Search our library of Biology questions

Top answers

Biology

All levels

Describe how the human body can prevent the entry of organisms that cause disease. Include physical barriers and chemical defences in your answer.

Physical barriers:

skin to prevent entry of organisms into the bloodstream
cilia lining the nasal passages / bronchi to prevent entry to lungs / remove mucus

Answered by Khadija M. • Biology tutor

9497 Views

Which of these DNA mutations is likely to have the greatest effect on the structure of the encoded protein? Justify your answer. •Single base substitution •15 bases base deletion •Insertion of 2 bases

The most serious of these mutations will be the insertion of 2 bases. Becasue the genetic code is read in triplets, a 2 base insetion will alter the reading frame of the code causing a frameshift mutation...

Answered by Emma M. • Biology tutor

21712 Views

Describe the mechanism(s) as to which an enzyme binds to a substrate.

Two models have been proposed. The first being the 'Lock and Key Model' which simply describes the way in which the active site of an enzyme is complementary to the substrate shape, meaning that only the ...

Answered by Nicole B. • Biology tutor

2728 Views

Which of the basic life processes is described here? The ability of multicellular organisms to regulate their internal environment so that it stays optimum for cellular survival.

Homeostasis

Answered by Alice M. • Biology tutor

2610 Views

Explain the processes that lead to the contraction of a single muscle

A nervous impulse travels to the neuromuscular junction and causes the release of acetylcholine into the synaptic cleft. Depolarisation of the motor end plate spreads through the muscle via transverse tub...

Answered by Prashan B. • Biology tutor

2295 Views