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Biology Y12 > Biological molecules > Flashcards

Biological molecules Flashcards

1
Q

What is a monomer?

A

A small, soluble molecule which can join to other similar monomers

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2
Q

What is a polymer?

A

A large, insoluble molecule which is made up of many similar repeating monomers

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3
Q

Give 3 examples of monomers, their polymers and biological molecules

A
  1. Monomer: monosaccharides
    Polymer: disaccharides/polysaccharides
    Biological molecule: carbohydrates
  2. Monomer: amino acids
    Polymer: polypeptides/proteins
    Biological molecule: proteins
  3. Monomer: nucleotides
    Polymer: polynucleotides
    Biological molecule: DNA/RNA
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4
Q

What is a condensation reaction?

A

A reaction which forms a chemical bond between monomers whilst releasing a water molecule to make a polymer

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5
Q

What is a hydrolysis reaction?

A

A reaction that breaks the chemical bond between monomers whilst adding a water molecule

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6
Q

What is the difference between alpha and beta glucose?

A

The structure (in terms of the far right OH)

Alpha
Below
Beta
Above

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7
Q

What is the chemical formula for disaccharides?

A

C12H22O11 (there are 2 less hydrogen and 1 less oxygen than C12H24O12 because a water molecule is lost during condensation)

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8
Q

Which disaccharide does alpha glucose and alpha glucose form?

A

Maltose (malt sugar)

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9
Q

Which disaccharide does alpha glucose and fructose form?

A

Sucrose

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10
Q

Which disaccharide does alpha glucose and galactose form?

A

Lactose (milk sugar)

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11
Q

What is a polysaccharide?

A

Formed by the condensation of many glucose monomers

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12
Q

What type of bonds do disaccharides/polysaccharides have?

A

Glycosidic bonds

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13
Q

Give 3 examples of polysaccharides

A

Glycogen, starch and cellulose

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14
Q

Which monomers form glycogen, starch and cellulose?

A

Glycogen and starch - alpha glucose
Cellulose - beta glucose

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15
Q

How does the structure of beta glucose change in a condensation reaction?

A

Every other beta glucose molecule is inverted/flipped

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16
Q

How do you test for carbohydrates in REDUCING sugars?

A
  1. Add Benedict’s reagent
  2. Heat at 95°C
  3. Blue to brick-red colour change
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17
Q

How do you test for carbohydrates in NON-REDUCING sugars (sucrose)?

A
  1. Add hydrochloric acid and heat (adds a water molecule so it can be hydrolysed)
  2. Neutralise with sodium hydrogen carbonate
  3. Add Benedict’s reagent
  4. Heat at 95°C
  5. Blue to brick-red colour change
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18
Q

What happens when a chemical test is performed on sucrose?

A

Precipitate formed is twice the mass of the sample

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19
Q

How do you test for carbohydrates in STARCH?

A
  1. Add iodine in potassium iodide
  2. Yellow-brown to blue-black colour change
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20
Q

How is the structure of starch related to its function?

A
  • Branched (glucose hydrolysed more quickly)
  • Helix shape (compact so lots can fit in a small space for storage)
  • Insoluble (doesn’t affect water potential/osmosis)
  • Large molecule (can’t diffuse out of plant cells)
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21
Q

How is the structure of glycogen (animal cells only) related to its function?

A

*Similar to starch (helix, insoluble)
* More highly branched and shorter chains (larger surface area so glucose hydrolysed more quickly)

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22
Q

How is the structure of cellulose related to its function?

A

Many hydrogen bonds - creates crossbridges between chains of cellulose molecules (microfibrils) which make it stronger (structural carbohydrate)

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23
Q

Give 2 examples of lipids

A

Triglycerides and phospholipids

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24
Q

What is the difference between saturated and unsaturated fatty acids?

A

Saturated = single bonds between carbons in long hydrocarbon chain

Unsaturated = double bonds

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25
Q

How are triglycerides formed?

A

By the condensation of one molecule of glycerol and 3 molecules of fatty acids

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26
Q

Why are triglycerides not polymers?

A

Aren’t made up of same repeating monomers

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27
Q

What is this called?

        O
        || OH --- C
A

Carboxylic acid

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28
Q

What types of bonds do triglycerides/phospholipids have?

A

Ester bonds C - O - C

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29
Q

How are phospholipids different to triglycerides?

A

Have a phosphate molecule instead of the 3rd fatty acid

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30
Q

In relation to a phospholipid molecule, what do the terms “hydrophilic” and “hydrophobic” mean?

A

The phosphate head is hydropholic (attracts water) and the fatty acid tails are hydrophobic (repel water) - form a phospholipid bilayer in a cell membrane

31
Q

What is the test for lipids?

A
  1. Crush sample
  2. Add ethanol
  3. Shake
  4. THEN add water
  5. White emulsion obtained if lipid is present
32
Q

What does “R” mean in the structure of a molecule?

A

The rest/the long hydrocarbon chain

33
Q

What is the formula for finding the unknown value for glucose concentration?

A

C1 x V1 (stock) = C2 x V2 (known)

C = concentration
V = volume

34
Q

What elements are amino acids made up of?

A

CHONS

Carbon
Hydrogen
Oxygen
Nitrogen
Sometimes sulfur

35
Q

Draw the general structure of an amino acid

A

H R O
| | ||
N - C - C
| | |
H H OH

36
Q

What is this group called in an amino acid?

H
|
N
|
H

A

Amine group

37
Q

How is a dipeptide formed?

A

By the condensation of 2 amino acids

38
Q

Which type of bonds do dipeptides/polypeptides have?

A

Peptide bonds C - N

39
Q

What is the primary structure of protein?

A

Amino acid sequence in protein

40
Q

Why is the primary structure of protein so important?

A

Determines the rest of the structure

41
Q

What is the secondary structure of protein?

A

Held together by hydrogen bonds between carboxyl and amine groups (alpha helix and beta pleated sheet)

42
Q

What is the tertiary structure of protein?

A

Compact globular structure formed by the folding of a whole polypeptide chain. Held together by hydrogen, ionic and di-sulfide bonds between the R groups

43
Q

What is the quaternary structure of protein?

A

More than one polypeptide chain

44
Q

What does the shape of a protein determine?

A

Its function

45
Q

What is the biochemical test for proteins?

A
  1. Mix Biuret solution with the sample
  2. Solution will turn from blue to purple if protein is present (only works with proteins, not amino acids)
46
Q

What happens when proteins denature?

A

Lose their specific 3D tertiary structure (hydrogen, ionic and di-sulfide bonds are broken)

47
Q

What are enzymes?

A

Globular proteins which act as biological catalysts by providing an alternative reaction pathway with lower activation energy

48
Q

How are enzymes specific?

A

Have a specific 3D tertiary structure which is specific to one substrate so they form enzyme-substrate complexes

49
Q

How do enzymes increase rate of reaction?

A

Lower activation energy

50
Q

What is the lock and key hypothesis?

A

That the shape of the active site is exactly complementary to the shape of the substrate molecule

51
Q

What is the induced fit hypothesis?

A

The active site changes shape slightly to fit the substrate which forms an enzyme-substrate complex. As it changes the enzyme puts strain on the substrate molecule which puts stress on a bond and lowers the activation energy needed to break the bond

52
Q

What is a competitive inhibitor?

A

Similar in shape to the substrate and temporarily blocks the enzyme’s active site so less enzyme-substrate complexes can form

53
Q

What is a non-competitive inhibitor?

A

Permanently binds to the enzyme (but not at the active site) and changes the shape of the active site so it is no longer complementary to its substrate so no enzyme-substrate complexes can form

54
Q

What 3 things make up the structure of a DNA nucleotide?

A

Nitrogenous base, deoxyribose sugar, phosphate group

55
Q

Which elements are DNA nucleotides made up of?

A

CHOPN

Carbon
Hydrogen
Oxygen
Phosphorus
Nitrogen

56
Q

Which bases are single/double ring?

A

Single = thymine, cytosine
Double = adenine, guanine

57
Q

What are the base pairing rules?

A
  1. Adenine always pairs with thymine by 2 hydrogen bonds
  2. Cytosine always pairs with guanine by 3 hydrogen bonds
58
Q

Which type of bonds do dinucleotides/polynucleotides have?

A

Phosphodiester bonds O - P

59
Q

How is DNA a long, stable molecule?

A

Has a strong sugar-phosphate backbone

60
Q

Describe the structure of DNA

A
  • Strands run in opposite directions (anti-parallel)
  • Ladder twists to form double helix
61
Q

How does RNA differ from DNA?

A
  • Single chain
  • Shorter strands
  • Thymine replaced by URACIL
  • RIBOSE sugar instead of deoxyribose
62
Q

What is the triplet code?

A
  • Gene = DNA base sequence that codes for a polypeptide/functional RNA
  • Triplet = 3 DNA bases code for 1 amino acid
63
Q

What were the names of the scientists who studied the structure of DNA?

A

Watson and Crick

64
Q

Why is DNA replication semi-conservative?

A

Each new DNA molecule contains one strand from the ORIGINAL molecule and one NEW strand

65
Q

What are the 4 steps of semi-conservative replication?

A
  1. Double helix unwinds
  2. DNA helicase separates 2 strands (hydrogen bonds between bases broken)
  3. New nucleotides attracted to exposed complementary bases on template strand (hydrogen bonds form)
  4. DNA polymerase joins adjacent nucleotides using condensation reaction (forms sugar-phosphate backbone joined by phosphodiester bonds)
66
Q

How do you remember what the 2 enzymes do in semi-conservative replication?

A

DNA Helicase = breaks Hydrogen bonds

DNA Polymerase = forms Phosphodiester bonds

67
Q

What is the evidence for semi-conservative replication?

A

Gen 0: 15N/15N (heavy)

Gen 1: 14N/15N (hybrid)

Gen 2: hybrid and 14N/14N (light)

Gen 3: same as gen 2

68
Q

What 3 things make up an ATP nucleotide?

A

Adenine, ribose sugar and 3 phosphate groups

69
Q

How is energy stored in ATP released?

A

High energy bond between last 2 phosphate groups is hydrolysed which releases energy

70
Q

How is ATP broken down and reformed?

A

Respiration –> ATP –> ATP hydrolase –> energy for active transport, mitosis etc. –> ADP + Pi (inorganic phosphate used to make molecules more reactive - phosphorylation) –> ATP synthase –> respiration/energy

71
Q

Why is ATP useful?

A
  • Contains energy stored in phosphate bond
  • Hydrolysis of ATP can be coupled with energy-requiring reactions within cells (active transport, mitosis)
  • Inorganic phosphate released makes molecules more reactive
72
Q

What is an inorganic ion?

A

An ion which doesn’t contain carbon e.g. H+ used for CO2/O2 transport, PO4(3-) used for ATP/DNA

73
Q

Why is water important biologically?

A
  • Polar solvent - dissolves polar molecules/ions
  • Polar molecule - hydrogen bonds allow cohesion/transport of water through system
  • High specific heat capacity - temp. of cytoplasm doesn’t fluctuate much
  • Low latent heat of vapourisation - allows cooling effect (sweating)

Biology Y12 (13 decks)

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