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A Level Biology > Biological Molecules (and water) > Flashcards

Biological Molecules (and water) Flashcards

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1
Q

Intramolecular bonds vs intermolecular bonds

A

Intra - within molecules

Inter - between molecules

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2
Q

Dipolar def

A

Molecule contains a pair of equal and opposite electric charges separated by a small distance

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3
Q

Lower case delta sign

A

Signifies a small amount of charge

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4
Q

What is the intermolecular bond in water?

A

Hydrogen bonds

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5
Q

What are the properties of hydrogen bonds?

A

1/10th the strength of a covalent bond (quite weak), but occur in huge numbers

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6
Q

Explain the water coin test

A

The coin was able to hold more drops of water compared to drops of ethanol. This is because water has stronger intermolecular forces called hydrogen bonds as it is dipolar meaning they stick together more?

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7
Q

Specific heat capacity of water + def

A

(Amount of heat energy needed to heat 1kg of a substance by 1°C). Water has a high shc

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8
Q

Specific latent heat of water + def

A

(Amount of heat energy needed to convert water into water vapour) has a LARGE latent heat of vapourisation

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9
Q

Structure of a water molecule

A

Has a permanent dipole. Hydrogen atoms have a slight positive charge because oxygen is more electronegative and therefore attracts the electrons giving is a slight negative charge

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10
Q

Properties of water

A

High specific heat capacity, large latent heat of vaporisation, high cohesion and surface tension, transparent, high density compared to air and ice

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11
Q

Water as thermostable

A

Water has a small temperature range meaning aquatic organisms can survive. Hydrogen bonds restrict movement causing them to resist an increase in kinetic energy. The high specific heat capacity causes a buffer in temperature changes. Oceans and cells have a stable environment

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12
Q

Cohesion in water + def + eg

A

(Sticking together of particles of the same substance). High cohesion due to hydrogen bonding and polarity (The intermolecular forces between the slightly positively charged end of one molecule to the negative end of another or the same molecule). Attracted to each other and so stick together e.g. water in the xylem

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13
Q

Surface tension in water + eg

A

When water molecules meet air, they tend to be pulled back to the body of water. Acts like a skin. Strong enough to support pond skaters

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14
Q

Importance of water

A

Metabolism, solvent, evaporation, support, transparent, mechanical support and buoyancy

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15
Q

Water in metabolism

A

Breaks down complex molecules in hydrolysis e.g. proteins into amino acids, used in chemical reactions, reactant in photosynthesis and hydrolysis, product in aerobic respiration and condensation

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16
Q

Water as a solvent

A

Many substances dissolve in water, readily dissolves gases e.g. oxygen and carbon dioxide, wastes e.g. urea and ammonia, inorganic ions, small hydrophilic molecules e.g. amino acids, monosaccharides and ATP

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17
Q

Hydrophilic molecules def, exp, eg and properties

A

Water loving - ions or polar molecules attracted to water molecules. The water molecules are attracted to the positive/negative charges of the ion and surround it, carrying it into solution. E.g. Salt, ions, amino acids. Dissolve readily in water

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18
Q

Hydrophobic molecules def, exp, eg and properties

A

Water fearing - consist of non-polar bonds meaning water is not attracted to it. Water molecules don’t surround them on surface and therefore don’t carry them into solution. E.g. Oil, fat, hormones like testosterone. Insoluble in water

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19
Q

Water in evaporation

A

Due to a large latent heat of evaporation, water has a cooling effect. For example, in sweating, water evaporates off the skin, and with it, takes heat energy away from the body. This aids in thermoregulation as the body temperature can be controlled

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20
Q

How do hydrogen bonds form?

A

In every water molecule, there are two pairs of lone electron that are not involved in the covalent bonds. These are negatively charged and therefore attract the slightly positively charged hydrogen atoms from other water molecules to form hydrogen bonds, without which water would be a gas

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21
Q

Water used as support

A

Water is a liquid which cannot be easily compressed. This means that it is used in hydrostatic skeletons of organisms such as earthworms and also keeps turgor pressure in herbaceous plants

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22
Q

Water being transparent

A

Light is able to travel through the water due to its transparency. This means that aquatic plants underwater are able to photosynthesise. Moreover, there is a jelly-like fluid in the eye which enables light rays to be able to penetrate and reach the retina

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23
Q

Water as mechanical support and buoyancy

A

Since ice is less dense than water, it floats and forms on the top surface of the water. This means that aquatic organisms below are still able to move. Moreover, the ice acts as a insulator so it keeps the heat underneath so the organisms can survive

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24
Q

Disaccharides def + eg

A

Pairs of sugar units e.g. maltose, sucrose and lactose

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25
Q

Monosaccharides def + eg

A

Single sugar units e.g. Glucose, fructose, galactose (hexoses - 6 carbons)

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26
Q

Polysaccharide def + eg

A

Many repeating sugar units e.g. Glycogen, starch and cellulose

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27
Q

General formula for carbohydrates

A

Cn(H2O)n if n is between 3 and 7

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28
Q

Isomer def + eg

A

Same formula but different arrangement. This means that they all have different properties e.g. alpha-glucose and beta-glucose

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29
Q

Maltose

A

Glucose + glucose (alpha). Malt sugar

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30
Q

Sucrose

A

Glucose + fructose. Table sugar

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31
Q

Lactose

A

Glucose + galactose. Milk sugar

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32
Q

Monomer

A

A single unit

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33
Q

Polymer

A

A chain of repeating units

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34
Q

Hexoses purpose

A

Glucose - blood sugar, substrate. Fructose - fruit sugar. Galactose - dairy products

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35
Q

Condensation reaction

A

Joining molecules together by removing a molecule of water

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36
Q

Condensation in carbohydrates

A

Two monosaccharides join to become a disaccharide and forms a glycosidic

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37
Q

Hydrolysis reaction

A

Breaking molecules apart by adding a molecule of water

38
Q

Hydrolysis reaction in carbohydrates

A

A disaccharide is split to become two monosaccharides as a glycosidic bond is broken

39
Q

Structural difference between alpha and beta glucose

A

Hydroxyl group OH is below the carbon ring (carbon 1) in alpha. Whereas it is above the carbon ring in beta

40
Q

Reducing sugar def + eg

A

A sugar that can donate electrons to another chemical. In a redox reaction, it reduces other chemicals and is itself oxidised. e.g. maltose

41
Q

Reducing sugar test

A

Benedict’s reagent (alkaline copper II sulfate solution). Heated in a water bath. Semi-quantitative results: blue (negative), green, yellow, orange, red brown (positive). Works as the copper II sulfate is reduced by the aldehyde functional group of the reducing sugar (mainly the hydrogen atom). It donates its electron to the copper II ions to make insoluble red copper I precipitate
Cu2+ + e- > Cu+

42
Q

Non-reducing sugar test

A

Food sample must be hydrolysed into its monosaccharide components. Benedict’s reagent and heat. If still blue, no reducing sugar is present so add dilute hydrochloric acid and heat in water bath to hydrolyse it. Add sodium hydrogen carbonate to neutralise it. Heat again then add Benedict’s reagent. It will now change colour as reducing sugars are produced from hydrolysis

43
Q

Non-reducing sugar def + eg

A

A sugar that does not donate electrons to other chemicals in redox reactions. E.g. Sucrose

44
Q

Starch test

A

Iodine or potassium iodide solution. From orange brown to blue black

45
Q

Storage polysaccharides

A

Glycogen and starch. Formed by the condensation of alpha glucose

46
Q

Structural polysaccharides

A

Cellulose. Formed by condensation of beta glucose

47
Q

Starch properties

A

Fully digestible, doesn’t change water potential (insoluble) meaning water is not drawn to the cell in osmosis, osmotically inert, readily converts to sugars, large so doesn’t diffuse out of plant cells, compact a lot is stored in a small space, hydrolysed and easily transported

48
Q

Starch structure

A

Branched ends, large, compact, helical, formed by 200-100000 alpha glucose molecules, made of 20-30% amylose and 70-80% amylopectin

49
Q

Starch functions

A

Found in plants and not animals. Occur in seeds, grains and storage organs. Major energy source in diets. Readily used in respiration. Acted on by enzymes simultaneously leading to a rapid release of glucose

50
Q

Amylose

A

Alpha 1, 4 glycosidic bonds. Straight chain polymer. Floppy chain and cooks up into a spring-like helix. Broken down in hydrolysis by alpha and beta amylase enzymes. Stains blue in iodine. More water soluble and doesn’t swell

51
Q

Amylopectin

A

Alpha 1, 4 and 1, 6 glycosidic bonds. Branched chain polymer. More open molecular structure. Linear lengths. Hydrolysed at 1,4 bonds by amylase but not 1,6 due to cross links. Stains red brown in iodine. Less water soluble and does swell in hot water

52
Q

Glycogen properties

A

Insoluble - water is not drawn to the cell by osmosis and doesn’t diffuse out of cells. Compact - a lot is stored in a small space. More rapidly broken down to form glucose

53
Q

Glycogen structure

A

Shorter chains, more highly branched, has more ends, alpha 1,4 and 1,6 glycosidic bonds, 3x more branched than amylopectin

54
Q

Glycogen functions

A

Found in I maps and bacteria (never plants). Aka animal starch. Major carbohydrate storage product. Stored as small granules in muscles and the liver (as a stored form of glucose). Can be acted on simultaneously by enzymes to be used in respiration which is important for animals with a high metabolic rate. Yields large amounts of glucose to crest ATP

55
Q

Cellulose properties

A

Indigestible for humans but not for ruminants e.g. cows who have a symbiotic gut where bacteria digest the fibre. High tensile strength as it has many hydrogen bonds but still flexible. Tough versatile material. Exerts an inward pressure that stops any further influx of water. Resistant to hydrolysis due to cross linking preventing access by water

56
Q

Cellulose structure

A

Made of beta glucose monomers at 1,4 glycosidic bonds. Straight, unbranched chains running parallel to each other. Cross linked by hydrogen bonds between adjacent chains. Every other molecule is rotated 180° so OH groups are free on the sides. Fibrous. Group together to form microfibrils which arrange in groups called fibres

57
Q

Cellulose functions

A

Plant cell walls, provides rigidity, prevents cell from bursting, keeps it turgid, provides maximum surface area for photosynthesis, ideal in plants that readily synthesise excess carbohydrate

58
Q

Amino acid

A

The monomer unit in proteins

59
Q

Polypeptide

A

The polymer chain in protein

60
Q

Denaturation

A

Permanent loss of function through a change in shape

61
Q

Protein basic structure

A

Amino group (H2N), side group (CHR), carboxylic acid group (COOH)

62
Q

Zwitterion

A

Has positive and negative charges

63
Q

Amphoteric

A

Acts as an acid and a base

64
Q

Dipeptide

A

Two peptides

65
Q

Polymerisation

A

Forming monomers together to make polymers

66
Q

Triglyceride

A

3 fatty acids + 1 glycerol

67
Q

Phospholipid

A

2 fatty acids + glycerol + phosphate

Aka diglyceride

68
Q

Bond between glycerol and carboxylic acid

A

Ester bond COO

69
Q

Saturated fat

A

Only consists of single bonded carbons

70
Q

Unsaturated fats

A

Consists of one or more double bonded carbon to carbon atom, at least two hydrogens missing

71
Q

Monounsaturated and polyunsaturated

A

Mono - only one double bond, poly - more than one

72
Q

Globular proteins eg + properties + structure

A

E.g. enzymes, hormones, antibodies, plasma proteins, haemoglobin. Molecules curl into a ball shape. Hydrophilic R groups on outside. Hydrophobic R groups cluster in the centre. Soluble

73
Q

Structural proteins eg

A

Keratin e.g. horns, nails, hair. Collagen e.g. in tendons

74
Q

Function of lipids

A

Energy store (calories) - contain more CH bonds than carbohydrates. Heat and electrical insulation - hibernating animals, slow conductor of heat, myelin sheath in nerve cells. Water proofing - insoluble in water. Buoyancy - many single celles organisms produce oil drops to aid this. Shock absorption - protection of organs

75
Q

What is the difference between collisions and successful collisions? (In enzymes)

A

Collisions involve molecules bumping each other. These are successful only when the substrate manages to bump into and attach to the active site of the enzyme

76
Q

What are enzymes and how do they work?

A

They are globular proteins and biological catalysts that speed up the rate of reaction while remaining chemically unchanged. This happens as they lower the activation energy of the reaction by stretching the bonds in the reactants, making it easier to achieve the transition state

77
Q

Describe the 3D structure of enzymes

A

Globular proteins. Specific shape due to amino acid sequence in primary structure. Active site made of amino acids forming a small depression within the enzyme

78
Q

What is an enzyme-substrate complex?

A

When substrates (the molecule which the enzyme acts on) fit into the active site of the enzyme. It is held by bonds that temporarily form between certain amino acids of the active site and groups on the substrate

79
Q

Describe induced fit

A

The model proposes that the active site forms as the enzyme and substrate interact. The proximity of the substrate (change in the environment of the enzyme) leads to a change in the enzyme, forming the functional active site. It becomes flexible and moulds itself around the substrate. As the shape changes, the enzyme puts a strain on the substrate which distorts a particular bond to lower the activation energy

80
Q

Limitations of the lock and key model

A

Suggests a rigid structure. But other molecules can bind to enzymes at other sites. This alters the activity making it flexible

81
Q

What does a change in pH alter?

A

The charges on the amino acids. A major change breaks the bonds in the tertiary structure

82
Q

What is one feature of starch that allows it to act as a storage substance?

A

It is osmotically inert, meaning it prevents lysing by the uptake of water

83
Q

Alpha vs beta glucose

A

OH below is alpha

OH above is beta

84
Q

How is cellulose’ structure related to its role in plant cells walls?

A

They are long straight unbranched chains of glucose. They are joined by hydrogen bonds. They form fibrils. Linkages at the sides as well as above and below the chain. Has a rigid shape

85
Q

Test for lipids

A

Emulsion test. Food sample needs to be crushed and dissolved ethanol to give a solution. Water is added after the ethanol. It should be shaken and an emulsion form if it contains lipids

86
Q

What is the name given to the sequence of amino acid in a protein molecule?

A

The primary structure

87
Q

What is one property of collagen that makes a useful component of blood vessel walls?

A

It is tough, strong and insoluble

88
Q

What is collagen’s structure?

A

Has peptide bonds between amino acids. Has a high proportion of glycine regularly repeated for closeness. Made of three polypeptides. Has adjacent chains that intertwine. There are crossed things will just staggered. They are covalently cross-linked molecules. Make fibrosis. Secondary structure has a triple helix.

89
Q

What is function of haemoglobin?

A

Transport of oxygen

90
Q

How does the structure of haemoglobin differ from collagen?

A

Haemoglobin has hydrophobic R groups on the inside. Haemoglobin has 4 chains rather than three. Haemoglobin has an alpha helix rather than a beta tube. Sub units are different types

A Level Biology (8 decks)

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