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Biology > Topic 1 - Biological Molecules > Flashcards

Topic 1 - Biological Molecules Flashcards

(38 cards)

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1
Q

Monomer

A

Single sugar monomer

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2
Q

Disaccharide

A

two monosaccharides

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3
Q

Polysaccharide

A

many monosaccharides

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4
Q

What reaction takes place to form disaccharides and polysaccharide bonds

A

Condensation reaction

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5
Q

3 types of monosaccharides

A

Glucose
Fructose
Galactose

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6
Q

Describe glucose

A
  • Monosaccharide
  • Contains 6 carbon atoms in each molecule
  • Main substrate for respiration
  • 2 isomers; alpha and beta
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7
Q

Ribose structure

A
  • Monosaccharide
  • 5 carbon atoms
  • Pentose sugar
  • Component of RNA
  • DNA contains isomer (deoxyribose)
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8
Q

Examples of disaccharides and the monosaccharides that make them up

A
  • Maltose (2 glucose)
  • Sucrose (glucose & fructose)
  • Lactose (glucose and galactose)
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9
Q

Polysaccharides examples

A
  • Glycogen (alpha glucose)
  • Starch (alpha glucose)
  • Cellulose (beta glucose)
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10
Q

Glycogen structure

A
  • Main energy storage molecule in animals
  • 1,4 and 1,6 glycosidic bonds
  • Large number of side branches (can be hydrolysed and energy released quickly)
  • Relatively large but compact molecule thus maximising amount of energy it can store
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11
Q

Structure of starch

A

Mixture of 2 polysaccharides;

  • Amylose - unbranched chain of glucose
  • 1,4 glycosidic bonds
  • Coiled and very compact (can store lots of energy)
  • Amylopectin - 1,4 & 1,6 glycosidic bonds
  • Branched molecule
  • Rapidly digested by enzymes (energy released quick)
  • Compact but not as compact as amylose
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12
Q

Cellulose structure

A
  • Long, unbranched chains of glucose
  • 1,4 glycosidic bonds
  • Microfibres and microfibrils are strong threads made of long cellulose chains joined by hydrogen bonds & provide structural support
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13
Q

Lipids definition

A

Biological molecules which are only soluble in organic solvents such as alcohols. 2 types; saturated and unsaturated

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14
Q

Saturated lipids

A

E.g. in animal fats

Only contain carbon-carbon single bonds

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15
Q

Unsaturated lipids

A

E.g. found in plants

Contain carbon-carbon double bonds and melt at lower temperatures than saturated fats

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16
Q

Properties of lipids

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A
  • Waterproof because the fatty tail is hydrophobic
  • Very compact
  • Non-polar and insoluble (good for storage as they don’t interfere with water-based reactions in cytoplasm)
  • Conduct heat slowly therefore provide thermal insulation
17
Q

Examples of lipids

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A
  • Triglycerides (1 glycerol & 3 fatty acids joined by ester bonds formed in condensation reaction, used as energy reserves in plant/animal cells)
  • Phospholipids (phosphate heads are hydrophillic tails are hydrophobic, form bilayer)
18
Q

Structure of proteins

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A

Determined by order and number of amino acids, bonding present & shape of protein

Primary structure - linear sequence of amino acids

Secondary structure - folding of polypeptide chain into alpha helix or beta pleated sheet

Tertiary structure - 3D folding of secondary structure into complex shape (determined by type of bonding)

Quaternary structure - 3D arrangement of more than one polypeptide

19
Q

Fibrous proteins

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A
  • Long parallel polypeptides
  • Very little tertiary/quaternary structure (mainly secondary)
  • Occasional cross-linkages which form microfibres for tensile strength
  • Insoluble
  • Used for structural purposes

Collagen - high tensile strength due to large number of hydrogen bonds

20
Q

Globular proteins

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A
  • Complex tertiary/quaternary structures
  • Form colloids in water
  • Many uses e.g. hormones, antibodies

Haemoglobin - water-soluble globular protein, carry oxygen in blood

21
Q

Nucleotides

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A

Consist of pentose sugar, nitrogen-containing base and a phosphate group

22
Q

Pyramidines vs purines

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A

Pyramidines- smaller (one ring) cytosine, uracil, thymine

Purines - bigger (2 ring) guanine, adenine

23
Q

Structure of DNA

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A
  • Double helix
  • 2 polynucleotides joined by hydrogen bonds between complementary bases
  • 2 bonds between adenine/thymine
  • 3 bonds between cytosine/guanine
24
Q

Steps of semi-conservative replication

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A

1) DNA double helix unwinds as hydrogen bonds are broken between complementary bases. DNA helicase catalyses the unraveling of the DNA double helix
2) One of the strands used as template. Free nucleotides line up and complementary base pairing occurs between template strand and free nucleotides
3) Adjacent nucleotides joined by phosphodiester bonds formed in condensation reactions. This is catalysed by DNA polymerase
4) The new DNA molecules automatically fold into double helices as hydrogen bonds are formed within the molecules

Semi conservative because new DNA molecules contain an original strand of DNA and one newly-synthesised strand of DNA

25
Genetic code
Consists of triplets of bases called codons Each codon codes for an amino acid Amino acid joined by peptide bonds to form polypeptide chain
26
Features of the genetic code
- Non-overlapping (each triplet is only read once) - Degenerate (more than 1 triplet codes for same amino acid) - Universal (same in all organisms) - Contain stop and start codons which stop/start protein synthesis
27
Transcription
- DNA helicase breaks hydrogen bonds between complementary bases of DNA double helix and DNA uncoils - One of the strands used as template to make mRNA molecule. Template strand = antisense strand. Coding strand = sense strand and has the same nucleotide sequence as the strand being synthesised - Free nucleotides line up on template strand by complementary base pairing and adjacent nucleotides are joined together by phosphodiester bonds (forms molecule of mRNA) - This catalysed by RNA polymerase - mRNA moves out of nucleus through nuclear pore and attaches to a ribosome in cytoplasm
28
Translation
- mRNA attaches to a ribosome on RER. A tRNA molecule which has specific amino acid attached to amino acid binding site, binds to mRNA via anticodon - Hydrogen bonds from between anticodon of tRNA and codon of mRNA - A second tRNA molecule binds to next codon of mRNA and the two amino acids form a peptide bond - A third tRNA molecule joins and the first one leaves the ribosome - Process repeated leading to formation of a polypeptide chain until a stop codon is reached on mRNA
29
Enzymes
Biological catalysts which increase the rate of chemical reaction by lowering the activation energy. They are specific to substrates they bind to to create enzyme substrate complexes
30
Factors affecting the rate of enzyme-controlled reactions
- Enzyme concentration (rate increases with this until a point of plateau as all enzymes saturated) - Substrate concentration (rate increases with this until plateau when enzyme conc becomes limiting factor) - Temperature (rate increases till optimum temp the rate drops due to denaturation)
31
Inhibitors
Substances which stop the enzyme from binding to its substrate, therefore controlling the progress of a reaction. May be reversible or irreversible
32
Competitive inhibition
An inhibitor molecule competes with the substrate for binding to the active site of the enzyme, therefore preventing the substrate from binding. Can be reversed by increasing substrate concentration
33
Non-competitive inhibition
An inhibitor doesn't bind to active site but binds to a different part of the enzyme. This decreases the reaction rate as the active site doesn't fit the substrate and the substrate cannot bind to the enzyme. Cannot be reversed by increasing substrate concentration
34
Nitrate ions function
Required to make DNA and amino acids
35
Calcium ions use
Needed to form calcium pectate for the middle lamellae in plants
36
Phosphate ions use
Required to make ADP and ATP and DNA and RNA
37
Magnesium ions use
Needed to produce chlorophyll
38
Properties of water
- Polar solvent due to uneven distribution of charge - High specific heat capacity (lots of energy needed to change temp, minimises temp fluctuations) - Relatively large latent heat of vaporisation (evaporation provides cooling effect) - Cohesion and adhesion (hydrogen bonds) - High surface tension - Maximum density is at 4 degrees C (ice less dense than water, so ice float on water creating insulating layer) - Incompressible

Biology (10 decks)

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