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AS Biology > 1A - Carbohydrates (and monomers and polymers) > Flashcards

1A - Carbohydrates (and monomers and polymers) Flashcards

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1
Q

In what 3 ways might atoms combine with each other?

A

Covalent bonding, ionic bonding and hydrogen bonding.

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2
Q

What is covalent bonding?

A

Atoms share a pair of electrons in their outer shells so that the outer shells of both atoms are filled and a more stable compound called a molecule is formed.

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3
Q

What is ionic bonding?

A

Ions with opposite charges attract each other and this electrostatic attraction is known as an ionic bond.

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4
Q

Which are weaker - covalent or ionic bonds?

A

Ionic bonds

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5
Q

What is hydrogen bonding?

A

The electrons within a molecule aren’t evenly distributed and tend to spend more time in one position so this region is more negatively charged than the rest of the molecule.

A molecule with an uneven distribution of charge is said to be polarised. (It is a polar molecule).

The negative region of one polarised molecule and the positively charged region of another attract each other.

A weak electrostatic bond is formed between the two and although each individual bond is weak, they collectively form important forces that alter the physical properties of the molecule - water.

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6
Q

What is a polymer?

A

A large complex molecule made of long chains of monomers joined together.

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7
Q

What is a monomer?

A

A sub-unit of a polymer.

A basic molecular unit.

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8
Q

Through what process is a polymer formed?

A

Polymerisation. (condensation reaction)

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9
Q

What element are monomers usually based on?

A

Carbon

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10
Q

What is the basic sub-unit (monomer) of a polysaccharide?

A

A monosaccharide.

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11
Q

What is a condensation reaction?

A

The formation of a disaccharide (or polysaccharide) through the chemical bonding of two (or more) monosaccharides. A water molecule is formed and released in the process to form a glycosidic bond.

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12
Q

How can polymers be broken back down into monomers?

A

Hydrolysis reaction.

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13
Q

What is a hydrolysis reaction?

A

The process where polymers are broken down into monomers where water is taken in to break the glycosidic bond.

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14
Q

What is metabolism?

A

All the chemical reactions that take place in living organisms.

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15
Q

What element is life based on?

A

Carbon.

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16
Q

What makes carbon so versatile?

A

They very readily form bonds with other carbon atoms and other elements causing length to build up creating the backbone of all life.

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17
Q

What 4 elements are biological monomers mainly made out of?

A

Carbon
Oxygen
Hydrogen
Nitrogen

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18
Q

What are the basic monomers of carbohydrates?

A

Sugars (saccharide).

Monosaccharides.

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19
Q

What is a single monomer of a carbohydrate called?

A

A monosaccharide.

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20
Q

What can a pair or monosaccharides combine to form?

A

A disaccharide.

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21
Q

What do monosaccharides in large number combine to form?

A

Polysaccharides.

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22
Q

What are monosaccharides like?
Taste?
Solubility?
Formula?

A

They are sweet tasting, soluble substances which have the general formula (CH2O)n where n can be any number from 3 to 7.

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23
Q

What are examples of monosaccharides?

A

Galactose
Fructose
Glucose

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24
Q

What type of sugar is glucose, what is its general formula and what are the two isomers of glucose?

A

Hexose sugar
C6H12O6
Alpha and Beta

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25
Q

Why are there 2 isomers of glucose?

A

Because the atoms of carbon, hydrogen and oxygen can be arranged in different ways.

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26
Q

What does it mean if a sugar is reducing?

A

Reduction is a chemical reaction involving the gain of electrons or hydrogen.

A reducing sugar is a sugar that can donate electrons to (or reduce) another chemical, in this case Benedict’s reagent.

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27
Q

What is the test for reducing sugars?

A

Benedict’s test

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28
Q

What is Benedict’s reagent?

A

An alkaline solution of copper(II) sulfate.

29
Q

What happens when a reducing sugar is heated with Benedict’s reagent?

A

It forms an insoluble red precipitate of copper(I) oxide.

30
Q

Explain how to do Benedict’s test to test for reducing sugars:

A

Add 2cm3 of the food sample to be tested to a test tube. If the sample isn’t already in liquid form, first grind it up in water.

Add an equal volume of Benedict’s reagent.

Heat the water in a gently boiling water bath for 5 minutes.

31
Q

What is a positive result to Benedict’s test?

A

Solution turns orange-brown.

32
Q

What is maltose formed from?

A

Glucose joined to glucose.

33
Q

What is sucrose formed from?

A

Glucose joined to fructose.

34
Q

What is lactose formed from?

A

Glucose joined to galactose.

35
Q

What bond is made during a condensation reaction?

A

A glycosidic bond.

36
Q

What do you have to do first in order to detect a non-reducing sugar?

A

It first must be hydrolysed into its monosaccharide components by hydrolysis.

37
Q

How do you test for a non-reducing sugar?

A
  • Carry out Benedict’s test to check that there are first no reducing sugars.
  • Once there are no reducing sugars present, add 2cm3 of the food sample to 2cm3 of dilute HCl and place the test tube into a gently boiling water bath for 5 minutes.
  • The dilute HCl with hydrolyse any disaccharide present into its monosaccharide forms.
  • Slowly add some sodium hydrocarbonate solution to the test tube to neutralise the HCl (Benedict’s reagent will not work in acidic solutions).
  • Test with pH paper to check that the solution is alkaline.
  • Re-test the resulting solution by heating it with 2cm3 of Benedict’s reagent in a gently boiling water bath for 5 minutes.
  • If a non-reducing sugar was present in the original sample, the Benedict’s reagent will now turn orange-brown due to the reducing sugars that were produced from the hydrolysis of the non-reducing sugar.
38
Q

Describe the structure/properties of polysaccharides:

A

They are very large molecules and are insoluble making them suitable for storage.

39
Q

What form is starch found in and what is it made of?

A

Small granules or grains.

Made from 200-100,000 alpha glucose molecules.

40
Q

What is the test for starch?

A

Iodine test

41
Q

What is a positive result of the iodine test?

A

The colour will change from yellow to blue-black.

42
Q

Describe the test for starch:

A
  • Add 2cm3 of the sample being tested into a test tube (or add two drops of the sample into a depression on a spotting tile).
  • Add 2 drops of iodine solution and shake or stir.
  • The presence of starch is indicated by a blue-black colouration.
43
Q

What are 3 examples of disaccharides?

A

Maltose
Sucrose
Lactose

44
Q

What are 3 polysaccharides and from what monomers are they formed?

A 
Cellulose = Chains of beta glucose
Glycogen = Alpha glucose molecules
Starch = Many alpha glucose molecules (but differently)
45
Q

How are carbohydrates commonly used?

A

As respiratory substances (glucose is used in respiration).

They form structural components in plasma membranes and cell walls (cellulose).

46
Q

What are the 3 biological molecules?

A

Carbohydrates
Lipids
Proteins

47
Q

What are the common functions of lipids in the body?

A

The bilayer of plasma membranes.

48
Q

What are the common functions of proteins in the body?

A

They form cell structures and are important as enzymes, chemical messengers and components of blood.

49
Q

Are carbohydrates mostly monomers or polymers?

A

Polymers

50
Q

What type of sugar is glucose?

A

A hexose sugar

51
Q

What is the difference in the structure of alpha and beta glucose?

A

Their H and OH are different ways around;
Alpha glucose = H on top.
Beta glucose = OH on top.

52
Q

How are monosaccharides joined together?

A

Through a condensation reaction.

53
Q

What are monosaccharides with 3 carbon atoms called, what is their general formula and what is an example of one?

A

Triose
C3H6O3
Glyceraldehyde

54
Q

What are monosaccharides with 4 carbon atoms called, what is their general formula and what is an example of one?

A

Tetrose
C4H8O4
Erythrose

55
Q

What are monosaccharides with 5 carbon atoms called, what is their general formula and what is an example of one?

A

Pentose
C5H10O5
Ribose

56
Q

What are monosaccharides with 6 carbon atoms called, what is their general formula and what is an example of one?

A

Hexose
C6H12O6
Glucose

57
Q

What are monosaccharides with 7 carbon atoms called, what is their general formula and what is an example of one?

A

Heptose
C7H14O7
Glycero-D-manno-heptose

58
Q

How can Fructose and Glucose join to make sucrose?

A

By going through a condensation reaction where water is formed and then removed and so a glycosidic bond is formed.

59
Q

How can lactose be broken down into glucose and galactose?

A

By going through a hydrolysis reaction where water is added to break the glycosidic bond between the monomers.

60
Q

What is the structure of glycogen?

A

It is very similar in structure to starch but has shorter chains and is more highly branched. Therefore, we know it is made out of alpha glucose monomers.

61
Q

What is the function of glycogen?

A

It is the major carbohydrate storage product of animals. It is stored as small granules mainly in the muscles and liver.

62
Q

What is the role of glycogen’s structure in its function?

A

Its structure helps it with storage because:

  • It is insoluble so doesn’t tend to draw water into the cell by osmosis and it doesn’t diffuse out of cells.
  • It is compact so a lot can be stored in a small space.
  • It is more highly branched than starch and so has more ends that can be acted on simultaneously by enzymes.
  • Therefore, it is more rapidly broken down by enzymes to form glucose monomers, which are used in respiration. This is important to animals which have a much higher metabolic rate and respiratory rate than plant because they are more active.
63
Q

What is the structure of starch?

A

Made up of chains of alpha glucose monosaccharides linked by glycosidic bonds that are formed by condensation reaction. The chains may be branched or unbranched and the unbranched chain is wound into a tight coil that makes the molecule very compact.

64
Q

What is the function of starch?

A

It is found in many parts of a plant in the form of small grains. It forms an important component of food and is the major energy source in most diets. Starch is never found in animal cells.

65
Q

What is the role of starch’s structure in its function?

A

Starch is suited for energy storage as:

  • It is insoluble so it doesn’t affect water potential and so water isn’t drawn into the cells by osmosis. Being large and insoluble also means that it does not diffuse out of cells.
  • It is compact so a lot can fit in a small space.
  • When hydrolysed it forms alpha glucose which is both easily transported and readily used in respiration.
  • The branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly.
66
Q

What is the structure of cellulose?

A

Differs from starch and glycogen as it is made of monomers of beta glucose instead of alpha glucose. Cellulose has straight, unbranched chains which run parallel to each other allowing hydrogen bonds to form cross links between adjacent chains. The hydrogen bonds on their own don’t add much strength to the molecule, the sheer number of them makes a considerable contribution to strengthening cellulose. The cellulose molecules are grouped together to form microfibrils which are then arranged in parallel groups called fibres.

67
Q

What is the function of cellulose?

A

It is a major component of plant cell walls and provides rigidity to the plant cell. It also prevents the cell from bursting as water enters it by osmosis. It does this by exerting an inward pressure that stops any further influx of water. This means that living plant cells are turgid and push against each other.

68
Q

What is the role of cellulose’s structure in its function?

A

Its structure helps provide support and rigidity because:

  • Cellulose molecules are made of beta glucose monomers and so form long, straight unbranched chains.
  • Cellulose chains run parallel to each other and are cross linked by hydrogen bonds which add collective strength.
  • Molecules are grouped to form microfibrils which are then grouped to form fibres, all of which provides yet more strength.

AS Biology (47 decks)

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