Need someone help me do cell bio homework.
***** Choose any/ ONLY 10 questions*****
- Polysaccharides offer possibilities of enormous structural complexity. How does this arise? Compare and contrast polysaccharides with polynucleotides and polypeptides.
- Life, at least in the form found on Earth, could not exist without water. Why is water so important in living systems?
- If you were designing a DNA-based genetic code from scratch (one that still uses the four bases A, T, C and G and which still specifies 20 amino acids) how might the present code be improved?
- Glucocorticoid hormones are among the many regulators of gene expression in humans. Describe the key steps that lead to a change in gene regulation when the hormone enters the cell.
- You have learned that the sequence of amino acids in a protein contains all of the information necessary to specify the final structure, and that a completely disordered polypeptide chain will refold into the correct shape if allowed to do so. Insulin is a small protein that consists of two chains held together by disulphide bonds. It is made by synthesis of a larger, single chain called proinsulin that undergoes post translational modification, including proteolysis, to make the active hormone. If one dissolves insulin in 8 moles liter-1 urea plus a reagent to break the disulphide bonds and then slowly removes urea and reagent the activity does NOT return to a significant extent. Suggest an explanation of this paradox – why is insulin folded correctly the first time it is made, but cannot fold correctly if artificially disordered and then allowed to reform?
- Why is fusing vesicles to a membrane or pulling vesicles off a membrane an intrinsically difficult thing to do? How is the cell thought to accomplish these steps?
- What happens in a lysosome? Where do its contents come from?
- We have listed NADH as one of the four principle cell energy currencies, but many professors think this classification is inappropriate. Explain what is meant by the term energy currency, and argue the case that NADH should not be described as an energy currency.
- Oligomycin is an antibiotic that blocks ATP synthase. If mitochondria are treated with oligomycin what will happen to their oxygen consumption (assume that they have adequate supplies of ADP, phosphate and acetyl CoA)? Why does this happen?
- Explain the concepts of (membrane-bound) channel and carrier. How can these two be so similar structurally, yet so different thermodynamically?
- Explain how the properties of the voltage-gated sodium channel make possible the generation of the action potential.
- What is an intracellular messenger? Many scientists include inositol trisphosphate (IP3) as an intracellular messenger. Discuss this question, giving arguments for and against the inclusion of IP3 in the list of intracellular messengers.
- Describe some of the signaling pathways downstream of activated receptor tyrosine kinases. How is it that different receptor tyrosine kinases on the surface of the same cell can have different downstream effects?
- Explain how the processes of mitosis and meiosis operate to ensure that progeny cells end up with, respectively, two and one complete copies of the genome. Explain the process and function of meiotic recombination.
- Discuss the internal and external cues that control whether a vertebrate cell initiates apoptosis