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What is the difference between xylem and phloem tubes?

Xylem passively and unidirectionally transports water (by osmosis) from the roots to the leaves of a plant, whereas phloem uses active transport to bidirectionally transport food from the leaves to growing p...
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Answered by Taha S. • Biology tutor
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Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells.

It is possible to separate out the different organelles of a cell by spinning a homogenised solution of them at different speeds using an ultracentrifuge. The cells must first be placed in a cold, isotonic b...
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Answered by Kate W. • Biology tutor
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Explain how blood glucose levels are controlled in the body of someone who does not have diabetes.

If blood sugar levels are too high insulin is released from the pancreas so glucose is moved into cells. If blood sugar levels are too low glucagon is released and stimulates conversion of glycogen to glucos...
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Answered by Isabelle L. • Biology tutor
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What is the significance of performing mouth-to-mouth breaths during CPR?

Exhaled air contains a higher percentage of CO2 than inhaled air, due to it being a waste product of respiration. By breathing excess CO2 into the patient, the blood acidity will decrease and will be detecte...
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Answered by Phoebe D. • Biology tutor
3324 Views

Explain the mechanism by which DNA is replicated

DNA is replicated by semi-conservative replication meaning that each double stranded DNA molecule replicates to form two new double stranded molecules - each with one original and one new strand. This occurs...
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Answered by Georgie C. • Biology tutor
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