Search our library of Biology questions

Top answers

Biology

All levels

Describe how the rhythmicity of the heart is established and maintained with respect to the different stages in the cardiac cycle (6 marks)

The Sinoatrial Node (SAN) generates the wave of excitation/ Action potential (AP).

The AP spreads across the atrial walls, stimulating the myocardial cells to contract This initiates the atrial sys...

Answered by Haider M. • Biology tutor

6249 Views

Explain how the structure of RNA differs from that of DNA? (3 marks)

RNA is single-stranded, DNA is double-stranded.

RNA contains the base Uracil, DNA contains thymine instead.

RNA contains the sugar Ribose, DNA has Deoxyribose instead.

Answered by Haider M. • Biology tutor

20818 Views

What are the events in synaptic transmission?

The presynaptic action potential reaches the synaptic knob. 2) The terminal is depolarised. 3) Voltage gated calcium channels in the presynaptic knob open. 4) Calcium enters through the calcium chan...

Answered by Tutor33676 D. • Biology tutor

29410 Views

How does the Meselson and Stahl Experiment provide evidence for the semi conservative theory of DNA replication?

Before we start on the specifics of the experiment itself we need to understand how DNA replication occurs on a molecular level. DNA is made up of four different bases; A, C, G and T....

Answered by Julia D. • Biology tutor

25334 Views

One form of muscle disease is caused by a mutant myosin allele. It prevents myosin from binding to other myosin molecules, thus preventing contraction. Suggest why.

Sarcomeres are formed of myosin and actin filaments which are interleaved. If myosin cannot bind to each other then thick filaments cannot be formed. Thus, there is nothing to anchor myosin so actin canno...

Answered by Jade W. • Biology tutor

10633 Views