Biochemistry Lipids and Membranes

Question 1

Which type of fatty acid contains one double bond?

Accepted Answer

Monounsaturated fatty acid

Answer

Monounsaturated fatty acids contain exactly one carbon-carbon double bond, such as oleic acid (18:1, Δ9), and are liquid at room temperature.

Question 2

The fluid mosaic model of the cell membrane was proposed by:

Accepted Answer

Singer and Nicolson

Answer

Singer and Nicolson (1972) proposed the fluid mosaic model, describing the membrane as a dynamic lipid bilayer with embedded proteins that can move laterally.

Question 3

Which lipid class forms the structural backbone of the cell membrane bilayer?

Accepted Answer

Phospholipids

Answer

Phospholipids are amphipathic molecules with a hydrophilic phosphate head group and hydrophobic fatty acid tails that spontaneously form bilayers in aqueous environments.

Question 4

Cholesterol in animal cell membranes functions to:

Accepted Answer

Modulate membrane fluidity

Answer

Cholesterol inserts between phospholipid tails, reducing fluidity at high temperatures and preventing crystallization at low temperatures, thereby buffering membrane fluidity.

Question 5

Eicosanoids (prostaglandins, thromboxanes, leukotrienes) are derived from which fatty acid precursor?

Accepted Answer

Arachidonic acid (20:4)

Answer

Arachidonic acid (20:4, ω-6) is released from membrane phospholipids by phospholipase A2 and serves as the substrate for cyclooxygenases and lipoxygenases to produce eicosanoids.

Biochemistry Practice Test

Biochemistry Practice Test

Biochemistry Lipids and Membranes