Nucleic acids and proteins
What is the role of mRNA in protein synthesis?
carries the genetic code from the nucleus to the ribosome
What is a promoter region in a gene?
sequence where RNA polymerase binds to initiate transcription.
Identify the organelle where photosynthesis occurs.
Photosynthesis occurs in the chloroplasts.
What are the three main stages of aerobic cellular respiration?
Glycolysis, Krebs cycle, and the electron transport chain.
What is the role of antibodies?
Antibodies bind to specific antigens, neutralizing pathogens or marking them for destruction by other immune cells.
Describe how the sequence of nucleotides in DNA determines the sequence of amino acids in a protein.
The sequence of DNA bases (triplets) is transcribed into codons on mRNA. Each codon specifies an amino acid, which are linked together in the order dictated by the mRNA to form a polypeptide.
Explain how transcription factors influence gene expression.
Transcription factors bind to specific DNA sequences (enhancers or silencers) to either promote or inhibit the binding of RNA polymerase, thus regulating gene expression.
Explain the role of chlorophyll in the light-dependent stage.
Chlorophyll absorbs light energy, exciting electrons that initiate the electron transport chain, leading to ATP and NADPH production.
Describe the role of NADH and FADH₂ in the electron transport chain.
They donate electrons to the ETC (providing energy to pump protons across the mitochondrial membrane, creating a proton gradient for ATP synthesis.)
State two difference between innate and adaptive immune responses.
Innate immunity is non-specific and immediate (e.g. inflammation), while adaptive immunity is specific, slower, and involves memory (e.g. B and T cells).
A mutation changes one base in the coding region of a gene. Explain how this may or may not affect the resulting protein.
The effect depends on the nature and position of the change.
A researcher silences a repressor gene in a prokaryotic operon. Predict the outcome on the expression of the structural genes.
Without the repressor, the operon would be continuously transcribed, leading to expression of the structural genes.
A plant is exposed to green light only. Predict the impact on photosynthesis.
Photosynthesis would decrease significantly/not occur
Compare energy efficiency in aerobic vs anaerobic respiration.
Aerobic respiration yields up to 30–32 ATP per glucose, while anaerobic yields only 2 ATP, making it far less efficient.
A patient lacks T-helper cells. Predict the impact.
Without T-helper cells, B cells cannot be fully activated, reducing antibody production, and cytotoxic T cell activation is impaired. Overall immunity is severely compromised.
Compare the processes of transcription and translation.
Transcription occurs in the nucleus and involves RNA polymerase synthesising pre-mRNA from a DNA template. Translation occurs in the cytoplasm at the ribosome, where tRNA matches codons with amino acids to form a polypeptide.
Contrast gene regulation in prokaryotes and eukaryotes.
Prokaryotic regulation is often via operons and occurs mainly at transcription. Eukaryotic regulation is more complex, involving transcription factors, and regulation at transcriptional, post-transcriptional, and translational levels.
Analyse the interdependence of the two stages of photosynthesis.
The light-dependent stage produces ATP and NADPH used in the light-independent stage to fix carbon dioxide. Without these products, the LI cannot proceed.
Assess the sustainability of biomass fuels vs fossil fuels.
Biomass is renewable and carbon-neutral if managed properly, but may compete with food crops. Fossil fuels are non-renewable and release stored carbon, contributing to climate change.
Compare primary and secondary immune responses.
Primary response is slower and produces fewer antibodies. Secondary response is faster and stronger due to memory cells formed after the first exposure.
A cell produces a defective enzyme despite having a normal DNA sequence. How?
Possible reasons include faulty RNA splicing, incorrect folding of the protein, or post-translational modifications being disrupted.
Explain how a gene can be silenced.
If RNA complementary to the mRNA sequence is introduced, the gene can be transcribed but not translated = silenced
Evaluate the claim that increasing CO₂ indefinitely increases photosynthesis.
Initially, higher CO₂ boosts photosynthesis, but the rate plateaus once other factors (light intensity, temperature) become limiting. Excess CO₂ alone cannot sustain indefinite increases.
Justify why muscle cells use anaerobic respiration during intense exercise.
Oxygen supply cannot meet demand during intense activity, so cells use anaerobic respiration to generate ATP quickly, despite its low efficiency.
Describe the production of monoclonal antibodies
antigen introduced into an animal
plasma cells extracted
plasma cell fused with a myeloma to make a hybridoma
hybridoma makes specific monoclonal antibodies