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AQA A level Biology > Biological molecules > Flashcards

Biological molecules Flashcards

1
Q

What are monomers?

A

Monomers are the smaller units from which larger molecules are made.

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2
Q

What are polymers?

A

Polymers are molecules made from a large number of monomers joined together.

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3
Q

Examples of monomers

A

Monosaccharides, amino acids and nucleotides

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4
Q

What is a condensation reaction?

A

A condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

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5
Q

What is a hydrolysis reaction?

A

A hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule.

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6
Q

What are monosaccharides?

A

Monosaccharides are the monomers from which larger carbohydrates are made.

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7
Q

Examples of monosaccharides

A

Glucose, galactose and fructose

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8
Q

What bond does a condensation reaction of two monosaccharides form?

A

Glycosidic bond

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9
Q

What does a condensation reaction of two monosaccharides form?

A

Disaccharide

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10
Q

Examples of disaccharides

A

Maltose, sucrose, lactose

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11
Q

What monosaccharides form maltose?

A

The condensation of two glucose molecules

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12
Q

What monosaccharides form sucrose?

A

The condensation of a glucose molecule and a fructose molecule

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13
Q

What monosaccharides form lactose?

A

The condensation of a glucose molecule and a galactose molecule.

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14
Q

What are the isomers of glucose?

A

alpha- glucose and beta-glucose

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15
Q

What are polysaccharides?

A

Long chain polymers formed by the condensation of many glucose units.

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16
Q

Examples of polysaccharides

A

Starch, glycogen, cellulose

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17
Q

Which polysaccharides are formed by a-glucose molecules?

A

Starch and glycogen

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18
Q

Which polysaccharides are formed by b-glucose molecules?

A

Cellulose

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19
Q

What are the two groups of lipids?

A

Triglycerides and phospholipids

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20
Q

What forms triglycerides?

A

Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid.

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21
Q

What forms an ester bond?

A

A condensation reaction between glycerol and 3x fatty acids (RCOOH)

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22
Q

What is the emulsion test for lipids?

A
  • Add ethanol and shake the test tube to dissolve any lipids in sample
  • Add water and gently shake
  • Milky white emulsion indicates a positive result
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23
Q

What are the properties of triglycerides?

A

Source of energy- high ratio of energy storing carbon- hydrogen bonds to carbon atoms
Energy storage- low mass to energy ratio (animals reduce mass they carry)
Insoluble- large, non polar molecules so have no osmotic effect
Source of water- high ratio of hydrogen- oxygen atoms and release water when oxidised (good for organisms in deserts)

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24
Q

Difference between unsaturated and saturated fatty acids

A

Unsaturated- one or more carbon double bonds
Saturated- no carbon double bonds

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25
Q

What are amino acids?

A

Amino acids are the monomers from which proteins are made.

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26
Q

What is formed by the condensation reaction of two amino acids?

A

A peptide bond

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27
Q

What is formed by the condensation reaction of many amino acids?

A

Polypeptide

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28
Q

What is the biuret test for proteins?

A
  • Add sodium hydroxide solution
  • Add drops of dilute copper (II) sulfate solution and gently mix
  • Positive result turns blue to a purple colour
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29
Q

What is a functional protein?

A

containing one or more polypeptides

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30
Q

What is the induced fit model?

A

Proposal that active site forms as enzyme and substrate interact, the proximity of the substrate causes a change in enzymes functional active site (enzyme is flexible and moulds around substrate)
As it changes shape, enzyme puts a strain of substrate distorting bonds in substrate lowering activation energy.

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31
Q

What are the functions of DNA and RNA?

A

They are important information-carrying molecules. In all living cells, DNA holds genetic information and RNA transfers genetic information from DNA to the ribosomes.

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32
Q

What makes up a nucleotide?

A

A pentose, a nitrogen-containing organic base and a phosphate group.

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33
Q

Examples of polymers

A

DNA, RNA, polypeptides, polysaccharides

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34
Q

What are ribosomes made up of?

A

Ribosomes are formed from RNA and proteins.

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35
Q

What forms a phosphodiester bond?

A

A condensation reaction between two nucleotides.

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36
Q

Components of DNA

A

Deoxyribose sugar, a phosphate group and nitrogen containing organic bases adenine, cytosine, guanine or thymine.

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37
Q

Components of RNA

A

Ribose sugar, a phosphate group and nitrogen containing organic bases adenine, cytosine, guanine or uracil.

38
Q

What forms ATP?

A

A molecule of ribose, a molecule of adenine and three phosphate groups.

39
Q

Properties of water

A

Metabolite, solvent, relatively high heat capacity, large latent heat of vapourisation, strong cohesion

40
Q

Test for reducing sugars

A
  • Add benedicts reagent
  • Heat in a water bath for 5 mins
  • Positive result turns from blue to yellow/green/ brick red
41
Q

What is a reducing sugar?

A

A sugar which can donate electrons (reduce) to another chemical.

42
Q

Test for non-reducing sugars

A
  • Add benedicts reagent
  • Heat in a water bath for 5 mins
    (if colour change doesnt occur a reducing sugar isnt present)
  • Add dilute hydrochloric acid
  • Heat in a water bath for 5 mins
  • Add sodium carbonate to neutralise acid
  • Add benedicts reagant
  • Test with pH paper to check solution is alkaline
  • The place again in water bath for 5 mins
  • Positive result turns yellow/green/brick red
43
Q

Why is there different tests for sugars?

A

In order to dectect a non-reducing sugar, it must be hydrolysed into its monosaccharide components as the disaccharides do not change the colour of Benedicts reagent.

44
Q

Test for starch

A
  • Add drops of iodine solution and shake or stir
  • Positive result turns from yellow to blue/ black
45
Q

Starch

A

Polysaccharide found in parts of a plant in small grains (seeds and storage organs)
A- glucose monomers

45
Q

Roles of starch

A

Insoluble - doesn’t have an osmotic effect
Compact and Helical- a lot can be stored in a small space
a- glucose- easily transported and readily used in respiration
Large- doesn’t diffuse out of cells

45
Q

Glycogen

A

Polysaccharide found in animals and bacteria, major carbohydrate storage product of animals served as small granules in the muscles and liver.
A- glucose monomers
1, 4 and 1.6 glycosidic bonds

46
Q

Roles of glycogen

A

Insoluble- has no osmotic effect
Compact- a lot can be stored in a small space
Highly branched- more ends and so hydrolysis occurs quicker, rapidly breaking glycogen down to form glucose monomers for respiration
High metabolic rate- higher respiratory rate

47
Q

Cellulose

A

Polysaccharide found in plant cell walls providing rigidity to the cell.
B- glucose monomers
1,4 glycosidic bonds

48
Q

Roles of cellulose

A

B - glucose monomers - form long straight unbranched chains which run parallel to each other and are cross linked by H+ bonds adding collective strength
Microfibrils- form fibres providing more strength
Permeable- allows solutes to leave or reach plasma membrane

49
Q

Roles of lipids

A

Source of energy, waterproofing, insulation, protection

50
Q

Name for single double bond

A

Mono- unsaturated

51
Q

Name for more than one double bond

A

Polyunsaturated

52
Q

What makes up phospholipids

A

Hydrophillic head- interacts and is attracted to water, not with fat
Hydrophobic tail- repels water, mixes with fat

53
Q

Structure of an amino acid

A

Amino group (NH2) carboxyl group (COOH)
hydrogen atom (H) variable group (R)

54
Q

Formation of a peptide bond

A

Condensation reaction combining a OH from carboxyl group of one amino acid and with a H from amino group of another amino acid

55
Q

Polypeptides structure

A

Primary, secondary, tertiary, quaternary

56
Q

Conditions for a reaction to take place

A
  • Collision of molecules with sufficient energy
  • Free energy of products must be less than substrates
  • Activation energy required
57
Q

What is the activation energy?

A

The minimum amount of energy needed to activate the reaction

58
Q

Enzyme structure

A

Globular protein
Active site- functional region of enzyme, made up of amino acids

59
Q

What is a substrate?

A

Molecule which the enzyme acts on, this forms an enzyme- substrate complex where substrate is held in active site by bonds temporarily formed between amino acids

60
Q

Factors affecting enzyme action

A

Temperature, pH, enzyme concentration, substrate concentration

61
Q

Complementary base pairing in DNA

A

Adenine - Thymine
Guanine - Cytosine

62
Q

Who worked out the structure of DNA?

A

James Watson and Francis Crick in 1953
- following work by Rosalind Franklin on the X- ray diffraction patterns of DNA

63
Q

Stability of DNA

A
  • Phosphodiester backbone protects organic bases in double helix
  • Hydrogen bonds link organic base pairs forming bridges between phosphodiester uprights
64
Q

Properties of DNA

A

Large molecule- carries large amount of genetic information
Helical cylinder- protects genetic information from external forces
Base pairing- allows DNA to be replicated
Hydrogen bonds- join two strands allowing them to separate during replication
Stable structure- persistent mutations are rare

65
Q

Uses of ATP

A

Metabolic processes, movement, active transport, secretion, activation of molecules

66
Q

Hydrolysis of ATP

A

ATP + H20 = ADP + Pi + E
- reaction catalysed by ATP hydrolase

67
Q

Condensation of ADP

A

Conversion of ATP to ADP is a reversible reaction and so through the synthesis of ATP from ADP it is catalysed by enzyme ATP synthase. Also includes addition of phosphate molecule to ADP

68
Q

Enzyme involved in hydrolysis of ATP

A

ATP hydrolase

69
Q

Enzyme involved in synthesis of ATP

A

ATP synthase

70
Q

Occurences of the synthesis of ATP from ADP

A
  • Chlorophyll- containing plant cells during photosynthesis (photophosphorylation)
  • Plant and animal cells during respiration (oxidative phosphorylation)
  • Plant and animal cells when phosphate groups are transferred from donor molecules to ADP (substrate-level phosphorylation)
71
Q

Inorganic ions

A
72
Q

Amylose

A

Staight chain
Unbranched and compact so broken down slowly by enzymes
1.4 glycosidic bonds

73
Q

Amylopectin

A

Branched chain so has more accessible ends
More easily broken down by enzymes to release glucose
1,4 and 1,6 glycosidic bonds

74
Q

Semi conservative replication

A

-unwinding of the double helix
-breakage of hydrogen bonds between complementary bases in the polynucleotide strands
-the role of DNA helicase in unwinding DNA and breaking its hydrogen bonds
- attraction of new DNA nucleotides to exposed bases on template strands and base pairing
-the role of DNA polymerase in the condensation reaction that joins adjacent nucleotides.

75
Q

Role of DNA polymerase

A

The condensation reaction that joins adjacent nucleotides.

76
Q

Role of lipids
- insulation

A

Fats are slow conductors of heat and when stored beneath the body surface help to retain body heat. They also act as electrical insulators in the myelin sheath around nerve cells.

77
Q

Role of lipids
- source of energy

A

When oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water.

77
Q

Role of lipids
- waterproofing

A

Lipids are insoluble in water and therefore useful as a waterproofing. Both plants and insects have waxy, lipid cuticles that conserve water, while mammals produce an oily secretion from the sebaceous glands in the skin.

78
Q

Role of lipids
- protection

A

Delicate organs are surrounded by a layer of fat.

79
Q

Structure of phospholipids
- head and tail

A

a hydrophilic ‘head’- interacts with water (is attracted to it) but not with fat
a hydrophobic ‘tail’- which repels from water but mixes readily with fat.

80
Q

Properties of phospholipids

A
  • Phospholipids are polar molecules so in an aqueous environment, phospholipid molecules form a bilayer within cell-surface membranes
  • The hydrophilic phosphate ‘heads’ of phospholipid molecules help to hold at the surface of the cell-surface membrane.
  • The phospholipid structure forms glycolipids by combining with carbohydrates within the cell-surface membrane, important in cell recognition.
81
Q

Primary structure of a polypeptide

A

The sequence of amino acids in a polypeptide chain that are joined by peptide bonds.

82
Q

Secondary structure of a polypeptide

A

Folding of the polypeptide chain due to hydrogen bonding into an alpha helix structure or beta pleated sheet

83
Q

Tertiary structure of a polypeptide

A

A specific 3D shape of a protein after further folding. Maintained by different bonds, disulfide bridges, ionic bonds and hydrogen bonds.

84
Q

Disulfide bridges

A

Fairly strong and therefore not easily broken.

85
Q

Ionic bonds

A

Formed between any carboxyl and amino groups that are not involved in forming peptide bonds. They are weaker than disulfide bonds and are easily broken by changes in pH.

86
Q

Hydrogen bonds

A

Numerous but easily broken. It is the 3-D shape or a protein that is important when it comes to how it functions. It makes each protein distinctive and allows it to recognise, and be recognised by, other molecules. It can then interact with them in a very specific way.

86
Q

Competitive inhibitors

A

Have a molecular shape similar to that of the substrate. This allows them to occupy the active site of an enzyme. They therefore compete with the substrate for the available active substrate molecule sites.

86
Q

Non-competitive inhibitors

A

Non-competitive inhibitors attach themselves to the enzyme at a binding site which is not the active site. Upon attaching to the enzyme it changes the shape of the active site in such a way that substrate molecules can no longer occupy it. and so the enzyme cannot function

AQA A level Biology (8 decks)

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