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Describe the structure of DNA

Deoxyribonucleic acid (DNA) is the hereditary material in almost all organisms and is responsible for carrying out genetic instructions in the cell. DNA is a polymer of nucleotides and each nucleotide has 3 ...
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Answered by Joe P. • Biology tutor
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Briefly describe the structure and function of the membrane-bound organelles present in a mammalian cell.

Nucleus - This is the largest organelle within the cell and contains all the cell's genetic information (with the exception of the mitochondrial genome). Structurally, it has a double membrane, known as the ...
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Answered by Elizabeth F. • Biology tutor
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How do expiration and inspiration occur by the action of the lungs?

Inspiration: The first stage of inspiration is contraction of the diaphragm, which causes it to move downwards, and contraction of the external intercostal muslces (the muscles between the ribs), which cause...
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Answered by Lois B. • Biology tutor
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Describe the function of ribosomes in protein synthesis.

Ribosomes, which are made up of rRNA, are instrumental in the translation of mRNA into proteins. The ribosome has a large and a small subunit, which sandwich around a strand of mRNA. This mRNA attaches to th...
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Answered by Luke G. • Biology tutor
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Explain how the proteins troponin, tropomyosin, actin and myosin regulate muscle contraction.

When the muscle is relaxed, tropomyosin fibres wrap around the actin filament, covering up the sites at which myosin can bind with actin. During muscle contraction, Ca2+ ions bind to troponin complexes on th...
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Answered by Alice T. • Biology tutor
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