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A-LEVEL BIOLOGY > BIOLOGICAL MOLECULES > Flashcards

BIOLOGICAL MOLECULES Flashcards

1
Q

What are the most common elements in the human body? (6)

A

-hydrogen
-oxygen
-carbon
-nitrogen
-calcium
-phosphorus

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2
Q

What are the compositions of the most common elements in the human body? (6)

A

-H2 = 63%
-O2 = 25.5%
-C = 9.5%
-N = 1.4%
-Ca = 0.3%
-P = 0.2%

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3
Q

What are the most common elements in the atmosphere? (6)

A

-oxygen
-sulfur
-aluminium
-iron
-calcium
-sodium

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4
Q

What are the compositions of the most common elements in the atmosphere? (6)

A

-O2 = 47%
-S = 28%
-Al2 = 7.9%
-Fe = 4.5%
-Ca = 3.5%
-Na = 2.5%

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5
Q

What is an acid? (1)

A

An acid is a compound that releases hydrogen ions into a solution.

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6
Q

What is meant by dissociate? (1)

A

Means separate into its constituent ions.

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7
Q

What are some examples of organic acids? (2)

A

Citric acid and Ethanoic acid…..

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8
Q

What is a base? (1)

A

A compound that can take up hydrogen ions in a solution.

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9
Q

What is the pH of a base? (1)

A

Around 7.

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10
Q

What are some properties of a base? (2)

A

-neutralises acid
-is insoluble in water

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11
Q

What is an alkali? (2)

A

Bases hat are soluble in water. E.g sodium hydroxide.

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12
Q

What is meant by pH? (2)

A

A measure of the acidity and alkalinity of a solution, or a measure of hydrogen ions.

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13
Q

What is pH measured in? (1)

A

Log (10) H+ concentration.

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14
Q

What is the pH for strong acids? (1)

A

Have a value of less than 7.

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15
Q

What is the pH of strong alkalis? (1)

A

Have a value of more than 7.

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16
Q

How can pH be measured? (1)

A

Can be measured using universal indicator.

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17
Q

What is meant by metabolism? (1)

A

All the chemical reactions that occur within an organism.

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18
Q

What organic ions are used in plants? (4)

A

-nitrate
-calcium
-magnesium
-phosphate

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19
Q

How is nitrate used in plants, in terms of organic ions? (2)

A

Used to synthesis the nitrogenous bases in DNA and RNA nucleotides and synthesises the amino groups of amino acids.

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20
Q

How is calcium used in plants, in terms of organic ions? (1)

A

Used to synthesis calcium pectate, which exists as a layer called the middle lamella, between the walls of adjacent plant cells.

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21
Q

How is magnesium used in plants, in terms of organic ions? (1)

A

Used to synthesis the photosynthetic pigment, chlorophyll.

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22
Q

How is phosphate used in plants, in terms of organic ions? (2)

A

Used to synthesise adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and to synthesise DNA and RNA.

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23
Q

What is a covalent bond? (1)

A

A relatively strong bond between two atoms in which electrons are shared between them.

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24
Q

What is a polar molecule? (1)

A

A molecule that contains weak positive charges and weak negative charges.

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25
Q

What is a hydrogen bond? (1)

A

A relatively weak link between who atoms in which a weakly negative atom attracts another weakly positive atom.

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26
Q

What is cohesion? (1)

A

The force by which hydrogen bonds hold polar molecules together, or to a charged surface.

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27
Q

What does hydrophilic mean? (1)

A

Refers to substances that will mix with water.

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28
Q

What does hydrophobic mean? (1)

A

Refers to substances that will not mix with water.

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29
Q

What is the specific heat capacity of water? (1)

A

Is very high at 4.184 kJ kg (-1) degrees (-1)

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30
Q

Is water incompressible and why? (2)

A

Water IS incompressible because here is much less distance between the molecules in a liquid than in a gas because of this a water-filled cavity within an organism can act as a hydrostatic skeleton.

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31
Q

What is the maximum density of water? (1)

A

Density of 4 degrees.

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32
Q

What are organic compounds? (2)

A

A compound of which carbon atoms are linked by covalent bonds to each other and to hydrogen molecules. The molecules can be very large and can exist as rings or chains of carbon atoms.

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33
Q

What are carbohydrates made up of? (3)

A

Carbon, hydrogen and oxygen.

34
Q

What are monosaccharides? (1)

A

Are known as simple sugars.

35
Q

What are the monosaccharides? (3)

A

-triose
-pentose (ribose and deoxyribose)
-hexose (glucose, fructose and galactose)

36
Q

What are disaccharides? (1)

A

Two simple sugars chemically linked by a glycosidic bond during a condensation reaction.

37
Q

What are the disaccharides? (3)

A

-sucrose = glucose + fructose

-lactose = glucose + galactose

-maltose = glucose + glucose

38
Q

What are polysaccharides? (1)

A

Very many simple sugars chemically linked by glycosidic bonding.

39
Q

What are the polysaccharides? (3)

A

-starch (fuel store in plants)

-glycogen (a fuel store in animals)

-cellulose (a major component of plant cell walls)

40
Q

What s the formula for glucose? (1)

A

C(6)H(12)0(6)

41
Q

What are isomers? (1)

A

Two or more different structural formulae of the same molecular formula.

42
Q

What are the isomers of glucose? (2)

A

Alpha (a) glucose and beta (b) glucose.

43
Q

What is the chemical formula for water? (1)

A

H(2)O

44
Q

What are the bonds called within a water molecule? (1)

A

Covalent bonds

45
Q

What charges are on the atoms in a water molecule? (2)

A

Oxygen-negatively charged (delta negative)

Hydrogen-positively charged (delta positive)

46
Q

Why is the oxygen atom of a water slightly negatively charged? (1)

A

Since oxygen has more protons in its nucleus than the hydrogen atoms, the electrons being shared in its covalent bond are more strongly attracted to the nucleus of the oxygen atom therefore they move closer to the oxygen atom, thus giving it a slightly negative charge.

47
Q

What is it called when an atom has unequal charges? (1)

A

A molecule is said to carry an unequal distribution of electrical charge within it, also known as a polar molecule or dipole molecule.

48
Q

What are hydrogen bonds? (1)

A

Are weak bonds but are strong enough to Hold molecules together e.g water molecules.

49
Q

What does cohesion cause? (1)

A

Cohesion causes surface tension, in which the outer most molecules of water form hydrogen bonds with water molecules below them, which gives water a very high surface tension.

50
Q

Why is water incompressible? (2)

A

There is much less distance between the molecules in a a liquid than in a gas and the intermolecular force of the hydrogen bonds aid this property, because of this a water filled cavity within an organism can act as a hydrostatic skeleton.

51
Q

What does the formation of ice do? (1)

A

Allows ice to float on the top of very cold water, which insulated the water beneath it, as a consequence water rarel freezes solid allowing life to survive underneath it at freezing temperatures.

52
Q

What are elements are usually within a protein? (5)

A

-sulphur

-nitrogen

-hydrogen

-oxygen

Carbon

53
Q

What are monomer’s? (1)

A

Amino acids

54
Q

What are the 2 separate groups of which amino acids contain? (2)

A

Two functional groups:
-an amino group
-a carboxyl group

55
Q

What is the chemical symbol for a amino group? (1)

A

-NH3

56
Q

What is the chemical symbol for a carboxyl group? (1)

A

-COOH

57
Q

What can an amino acid ionise? (3)

A

-as an acid
-as a base
-as both

58
Q

What is meant by being amphoteric? (1)

A

When molecules can ionise as both an acid and a base such as an amino acid.

59
Q

What is meant by being a zwitterion? (1)

A

An ion with both a positive and negative charge or in simpler words being a double ion.

60
Q

How many naturally occurring amino acids are present in organisms? (1)

A

There are 20 naturally occurring amino acids

61
Q

What are three examples of naturally occurring amino acids? (3)

A

-glycerine
-alanine
-leucine

62
Q

What reaction happens when 2 amino acids form? (1)

A

A condensation reaction.

63
Q

What is formed when two amino acids react?(1)

A

A dipeptide.

64
Q

What happens during the condensation reaction of 3 amino acids? (1)

A

A covalent bond known as a peptide bond forms between the amino group of one amino acid and the carboxyl group of the other.

65
Q

What is the general formula for an amino acid? (1)

A

NH2 -CHR -COOH

66
Q

How is a tripeptide formed? (1)

A

When a further condensation reaction happens between a dipeptide and another amino acid.

67
Q

What are the four structures of a protein? (4)

A

-primary structure
-secondary structure
-tertiary structure
-quaternary structure

68
Q

What is the primary structure of a protein? (1)

A

The sequence of amino acids forming the polypeptide.

69
Q

What is the secondary structure of a protein?

A

Develops immediately after its formation when parts of the polypeptide chain becomes folded or twisted, or both. There are two types: a helix and B pleated sheets.

70
Q

What are the most common shapes of a secondary structure protein? (2)

A

-formed by coiling = an (a) helix

-formed by folding into sheets = an (B) sheets

71
Q

What is a tertiary structure of a protein? (1)

A

when the molecule is further folded and held in a particular complex three dimensional shape.

72
Q

What is the quaternary structure of a protein? (1)

A

Arses when two or more polypeptides become held together, forming a complex, biologically active molecule.

73
Q

What are fibrous proteins? (1)

A

-contain long, coiled polypeptide chains,shaped like a rod or wire.

74
Q

What is an example of a fibrous protein? (3)

A

Collagen, a component of bones and tendons contains three polypeptide chains held together by covalent bonds and hydrogen bonds forming a ripple helix. Making it resistant to denaturing and provides strength.

75
Q

What is a globular protein? (1)

A

Are spherical, polypeptide chains wind in such a way that their hydrophilic amino acids are at the surface whilst their hydrophobic amino acids are at the core.

76
Q

What is an example of a globular protein? (4)

A

Haemoglobin, the respiratory pigment found in red blood cells, consists of 4 polypeptide chains, bound to an iron containing harm group. Binds to oxygen , this causes the shape of the molecule making it easier to bind with.

77
Q

What is denaturation? (1)

A

A change in the shape of a protein that alters, or destroys the ability of a protein to carry out its function.

78
Q

What can cause denaturation? (4)

A

-high temperature
-change in pH
-heavy metal ions
-some organic solvents

79
Q

What are the functions of haemoglobin structure? (3)

A

-globular - can be soluble because the amino acid chain can twist in a way that polar groups lie on the surface.

-polypeptide joined to a haem group - haem group binds to oxygen.

-four polypeptide and haem groups - binds to 4 times more oxygen than one haem group would.

80
Q

How does the structure of collagen affect its functions? (3)

A

-3 helix’s are held by a large number of hydrogen bonds- because every third amino acid is a small glycerine which can fit into a very small space on either side of the triple helix.

-on either side of the glycerines are praline and hydroxyproline which have big R groups - these groups keep out of each others way to maintain the strong, insoluble fibrous structure.

-molecules cross link - provides further strength.

A-LEVEL BIOLOGY (34 decks)

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