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CCEA AS Biology Units 1, 2 And 3 > (U1) Molecules > Flashcards

(U1) Molecules Flashcards

1
Q

Why is water a good solvent?

A
  • Due to their polarity, water molecules are attracted to other polar molecules
  • this allows them to form clusters around the solute and therefore dissolve them
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2
Q

What is a polar molecule?

Why is water a polar molecule?

A
  • A molecule where individual atoms have slight, opposite charges due to uneven distribution of covalent bonds (electron slightly more attracted to one of the molecules)
  • the oxygens have a slight -ve charge, hydrogens slight +ve
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3
Q

In what 3 ways is water used within the body?

A
  • most of the reactions in cells take place in aqueous solutions (in water)
  • water acts as a transport medium
  • it has different effects on hydrophobic and hydrophilic molecules (e.g. fat won’t dissolve in water) - key for membrane structure
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4
Q

What are calcium ions used for by humans and plants? (4)

A
  • helps produce calcium pectate for use in plant cell walls
  • a component of bones and teeth
  • key in blood clotting
  • key in muscle contraction
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5
Q

What are Iron ions used for by humans and plants? (2)

A
  • in the haem group of haemoglobin (oxygen carrier in RBCs)
  • key constituent of electron carriers in respiration
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6
Q

What are magnesium ions used for in plants?

A

Helps make chlorophyll able to absorb light

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7
Q

What are potassium ions used for in humans?

A

Maintaining electrical gradients across neurones

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8
Q

What are nitrate ions used for by humans and plants?

A

A component of amino acids, nucleic acids and chlorophyll

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9
Q

What are phosphate ions used for by humans and plants? (2)

A
  • helps form phospholipids for cell membranes
  • component of bio molecules like ATP (adenosine triphosphate) and nucleic acids
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10
Q

What are Hydrogencarbonate ions used for by humans and plants?

A

Used as a natural buffer

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11
Q

What are buffers? (2)

Why are they needed?

A
    • Chemicals or substances that resist changes to pH - meaning pH is maintained
    • when small volumes of acid/alkali are added
    • pH changes can result in enzyme denaturation, buffers prevent this and allow enzymes to operate at their optimum pH
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12
Q

Give 2 examples of buffers

A
  • HCO3- ions
  • blood proteins e.g. albumin
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13
Q

What are ions?

A

Charged particles

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14
Q

Name 7 inorganic ions

and

state their formula

A
  • calcium - Ca2+
  • iron - Fe2+
  • magnesium - Mg2+
  • potassium - K+
  • nitrate - NO3-
  • phosphate - PO43-
  • hydrogen-carbonate - HCO3-
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15
Q

What are organic molecules?

Name 3 examples

A
  • complex carbon containing molecules
  • carbohydrates, proteins and lipids
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16
Q

What are monomers and polymers?

What is the name of the process used to form polymers?

and

what does it entail?

A
  • mono - individual subunits
  • poly - many subunits joined together
  • polymerisation - adding monomers together to form polymers
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17
Q

What elements are contained in carbohydrates?

A
  • carbon
  • hydrogen
  • oxygen
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18
Q

What is the ratio between the number of hydrogen and oxygen atoms in carbohydrates?

A

2 hydrogen : 1 oxygen

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19
Q

What are the 3 types of carbohydrates?

A
  • monosaccharides
  • disaccharides
  • polysaccharides
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20
Q

What are monosaccharides?

Which 3 categories are biologically important?

A
  • simple sugars with different categories depending on no. of carbons
  • important ones:
  1. trioses (3 carbons),
  2. pentoses (5 carbons) and
  3. hexoses (6 carbon)
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21
Q

What are disaccharides? (2)

A
  • Double sugars formed from 2 monosaccharide monomers
  • which join through condensation reactions
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22
Q

What are polysaccharides? (2)

A
  • Complex molecules consisting of many monosaccharide monomers
  • bonded through condensation reactions
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23
Q

What is DNA Helicase

and

How does it work? (3)

A
  • An enzyme
  • breaks hydrogen bonds between complementary bases (ATCG),
  • separating into 2 polynucleotide strands
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24
Q

What is DNA polymerase

and

How does it work?

A
  • an enzyme
  • joins mononucleotides together to form a new polynucleotide strand
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25
Q

Which 2 enzymes are used in DNA replication?

A
  • DNA helicase
  • DNA polymerase
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26
Q

Why is DNA replication referred to as being semi-conservative?

A

Each newly synthesized DNA molecule retains 1 parental strand and 1 newly synthesized strand

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27
Q

What are hydrogen bonds? (Biology)

How are they broken?

A
  • Weak bonds between hydrogen and oxygen ions in water due to uneven distribution of covalent bonds
  • broken by thermal energy
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28
Q

What are isomers?

Name 2 examples

A
  • Compounds with the same chemical formula but slightly different structural formula
  • a-glucose and ß-glucose
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29
Q

How do the structures of a-glucose and ß-glucose differ?

A
  • a-glucose: the hydroxyl group connected to carbon 1 points downward (hydrogen points up)
  • ß-glucose: the hydroxyl group points upward (hydrogen points down)
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30
Q

Which polysaccharide(s) contain a-glucose?

A
  • starch
  • glycogen
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31
Q

Which polysaccharide(s) contain ß-glucose?

A

Cellulose

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32
Q

What are the properties of disaccharides? (2)

A
  • soluble in water
  • sweet tasting
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33
Q

What are condensation reactions? (In amylose chains) (4)

A
  • reversible reactions where the Hydroxyl group of the Carbon 1 on a monosaccharide
  • and the hydrogen (from the hydroxyl group) of the carbon 4 on another
  • are ejected as a water molecule
  • leaving a 1-4 glycosidic bond
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34
Q

What is hydrolysis?

A
  • When a water molecule is added to a disaccharide
  • breaking the 1-4 glycosidic bond
  • and separating it into monosaccharides
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35
Q

Name 2 disaccharides

and

state their monosaccharide components

A
  • maltose - 2 a-glucose
  • sucrose - 1 a-glucose and 1 fructose
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36
Q

How is the structure of fructose visibly different to glucose?

A
  • Fructose has a pentagonal shape,
  • whereas both forms of glucose are hexagonal
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37
Q

What are the properties of polysaccharides? (2)

A
  • insoluble in water
  • not sweet
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38
Q

What are the 2 forms of starch chains?

A
  • Amylose
  • amylopectin
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39
Q

How is amylose structured? (3)

A
  • long chains of a-glucose with alpha 1-4 glycosidic bonds
  • that form a helical structure held in place by hydrogen bonds
  • chains are unbranched
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40
Q

How is amylopectin structured? (4)

A
  • long chains of alpha 1-4 glycosidic bonds
  • with branched ends
  • formed by alpha 1-6 glycosidic bonds
  • chains form helical shape held in place by hydrogen bonds
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41
Q

How is amylose different to amylopectin?

A
  • Amylopectin is branched and contains 1-6 glycosidic bonds
  • amylose does not
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42
Q

Why is starch a good storage molecule? (4)

A
  • amylose and amylopectin are compact and dense with glucose
  • insoluble, doesn’t affect cell’s water relations
  • large molecule, so doesn’t leave cell membrane
  • amylopectin: branching creates terminal ends - easily hydrolysed especially in rapid enzymatic breakdown
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43
Q

Where is starch found? (Amylose and amylopectin)

And

In what form?

A
  • Plant cytoplasm or chloroplasts
  • starch grains
44
Q

Where is cellulose found?

A

Plant cell walls

45
Q

How is glycogen structured (3)

What is its function and where is it found?

A
  • formed of chains of a-glucose
  • has a-1-4 and a-1-6 glycosidic bonds
  • meaning it is branched
  1. To store carbohydrates (for energy)
  2. Found as granules in mammalian liver and muscle cells
46
Q

How does glycogen’s structure compare and contrast with amylopectin? (6)

A

Contrasts:

  • glycogen is more branched and chains are shorter
  • glycogen has no unbranched chains
  • glycogen has proportionally more terminal ends, enabling faster hydrolysis

Comparisons:

  • both compact and insoluble - don’t affect cell water relations
  • both have a-1-4 and a-1-6 glycosidic bonds
  • both are formed of a-glucose monomers
47
Q

How is cellulose structured (5)

What is its function and where is it found?

A
  • ß-glucose monomers form 1-4 glycosidic bonds
  • every 2nd monomer is inverted
  • forming long, straight chains
  • nearby chains are hydrogen bonded together, forming a microfibril
  • many microfibrils form a cellulose fibre
  1. Structural support for plants
  2. Plant cell walls
48
Q

What effect does the flipping of alternate monomers in cellulose have on its structure? (2)

A
  • Chains are very straight
  • due to the -CH2OH groups alternating above and below the chain
49
Q

Why do hydrogen bonds form between adjacent cellulose chains?

A

Oxygen and the -CH2OH are available on both sides of chains

50
Q

What is the chemical formula of fructose?

A

C6H12O6

51
Q

What is the chemical formula of glucose?

A

C6H12O6

52
Q

What is the formula of Glycerol?

A

C3H8O3

53
Q

What group do fatty acids belong to?

A

Carboxylic / organic acids

54
Q

What elements do lipids contain?

A

Carbon, hydrogen and oxygen

55
Q

Although lipids are hydrophobic, what solvents do they dissolve in?

A

Organic ones like ether and ethanol

56
Q

What are the 2 main types of lipids

Where are they found?

A
  • triglycerides - fats and oils
  • phospholipids - cell membranes
57
Q

How are triglycerides formed? What else is formed?

What bonds are formed?

What is formed in the reverse of this, and what is this called?

A
  • Condensation reactions between 1 glycerol and 3 fatty acid molecules + 3 molecules of water liberated
  • ester bonds
  • 1 glycerol and 3 fatty acids reformed - Hydrolysis (by adding 3 molecules of water)
58
Q

Where do condensation reactions occur in triglycerides?

What is this process also known as?

A
  1. Between:
  • The (-OH) group of glycerol and
  • the (-COOH) group of fatty acids
  1. Esterfication
59
Q

What are the differences between saturated and unsaturated fatty acids? (2)

A
  • saturated consist of chains of single carbon bonds and hydrogen - unsaturated have at least 1 C=C double bond
  • unsaturated aren’t as straight structurally
60
Q

What is the name of an unsaturated fatty acid with 1 C=C bond?

A

Monosaturated fatty acids

61
Q

What is the name of an unsaturated fatty acid with more than 1 C=C bond?

A

Polyunsaturated fatty acids

62
Q

How are phospholipids formed?

A
  • condensation reactions between 1 glycerol molecule and 2 fatty acid molecules
  • as well as a phosphate group - replaces a fatty acid in a triglyceride
63
Q

What are the properties of phospholipids? (4)

A
  • fatty acid molecules are hydrophobic
  • phosphate makes the glycerol hydrophilic and soluble in water
  • they are polar - key in their role in cell membranes
  • cell membranes contain the steroid cholesterol, located among hydrocarbon chains
64
Q

What are the functions of triglycerides? (3)

A
  • energy store - release more energy per unit mass than carbs
  • insulation (thermally) e.g. as adipose tissue
  • protection of body organs
65
Q

What type of lipid are fats and oils?

What are the differences between both generally? (2)

A
  1. Triglycerides
    • fats are solid at room temp, oils are liquid
    • fats are usually animal products - oils are made by plants
66
Q

What elements are contained in a protein molecule?

A
  • carbon
  • hydrogen
  • oxygen
  • nitrogen
  • sometimes sulphur
67
Q

How many amino acids are in 1 protein?

A

20

68
Q

What is a protein’s shape determined by? (2)

A
  • It’s sequence of amino acids
  • and the bonds / attractions between their R-groups
69
Q

How does each amino acid differ?

A

Each has a different R group

70
Q

What is the R group of glycine?

A

-H

71
Q

What is the R group of alanine?

A

-CH3 (methyl group)

72
Q

What is the R group of cysteine?

A

-CH3 -SH

73
Q

What reaction is responsible for linking amino acids?

What bonds are produced?

What is the inverse reaction called?

A
  • Condensation
  • peptide bonds
  • hydrolysis
74
Q

What is a pair of bonded amino acids called?

A

A dipeptide

75
Q

What is a polypeptide?

A

Many amino acids joined together

76
Q

What are the 4 levels of structure in a protein?

A
  • primary
  • secondary
  • tertiary
  • quaternary
77
Q

What is a primary structure caused by? (protein)

A

The sequence of amino acids in a polypeptide chain

78
Q

What is a secondary structure caused by? (protein)

What shapes can they be?

A
  • hydrogen bonds between (-C=O)- and (-NH)+
  • a-helix (held by hydrogen bonds) or ß-pleated sheets - more rigid and less flexible (due to hydrogen bonds)
79
Q

What bonds/attractions can be present between R-groups in a tertiary structure? (protein)

What are their properties?

(4)

A
  • hydrogen bonds - weak and easily broken
  • ionic bonds - strong but weak with pH changes
  • disulfide bonds / bridges - very strong covalent bonds

+ hydrophobic interactions between amino acids and hydrophobic R-groups - R-groups tend to be surrounded by other parts of the polypeptide

80
Q

How are tertiary protein structures formed broadly? (3)

A
  • further folding
  • creating a 3d shape
  • due to a range of bonds between R-groups of amino acids in the chain

bonds covered in another card

81
Q

What do quaternary protein structures consist of? (2)

What are the 2 types?

A
    • 2 or more polypeptides
    • with some containing prosthetic groups - conjugated proteins
  2. Globular and fibrous
82
Q

What are prosthetic groups?

What are proteins containing prosthetic groups called?

A
  • Non-protein components of proteins e.g. the haem group of haemoglobin (which contains iron)
  • conjugated proteins
83
Q

Name 3 conjugated proteins

Include what type of protein they are.

A

Any 3 from:

Globular:

  • haemoglobin
  • glycoprotein
  • enzymes
  • insulin

Fibrous:

  • collagen
  • actin
  • keratin

Etc.

84
Q

What are prions? (2)

A
  • A type of protein
  • found in the mammalian nervous system and some other animals
85
Q

What is the notation for:

  1. Normal
  2. Disease causing

Prions?

A
  • normal = PrP / PrPc
  • disease causing = PrPsc
86
Q

Structurally, how do disease causing prions differ from normal prions? (2)

A
  • disease causing = missfolded
  • disease causing = greater proportion of ß-pleated sheets than a-helices
87
Q

Why does the presence of a disease causing prion pose a threat? (4)

A
  • causes a chain reaction where other normal prions become progressively missfolded
  • this increases no. of disease causing prions
  • if at a threshold level, neurodegenerative disorders can emerge in nervous tissue
  • this can lead to death
88
Q

What are the 2 key features of disease causing prions?

A
  • can replicate
  • are infectious
89
Q

How long can prions be incubated for?

A

5 to 20 years

90
Q

Name 3 ways diseases caused by prions can arise.

A
  • normal prions spontaneously adopt the PrPsc form
  • mutations in DNA bases coding for prion proteins —> disease-causing form can be passed to offspring
  • eating contaminated food with diseased prions
91
Q

Name 3 prion diseases

and

What animals they are found in

A
  • scraple in sheep
  • Bovine Spongiform Encephalopathy (BSE) - ‘mad cow disease’
  • variant Creutzfeldt-Jakob disease (vCJD) - in humans - acquired usually by eating beef with BSE
92
Q

What’s the subunit of a nucleic acid?

A

A nucleotide

93
Q

What are the components of a nucleotide?

A
  • phosphate
  • a Pentose sugar
  • a base
94
Q

What are the bases found in DNA?

Include how they pair

A
    • Adenine
    • Guanine
    • Cytosine
    • Thymine
  2. AT and CG
95
Q

What are the bases found in RNA?

Include how they pair

A
    • Adenine
    • Cytosine
    • Uracil
    • Guanine
  2. They don’t (single strand)
96
Q

Why are strands of DNA described as being anti parallel?

A

2 strands run in opposite directions

97
Q

What bonds are there between phosphates and pentose sugars in nucleic acids?

A

Phosphodiester links

98
Q

What are the differences between DNA and RNA? (4)

A
  • DNA contains deoxyribose sugar, RNA contains ribose sugar
  • subunits of DNA are deoxyribonucleotides, subunits of RNA are ribonucleotides
  • DNA is longer and double stranded, RNA is shorter and single stranded
  • DNA contains thymine, RNA contains Uracil instead
99
Q

What are the 3 types of RNA?

A
  • mRNA - messenger RNA
  • tRNA - transfer RNA
  • rRNA - ribosomal RNA
100
Q

What are the roles of the 3 types of RNA?

A
  • rRNA: component of ribosomes
  • tRNA: carries amino acids to ribosomes where protein synthesis takes place
  • mRNA: carries code from DNA in the nucleus to a ribosome where protein synthesis takes place
101
Q

What is the function of DNA? (2)

A
  • Acts as the genetic code for amino acid synthesis
  • according to base triplets
102
Q

What are the ends of a polynucleotide strand called?

Why are they called this?

A
  • 5’ ends and 3’ ends
  • 5’ ends are closest to the 5th carbon of a sugar
  • 3’ ends are closest to the 3rd carbon of a sugar
103
Q

What is a gene?

A

A sequence of DNA that codes for a polypeptide

104
Q

Outline the process of semiconservative replication (4)

A
  • DNA helicase breaks hydrogen bonds between complementary bases to reveal 2 polynucleotide strands
  • DNA polymerase moves along each strand and acts as a template for the synthesis of a new strand
  • DNA polymerase catalyses the joining of free deoxyribonucleotides to each original strand - new complementary strands form
  • process continues along entire length of DNA molecule
105
Q

Outline the Meselson Stahl experiment (4)

A
  • cultured E. coli using 15N
  • 15N incorporated into the bases of the DNA in all the bacteria over time; bacteria with 14N died and were replaced
  • bacteria were transferred to a medium with 14N
  • bacteria extracted and analysed using a centrifuge at intervals:
  1. While growing before 15N
  2. While growing in 15N
  3. 1st gen after transfer to 14N
  4. 2nd gen after transfer to 14N
106
Q

Explain the results of the Meselson Stahl experiment (3)

What trend would results follow after a further gen?

A
    • gen 0: all DNA at bottom of centrifuge tube - 15N bases
    • gen 1: DNA in middle - 1 strand 15N bases, 1 strand 14N bases —> medium mass
    • gen 2: half DNA = medium mass with 15N and 14N bases, other half only DNA with 14N bases (top)
  2. More DNA with 14N bases, less mixed DNA

CCEA AS Biology Units 1, 2 And 3 (15 decks)

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