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A Level Biology > 1 - Biological Molecules > Flashcards

1 - Biological Molecules Flashcards

1
Q

What is the function of H+ ions

A
  • maintains pH levels in body
  • movement of molecules across cell membranes
  • forms ATP in respiration & photosynthesis
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2
Q

What is the definition of metabolism?

A

The sum of all reactions that occur in an organism

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3
Q

Where are inorganic ions found?

A

in solution in the cytoplasm and body fluids of organisms

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4
Q

What is the function of Fe 2+ (iron) Ions?

A
  • component of haemoglobin
  • transports o2 around the whole body (o2 binds to it)
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5
Q

What is the function of PO4 3- (phosphate) Ions?

A

components of:
- nucleic acids (DNA/RNA)
- ATP
- phospholipids in cell membrane

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6
Q

What is the function of Na+ (sodium) Ions?

A

Co - transport of glucose and amino acids

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7
Q

What are the thermal properties of water

A

HIGH SPECIFIC HEAT CAPACITY:
- buffers changes in temperature

LARGE LATENT HEAT OF VAPORISATION:
- provides a cooling effect through evaporation

  • Good habitat for aquatic organisms as temperature more stable than land
  • Organisms mostly made of water so helps maintain a constant internal body temperature – important as temperature affects enzyme activity
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8
Q

What are the cohesive properties of water?

A

Cohesion: so supports columns of water in plants
- produces surface tension supporting organisms eg pond skaters on water

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9
Q

Describe property of water: solvent

A
  • metabolic reactions can occur
  • allows transport of substances
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10
Q

Describe a condensation reaction

A
  • Joins 2 molecules together
  • releases water
  • Forms a chemical bond e.g. glycosidic bond
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11
Q

Describe a hydrolysis reaction

A
  • Separates 2 molecules
  • uses water
  • Breaks a chemical bond
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12
Q

Describe anabolism

A
  • small to big
  • uses condensation reactions
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13
Q

Describe catabolism

A
  • big to small
  • uses hydrolysis reactions
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14
Q

What are monosaccharides and disaccharides?

A

Simple carbohydrates

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15
Q

What is maltose made up from?

A

Glucose + glucose

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16
Q

What is sucrose made up from?

A

Glucose + fructose

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17
Q

What is lactose made up from?

A

Glucose + galactose

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18
Q

How does a glycosidic bond form?

A

By a condensation reaction between two monosaccharides

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19
Q

Where is the OH in alpha glucose?

A

Below carbon 1

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20
Q

Where is the OH in beta glucose?

A

Above carbon 1

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21
Q

What are examples of polysaccharides?

A

Starch
Cellulose
Glycogen

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22
Q

What is the structure & function of glycogen?

A

F: glucose so provides respiratory substrate for energy release

S:
- polysaccharide of alpha glucose with (1,4) and (1,6) glycosidic bonds
- helical/ coiled/ branched so more ends for faster hydrolysis
- insoluble in water so does not affect water potential

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23
Q

What’s the function of starch?

A

Energy store in plant cells

  • helical = compact for storage in cell
  • insoluble in water
  • can’t leave cell
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24
Q

What’s the structure of starch?

A

Mixture of amylose and amylopectin

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25
Q

What’s the structure of amylose starch?

A
  • (1,4) glycosidic bonds
  • unbranched/linear
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26
Q

What’s the structure of amylopectin starch?

A
  • (1,4) & (1,6) glycosidic bonds
  • branched
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27
Q

What’s the function of cellulose? 6m

A
  • provides strength & structural support to plant cell walls:
  • unbranched/linear
  • long and straight chains
  • beta glucose
  • has crosslinks to form strong fibres
  • Lots of strong H bonds (strong in large numbers & hold chains together)
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28
Q

How are triglycerides formed?

A

By the Condensation of 1 molecule of glycerol and 3 fatty acids, and the removal of 3 molecules of water. Ester bond is formed.

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29
Q

What forms an ester bond?

A

A condensation reaction between glycerol and fatty acid

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30
Q

What are the functions of triglycerides?

A
  • Effective energy stores - have a large number of hydrocarbon chains so rich in energy
  • Insoluble in water so can be stored without affecting the cells water potential 
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31
Q

What is the structure of Phospholipids?

A

One of the fatty acids of the triglyceride is substituted by a phosphate containing group.

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32
Q

What do phospholipids form and why?

A

A bilayer in cell membrane allowing diffusion of small molecules due to its Phosphate heads and fatty acid tails

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33
Q

What are phosphate heads in phospholipids?

A

Polar/hydrophilic = attracted to/ interact with water
So face outwards

34
Q

What are fatty acid tails in phospholipids?

A

Non-polar/hydrophobic = repelled by water
So face inwards

35
Q

What’s the test for starch?

A

Iodine in potassium iodide solution turns blue/black

36
Q

Compare and contrast triglycerides & phospholipids (7m)

A
  • both contain ester bonds
  • triglyceride has 3 fatty acids , phospholipids have 2 + a phosphate group
  • both contain glycerol
  • phospholipids form bilayer but triglycerides don’t
  • fatty acids on both may be saturated or unsaturated
  • both contain C, H, O but phospholipids also contain P
37
Q

What are enzyme cofactors?

A

Enable enzyme controlled reactions to take place e.g. Coenzymes

38
Q

Explain how the active site of an enzyme causes a high rate of reaction/ explain the induced fit model

A
  • lowers activation energy
  • induced fit causes active site to change shape
  • so enzyme substrate complex cause bonds to form/break
39
Q

What is the role of a competitive inhibitor?

A

has a similar shape to the substrate so it binds to the active site & prevents enzyme substrate complexes forming
- (increasing substrate conc reduces effect on inhibitor)

40
Q

What overcomes inhibition in a enzyme?

A

Increased substrate concentration
- there is a greater probability of the substrate successfully colliding

41
Q

What is the role of a non-competitive inhibitor?

A

Binds to a different part of the enzyme (not active site) and changes shape of the active site so active site and substrate no longer complementary so no substrate can fit
OR
- Irreversibly denatures the enzyme (so increasing substrate conc has no effect on ROR)

42
Q

What is the effect of a non-competitive inhibitor?

A

Lowers the amount of enzymes that can do the reaction so rate of reaction decreases

43
Q

What are the factors affecting the rate of enzyme controlled reactions?

A
  • Enzyme concentration
  • substrate concentration
  • pH level
  • temperature
44
Q

How does enzyme concentration affect the rate of reaction?

A

increased rate of reaction as long as there is increased substrate concentration
- higher vmax can be achieved

45
Q

How does substrate concentration affect the rate of reaction?

A

Increasing substrate concentration increases rate of reaction INITIALLY

  • Eventually the rate of reaction will tail off as Vmax is achieved (all active sites are occupied and enzyme cannot work any faster)
46
Q

How does pH affect the rate of reaction?

A
  • affects ionic bonds
  • Highest rate of reaction is at optimum pH of enzyme
  • Extreme pH values denature enzyme permanently
47
Q

How does temperature affect the rate of reaction?

A

Higher temperature = higher rate of reaction (more kinetic energy so more collisions)
- maximum rate is at the enzymes optimum temperature
- above the optimum temperature bonds in tertiary structure start to break

48
Q

What is secondary protein structure made of?

A

hydrogen bonding between amino acids
Causing polypeptide chain to fold into Beta pleated sheets and alpha helixes

49
Q

Describe tertiary protein structure

A

formed by interactions between R groups - H bonds, ionic bonds & disulphide bridges
- gives things their specific 3D shape

50
Q

What are the roles of hydrogen bonds in protein?

A

can form in multiple places and help stabilise the structure

51
Q

Describe ionic interactions in a protein

A
  • Some amino acids have either a positive or negative charge
  • These charges attract the opposite charge & cause folding
52
Q

Describe disulphide bonds/bridges?

A

Covalent bonds that can only form between cysteine amino acids as they contain sulfur

53
Q

Describe quaternary protein structure

A
  • multiple polypeptide chains linked together formed by interactions between different polypeptides
54
Q

What are the roles of ATP?

A

Immediate source of energy:
- releases energy in small manageable amounts so no energy is wasted
- only one bond is hydrolysed (single reaction) to release energy fast

55
Q

Describe the structure of ATP

A

Nucleotide derivative
- 1 molecule of adenine
- ribose
- 3 phosphate groups

CANNOT BE STORED

56
Q

Describe the structure of ADP?

A

The same as ATP minus one phosphate

57
Q

Describe ATP hydrolysis

A

(ATP —> ADP + Pi)
- Catalysed by the enzyme ATP hydrolase
- to provide energy for other reactions
-  to add phosphate to other substances and make them more reactive

58
Q

Describe ATP condensation /synthesis

A

(ADP + Pi —> ATP)
- Catalysed by the same enzyme ATP synthase
- happens during respiration or photosynthesis

59
Q

How many hydrogen bonds do G and C form (in dna)

A

3

60
Q

How many hydrogen bonds do A and T form? (In dna)

A

2

61
Q

What are nucleotides made up of

A
  • a phosphate group
  • a sugar (deoxyribose/ribose)
  • a nitrogenous base (A/T/C/G)
62
Q

How are phosphodiester bonds formed?

A

Condensation between phosphate and deoxyribose

63
Q

3) Describe the Role of DNA polymerase in semi conservative dna replication

A
  • DNA polymerase synthesises new strands from the two parental template strands
  • free nucleotides form hydrogen bonds with their complementary base partner (C to G, A to T)
  • sugar phosphate backbone forms
  • phosphodiester bond is made
64
Q

1) Describe the Role of DNA helicase in semi conservative dna replication

A
  • DNA helicase unwinds the double helix and unzips the two polynucleotide strands
  • hydrogen bonds between complementary base pairs break
65
Q

2) What is a replication fork?

A

the 2 separated DNA strands act as templates for the synthesis of new complementary strands

66
Q

How are all dipeptides similar and different?

A

Similar:
- amine group at the end
- COOH group at the end

Different: different R groups

67
Q

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

A

Condensation reaction between amine and carboxyl

68
Q

What is the structure of DNA (5m)

A
  • polymer of nucleotides
  • each nucleotide formed by deoxyribose, a phosphate group and nitrogenous base
  • Phosphodiester bonds between nucleotides
  • Double helix held by H bonds
  • H bonds between adenine, thymine, guanine and cytosine
69
Q

What is the protein associated with DNA in a chromosome?

A

Histone

70
Q

Name the two scientists who proposed models of the chemical structure of DNA replication?

A

Watson and crick

71
Q

Give two features of DNA and explain how each one is important in semiconservative application

A

1) Weak hydrogen bonds between bases allow two strands to unzip
2) Two strands, so both can act as templates

72
Q

What’s the test for reducing sugars?

A

Benedict’s test - turns brick red

73
Q

What’s the test for non reducing sugars?

A
  • heat with acid and neutralise
  • heat with Benedict’s solution
  • turns red
74
Q

What’s the test for lipids

A
  • add ethanol to the sample and shake
  • add water
  • if it turns to milky emulsion it has lipids
75
Q

What’s the test for proteins?

A

Biuret turns purple

76
Q

Describe water’s High latent heat of evaporation

A
  • H bonds between molecules can absorb a lot of energy before breaking when water evaporates
  • evaporation is good for cooling (sweat) + maintaining body temp
77
Q

What is a monomer

A

A smaller molecule from which larger molecules are made of

78
Q

Describe how monomers join to form the primary structure of a protein

A
  • condensation reaction
  • to form a peptide bond between amino acids
  • primary structure is a sequence of amino acids
79
Q

Describe property of water: metabolite

A

A metabolite in condensation/hydrolysis

80
Q

Explain how differences in the primary structure of haemoglobin can provide evidence of phylogenetic relationships between species (5m)

A
  • mutations change base sequence
  • causing change in amino acid sequence
  • mutations build up over time
  • there are more mutations between distantly related species
  • closely related species have a recent common ancestor
81
Q

Describe primary protein structure

A

The sequence of amino acids in a polypeptide chain
The overall structure is determined by the relative position of R groups

A Level Biology (6 decks)

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