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Biology > 2.2 Biological molecules > Flashcards

2.2 Biological molecules Flashcards

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1
Q

What is a condensation reaction?

A

When two molecules are joined together with the removal of water

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2
Q

What is a hydrogen bond?

A

A weak interaction between a slightly negatively charged atom and a slightly positively charged

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3
Q

What is hydrolysis reation?

A

When a moleculre is split into two smaller molecules with the addition of water

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4
Q

What is a monomer?

A

a small molecule which binds to many other identical molecules to form a polymer

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5
Q

What is a polymer?

A

a larger molecule made from many smaller molecules called monomers

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6
Q

What are the monomers of proteins?

A

Amino acids

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7
Q

What are the polymers of monosaccharides?

A

polysaccharides

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8
Q

What are the monomers of DNA and RNA?

A

Nucleotides

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9
Q

What type of bond is represented by a single line?

A

Covalent bond

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10
Q

What type of bond is represented by a dasehed line?

A

Hydrogen bond

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11
Q

Is water a good solvent or solute?

A

solvent

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12
Q

What causes cohesion in water

A

hydrogen bonds

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13
Q

What allows organisms to float

A

the density of water

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14
Q

why does water take a lone time to heat up

A

A high specific heat capacity

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15
Q

Waters high specific heat capacity creates a …………. Enviroment

A

stable

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16
Q

Waters high latent heat vaporisation allows plants to do what in summer

A

cool themselves by evaporation

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17
Q

Is ice less or more dense than water?

A

less

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18
Q

Why is water slow to heat up or cool down?

A

It has a high specific heat capacity

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19
Q

Insect can walk on water because of?

A

surface tension

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20
Q

What property of water allows it to be an excellent transport medium?

A

it is a liquid

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21
Q

What are larger complex carbohydrates made from?

A

Monosaccharides

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22
Q

What are the common monosaccharides?

A

Glucose, galactose and fructose

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23
Q

What reaction forms the bond between two monosaccharides?

A

A condensation reaction.

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24
Q

What bond forms when monosaccharides join

A

A glycosidic bond.

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25
Q

What is a disaccharide?

A

A molecule made from 2 monosaccharides

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26
Q

How is a disaccharide formed?

A

A condensation reaction between 2 monosaccharides

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27
Q

What is maltose and what is it formed from?

A

A disaccharide formed from the consation reaction between 2 glucose molecules.

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28
Q

What is sucrose and what is it formed from?

A

A disaccharide formed from the consation reaction between a glucose and a fructose molecule.

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29
Q

What is lactose and what is it formed from?

A

A disaccharide formed from the condensation reaction between glucose and a galactose molecule.

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30
Q

What is an isomer?

A

A variation of a particular molecule. The formula stays the same, but the structure is slightly different.

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31
Q

How many carbon atoms in a ribose sugar?

A

5

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32
Q

How is a deoxyribose surar different to a ribose sugar?

A

It has 1 less oxygen, on carbon 2

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33
Q

What is a polysaccharide?

A

A complex carbohydrate formed from the condensation reactions of many monosaccharides.

34
Q

What is glycogen and what is it made of?

A

A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.

35
Q

What is starch and what is it formed from?

A

A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.

36
Q

What are the two types of polysaccharides that make up starch?

A

Amylose and amylopectin

37
Q

What is the purpose of glycogen?

A

It is an insoluble store of energy in animals.

38
Q

What is the purpose of starch?

A

It is an insoluble store of energy in plants, and an energy source for animals

39
Q

How is amylopectin different from amylose?

A

It is branched

40
Q

What is the structure of glycogen?

A

Heavily branched polymer of α-glucose molecules. Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.

41
Q

how is glycogen’s structure related to its function

A

insoluble so no osmosis/insoluble so does not diffuse out of cells/compact so lots stored in small space/highly branched so can be acted on simultaneously by enzymes

42
Q

What is the structure of starch?

A

Lightly branched polymer of α-glucose molecules. Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.

43
Q

how is starch’s structure related to its function

A

insoluble so doesn’t affect water potential and no osmosis/large so doesn’t diffuse out of cells/compact so lots stored in small space/hydrolysed to form a-glucose so easily transported and used for respiration/branched so more enzymes can act simultaneously

44
Q

Where are the branches formed on the amylopectin molecule?

A

between carbons 1 and 6

45
Q

What is cellulose?

A

A complex carbohydrate, a polysaccharide made from multiple β-glucose molecules.

46
Q

What is the purpose of cellulose?

A

It is an insoluble structural molecule for plants, especially for their cell walls.

47
Q

What is the basic structure of cellulose?

A

Straight lengths of polymers made of β-glucose molecules. Bonded with 1,4 glycosidic bonds.

48
Q

How are the monosaccharides in cellulose arranged?

A

down

49
Q

how is cellulose’s structure related to its function

A

made up of B-glucose so form long, straight unbranched chains/chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength/molecules are grouped to form microfibrils which are also grouped to form fibres which provides more strength

50
Q

Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.

A 
"- cellulose molecules form hydrogen bonds with each other to make microfibrils
- microfibrils join to make macrofibrils
- macrofibrils join to make fibres
- fibres are insoluble and tough
"
51
Q

What type of reaction forms cellulose

A

condensation

52
Q

Which polysaccharide makes up exoskeletons of insects and crustaceans?

A

Chitin

53
Q

Which polysaccharide makes up the cell walls of bacteria?

A

peptidoglycan

54
Q

What is added to the macrofibril structures to make them waterproof?

A

waxes

55
Q

Contrast saturated and unsaturated fatty acids.

A

Saturated:
● contain only single bonds
● straight-chain molecules have many contact points
● higher melting point = solid at room temperature
● found in animal fats

Unsaturated: ● contain C=C double bonds
● ‘kinked’ molecules have fewer contact points
● lower melting point = liquid at room temperature
● found in plant oils

56
Q

Relate the structure of triglycerides to their functions.

A

● High energy:mass ratio = high calorific value from oxidation (energy storage).
● Insoluble hydrocarbon chain = no effect on water potential of cells & used for waterproofing.
● Slow conductor of heat = thermal insulation e.g. adipose tissue.
● Less dense than water = buoyancy of aquatic animals.

57
Q

Describe the structure and function of phospholipids

A

Amphipathic: glycerol backbone attached to 2 hydrophobic fatty acid tails & 1 hydrophilic polar phosphate head.
● Forms phospholipid bilayer in water = component of membranes.
● Tails can splay outwards = waterproofing e.g. for skin.

58
Q

Are phospholipids and triglycerides polymers?

A

No; they are not made from a small repeating unit. They are macromolecules.

59
Q

Describe the structure and function of cholesterol.

A

Steroid structure of 4 hydrocarbon rings. Hydrocarbon tail on one side, hydroxyl group (-OH) on the other side.
Regulates the fluidity of the plasma membrane.

60
Q

What is the general structure of an amino acid?

A
  • COOH carboxyl / carboxylic acid group.
  • R variable side group consists of carbon chain & may include other functional groups e.g. benzene ring or -OH (alcohol)
  • NH2amine/ amino group.
61
Q

How do polypeptides form?

A

Condensation reactions between amino acids form peptide bonds (-CONH-).There are 4 levels of protein structure.

62
Q

Define primary and secondary structure of a protein.

A

Primary: sequence, number & type of amino acids in the polypeptide, determined by sequence of codons on mRNA.
Secondary: hydrogen bonds form between O 𝛿- attached to ‒C=O & H 𝛿+ attached to ‒NH.

63
Q

Describe the 2 types of secondary protein structure

A

α-helix:
● All N-H bonds on same side of protein chain.
● Spiral shape.
● H-bonds parallel to helical axis.
β-pleated sheet:
● N-H & C=O groups alternate from one side to the other.

64
Q

Define ‘tertiary structure’ of a protein. Describe the bonds present.

A

3D structure formed by further folding
●Disulfide bridges: strong covalent S-S bonds between molecules of the amino acid cysteine.
●Ionic bonds: relatively strong bonds between charged R groups (pH changes cause these bonds to break).
●Hydrogen bonds: numerous & easily broken

65
Q

Define ‘quaternary structure’ of a protein.

A

● Functional proteins may consist of more than one polypeptide.
● Precise 3D structure held together by the same types of bond as tertiary structure.
● May involve addition of prosthetic groups e.g metal ions or phosphate groups.

66
Q

Describe the structure and function of globular proteins

A

● Spherical & compact.
● Hydrophilic R groups face outwards & hydrophobic R groups face inwards = usually water-soluble.
● Involved in metabolic processes e.g. enzymes such as amylase, insulin (2 polypeptide chains linked by 2 disulfide bonds), haemoglobin.

67
Q

Describe the structure of haemoglobin.

A

● Globular conjugated protein with prosthetic group.
● 2 𝛼-chains, 2 𝛽-chains, 4 prosthetic haem groups.
● Water-soluble so dissolves in plasma.
● Fe2+ haem group forms coordinate bond with O2.
● Tertiary structure changes so it is easier for subsequent O2 molecules to bind (cooperative binding).

68
Q

Describe the structure and function of fibrous proteins.

A

● Can form long chains or fibres.
● Insoluble in water.
● Useful for structure and support e.g. collagen in skin.

69
Q

List the functions of collagen, elastin and keratin

A

Collagen: component of bones, cartilage, connective tissue, tendons.
Elastin: provides elasticity to connective tissue, arteries, skin, lungs, cartilage, ligaments.
Keratin: structural component of hair, nails, hooves/ claws, horns, epithelial cells of outer layer of skin.

70
Q

Describe how to test for proteins in a sample

A

Biuret test confirms presence of peptide bond

  1. Add equal volume of sodium hydroxide to sample at room temperature.
  2. Add drops of dilute copper (II) sulfate solution. Swirl to mix. (steps 1 & 2 make Biuret reagent).
  3. Positive result: colour changes from blue to purple Negative result: solution remains blue.
71
Q

Describe how to test for lipids in a sample

A
  1. Dissolve solid samples in ethanol.
  2. Add an equal volume of water and shake.
  3. Positive result: milky white emulsion forms
72
Q

Describe how to test for reducing sugars.

A
  1. Add an equal volume of Benedict’s reagent to a sample.
  2. Heat the mixture in an electric water bath at 100°C for 5 mins.
  3. Positive result: colour changes from blue to orange & brick-red precipitate forms.

Or use test strip coated in a reagent that changes colour if reducing sugar is present.

73
Q

Describe the Benedict’s test for non-reducing sugars.

A
  1. Negative result: Benedict’s reagent remains blue.
  2. Hydrolyse non-reducing sugars e.g. sucrose into their monomers by adding 1cm3 of HCl. Heat in a boiling water bath for 5 mins.
  3. Neutralise the mixture using sodium carbonate solution.
  4. Proceed with the Benedict’s test as usual
74
Q

Describe the test for starch

A
  1. Add iodine solution.

2. Positive result: colour changes from orange to blue-black.

75
Q

State the role and chemical symbol of nitrates and ammonium.

A

NO3-is used to make DNA, amino acids, NADP for photosynthesis & NAD for respiration.NH4+ can be converted to NO3- by saprobionts during nitrogen cycle. Produced by deamination of amino acids during ornithine cycle in liver

76
Q

State the role and chemical symbol of hydroxide and phosphate ions.

A

OH- ions affect pH & can interact with bonds in 3° protein structure to cause denaturation.PO43-is a component of ATP/ ADP for energy release & NADP.

77
Q

State the role and chemical symbol of sodium, potassium and chloride ions.

A

Na+ & K+ are involved in maintenance of resting potential of neurons/ generation of action potentials. Na+ is also involved in co-transport mechanisms.

Cl- is involved in inhibitory synapses to cause hyperpolarisation.

78
Q

State the role and chemical symbol of hydrogen and hydrogencarbonate ions

A

H+ & HCO3- form in organisms when CO2 dissolves in water.

H+ regulates pH & can interact with bonds in 3° protein structure to cause denaturation. H+ pump is involved in chemiosmosis & active loading in translocation.

79
Q

State the role and chemical symbol of calcium ions

A

Ca2+ is used to make calcium pectate to add stability to middle lamella of plant cell walls. Regulates exocytosis of neurotransmitter. Binds to troponin to stimulate muscle contraction.

80
Q

How can the concentration of a solution be measured quantitatively

A

● Use colorimetry to measure absorbance/ %transmission. Interpolate a calibration curve from solutions of known concentration.
● Use biosensors. A bioreceptor detects the presence of a chemical. A transducer converts the response into a detectable electrical signal

81
Q

Outline the principles and process of paper/ thin-layer chromatography.

A
  1. Use capillary tube to spot solution onto pencil ‘start line’ (origin) 1 cm above bottom of paper.
  2. Place chromatography paper in solvent. (origin should be above solvent level).
  3. Allow solvent to run until it almost touches other end of the paper. Molecules in mixture move different distances based on relative solubility in solvent/attraction to paper.
82
Q

What are Rf values? How can they be calculated?

A

Ratios that allow comparison of how far molecules have moved in chromatograms.

Rf value = distance between origin and centre of pigment spot / distance between origin and solvent front

Biology (15 decks)

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