Q 01/05

Roughly what percentage of an adult human's body weight is blood?

A) 7%

B) 12%

C) 18%

D) 25%

Answer · why

A) 7%

The average adult carries about 5 litres of it, at a density only slightly greater than water.

Q 02/05

Roughly how much blood does the average adult have?

A) About 2 litres

B) About 5 litres

C) About 8 litres

D) About 12 litres

Answer · why

B) About 5 litres

Roughly 55% of that volume is plasma and 45% is red blood cells.

Q 03/05

What is the straw-yellow liquid that makes up about 55% of blood?

A) Serum albumin

B) Lymph

C) Plasma

D) Hemoglobin

Answer · why

C) Plasma

It is 92% water; the term serum refers to plasma with the clotting proteins removed.

Q 04/05

Which iron-containing protein in red blood cells carries oxygen?

A) Myoglobin

B) Fibrinogen

C) Albumin

D) Hemoglobin

Answer · why

D) Hemoglobin

Each mammalian molecule can bind up to four oxygen molecules, and it is bright red when oxygenated and dark red when not.

Q 05/05

How many oxygen molecules can a single molecule of the red cells' oxygen-carrying protein bind?

A) 4

B) 1

C) 2

D) 3

Answer · why

A) 4

That is one per haem group; the reversible binding is what makes efficient oxygen transport possible.