Search our library of Biology A Level questions

Top answers

Biology

A Level

How can natural selection create two different species from one species?

For speciation to occur, two populations of a species must become reproductively isolated. This can result from either the formation of a geographic barrier between two populations of the species, prevent...

Answered by Sean K. • Biology tutor

2358 Views

The genetic code is described as degenerate, universal and overlapping. Explain these terms.

The genetic code is universal because all species use the same four bases A,T,C and G, and each base sequence codes for the same amino acid in all species. despite the 64 possible codons (sequence of thre...

Answered by Emily W. • Biology tutor

43790 Views

Explain the sliding filament theory of muscle contraction

Muscle contraction begins after an action potential reaches the required muscle and causes the calcium ion protein channels on the sarcoplasmic reticulum to open. This allows the calcium ions to diffuse d...

Answered by Isabel L. • Biology tutor

6273 Views

Human breast milk is produced and secreted by gland cells. These gland cells have adaptations that include many mitochondria and many Golgi vesicles. Explain the role of these cell adaptations in the production and secretion of breast milk.

(Many mitochondria) release energy / ATP for movement of vesicles / synthesis of protein / active transport; 2. (Many Golgi) vesicles transport protein / glycoprotein / milk to cell membrane / out o...

Answered by • Biology tutor

17878 Views

Describe how an enzyme increases the rate of a biochemical reaction?

An enzyme has an active site at which it binds to the substrates involved in the biochemical reaction. This results in the formation of an enzyme-substrate complex. The formation of such an intermediate c...

Answered by Rebecca S. • Biology tutor

2819 Views