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Human Biology

A Level

Describe the main events that occur during human fertilization.

Fertilization is an example of a typical cell-to-cell recognition process between the small, assymetrical and motile sperm cell and the large, spherical, immobile egg. As soon as the sperm is released ins...

Answered by Danai Athina I. • Human Biology tutor

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‘Smokers suffer from more lower respiratory tract infections.’ Justify this statement in light of respiratory tract protection mechanisms.

Smoke contains many harmful chemicals and carcinogens (such as polycyclic aromatic hydrocarbons). There are several ways in which smoking increases the likelihood of lower respiratory tract infections.

Answered by Ali K. • Human Biology tutor

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Explain how oxygen and carbon dioxide are transported within the blood?

Oxygen diffuses through the alveolar wall into the capillary beds surrounding the lungs, and here it enters the red blood cells (erythrocytes). It binds to protein contained within the red blood cell call...

Answered by Dominic T. • Human Biology tutor

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How does sodium/potassium pump help with actions potential generation in nerves?

Sodium/potassium pump does not directly affect action potentials or their propagation in the nerve and can even be blocked by certain substances and action potentials would still be generated for a while....

Answered by Adam S. • Human Biology tutor

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Explain how one risk factor can lead to the development of coronary heart disease (CHD)

The following risk factors are associated with CHD: smoking, blood pressure, diet, exercise, genetic influences. Smoking systemically affects the whole cardiovascular system, some ...

Answered by Ashiq A. • Human Biology tutor

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