h2 bio topical reminders

🍃 H2 bio last-minute reminders Disclaimer: notes are based on the 2025 syllabus!! These are general guidelines I got from my notes, teachers and friends. Styles of writing may differ from school to school, so please follow your own teachers’/school’s guidelines in internal exams. For the actual As…it’s kinda up to you lol FAQs 1. what does it mean by gene mutation in intron can affect binding site of splicing enzymes 1. Just means the spliceosome can’t recognise and bind anymore cause the intron sequences got changed, boundaries changed (complementary base pairing) 2. Does reverse transcriptase synthesise the second dna strand or is it dna pol in virus 1. DNA pol 3. Does post translational mod happen in proks too or only euk 1. can happen in proks, but not that significant 4. In telomerase is the new dna on the shortened end synthesised discontinuously or continuous 1. Continuous (should be) but this ain’t important lol Answering Qns - “With reference to figure” - quote time, data, aANYTHING to support point even if it’s just identifying stages of mitosis must be “anaphase from x min to x min” - ‼ ‼ “Comment” - split into quote data then inferences from data. Or describe structures (in detail!) then LINK structure and function. - Graph DECREASE/INCREASE GRADUALLY, SHARPLY - Anytime enzymes are mentioned in whatever topic and context must always say it is complementary in shape and charge to whatever substrate - LABEL diagram eg when they ask you to draw formation of a dipeptide or any bio molecule, label each monomer, label bond, label WATER - For any BONDS: specify BETWEEN WHAT AND WHAT eg H bonds BETWEEN CO AND NH GROUPS OF SAME POLYPEPTIDE - “Describe”: NAME the process please. Eg - vesicles fuse w membrane , transporting xxx out BY EXOCYTOSIS I know you’d miss this out.. - All drugs eg inhibitors must be stable and not easily broken down so it can remain in active site - limiting factors? WHAT KIND of limiting factor. HIGH temperature? LOW humidity? Cannot just like “temperature” - “EVALUATE effect”. Cannot say there is an effect or just quote data. Say stuff like INCREASE OR DECREASE, UPREGULATE DOWNREGULATE, WHAT effect it has

- “Suggest why this means this” / “this leads to this” -> explain, then provide a trend. Eg suggest why blood ALT concentration provides measure of damage to liver cells. Because: ALT presence is due to leakage from membranes and cell lysis, and MORE DAMAGE OF LIVER CELLS LEADS TO MORE ALT IN BLOOD. - Comparison: - must compare more in depth eg cannot just be like”virus has RNA dependent RNA polymerase while human cell does not” it must be like human cell has DNA POLYMERASE - When comparing different situations when different things bind to same receptor (eg cell sig) must preface by saying “bind PREFERENTIALLY” in whatever scenario. - Question parts that seem general but turn up as part of a larger question part eg 2020 measles qn - must answer specifically to the context (viruses strain emerging VIRUSES CANNOT EVOLVE AND SPECIATE.) - ‼ ‼ ‼ ‼ ‼ TRY NOT TO USE THE WORD “PRODUCING” pleaseee Carbo ● amylose amylopectin branched: multiple branch ends allow multiple enzymes to work on more sites AT THE SAME TIME increasing energy generation PER UNIT TIME ● If enzyme is added to solution eg amylase added to hydrolyse starch, BIURETS WILL BE POSITIVEEE ● If asked to draw chain, put a bracket outside the molecule and write n ● Glycosidic bond formation is catalysed by enzymes ● always state the observation shown even in SEQ, when it is a negative test do not just write negative test given, eg must say NO BLUE BLACK COLOURATION WHEN STARCH TEST ● Draw a chain and LABEL glycosidic bond ● Set list for comparison ○ monomer ○ type of bond between monomers ○ orientation of monomer ○ Presence of inter chain bonding ○ Structure of molecule ● Benedict’s test for NON REDUCING SUGAR ○ ‼ CONDUCT BENEDICTS ONCE FIRST then negative result ○ Boil equal volume of new sample of test solution with HCl for ~1min, COOL, add SODIUM BICARBONATE (alkaline medium!!) THEN conduct Benedict’s again. ○ NEGATIVE AT FIRST THEN POSITIVE LATER. this is the whole observation necessary. Cannot conclude from positive alone that non reducing is present. ● Amylase digests a(1-4) not beta I think ● a and b (1,4) whatever doesn’t only refer to glucose monomers. a and b just refers to the orientation of the monomer in the bond. So if they have other app questions like chitin etc I think still just quote the full original bond name 😔😔

Lipids ● no kink if trans bond ● a second role of cholesterol is that it provides mechanical stability due to forming weak hydrophobic interactions ● Always mention PER UNIT MASS eg twice as much energy FOR THE SAME MASS ● Phosphate head is CHARGED NOT POLAR Proteins ● haemoglobin has no disulfide so that subunits can move wrt each other and cooperative binding ○ Sickle cell is 6th position glutamic hydrophilic changed to valine hydrophobic ● every time mentioning the 4bonds (h, hydrophobic, ionic disulfide) MUST SAY ITS BETWEEN R GROUPS ● Glycine-X-Y but X and Y are only USUALLY proline and hydroxyproline. Which means glycine occurs most frequently (since it’s fixed) ● In bio, ionic bond is considered WEAK Enzymes ● note not ALL enzymes are globular proteins. Some are eg RNA enzymes ● R groups of the catalytic residues are what catalyses conversion (not backbone!!) ● substrate is the one that causes induced fit change ● absorption of thermal energy: ○ Increases kinetic energy more - ALWAYS mention KE whether it’s at increasing or decreasing rate ○ FORCEFUL collisions ○ increases frequency of collisions ○ Thermal agitation of ATOMS within the molecules bonds more likely to break ● For denaturation specify which bonds are broken wrt to the contact, catalytic residues etc ○ Temperature: intramolecular vibrations increase ○ Ph: ionic and hydrogen ● Non competitive inhibitors effectively decrease the availability of enzymes as it forms inactive enzyme-inhibitor complexes ● RATE X2 WITH EVERY 10C TEMP INCREASE ● every time there is “explain lowered activation energy” MUST STATE greater proportion of molecules with energy greater than equal to activation energy ● at lower sub conc: enzymes active sites *readily available/ sub conc limiting, increasing sub conc increases frequency of effective collisions ● if explaining why a change in one amino acid causes enzyme activity to decrease - relate amino acid to either part of catalytic or contact/structural residue to explain

● For ALLOSTERIC must always say ALLOSTER