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AQA A Level Biology > 3.1 Biological Molecules > Flashcards

3.1 Biological Molecules Flashcards

1
Q

State the different bonding atoms may have undergo to combine?

A

Hydrogen, Covalent, and Ionic Bonding

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2
Q

What are monomers?

A

Small units from which larger molecules are made (from)

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3
Q

What are polymers?

A

Large molecules made up many monomers joined together

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4
Q

Give three examples of monomers?

A

Monosaccharides, amino acids and nucleotides

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5
Q

What is the name of the process of making polymers?

A

Polymerisation

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6
Q

What is a condensation reaction?

A

A reaction where 2 molecules join together to form a chemical bond, eliminating a water molecule in the process.

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7
Q

What is a hydrolysis reaction?

A

Breakdown of a chemical bond between two molecules involving a water molecule

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8
Q

What is metabolism?

A

All the chemical processes that take place in a living organism

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9
Q

What are most biological molecules made up of?

A

Carbon, Hydrogen, Oxygen and Nitrogen

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10
Q

What is a monosaccharide?

A

A monomer which a larger carbohydrate is made from

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11
Q

Give examples of three common monosaccharides?

A

Glucose, Galactose and Fructose

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12
Q

If a pair of monosaccharides combine, then what is the compound called?

A

Disaccharide

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13
Q

What are the characteristics of a monosaccharide?

A

sweet
Soluble
(extra: has formula of CH20n)

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14
Q

What are isomers?

A

Molecules that have the same chemical formula but different arrangement

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15
Q

What are the isomers of monosaccharides?

A

a-glucose and J3-glucose

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16
Q

“All monosaccharides and some disaccharides are reducing sugars” - True or False?

A

True

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17
Q

What is meant by a reducing sugar?

A

A sugar that can donate electrons to reduce another chemical

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18
Q

What is the test for reducing sugars?

A

Benedict’s Test

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19
Q

Describe how to do the benedict’s test?

A

Add 2cm3 of liquid (grinded) food sample
Add equal volume of Benedicts reagent
Heat mixture in water bath for 5 mins
If orange-brown-brick red precipitate then present

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20
Q

What is the name of the disaccharide when:
Glucose and Glucose bond?

A

Maltose

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21
Q

What is the name of the disaccharide when:
Glucose and Fructose bond?

A

Sucrose

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22
Q

What is the name of the disaccharide when:
Glucose and Galactose bond?

A

Lactose

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23
Q

What is the reaction when two monosaccharides join?

A

Condensation Reaction

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24
Q

What is the name of the bond when two monosaccharides join?

A

Glycosidic Bond

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25
Q

Describe the formation of a disaccharide.

A

The condensation reaction of two monosaccharides forming a glycosidic bond involving the loss of water

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26
Q

What is the name of the reaction?
“Water added to the disaccharide causes the breakdown of the glycosidic bond between monosaccharides”

A

Hydrolysis Reaction

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27
Q

How do we know if we have a non-reducing sugar in a Benedict’s Test?

A

If the benedict’s reagent does not change colour after being heated for 5 minutes

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28
Q

What do we have to do in order to detect a non-reducing sugar? (not asking for the method)

A

Need to hydrolyse into monosaccharide components

(HCL will hydrolyse any disaccharide present)

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29
Q

Describe the test for non-reducing sugars?

A

Add 2cm3 of sample in equal volume of HCL
Place in water bath for 5 mins
Add some sodium hydrogen carbonate solution to neutralise HCL
Test with PH paper = alkaline
Re-test using the benedicts reagent in water bath for 5
It should now turn orange-brown

30
Q

What are polysaccharides?

A

Polymers formed by the condensation reaction of many monosaccharides

31
Q

What are the three main polysaccharides?

A

Starch,Glycogen and Cellulose

32
Q

What features make polysaccharides useful for storage?

A

Large molecules
Insoluble

33
Q

Glycogen and starch are formed by the […] of […] glucose

A

condensation , alpha

34
Q

Cellulose is formed by the […] of […] glucose

A

Condensation, beta

35
Q

Describe the test for starch?

A

Add 2cm3 of sample in test tue
Drop 2 drops of iodine
Shake or stir
If starch is present, the sample will be blue-black

36
Q

What is the main role of starch

A

Act as energy storage for plants

37
Q

What structural features benefit starch?

A

Insoluble → water potential not affected
Large → can’t leave cell
Helical → compact for storage in cell

38
Q

What is starch made up of?

A

Amylose and Amylopectin

39
Q

Describe the structure of amylose

A

Unbranched polysaccharide
Bonded by 1,4 glycosidic bonds
Coiled shape

40
Q

How does the coiled part of amylose help function of starch?

A

A lot of alpha glucose can be stored in a small area

41
Q

What is the limitation of amylose?

A

1,4 Glycosidic bonds mean glucose can only be hydrolysed off two end = slower hydrolysis

42
Q

Describe the structure of Amylopectin

A

Branched polysaccharide
Bonded w/ C1,C4 and C1,C6 glycosidic bonds

43
Q

How do the 1,4 and 1,6 glycosidic bonds benefit starch?

A

There is a greater number of terminal glucose = a FASTER HYDROLYSIS

44
Q

What is glycogen?

A

The storage for animals

45
Q

Describe structural features in glycogen that benefit role?

A

Insoluble = no osmosis and no diffusion
Compact = a lot of it can be stored in small space
Large → can’t leave
Very highly branched = more terminal glucose → faster hydrolysis of glucose for respiration

46
Q

Why is having highly branched structure in glycogen good for animals?

A

Faster hydrolysis of glucose can support animals with high energy release due to their high metabolic rate

47
Q

What is the function of cellulose?

A

Provides strength and structural support to plant cell walls

48
Q

Describe the structure of cellulose

A

Straight, unbranched chains
Parallel to each other
Hydrogen bonds (forming cross-linkages)

49
Q

How are the B-glucose arranged to create straight chains?

A

Adjacent glucose rotated by 180˚

This means hydroxyl group is able to form a condensation reaction.

50
Q

How does the structure of cellulose help its function?

A

Hydrogen bonds are strong in high numbers
Many H bonds link to form microfibrils
Provides strength and structural support to plant cell walls

51
Q

What is the function of cellulose?

A

Provides rigidity to the plant cell and prevents cell bursting due to osmotic pressure

52
Q

Describe how you would determine glucose concentration?

A
  1. Produce a dilution series of glucose solutions of known concentrations
  2. Perform a Benedict’s test on each sample
  3. Using a colorimeter, measure the absorbance of each sample and plot a calibration curve
  4. Repeat with the unknown sample and use graph to determine glucose concentration
53
Q

What are the main groups of lipids?

A

Triglycerides and Phospholipids

54
Q

What are the roles of lipids?

A

Cell membrane
Source of energy
Waterproof (insoluble)
Insulation
Protection ( stored around delicate organs)

55
Q

Explain the formation of a triglyceride

A

Condensation of 1 molecule of glycerol and 3 fatty acids forming three ester bonds

56
Q

Describe the structure of a triglyceride

A

3 fatty acids and 1 glycerol

57
Q

What does the hydrolysis of a triglyceride produce?

A

1 glycerol and three fatty acids

58
Q

Describe the properties of triglycerides related to its structure

A
  • High ratio of C-H bonds to C atoms = more energy released
  • Insoluble in water = no effect on the water potential
59
Q

How do you identify a saturated lipid?

A

No carbon-carbon double bonds on hydrocarbon chain (fully saturated with hydrogen)

60
Q

How do you identify an unsaturated lipid?

A

One or more C=C bonds in a hydrocarbon chain

61
Q

If a lipid structure had several double bonds, what may we suggest?

A

The molecule is caused to bend = not packed together anymore= meaning that it is most likely a liquid

62
Q

Describe the structure of a phospholipid

A

Glycerol
Phosphate (containing group)
Two fatty acids

63
Q

What are the two parts that make up the phospholipid?

A

Hydrophilic phosphate head
Hydrophobic Fatty acid tails

64
Q

Describe the formation of a phospholipid

A

The condensation reaction between 1 glycerol, 1 phosphate group and 2 fatty acids

65
Q

What is formed due to the amphipathic parts in a phospholipid?

A

Creation of a phospholipid bilayer

66
Q

Describe structure of phospholipid?

A
  • Forms bilayer → allowing diffusion of nonpolar/small molecules
  • Hydrophilic phosphate heads → orient to aqueous environment
  • Hydrophobic tails → orient to interior → repels polar/charger molecules
67
Q

Describe the test for lipids

A

Add sample of food
Add ethanol
Shake the tube
Add water and shake gently
If there is a cloudy, white colour then present

68
Q

What are amino acids?

A

The monomers from which proteins are made

69
Q

What is the general structure of amino acids?

A

NH2-CHR-COOH

70
Q

Describe the formation of dipeptides?

A

A condensation reaction between 2 amino acids forms a peptide bond

71
Q

Describe the formation of polypeptides?

A

Condensation of many amino acids

72
Q

What may a functional protein contain?

A

One or more polypeptides

AQA A Level Biology (9 decks)

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