2)
ii) Name the type of reaction that joins the glucose molecules together. (1)

A

i) Maltose + water
ii) Condensation

29
Q

Q2.
a) What is a monomer? (1)

A

A monomer is a smaller/repeating unit/molecule from which larger molecules/polymers are made.

30
Q

Q2.
b) Lactulose is a disaccharide formed from one molecule of galactose and one molecule of fructose.
Other than both being disaccharides, give one similarity and one different between the structure of lactulose and lactose. (2)

A

Similarity: Both contain galactose (mp1)
Difference: Lactulose has fructose while lactose had glucose (mp2)

31
Q

Q3.
a) Glycogen and cellulose are both carbohydrates.
Describe two differences between the structure of a cellulose molecules and a glycogen molecule. (2)

A
  1. Glycogen is a branched molecule while cellulose has straight chains.
  2. Cellulose is made of beta glucose while glycogen is made of alpha glucose
32
Q

Q3.
b) Starch is a carbohydrate often stored in plants.
Describe and explain two features of starch that make it a good storage molecule. (2)

A
  1. Amylose is coiled so is very compact and can fit many molecules in a small area.
  2. It is insoluble in water so does not effect water potential.
33
Q

Q3. Which test is used to show the presence of starch? (1)

A

Iodine/potassium iodine test

34
Q

Q4.
a) i) Name the monomers that form a cellulose molecule. (1)
ii) Name the bond which connects these monomers. (1)

A

a) i) Beta glucose
ii) Glycosidic bonds

35
Q

Q3.
b) i) What are two ways the structure of cellulose is different from the structure of starch.

A

b) i) - Starch has both 1,4 and 1,6 bonds while cellulose only has 1,4 bonds. - All starch glucose molecules are the same way up while cellulose glucose alternates

36
Q

Q3.
b) ii) Explain one way in which the structure of cellulose is linked to its function.

A

The weak hydrogen bonds (due to the number of them) result in a strong and rigid structure due to the bonding between the layers. As cellulose is needed in plant cell walls, it needs to be strong and firm. The cellulose chains form microfibrils which form cellulose fibres and this strengthens the cell wall.

37
Q

Q6
a) Describe the structure of glycogen.

A

Glycogen is a short branched molecule with many branches. It has 1,4 and 1,6 glycosidic bonds between carbons of alpha glucose molecules.

38
Q

Q6
b) Suggest how glycogen acts as a source of energy.

A

It is hydrolysed to glucose and glucose is used in respiration.

39
Q

Q7.
a) Explain the difference in the structure of a starch molecule and cellulose molecule.

A

Starch has chains of alpha glucose that don’t alternate while cellulose has chains of alternating beta glucose.

40
Q

Q7
b) Explain one way in which starch molecules are adapted to their function in plants.

A

The starch molecule amylose is coiled so it can be compact.

41
Q

Q7
c) Explain how cellulose molecules are adapted to their function in plants.

A

Cellulose is made of long chains of beta glucose joined via 1,4 glycosidic bonds. These chains are then joined by many hydrogen bonds which forms strong microfibrils to prevent damages to the cell wall.

42
Q

Q8.
a) Name the monomers from which a maltose molecule in made.
b) Name the type of chemical bond that joins the two monomers to form maltose.

A

a) Glucose + glucose
b) Glycosidic bonds

43
Q

Q9.
a) The formula for galactose is C6H12O6. What is the formula for lactose?

A

(C6H12O6 + C6H12O6) - H2O = C12H22O11

44
Q

Q9
b) i) Describe a chemical test you could carry out on a solution of lactose to show it is a reducing sugar.

A
  1. Add solution into boiling tube
  2. Add equal parts Benedict’s solution
  3. Heat in water bath at 95C for 5 minutes
  4. If reducing sugars are present, a red precipitate will form

A-level Biology Year 1 (19 decks)

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