Biology_A-level_Aqa
-
1-biological-molecules
1-1-biological-molecules-carbohydrates11 主题-
1-1-1-biological-molecules-key-terms
-
1-1-2-biological-molecules-reactions
-
1-1-3-monosaccharides
-
1-1-4-glucose
-
1-1-5-the-glycosidic-bond
-
1-1-6-chromatography-monosaccharides
-
1-1-7-disaccharides
-
1-1-8-starch-and-glycogen
-
1-1-9-cellulose
-
1-1-10-biochemical-tests-sugars-and-starch
-
1-1-11-finding-the-concentration-of-glucose
-
1-1-1-biological-molecules-key-terms
-
1-2-biological-molecules-lipids3 主题
-
1-3-biological-molecules-proteins5 主题
-
1-4-proteins-enzymes12 主题
-
1-4-1-many-proteins-are-enzymes
-
1-4-2-enzyme-specificity
-
1-4-3-how-enzymes-work
-
1-4-4-required-practical-measuring-enzyme-activity
-
1-4-5-drawing-a-graph-for-enzyme-rate-experiments
-
1-4-6-using-a-tangent-to-find-initial-rate-of-reaction
-
1-4-7-limiting-factors-affecting-enzymes-temperature
-
1-4-8-limiting-factors-affecting-enzymes-ph
-
1-4-10-limiting-factors-affecting-enzymes-enzyme-concentration
-
1-4-11-limiting-factors-affecting-enzymes-substrate-concentration
-
1-4-12-limiting-factors-affecting-enzymes-inhibitors
-
1-4-14-control-of-variables-and-uncertainty
-
1-4-1-many-proteins-are-enzymes
-
1-5-nucleic-acids-structure-and-dna-replication8 主题
-
1-5-2-nucleotide-structure-and-the-phosphodiester-bond
-
1-5-3-dna-structure-and-function
-
1-5-4-rna-structure-and-function
-
1-5-5-ribosomes
-
1-5-6-the-origins-of-research-on-the-genetic-code
-
1-5-8-the-process-of-semi-conservative-replication
-
1-5-9-calculating-the-frequency-of-nucleotide-bases
-
1-5-10-the-watson-crick-model
-
1-5-2-nucleotide-structure-and-the-phosphodiester-bond
-
1-6-atp-water-and-inorganic-ions4 主题
-
2-cell-structure2-1-cell-structure7 主题
-
2-2-the-microscope-in-cell-studies4 主题
-
2-3-cell-division-in-eukaryotic-and-prokaryotic-cells8 主题
-
2-4-cell-membranes-and-transport7 主题
-
2-5-cell-recognition-and-the-immune-system7 主题
-
2-6-vaccines-disease-and-monoclonal-antibodies6 主题
-
3-exchange-and-transport3-1-adaptations-for-gas-exchange6 主题
-
3-2-human-gas-exchange10 主题
-
3-2-1-the-human-gas-exchange-system
-
3-2-2-dissecting-the-gas-exchange-system
-
3-2-3-microscopy-and-gas-exchange-surfaces
-
3-2-4-investigating-gas-exchange
-
3-2-5-the-alveolar-epithelium
-
3-2-6-ventilation-and-gas-exchange
-
3-2-8-the-effects-of-lung-disease
-
3-2-9-pollution-and-smoking-data
-
3-2-10-risk-factor-data
-
3-2-11-correlations-and-causal-relationships
-
3-2-1-the-human-gas-exchange-system
-
3-3-digestion-and-absorption5 主题
-
3-4-mass-transport-in-animals6 主题
-
3-5-the-circulatory-system-in-animals8 主题
-
3-6-mass-transport-in-plants6 主题
-
4-genetics-variation-and-interdependence4-1-dna-genes-and-chromosomes7 主题
-
4-2-dna-and-protein-synthesis6 主题
-
4-3-genetic-diversity-mutations-and-meiosis7 主题
-
4-4-genetic-diversity-and-adaptation6 主题
-
4-5-species-and-taxonomy4 主题
-
4-6-biodiversity9 主题
-
5-energy-transfers-in-and-between-organisms-a-level-only5-1-photosynthesis-a-level-only5 主题
-
5-2-respiration-a-level-only7 主题
-
5-3-energy-and-ecosystems-a-level-only9 主题
-
5-4-nutrient-cycles-a-level-only4 主题
-
6-organisms-respond-to-changes-in-their-environments-a-level-only6-1-response-to-stimuli-a-level-only12 主题
-
6-1-1-survival-and-response
-
6-1-2-growth-factors-in-flowering-plants
-
6-1-3-indoleacetic-acid-iaa
-
6-1-4-taxes-and-kinesis
-
6-1-5-reflex-arcs
-
6-1-6-required-practical-investigating-animal-movement
-
6-1-7-the-pacinian-corpuscle
-
6-1-8-pacinian-corpuscles-generator-potential
-
6-1-9-investigating-touch-and-temperature-receptors
-
6-1-10-the-human-retina
-
6-1-11-myogenic-stimulation-of-the-heart
-
6-1-13-heart-rate
-
6-1-1-survival-and-response
-
6-2-nervous-coordination-a-level-only10 主题
-
6-3-skeletal-muscles-a-level-only6 主题
-
6-4-homeostasis-a-level-only11 主题
-
6-4-1-principles-of-homeostasis
-
6-4-2-negative-feedback
-
6-4-3-glucose-concentration-and-insulin
-
6-4-4-glucose-regulation-glucagon
-
6-4-5-glucose-regulation-adrenaline
-
6-4-6-glucose-regulation-the-liver
-
6-4-7-diabetes
-
6-4-8-required-practical-determining-the-concentration-of-glucose-in-urine
-
6-4-9-nephron-structure
-
6-4-10-nephron-function
-
6-4-11-control-of-blood-water-potential
-
6-4-1-principles-of-homeostasis
-
7-genetics-populations-evolution-and-ecosystems-a-level-only7-1-inheritance-a-level-only6 主题
-
7-2-populations-a-level-only3 主题
-
7-3-evolution-a-level-only5 主题
-
7-4-populations-in-ecosystems-a-level-only7 主题
-
8-the-control-of-gene-expression-a-level-only8-1-genetic-mutations-a-level-only2 主题
-
8-2-regulation-of-gene-expression-a-level-only11 主题
-
8-2-1-totipotent-cells
-
8-2-2-stem-cells
-
8-2-3-the-use-of-stem-cells
-
8-2-4-producing-tissue-cultures-of-explants
-
8-2-5-regulation-of-transcription
-
8-2-6-evaluating-data-about-genetic-expression
-
8-2-7-epigenetics
-
8-2-8-epigenetics-and-disease
-
8-2-9-rna-interference
-
8-2-10-two-types-of-tumours
-
8-2-11-tumour-development
-
8-2-1-totipotent-cells
-
8-3-using-genome-projects-a-level-only4 主题
-
8-4-gene-technologies-a-level-only13 主题
-
8-4-1-recombinant-dna-technology
-
8-4-2-producing-fragments-of-dna
-
8-4-3-investigating-the-specificity-of-restriction-enzymes
-
8-4-4-polymerase-chain-reaction
-
8-4-5-culture-of-transformed-host-cells
-
8-4-6-uses-of-recombinant-dna-technology
-
8-4-7-dna-probes-and-dna-hybridisation
-
8-4-8-screening-patients
-
8-4-9-genetic-counselling-and-personalised-medicine
-
8-4-10-variable-number-tandem-repeats
-
8-4-11-gel-electrophoresis
-
8-4-12-genetic-fingerprinting
-
8-4-13-uses-of-genetic-fingerprinting
-
8-4-1-recombinant-dna-technology
-
exam-guidance-and-skillsessay-guidance3 主题
8-2-9-rna-interference
RNA interference
-
RNA interference (RNAi) is a form of post-transcriptional modification which occurs in the cytoplasm
-
RNAi is sequence-specific silencing of gene expression and, therefore, can be very precise in silencing certain genes
Small interfering RNA
-
In eukaryotes and some prokaryotes, translation of the mRNA produced from target genes can be inhibited by RNA interference (RNAi)
-
Small, double-stranded RNA molecules called small interfering RNA (siRNA) bind to mRNA that has been transcribed from target genes (the genes to be ‘silenced’) as their base sequence is complementary
-
Each siRNA is attached to a protein complex, which can break down the mRNA that has been transcribed from target genes (the genes to be ‘silenced’)
-
Therefore, the mRNA is unable to be translated into proteins
-
The RNA interference pathway
-
Double-stranded RNA (dsRNA) is produced by RNA-dependent RNA polymerases (RDRs)
-
dsRNA is hydrolysed into smaller fragments, roughly 23 nucleotides long, called small interfering RNAs (siRNAs)
-
In the cytoplasm, siRNAs bind to protein complexes which use energy from ATP to separate the two strands of the siRNA
-
This exposes the nucleotide bases so they can pair with bases from an mRNA molecule
-
-
Once the target mRNA leaves the nucleus and enters the cytoplasm, single-stranded siRNA binds to the target mRNA through complementary base pairing
-
The mRNA molecule is cut into fragments by the enzyme/protein complex associated with the siRNA
-
Cut mRNA cannot be translated and therefore will not produce proteins
-
-
After the target mRNA has been cut up into fragments, the fragments are broken down into RNA nucleotides by enzymes
Therapeutic application
-
siRNAs created against viral genetic material will signal for their degradation and stop the virus from using the host’s cellular machinery to replicate itself
-
siRNAs can be used in cancer treatment by targeting oncogenes that have been expressed or upregulated
-
This reduces the number of proteins produced that can lead to cancer or that maintain cancerous growth
-
Examiner Tips and Tricks
It is important to state that siRNAs can target mRNA through complementary base pairing. The attachment of mRNA to siRNA localises the mRNA to the protein complex, which then carries out hydrolysis.