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A Level Biology > Topic 1 - Biological Molecules > Flashcards

Topic 1 - Biological Molecules Flashcards

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1
Q

What is a monomer?

A

a smaller / repeating) unit / molecule from which larger molecules / polymers are made;

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2
Q

What is a polymer?

A

made up of many identical / similar molecules / monomers / subunits

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3
Q

Condensation reaction

A

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

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4
Q

Hydrolysis reaction

A

breaks a chemical bond between two molecules and involves the use of a water molecule

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5
Q

Bonds in:
Lipids
Proteins
Carbohydrates
DNA

A

Ester
Peptide
Glycosidic
Phosphodiester

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6
Q

Monosaccharides in disaccharides:
Lactose
Sucrose
Maltose

A

Glucose and galactose
Glucose and fructose
2 glucose

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7
Q

Alpha and beta glucose structure

A

Orientation of the hydroxyl group which is on the same side in α-glucose and on the opposite sides in the β-glucose

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8
Q

Comparing cellulose and glycogen

A
  1. Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose (monomers);
  2. Cellulose molecule has straight chain and glycogen is branched;
  3. Cellulose molecule has straight chain and glycogen is coiled;
  4. glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds;
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9
Q

Starch structure and function

A
  1. Insoluble (in water), so doesn’t affect water potential;
  2. Branched / coiled / (α-)helix, so makes molecule compact;
    OR
    Branched / coiled / (α-)helix so can fit many (molecules) in small area;
  3. Polymer of (α-)glucose so provides glucose for respiration;
  4. Branched / more ends for fast breakdown / enzyme action;
  5. Large (molecule), so can’t cross the cell membrane
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10
Q

Cellulose structure and function

A
  1. Long and straight chains;
  2. Become linked together by many hydrogen bonds to form fibrils;
  3. Provide strength (to cell wall).
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11
Q

Describe how an ester bond is formed in a phospholipid molecule

A
  1. Condensation (reaction) OR Loss of water;
  2. Between of glycerol and fatty acid;
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12
Q

Unsaturated fatty acids

A

Double bonds (present) / some / two carbons with only one hydrogen / (double bonds) between carbon atoms / not saturated with hydrogen;

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13
Q

Triglycerides compared to phospholipids

A
  1. Both contain ester bonds (between glycerol and fatty acid);
  2. Both contain glycerol;
  3. Fatty acids on both may be saturated or unsaturated;
  4. Both are insoluble in water;
  5. Both contain C, H and O but phospholipids also contain P;
  6. Triglyceride has three fatty acids and phospholipid has two fatty acids plus phosphate group;
  7. Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;
    Accept ‘non-polar’ for hydrophobic and ‘polar’ for hydrophilic.
  8. Phospholipids form monolayer (on surface)/micelle/bilayer (in water) but triglycerides don’t;
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14
Q

Amino acid structure

A

A central carbon, a carboxyl group, amine group, a hydrogen atom and an R-group, or side-chain group

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15
Q

Protein structure

A
  1. Structure is determined by (relative) position of amino acid/R group/interactions;
  2. Primary structure is sequence/order of amino acids;
  3. Secondary structure formed by hydrogen bonding (between amino acids);
  4. Tertiary structure formed by interactions (between R groups);
  5. Creates active site in enzymes OR Creates complementary/specific shapes in antibodies/carrier proteins/receptor (molecules);
  6. Quaternary structure contains >1 polypeptide chain OR Quaternary structure formed by interactions/bonds between polypeptides;
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16
Q

Enzyme action

A
  1. Reduces activation energy;
    Accept ‘reduces Ea’.
  2. Due to bending bonds
    OR
    Without enzyme, very few substrates have sufficient energy for reaction
17
Q

Enzymes and temperature

A
  1. At low temperatures, molecules have less kinetic energy
  2. So less successful collision/less enzyme-substrate complexes form
  3. At higher temperatures (above optimum) denaturation is due to more (kinetic) energy;
  4. Breaks hydrogen / ionic bonds (between amino acids / R groups);
  5. Change in shape of the active site / active site no longer complementary so fewer enzyme-substrate complexes formed / substrate does not fit;
18
Q

Induced fit model

A
  1. Substrate is not complimentary to the enzyme active site.
  2. Active site alters shape to fit around substrate/forms an enzyme-substrate complex
  3. Bonds are stressed/bent
19
Q

Competitive inhibitor action

A
  1. Similar shape to the substrate/complimentary to the enzyme active site
  2. Binds to active site
  3. So less enzyme-substrate complexes can form
20
Q

Non-competitive inhibitor action

A

1.   Attaches to the enzyme at a site other than the active site;
Accept ‘attaches to allosteric/inhibitor site’
2.   Changes (shape of) the active site
OR
Changes tertiary structure (of enzyme);
3.   (So active site and substrate) no longer complementary so less/no substrate can fit/bind

21
Q

What is a DNA nucleotide?

A

A nitrogen-containing base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate group, and a sugar (deoxyribose in DNA; ribose in RNA).

22
Q

What happens in DNA replication?

A
  1. Strands separate / H-bonds break;
  2. DNA helicase (involved);
  3. Both strands / each strand act(s) as (a) template(s);
  4. (Free) nucleotides attach;
  5. Complementary / specific base pairing / AT and GC;
  6. H-bonds reform;
  7. DNA polymerase joins nucleotides (on new strand);
  8. Reject: if wrong function of DNA polymerase
  9. Forming phosphodiester bonds
  10. Semi-conservative replication / new DNA molecules contain one old strand and one new strand;
  11. Reject: if wrong context e.g. new DNA molecules contain half of each original strand
23
Q

DNA polymerase function

A
  1. Joins (adjacent DNA) nucleotides;
  2. (Catalyses) condensation (reactions);
  3. (Catalyses formation of) phosphodiester bonds (between adjacent nucleotides)
24
Q

DNA structure and function

A
  1. Weak / easily broken hydrogen bonds between bases allow two strands to separate / unzip;
  2. Two strands, so both can act as templates;
  3. Complementary base pairing allows accurate replication
25
Q

Eukaryote DNA compared to prokaryote/mitochondrial/chloroplast

A

1.   DNA shorter;
2.   Fewer genes;
3.   DNA circular not linear;
4.   Not associated with protein/histones, unlike nuclear DNA;
5.   Introns absent but present in nuclear DNA;
Ignore references to double and single stranded DNA

26
Q

Starch test

A
  1. Add iodine / stain specific for starch to the slide / cells / tissue / add iodine / stain specific for starch and examine under microscope;
  2. Blue-black / blue / black / purple;
27
Q

Protein test

A
  1. Add biuret (reagent);
  2. (Positive result) purple/lilac/violet /mauve;
28
Q

Non reducing sugars test

A
  1. Heat with acid and neutralise;
  2. Heat with Benedict’s (solution);
  3. Red precipitate/colour;
29
Q

Emulsion test

A
  1. Dissolve in alcohol, then add water;
  2. White emulsion shows presence of lipid.
30
Q

ATP synthase reaction

A

ADP + Pi ⟶ ATP + H2O

31
Q

ATP compared to DNA nucleotide

A
  1. ATP has ribose and DNA nucleotide has deoxyribose;
  2. ATP has 3 phosphate (groups) and DNA nucleotide has 1 phosphate (group);
  3. ATP – base always adenine and in DNA nucleotide base can be different / varies;
32
Q

Properties of water and why they are important

A

1.   A metabolite in condensation/hydrolysis/ photosynthesis/respiration;
2.   A solvent so (metabolic) reactions can occur
OR
A solvent so allowing transport of substances;
3.   High heat capacity so buffers changes in temperature;
4.   Large latent heat of vaporisation so provides a cooling effect (through evaporation);
5.   Cohesion (between water molecules) so supports columns of water (in plants);
6.   Cohesion (between water molecules) so produces surface tension supporting (small) organisms

A Level Biology (5 decks)

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