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What is the link between electrical activity of the heart and its contraction?

The electrical current is produced in the SA node (the primary pacemaker of the heart) and travels to the AV node via fibres in the walls of the atria. These impulses cause the muscular walls of the atria to...
SM
Answered by Stephen M. • Biology tutor
6905 Views

Can you explain the oxygen dissociation curve.

What is the graph telling us? On the graph, we can see two axes. We have partial pressure of oxygen on the X axis and Hb saturation on the Y axis. Partial pressure is another way of saying how much oxygen th...
TK
Answered by Thomas K. • Biology tutor
2955 Views

Describe the process of breathing

The diaphragm contracts, moving downwards. The external intercostal muscles contract, and the internal intercostal muscles relax. Pressure in the chest cavity decreases, forcing air into the lungs. The diaph...
AC
Answered by Ailin C. • Biology tutor
3085 Views

What are the key steps in DNA replication during the S-phase of the cell cycle?

The enzyme DNA helicase 'unzips' the double helix DNA structure but disrupting the hydrogen bonds between the bases. This forms a replication fork that becomes the template for replication.Replication then b...
NE
Answered by Natasha E. • Biology tutor
5062 Views

Name a non-reducing sugar and outline a test which can identify its presence. (6)

Sucrose (1)Rule out reducing sugars - heat in a water bath. Add Benedict's solution. Should remain blue. (1)Add dilute HCl to a new sample and heat in a water bath (1)Neutralise with NaHCO3 (1)Add Benedict's...
AR
Answered by Annie R. • Biology tutor
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