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Biology: 3.1 Biological Molecules > 3.1.2 Carbohydrates > Flashcards

3.1.2 Carbohydrates Flashcards

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1
Q

(Carbohydrates) What monomers make up carbohydrates?

A

Monosaccharides

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2
Q

(Carbohydrates) What are three examples of monosaccharides?

A

Glucose, fructose and galactose.

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3
Q

(Carbohydrates) Glucose is a hexose sugar, what is a hexose sugar?

A

A monosaccharide with six carbon atoms in each molecule.

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4
Q

(Carbohydrates) Alpha and beta glucose are isomers. What is an isomer?

A

A molecule with the same molecular formula as each other, but with the atoms connected in a different way.

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5
Q

(Carbohydrates) When is a disaccharide formed?

A

When two monosaccharides join together by condensation reactions.

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6
Q

(Carbohydrates) What type of bond is formed when monosaccharide join together?

A

A glycosidic bond forms between the two monosaccharides as a molecule of water is released.

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7
Q

(Carbohydrates) Surcose is a disaccharide formed a condensation reaction between what two molecules?

A

A glucose molecule and a fructose molecule.

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8
Q

(Carbohydrates) Lactose is a disaccharide formed between what two molecules?

A

A glucose molecule and a galactose molecule.

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9
Q

(Carbohydrates) When is a polysaccharide formed?

A

When more than two monosaccharides are joined together by a condensation reaction.

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10
Q

(Carbohydrates) What can polysaccharides be broken down into?

A

Into their constituent monosaccharides by hydrolysis reactions.

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11
Q

(Carbohydrates) Where do cells get energy from?

A

Glucose

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12
Q

(Carbohydrates) What two polysaccharides of alpha-glucose is starch a mixture of?

A

Amylose and amylopectin

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13
Q

(Carbohydrates) Is starch soluble or insoluble in water?

A

Insoluble

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14
Q

(Carbohydrates) Starch is insoluble in water and doesn’t affect water potential, so was doesn’t it cause?

A

It doesn’t cause water to enter the cells by osmosis, which would make them swell - good for storage.

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15
Q

(Carbohydrates) Describe the structure of the polysaccharide ‘amylose’.

A
  • Long, coiled, unbranched chain of alpha-glucose
  • Angles of glycosidic bonds give it a coiled structure
  • Which makes it compact: good for storage
  • Glycosidic C1-4 bonds formed through condensation reaction
  • Polymer of alpha glucose
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16
Q

(Carbohydrates) Describe the structure of the polysaccharide ‘amylopectin’.

A
  • Long, branched chain of (polymer of) alpha-glucose
  • Glycosidic C1-4 bonds form chains with C1-6 side branches
  • Side branches allow enzymes that break down the molecule to get the glycosidic bonds easily, glucose can be released easily
17
Q

(Carbohydrates) What do animal cells store excess glucose as?

A

Glycogen

18
Q

(Carbohydrates) Describe the structure of the polysaccharide ‘glycogen’.

A
  • Similar structure to amylopectin, but with more side branches
  • Loads of branches means that glucose stored can be released quickly (important for energy release)
  • Glycosidic C1-4 bonds from chains with C1-6 side branches
  • Very compact molecule, good for storage
  • Insoluble
19
Q

(Carbohydrates) Describe the structure of the polysaccharide ‘cellulose’.

A
  • Fibrous
  • Unbranched
  • Provides structure in plants
  • Consists of several thousand beta-glucose joined together in a long straight chain by beta 1-4 glycosidic links
20
Q

(Carbohydrates) What happens when beta-glucose molecules bond in cellulose?

A

Form straight cellulose chains that are linked together with hydrogen bonds to form microfibrils.

21
Q

(Carbohydrates) What do microfibrils provide in cellulose?

A

Structural support for cells.

22
Q

(Carbohydrates) Describe the food test for starch.

A

Add 2cm3 of iodine in a potassium iodine solution. Colour change from orange to blue/black.

23
Q

(Carbohydrates) Maltose is a disaccharide formed by a condensation reaction was what two molecules?

A

Two glucose molecules

24
Q

(Carbohydrates) What are the 4 functions of monosaccharides?

A
  • Source of energy in respiration
  • Building blocks for much larger polysaccharide molecules - starch, glycogen, cellulose, chitin
  • Required to build nucleotides (deoxyribose in DNA, ribose in RNA, ATP)
  • Intermediates in biochemical reactions
25
Q

(Carbohydrates) How are monosaccharides a source of energy in respiration?

A

C-C and C-H bonds break to form CO2 and water, realising energy to make ATP.

26
Q

(Carbohydrates) What do disaccharides form?

A

1-4 glycosidic bonds

27
Q

(Carbohydrates) Describe the formation of maltose. (4)

A
  • 2 alpha glucose molecules
  • Condensation reaction
  • A water molecule is released
  • Forming a C1-C4 glycosidic bond
28
Q

(Carbohydrates) Describe the test for reducing sugars.

A
  • Add 2cm3 Benedict’s solution to the sample
  • Heat in water bath, 90 degrees for 5 mins
  • Colour change from light blue to red/orange precipitate
29
Q

(Carbohydrates) Is maltose (x2 alpha glucose) reducing or non reducing?

A

Reducing

30
Q

(Carbohydrates) Is sucrose (glucose and fructose) reducing or non reducing?

A

Non-reducing

31
Q

(Carbohydrates) Is lactose (glucose and galactose) reducing or non-reducing?

A

Reducing

32
Q

(Carbohydrates) Describe the test for non-reducing sugars.

A
  • Complete Benedict’s test and if it stays blue (negative)
  • Boil with hydrochloridic acid for 5 mins then neutralise with alkali
  • Repeat Benedict’s test by heating at 90 degrees for 5 mins
  • Colour change from light blue to red/orange
33
Q

(Carbohydrates) What are the features of starch in plants? (6)

A
  • Consists of mainly the polysaccharide amylose
  • Storage polysaccharide for energy
  • Compact, good for storage
  • Coiled by hydrogen bonding within the chain
  • Insoluble (cell’s water potential/enzymes aren’t affected/cannot diffuse out of cells)
  • Hydrolysis of starch releases glucose for respiration to make ATP
34
Q

(Carbohydrates) What are the biological roles of starch and glycogen? (3)

A
  • Insoluble (doesn’t affect water potential)
  • Compact storage of chemical energy (many C-C, C-H bonds)
  • Branches in glycogen allow rapid enzymatic hydrolysis and release to glucose when required by amylase
35
Q

(Carbohydrates) Describe hydrogen bonding between cellulose strands. (4)

A
  • Each alternate beta-glucose unit is rotated 180
  • Extensive hydrogen bonding can occur on either side of parallel chains
  • Forming microfibrils - layered to macrofibrils - layered to cellulose
  • Tensile / strong / fibrous polymer
36
Q

(Carbohydrates) How does high tensile strength benefit cellulose, and what does this prevent?

A

Strength whilst remaining flexible which prevents osmotic lysis of plant cells.

37
Q

(Carbohydrates) Describe a turgid cell.

A

Water enters by osmosis, vacuole swells and pushes against cell wall

38
Q

(Carbohydrates) Describe flaccid cell.

A

Water lost from cell, vacuole shrinks, cell loses shape.

39
Q

(Carbohydrates) Describe chitin polysaccharide.

A

Very tough with amino acids added, forming a mucopolysaccharide.

Biology: 3.1 Biological Molecules (8 decks)

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