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Alevel Biology OCR > 2.1.2 - Biological Molecules > Flashcards

2.1.2 - Biological Molecules Flashcards

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1
Q

What are the roles of water?

A
  • solvent
  • transport medium
  • coolant
  • habitat
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2
Q

What are the properties of water?

A
  • floats as ice
  • is polar and can form H-bonds (so can be a solvent and can undergo cohesion and adhesion)
  • thermally stable
  • metabolic
  • liquid at room temp
  • transparent
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3
Q

Why is the fact water floats as ice beneficial for organisms?

A
  • provides a habitat (eg. for polar bears, penguins, etc)

- forms an insulating layer so animals in water below don’t freeze

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4
Q

Why is the fact water is polar and can form hydrogen bonds beneficial for organisms?

A
  • polar substances can be dissolved in it
  • useful for transport
  • cohesion and tension allows water to move up the xylem in plants
  • water’s cohesion gives water a surface tension, making it a habitat (eg. pond skaters)
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5
Q

Why is the fact water is thermally stable beneficial for organisms?

A

-provides a constant environment for organisms

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6
Q

Why is the fact water is metabolic beneficial for organisms?

A

-can be used in rxns like photosynthesis and hydrolysis rxns

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7
Q

Why is the fact water is a liquid at room temperature beneficial for organisms?

A
  • can transport substances
  • organisms can live in it
  • less dense organisms can float
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8
Q

Why is the fact water is transparent beneficial for organisms?

A

-sunlight can reach organisms in shallow water so they can still photosynthesise

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9
Q

What is a polymer?

A

a molecule made up of many similar, smaller, repeating molecules (monomers) bonded together

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10
Q

What are monosaccharides?

A

the monomers that make up carbohydrates

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11
Q

What are the two types of glucose?

A

alpha glucose

beta glucose

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12
Q

What elements are all carbohydrates made up of?

A

carbon
hydrogen
oxygen

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13
Q

What are the 4 biological molecules?

A

water
carbohydrates
lipids
protein

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14
Q

What are the properties and structure of glucose?

A
  • hexose monosaccharide (6 carbons)
  • ring structure
  • > makes it soluble so can easily be transported
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15
Q

What bonds join monosaccharides?

A

glycosidic bond

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16
Q

What are disaccharides?

A

two monosaccharides bonded together

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17
Q

What is a condensation reaction?

A

a reaction that joins smaller molecules together by forming a covalent bond(s) to form one larger molecule
water molecule is released

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18
Q

What is a hydrolysis reaction?

A

a reaction that uses a water molecule to break a covalent bond to form smaller molecules from a larger one
(opposite to condensation reaction)

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19
Q

What is a polysaaccharide?

A

a long chain of monosaccharides

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20
Q

Which two monosaccharides form maltose?

A

α-glucose and α-glucose

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21
Q

Which two monosaccharides form sucrose?

A

α-glucose and fructose

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22
Q

Which two monosaccharides form lactose?

A

α-glucose/β-glucose and galactose

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23
Q

Give three types of polysaccharide.

A

starch
cellulose
glycogen

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24
Q

What are the two types of starch?

A

amylose

amylopectin

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25
Q

What is the structure of amylose? (And how does that help it with its function?)

A
  • long, unbranched chain of α-glucose
  • coiled structure (compact - good for storage)
  • insoluble in water (doesn’t cause water to enter cells via osmosis)
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26
Q

What is the structure of amylopectin? (And how does that help it with its function?)

A
  • long, branched chain of α-glucose (side branches allow enzymes to get at the glycosidic bond easily so that glucose can be released easily)
  • insoluble in water (doesn’t cause water to enter cells via osmosis)
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27
Q

How do plants store excess glucose?

A 
as starch 
(when a plant needs more glucose for energy it breaks down the starch to release energy)
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28
Q

How do animals store excess glucose?

A

as glycogen

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29
Q

What is the structure of glycogen? (And how does that help it with its function?)

A

long, branched structure -similar to amylopectin but with more branches (useful for energy release)

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30
Q

What is cellulose?

A

the major component of cell walls in plants

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31
Q

What is the structure of cellulose?

A
  • long, unbranched chains of beta-glucose
  • straight, parallel cellulose chains
  • cellulose chains are linked together by hydrogen bonds which form strong fibres called microfibrils (these provide structural support for the cells)
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32
Q

What are reducing sugars?

A

sugars that donate electrons or reduce another molecule

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33
Q

How do you test for reducing sugars?

A
  • add Benedict’s solution (alkaline solution of copper II sulphate)
  • heat in water bath
    positive: brick red (precipitate)
    negative: blue
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34
Q

How does the Benedict’s test work?

A

reducing sugars reduce the copper ions (give electrons to Cu2+)

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35
Q

How do you test for non-reducing sugars?

A
  • boil with dilute hydrochloric acid
  • neutralise with sodium hydrogen carbonate
  • repeat Benedict’s test (add benedicts and heat in water bath)
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36
Q

How do you test for starch?

A
  • add iodine
    positive: blue/black
    negative: yellow/brown
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37
Q

What are amino acids?

A

the monomers that make up proteins

38
Q

What is a dipeptide?

A

two amino acids bonded together by a peptide bond

39
Q

What is a polypeptide?

A

(a protein)

several amino acids bonded together

40
Q

What elements are proteins made up of?

A 
carbon
hydrogen
oxygen
nitrogen
sulphur
41
Q

What bond joins amino acids?

A

peptide bond

42
Q

What happens when two amino acids are joined?

A

amine group (H2N) joins to the carboxyl group (COOH)
water molecule is released
peptide bond is formed
occurs in a condensation reaction

43
Q

What properties do globular proteins have?

A
  • compact and roughly spherical
  • have hydrophilic R-group on the outside of the molecule, making them water soluble
  • have a tertiary structure
44
Q

What are conjugated proteins?

A

globular proteins that contain a prosthetic group (a non-protein component)

45
Q

Name some examples of globular proteins

A

haemoglobin
insulin
catalse

46
Q

What is haemoglobin? And what properties does it have?

A

the red pigment in red blood cells which carries oxygen around the body
globular protein
-made from 4 polypeptide chains (2α and 2β subunits)
-each subunit has a haem prosthetic (iron) making a conjugated protein

47
Q

What is insulin? And what properties does it have?

A

hormone involved in blood glucose concentration regulation
globular protein
-soluble (needs to be transported in blood)
-has 2 polypeptide chains held by disulfide bonds

48
Q

What is catalase? And what properties does it have?

A

an enzyme that catalyses the breakdown of hydrogen peroxide (can be dangerous)
globular protein
-has 2 haem prosthetic groups

49
Q

What properties do fibrous proteins have?

A
  • strong, long molecules (not folded into complex shapes)
  • contains lots of hydrophobic R-groups, making it insoluble
  • flexible
50
Q

Name some examples of fibrous proteins

A

collagen
keratin
elastin

51
Q

What is collagen? And what properties does it have?

A

found in connective tissues (eg. skin, tendons, bone, etc)

  • contains 3 polypeptide chains in a triple helix
  • very strong and tightly packed (due to hydrogen bonds between chains in helix)
  • hydrogen bonds can bond multiple collagens together
52
Q

What is keratin? And what properties does it have?

A

present in hair, nails, skin, etc

  • amount of disulfide bonds affect its structure:
    • lots of disulfide bonds = hard and tough (eg. nails)
    • not many disulfide bonds = flexible (eg. hair)
53
Q

What is elastin? And what properties does it have?

A

found in elastic fibres (eg. blood vessels, alveoli in lungs, etc)
-has ability to stretch and expand and then go back to its normal shape

54
Q

What elements are lipids made up of?

A

carbon
hydrogen
oxygen

55
Q

What elements are nucleic acids made up of?

A 
carbon
hydrogen
oxygen
nitrogen
phosphorus
56
Q

How do you test for proteins?

A

-add biuret reagent (mixture of sodium hydroxide and copper sulphate)

positive: blue
negative: lilac

57
Q

What are the levels of protein structure?

A
  • primary
  • secondary
  • tertiary
  • quaternary
58
Q

What is the primary structure of a protein?

A

the sequence of amino acids

  • involves peptide bonds
  • directed by DNA
  • influences how polypeptide folds
59
Q

What bond(s) are involved in the primary structure of a protein?

A

peptide bonds

60
Q

What is the secondary structure of a protein?

A

the folding of the amino acid chain
either:
-alpha helix (coiled)
-beta pleated sheet (folded)

61
Q

What bond(s) are involved in the secondary structure of a protein?

A

hydrogen bonds

62
Q

What is the tertiary structure of a protein?

A

the folding of the protein into its final shape

-involves hydrophilic/hydrophobic interactions, hydrogen bonds, ionic bonds and/or disulfide bridges

63
Q

What bond(s) are involved in the tertiary structure of a protein?

A
  • hydrophilic/hydrophobic interactions
  • hydrogen bonds
  • ionic bonds
  • disulfide bridges
64
Q

What is the quaternary structure of a protein?

A

when several polypeptide chains (units) are joined together

-doesn’t happen in all proteins

65
Q

What bond(s) are involved in the quaternary structure of a protein?

A
  • hydrophilic/hydrophobic interactions
  • hydrogen bonds
  • ionic bonds
  • disulfide bridges
66
Q

What are the uses of proteins?

A
  • enzymes
  • hormones
  • antibodies
  • transport (carrier/channel proteins in cell membranes)
  • growth
  • repair
67
Q

What is the general structure of an amino acid?

A
  • amine group (NH2)
  • carboxy group (COOH)
  • variable group
68
Q

What are fatty acids made up of?

A

a carboxylate group and a hydrocarbon chain

69
Q

What is a saturated fatty acid?

A

a fatty acid with no double bonds between carbon atoms

70
Q

What is an unsaturated fatty acid?

A

a fatty acid with double bonds between carbon atoms
-C=C bonds cause a “kink” in the hydrocarbon chain, meaning the fatty acids can’t pack so closely together (hence, are often liquid at room temp)

71
Q

What is a triglyceride made of?

A

three fatty acids bonded to one glycerol molecules

72
Q

How is a triglyceride formed?

A

in an esterification (condensation) rxn

-OH of glycerol reacts with OH of fatty acid to form an ester bond and release a molecule of water

73
Q

What is a phospholipid made up of?

A

two fatty acids and one phosphate group bonded to a glycerol molecule

74
Q

What are the hydrophobic/hydrophilic properties of phospholipids?

A
  • phosphate head is hydrophilic
  • fatty acid tails are hydrophobic
  • molecule is generally insoluble in water
  • can form a bilayer
75
Q

What are sterols?

A

lipids with a four carbon ring structure with a hydroxy group

  • hydroxy group is polar and hydrophilic but the rest of the molecule is hydrophobic
    eg. cholesterol
76
Q

What is cholesterol?

A

a sterol made in the liver which is found in biological membranes to make the membranes more rigid/less fluid by binding to the hydrophobic tails of phospholipids so that they pack more closely together

77
Q

How do you test for lipids?

A

via the emulsion test

  • mix sample with ethanol (causes it to dissolve)
  • then mix sample with water (causes it to precipitate

positive: cloudy
negative: clear

78
Q

What ions are involved in biological processes?

A 
Ca2+
Na+
K+
H+
NH4 +
NO3 -
HCO3 -
Cl-
PO4 3-
OH-
79
Q

How can biological molecules be separated?

A

by paper or thin layer chromatography

80
Q

Rf =

A

distance moved by solute
_____________________
distance moved by solvent

81
Q

How can the concentration of a substance in a solution be measured quantitatively?

A
  • using a colorimeter

- using a biosensor

82
Q

What are calcium ions used for in living organisms?

A
  • nerve impulse transmission

- muscle contraction

83
Q

What are sodium ions used for in living organisms?

A
  • nerve impulse transmission

- kidney function

84
Q

What are potassium ions used for in living organisms?

A
  • nerve impulse transmission

- stomatal opening

85
Q

What are hydrogen ions used for in living organisms?

A
  • catalysing reactions

- determining pH

86
Q

What are ammonium ions used for in living organisms?

A

-producing nitrate ions (by bacteria)

87
Q

What are nitrate ions used for in living organisms?

A
  • supplying nitrogen to plants

- amino acid and protein formation

88
Q

What are chloride ions used for in living organisms?

A

-balancing charge of Na+ and K+ ions in cells

89
Q

What are phosphate ions used for in living organisms?

A
  • cell membrane formation
  • nucleic acid and ATP formation
  • bone formation
90
Q

What are hydroxide ions used for in living organisms?

A
  • catalysing reactions

- determining pH

Alevel Biology OCR (26 decks)

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