OCR biology paper 3 was a horrible paper
Edit after marking : not too bad esp cuz it was meant to be hard also this is based on the uoms someone made
1. Gas exchange/nerves
-smooth muscle then cartilage (2)✅
- ciliated epithelilal cells: waft mucus to throat out of airway (2)✅
-goblet cells: secrete mucus that traps pathogens/dust✅
-autonomic as via medulla oblongata. Rapid, automatic response ie reflex. Idk if u need to specify cranial. (2)✅❌
SA:V= 46(.1): 1 (3)✅
large rate of diffusion of O2 out and CO2 in ✅
2. Respiration
UV light in dark room. TLC plate fluoresces so spots seen as dark spots. (1)✅
Rf = 0.3 (24/80) (2)✅
molecule d is a pyrimidine nucleoside required as a free DNA nucleotide in S phase. S phase (DNA replication) cannot occur without it. Checkpoint detects this and stops interphase. (3)✅
E in matrix, F on inner membrane (2)✅
Tick box: all crosses except tick on the right middle box (the one abt NAD being reduced in link reaction) (2)🤨
Disagree:NAD AND FAD USED TO OXIDISE MOLECULES
-ATP q: some ATP is used for active transport of pyruvate into mitochondria (1)❌
-Coenzyme q: transfer chemical groups between enzymes/reactions eg NAD transferring NAD from matrix to mitochondrial inner membrane. Are recycled in metabolic pathways (3)🤨
Coenzymes bind to an enzymes to change its active site to make it complementary etc
- Graph: Without vitamin C leads to higher adenylyl cyclase activity. Quote data to show this. But, no stats test (or evidence of repeats!) to show that difference is significance so not much confidence in this conclusion. (2)❌❌
I don’t remember that but also I may have misread the graph 💀
3. Maize- genes and photosynthesis
-after 150s, GM plant wastes les energy as heat so more light energy put to light dependent stage. Greater rate of ATP and reduced NADP production. Allows greater rate of RuBP regeneration and thus CO2 fixation(2)✅
-computational biology q: facilitates access to large amounts of data. Can compare sequences and quickly identify allelic differences. more closely related=more similar sequences. (4)✅✅✅❌
-Inheritance cross: should obtain a 3:1:3:1 (or 6:2:6:2) ratio of offspring phenotype. this ratio relates to purple/smooth, purple/wrinkled, yellow/smooth, yellow/wrinkled (total of 4)✅
4.Biodiversity
To get 6 you must talk about For AND Against AND validity . 2 of those= 4, 1 of those= 2
(6)
Points For:
-proportion of measured species endangered falls (quote data) between 2000 and 2020- fig 4.2
-Fig 4.1= fully protected species= lower percentage endangered so could be down to CITES
points against✅
-endangered species in 4.2 rises✅
- species protected by permits still high endangerment. Question how effective permits are✅
Validity:
-don't know if CITES caused these effects or sth else✅
-don't know data before CITES to know true effect. ✅
Genetic bottleneck (1)❌
Behavioural, anatomical, physiological, anatomical(2)✅
Speciation q: could argue both sides. overlapping ranges indicates sympatric, one of the birds on different island so could be allopatric, different habitats so could be allopatric, perhaps alps could lead to allopatric etc- this was a dodgy q, as was the 6 marker (4)✅
5. Respiration
-could talk about similar shape graphs- exponential growth of CO2 production. Maltose always higher than glucose, quote data (2)✅
-at one point overlap so similar (quote data), but one starts off lower than other, than one rises higher than other, sucrose plateaus whilst fructose rises still so not that similar (2)✅
- serial dilution (again!): stir (even distribution), micropipette (greater resolution/lower percentage instrument uncertainty) (2)🤨✅
I think u could have also said clean the pipettes after every use or something
-Gap fill: distilled, stoppered (closed), standard deviations (3)✅
6. A very dodgy q. Have to refer to both homeobox and brain in detail for 6 (6)
- homeobox= control body devlopment. Hox= subset found in animals. ✅
-Hox controls development of body plan along anterior=posterior axis❌
-Hox displays collinearity (spatial and temporal). This means position on chromosome aligns to position of development. Controls what develops where❌
-regulates genes for mitosis/apoptosis. Example of tissue between fingers. Mitosis= grows apopotosis= programmed cell death so tissue degradation✅
-how homeobox functions: 60 amino acid homeodomain sequence, binds to promoter, rise or fall in gene transcription. ❌
-Brain: neurone differentiation regulated. Describe parts of brain and how homeobox allows distinguising of the parts. Brain wrinkling of humans caused by apoptosis- associated with higher thought function❌
7. perhaps eukarya and archaea most closely related cos of histones and SFB+ perhaps archaea and bacteria most closely related cos of no mitochondria and 70s ribosomes (different to eukarya). Cannot conclude which are most closely related. Can conclude that bacteria and eukarya least closely related. (3)✅
DNA polymerase: joins free DNA nucelotides via catalysis of condensation recations that cause phosphodiester bond formation. (1)✅
Helicase: breaks Hydrogen bonds between complementary strand allowing them to acts as templates during DNA replication(1)✅
Edit: I got A A* A*
A IN BIO
BUT YH I GOT INTO KCL MEDSCHOOL