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AQA A level Biology > Biological molecules > Flashcards

Biological molecules Flashcards

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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 a fatty acid (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

What are the properties of phosphoipids?

A

Polar molecules- in aqueous environment, they form a bilayer
Glycolipids- combine with carbohydates in cell surface membrane, good for cell recognition

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25
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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26
Q

What are amino acids?

A

Amino acids are the monomers from which proteins are made.

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27
Q

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

A

A peptide bond

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28
Q

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

A

Polypeptide

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29
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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30
Q

What is a functional protein?

A

containing one or more polypeptides

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31
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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32
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.

33
Q

What makes up a nucleotide?

A

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

34
Q

Examples of polymers

A

DNA, RNA, polypeptides, polysaccharides

35
Q

What are ribosomes made up of?

A

Ribosomes are formed from RNA and proteins.

36
Q

What forms a phosphodiester bond?

A

A condensation reaction between two nucleotides.

37
Q

Components of DNA

A

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

38
Q

Components of RNA

A

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

39
Q

What forms ATP?

A

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

40
Q

Properties of water

A

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

41
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
42
Q

What is a reducing sugar?

A

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

43
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
44
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.

45
Q

Test for starch

A
  • Add drops of iodine solution and shake or stir
  • Positive result turns from yellow to blue/ black
46
Q

Starch

A

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

46
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

46
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

47
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

48
Q

Cellulose

A

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

49
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

50
Q

Roles of lipids

A

Source of energy, waterproofing, insulation, protection

51
Q

Name for single double bond

A

Mono- unsaturated

52
Q

Name for more than one double bond

A

Polyunsaturated

53
Q

What makes up phospholipids

A

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

54
Q

Structure of an amino acid

A

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

55
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

56
Q

Polypeptides structure

A

Primary, secondary, tertiary, quaternary

57
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
58
Q

What is the activation energy?

A

The minimum amount of energy needed to activate the reaction

59
Q

Enzyme structure

A

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

60
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

61
Q

Factors affecting enzyme action

A

Temperature, pH, enzyme concentration, substrate concentration

62
Q

Complementary base pairing in DNA

A

Adenine - Thymine
Guanine - Cytosine

63
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

64
Q

Stability of DNA

A
  • Phosphodiester backbone protects organic bases in double helix
  • Hydrogen bonds link organic base pairs forming bridges between phosphodiester uprights
65
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

66
Q

Uses of ATP

A

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

67
Q

Hydrolysis of ATP

A

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

68
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

69
Q

Enzyme involved in hydrolysis of ATP

A

ATP hydrolase

70
Q

Enzyme involved in synthesis of ATP

A

ATP synthase

71
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)
72
Q

Inorganic ions

A
73
Q

Amylose

A

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

74
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

75
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.

76
Q

Role of DNA polymerase

A

The condensation reaction that joins adjacent nucleotides.

AQA A level Biology (6 decks)

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