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Biology > Section 1- Biological molecules > Flashcards

Section 1- Biological molecules Flashcards

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1
Q

What is a monomer?

A

Smaller units from which larger molecules are made.

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2
Q

What are polymers?

A

Molecules made from a larger number of monomers joined together.

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3
Q

What is polymerisation?

A

Process by which polymers are formed by monomers.

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4
Q

What is a condensation reaction?

A

Where 2 molecules are joined together forming a chemical bond with the elimination of water.

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5
Q

What is a hydrolysis reaction?

A

Breaks chemical bond between two molecules and involves the use of water.

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6
Q

What are the 3 types of monosaccharide?

A

Glucose
Fructose
Galactose

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7
Q

What does GLUCOSE + GLUCOSE form?

A

MALTOSE + water

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8
Q

What does GLUCOSE + FRUCTOSE form?

A

SUCROSE + water

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9
Q

What does GLUCOSE + GALACTOSE form?

A

LACTOSE + water

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10
Q

What bond form between disaccharide?

A

Glyosidic bond

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11
Q

What reaction occurs to join monosaccharides?

A

Condensation reaction

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12
Q

What are the 3 polysaccharides?

A

Starch
Cellulose
Glycogen

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13
Q

What are features of starch?

A

Alpha glucose
Plant energy storage
Branched: amylopectin
Unbranched: amylose

Insoluble
Compact

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14
Q

What are features of glycogen?

A

Alpha glucose
Animal energy storage
Short chains
Highly branched

Insoluble
Compact

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15
Q

What are features of cellulose?

A

Beta glucose
Straight, unbranched chains running parallel
Linked by hydrogen bonds
Plant cell wall- provides rigidity

Microfibrils- Macrofibrils- Fibres

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16
Q

What reaction occurs for polysaccharides and what bond?

A

Condensation reaction

Glyosidic bond

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17
Q

What are the 5 reducing sugars?

A 
Glucose
Galactose
Fructose
Lactose
Maltose
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18
Q

How do you conduct the Benedict’s test?

A
  1. Add Benedict’s solution to sample
  2. Heat it
  3. Spectrum of colours
Positive= Brick red
Negative= Blue
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19
Q

What is the non-reducing sugar?

A

Sucrose

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20
Q

How do you test for non-reducing sugar?

A
  1. Add Hydrochloric acid and heat it
    (to hydrolyse non-reducing)
  2. Neutralise solution using sodium hydrogen carbonate
  3. Add Benedict’s solution and heat
  4. Spectrum of colours
    Positive= Brick red
    Negative= Blue
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21
Q

What are the roles of lipids?

A
  • Source of energy
  • Waterproofing
  • Insulation
  • Protection
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22
Q

What are triglycerides made up of?

A

Glycerol

3x fatty acid

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23
Q

How are triglycerides formed?

A
  1. Condensation reaction
  2. Formation of 3 water molecules
  3. Ester bond
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24
Q

What are saturated fatty acids?

A

No double carbon bonds between carbon atoms

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25
Q

What are mono-unsaturated fatty acids?

A

One double bond between carbon atoms

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26
Q

What are poly-unsaturated fatty acids?

A

More than one double bond between carbon atoms

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27
Q

What is the advantage on an insect polymerising sugars into polysaccharides?

A

Polysaccharides are insoluble

Do not affect water potential

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28
Q

How can the active site of an enzyme cause a high rate of reaction?

A

Induced fit: active site changes shape when substrate collides

Enzyme lowers activation energy

Enzyme-substrate complex causes bonds to form/ break

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29
Q

How does a non-competitive inhibitor reduce the rate of an enzyme-controlled reaction?

A

Inhibitor binds to allosteric site

Active site has changed shape

Active site and substrate no longer complementary so less substrate can fit

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30
Q

How do you test for amylase?

A

Add Biuret solution, becomes purple

Add starch to test for reducing sugar

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31
Q

Why do large molecules often contain carbon?

A

Carbon atoms readily link to one another to form a chain

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32
Q

What is the name for a molecule that is make up of many similar repeating units?

A

Polymer

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33
Q

Why does Benedict’s reagent turn red when heated with a reducing sugar?

A

Sugar donated electrons that reduce blue copper sulphate to orange copper oxide

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34
Q

How does the structure of triglycerides relate to their properties?

A

Non-polar molecules = insoluble in water

High ratio energy-storing carbon-hydrogen bonds to carbon atoms = good source of energy

Low mass: energy ratio = good storage molecule

High ratio of hydrogen : oxygen atoms, release water when oxidised = source of water

35
Q

How does the structure of phospholipids relate to their properites?

A
  • Polar molecules = form bilayer
  • Hydrophilic heads help to hold at surface of membrane
  • Phospholipid structure allows them to form glycolipids = important in cell recognition
36
Q

How do you test for proteins?

A

Biuret test which detects peptide bond:

  1. Place sample in sodium hydroxide
  2. Add copper sulfate solution and mix
  3. Purple colour indicates presence of peptide bond
37
Q

What is the semi-conservative model in DNA replication?

A

Original DNA molecule split into 2 separate strands
Strands acted as templates

1 old strand, 1 new strand

38
Q

Who proposed evidence for the semi-conservative model?

A

Watson and Crick

39
Q

What was the Meselon and Stahl experiment in semi-conservative replication?

A

Using 2 isotopes of nitrogen - heavy nitrogen 15N and light 14N

  1. Grew E.coli for several generations in each isotope
  2. Cells harvested, DNA isolated, centrifuged.
    - DNA formed separate bands according to densities.
  3. E.coli from 15N moved with 14N
    After 1 generation band in between space formed
40
Q

What is the covalent chemical bond which links 2 amino acids?

A

Disulphide bridge

41
Q

What is a visible similarity between fructose and a-glucose?

A

Both C6H12O6

42
Q

What does hydrophilic mean?

A

Interacts and is attracted to water

43
Q

What does hydrophobic mean?

A

Orients itself away from water

44
Q

What 2 parts is a phospholipid made up of?

A

Hydrophilic head

Hydrophobic tail

45
Q

How do you test for lipids?

A

Emulsion test:

  1. Add ethanol to sample
  2. Shake thoroughly
  3. Add water and shake again
  4. Milky-white emulsion indicated presence of lipid.
46
Q

What would be a suitable control test for the emulsion test?

A

Repeat test but use water instead of sample.

Final solution should remain clear.

47
Q

Why does the cloudy white colour form when testing for a lipid?

A

Lipid in sample being finely dispersed in water to form an emulsion.

Light passing through emulsion is refracted as it passes from oil droplets to water droplets, appearing cloudy.

48
Q

What are the 4 chemical groups in an amino acid?

A

Amino group
Carboxyl group
Hydrogen atom
R group

49
Q

How does amino acids form?

A

Condensation reaction

Combining OH from carboxyl group and H from amino group of another amino acid.

50
Q

What is the link between 2 amino acids called?

A

Peptide bond

Between carbon atoms and nitrogen atom

51
Q

What is the primary structure of a protein?

A

Sequence, type, number of amino acids

52
Q

What is the secondary structure of a protein?

A

Weak hydrogen bonds form.

Causing alpha helix or beta pleated sheet.

53
Q

What is the tertiary structure of a protein?

A

Bonds formed between twisting a-helix:

Disulfide bridges- strong
Ionic bonds- broken by change in pH
Hydrogen bonds- easily broken

54
Q

What is the quaternary structure of a protein?

A

More than one polypeptide chain.

linked in various ways

55
Q

What is the structure and function of fibrous proteins?

A

Can form long chains/ fibres

Insoluble in water

Useful for structure and support

56
Q

What is the structure and function of globular proteins?

A

Spherical and compact

Carry out metabolic functions (enzymes)

57
Q

What is the activation energy?

A

The minimum amount of energy needed to activate the reaction.

58
Q

What is the induced fit model of enzyme action?

A

Enzyme is flexible and can mould itself around substrate.

Enzyme alters shape in presence of substrate.

59
Q

How is the activation energy lowered using the induced fit model?

A

When enzyme changes shape, strain is put on substrate molecule.

Stain distorts a particular bond and lowers activation energy needed to break bond.

60
Q

Why are enzymes effective in tiny quantities?

A

They are not used up in the reaction and so can be used repeatdly.

61
Q

Why would changing one amino acid in the active site prevent the enzyme from functioning?

A

Changed amino acid may no longer bind to substrate.

62
Q

Why would changing certain amino acids that are not part of the active site also prevent the enzyme from functioning?

A

Changed amino acid may be one that forms hydrogen bond with other amino acids.

Could cause change in tertiary structure if hydrogen bond does not form.

63
Q

What is the effect of temperature on enzyme action?

A

Increases kinetic energy
More collisions due to more rapid movement

Too high:
Enzyme denatures, break in hydrogen bonds
Change in tertiary structure/ active site
Rate decreases

64
Q

What is the effect of pH on enzyme action?

A

Away from optimum:
Change in pH alters charges on amino acids
Causes bonds in tertiary structure to break
Changes active site

65
Q

What is the effect of enzyme concentration on the rate of reaction?

A

If substrate is limiting:
rate will stabilise to constant
All available substrate is already being used

If substrate is excess:
increase in rate of reaction

66
Q

What is the effect of substrate concentration on the rate of enzyme action?

A

If enzyme is limiting:
Rate will stabilise to constant
All available substrate is already being used

If enzyme is excess:
Increase in rate of reaction

67
Q

What are competitive inhibitors?

A

Bind to the active site of an enzyme
Inhibitor has complementary shape to active site
Compete with substrate for active site
Inhibitor is not permanent

68
Q

What are non-competitive inhibitors?

A

Bind to allosteric site of enzyme
Inhibitor alters shape of enzyme active site
Substrate can no longer occupy enzyme

69
Q

What is the difference between competitive and non-competitive inhibitors?

A

Competitive:
Bind to active site
E-S complex form when inhibitor release
Increasing substrate concentration, decreases effect

Non-competitive:
Bind to allosteric binding site
Causes permanent change
Increasing substrate concentration has no effect

70
Q

How is a peptide bond formed between 2 amino acids to form a dipeptide?

A

Condensation reaction of 2 amino acids

Between amino group and carboxyl group

71
Q

2 proteins have the same number and type of amino acid but different tertiary structure.
Why?

A

Different sequence of amino acids

Causes hydrogen bonds in different places

72
Q

How do you test for sucrase?

A

Biuret test

Purple colour = positive

73
Q

What is the process of producing a calibration curve?

A
  1. Make maltose solutions of known concentrations and do Benedict test
  2. Use colorimeter to measure value of each solution and plot calibration curve
    X-axis: concentration
    Y-axis: colorimeter reading
  3. Find concentration of sample from calibration curve
74
Q

What are 4 factors that affect enzyme activity?

A
  1. Enzyme concentration
  2. Substrate concentration
  3. Temperature
  4. PH
75
Q

How is a control set up in a practical measuring enzyme activity?

A

Replace enzyme solution with distilled water or boiled enzyme solution

76
Q

How can results of practical measuring enzyme activity be used to find initial rate of reaction?

A

Plot results on graph of ‘rate of reaction’ against ‘time’

Draw tangent at time

77
Q

What is the effect of temperature on enzyme activity?

A

Temperature increases:

  • Kinetic energy increases
  • E-S complexes form
  • Rate of reaction increases up to optimum temperature
78
Q

What happens after temperature reaches optimum and goes beyond that in enzyme activity?

A
  • Enzyme tertiary structure breaks
  • Changes shape of active site
  • Substrate and enzyme no longer complementary
  • Rate of reaction decreases
79
Q

What is the practical method to measuring the effect of concentration of enzyme activity, using trypsin and milk?

A
  1. Place X on bench
  2. Measure 5ml of milk and place in flat bottomed tube
  3. Measure 5ml of 0.25% trypsin
  4. Add trypsin to test tube and time how long it takes for milk to go clear- when X can be seen.
  5. Record time
  • Repeat for all other concentrations of trypsin
  • Repeat each concentration 3 times
80
Q

What is the risk associated with handling enzymes?

A

Low risk
Avoid contact with skin
Wear eye protection

81
Q

How would you make a 1 in 10 dilution using bacteria and sterile liquid and then how would you use that to make a 1 in 1000 dilution of the original liquid culture of bacteria?

A

Add 1 part bacteria to 9 parts sterile liquid to make 10(-1) dilution.

Repeat using 9 parts fresh liquid and 1 part of 10(-1) and 10(-2) dilutions to make 10(-3) dilution.

82
Q

What is a control experiment when testing for starch and why is it important?

A

Disc should be soaked in pure amylase

Show how amylase is responsible for colour change.

83
Q

How do R groups interact to form the tertiary structure of a protein?

A

Some R groups repel

Disulphide bridges between cysteine

Ionic bonds between oppositely charged R groups

Hydrogen bonds

84
Q

What is the Biuret solution?

A

Sodium hydroxide and copper sulfate

Biology (25 decks)

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