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Very thin walls result in a short diffusion distance which makes gas exchange particularly favourable.

Lots of branches and sacs result in a large surface area so gas exchange can be maxi...

Exons are coding regions of DNA, and are copied into mRNA and transcribed as proteins.

Introns are non-coding regions of DNA, and are spliced out of pre-mRNA so are not copied into mRNA.<...

A hydrocarbon is a molecule that contains only hydrogen and carbon atoms.

Any two of the follwing properties are suitable answers:

Low boiling points, low viscosities or hig...

Both aldehydes and ketones have a carbonyl functional group (C=O), however in aldhydes the carbonyl carbon atom is the terminal carbon of the chain, whereas in ketones the carbonyl carbon has two alkyl...

Covalent bonding is the sharing of pairs of electrons between two non-metallic atoms.

Ionic bonding is where electrons are transferred from one atom to another, usually from a metallic at...