Topic 1 - Biological Molecules Flashcards
What is a monomer?
a smaller / repeating) unit / molecule from which larger molecules / polymers are made;
What is a polymer?
made up of many identical / similar molecules / monomers / subunits
Condensation reaction
joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water
Hydrolysis reaction
breaks a chemical bond between two molecules and involves the use of a water molecule
Bonds in:
Lipids
Proteins
Carbohydrates
DNA
Ester
Peptide
Glycosidic
Phosphodiester
Monosaccharides in disaccharides:
Lactose
Sucrose
Maltose
Glucose and galactose
Glucose and fructose
2 glucose
Alpha and beta glucose structure
Orientation of the hydroxyl group which is on the same side in α-glucose and on the opposite sides in the β-glucose
Comparing cellulose and glycogen
- Cellulose is made up of β-glucose (monomers) and glycogen is made up of α-glucose (monomers);
- Cellulose molecule has straight chain and glycogen is branched;
- Cellulose molecule has straight chain and glycogen is coiled;
- glycogen has 1,4- and 1,6- glycosidic bonds and cellulose has only 1,4- glycosidic bonds;
Starch structure and function
- Insoluble (in water), so doesn’t affect water potential;
- Branched / coiled / (α-)helix, so makes molecule compact;
OR
Branched / coiled / (α-)helix so can fit many (molecules) in small area; - Polymer of (α-)glucose so provides glucose for respiration;
- Branched / more ends for fast breakdown / enzyme action;
- Large (molecule), so can’t cross the cell membrane
Cellulose structure and function
- Long and straight chains;
- Become linked together by many hydrogen bonds to form fibrils;
- Provide strength (to cell wall).
Describe how an ester bond is formed in a phospholipid molecule
- Condensation (reaction) OR Loss of water;
- Between of glycerol and fatty acid;
Unsaturated fatty acids
Double bonds (present) / some / two carbons with only one hydrogen / (double bonds) between carbon atoms / not saturated with hydrogen;
Triglycerides compared to phospholipids
- Both contain ester bonds (between glycerol and fatty acid);
- Both contain glycerol;
- Fatty acids on both may be saturated or unsaturated;
- Both are insoluble in water;
- Both contain C, H and O but phospholipids also contain P;
- Triglyceride has three fatty acids and phospholipid has two fatty acids plus phosphate group;
- Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;
Accept ‘non-polar’ for hydrophobic and ‘polar’ for hydrophilic. - Phospholipids form monolayer (on surface)/micelle/bilayer (in water) but triglycerides don’t;
Amino acid structure
A central carbon, a carboxyl group, amine group, a hydrogen atom and an R-group, or side-chain group
Protein structure
- Structure is determined by (relative) position of amino acid/R group/interactions;
- Primary structure is sequence/order of amino acids;
- Secondary structure formed by hydrogen bonding (between amino acids);
- Tertiary structure formed by interactions (between R groups);
- Creates active site in enzymes OR Creates complementary/specific shapes in antibodies/carrier proteins/receptor (molecules);
- Quaternary structure contains >1 polypeptide chain OR Quaternary structure formed by interactions/bonds between polypeptides;
Enzyme action
- Reduces activation energy;
Accept ‘reduces Ea’. - Due to bending bonds
OR
Without enzyme, very few substrates have sufficient energy for reaction
Enzymes and temperature
- At low temperatures, molecules have less kinetic energy
- So less successful collision/less enzyme-substrate complexes form
- At higher temperatures (above optimum) denaturation is due to more (kinetic) energy;
- Breaks hydrogen / ionic bonds (between amino acids / R groups);
- Change in shape of the active site / active site no longer complementary so fewer enzyme-substrate complexes formed / substrate does not fit;
Induced fit model
- Substrate is not complimentary to the enzyme active site.
- Active site alters shape to fit around substrate/forms an enzyme-substrate complex
- Bonds are stressed/bent
Competitive inhibitor action
- Similar shape to the substrate/complimentary to the enzyme active site
- Binds to active site
- So less enzyme-substrate complexes can form
Non-competitive inhibitor action
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
What is a DNA nucleotide?
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).
What happens in DNA replication?
- Strands separate / H-bonds break;
- DNA helicase (involved);
- Both strands / each strand act(s) as (a) template(s);
- (Free) nucleotides attach;
- Complementary / specific base pairing / AT and GC;
- H-bonds reform;
- DNA polymerase joins nucleotides (on new strand);
- Reject: if wrong function of DNA polymerase
- Forming phosphodiester bonds
- Semi-conservative replication / new DNA molecules contain one old strand and one new strand;
- Reject: if wrong context e.g. new DNA molecules contain half of each original strand
DNA polymerase function
- Joins (adjacent DNA) nucleotides;
- (Catalyses) condensation (reactions);
- (Catalyses formation of) phosphodiester bonds (between adjacent nucleotides)
DNA structure and function
- Weak / easily broken hydrogen bonds between bases allow two strands to separate / unzip;
- Two strands, so both can act as templates;
- Complementary base pairing allows accurate replication
