Biology Questions and Answers

Answer: B

Surplus red cells are stored mainly in the spleen.

It holds a reserve that contraction of its smooth muscle can release into the circulation during haemorrhage or strenuous exercise. The spleen also filters out worn-out red cells, which is why it is called the graveyard of erythrocytes.

Answer: A

Henna colours skin and hair by reacting with protein and amino acids.

Its dye, lawsone, binds to the keratin of skin and hair, which is why the colour is fast on those tissues but washes off anything else. The reaction is with the amino groups of the protein.

Answer: A

Bronchitis is a disease of the respiratory tract - inflammation of the bronchi, the airways leading to the lungs.

The lining swells and produces excess mucus, causing the persistent cough. Acute bronchitis usually follows a viral infection; the chronic form is caused chiefly by smoking.

Answer: A

Plants growing in saline water are halophytes, from the Greek halos, salt.

Mangroves are the familiar example. They exclude salt at the root, excrete it through leaf glands, or shed it in old leaves, and many have stilt roots and breathing roots for the waterlogged mud.

Answer: C

The embryo is found in the seed.

It is the young plant formed after fertilisation, consisting of the radicle, plumule and one or two cotyledons, packed with the stored food it will use until it can photosynthesise.

Answer: C

Cancer cells are damaged by radiation because they are undergoing rapid division.

DNA is most vulnerable while it is being replicated and the chromosomes separated, so dividing cells are far more radiosensitive than resting ones. It is also why radiotherapy affects hair follicles, bone marrow and gut lining - the body's other fast-dividing tissues.

Answer: A

Systemic lupus erythematosus is an autoimmune disease.

The immune system makes antibodies against the body's own nuclear material, and the resulting inflammation affects skin, joints, kidneys, heart and brain. Anaphylaxis and farmer's lung are allergic rather than autoimmune.

Answer: A

Blood is slightly alkaline, at pH 7.35 to 7.45.

It is held there by the bicarbonate buffer, by the lungs regulating carbon dioxide and by the kidneys excreting acid. Outside about 6.8 to 7.8 life cannot continue.

Answer: C

Hippocrates is called the father of medicine.

Working on Kos in the fifth century BC, he separated medicine from superstition, insisting that disease has natural causes. The Hippocratic Oath is named after him.

Answer: B

Prokaryotic and eukaryotic cells both contain DNA.

They also share ribosomes, a plasma membrane and cytoplasm. What the prokaryote lacks is a nuclear membrane and every membrane-bound organelle, so its DNA lies free in the cytoplasm as a single circular chromosome.