Which of the following statements are CORRECT about the function of fetal bovine serum in animal cell culture?
P. It stimulates cell growth
Q. It enhances cell attachment
R. It provides hormones and minerals
S. It maintains pH at 7.4
P and Q only
P and S only
P, Q and R only
P, Q, R and S
ANSWER
The answer is (C): P, Q and R only. FBS supplies growth factors, attachment factors, hormones and minerals, while pH 7.4 is held by the bicarbonate and CO2 buffer system of the medium, not by the serum.
Official answer: CSource: Official answer key, GATE 2019 BT (IIT Madras)
Fetal bovine serum (FBS) is the usual supplement added to animal cell culture media, typically at 5 to 10 percent. It supplies what a basal medium of salts, sugars, amino acids and vitamins lacks. Judge each statement by asking whether it is a function serum is added for.
P is correct. Serum carries growth factors such as PDGF, EGF and FGF, and insulin-like growth factors. These stimulate cells to divide, which is the main reason serum is added.
Q is correct. Serum contains attachment and spreading factors, mainly fibronectin and vitronectin. They adsorb to the culture surface and let anchorage-dependent cells attach and spread.
R is correct. Serum supplies hormones (for example insulin and hydrocortisone) and minerals and trace elements (for example iron carried by transferrin, zinc and selenium), along with lipids.
S is not correct. Holding the medium at pH 7.4 is the job of the medium's buffer system: sodium bicarbonate in equilibrium with the atmosphere of the incubator (usually 5 percent ), sometimes with HEPES added. Serum proteins have only a minor buffering effect, and serum is not what sets or maintains the pH; serum-free media hold pH 7.4 perfectly well with the same buffer system. So pH maintenance is not a function of FBS.
Only P, Q and R are true, so the answer is option (C). Option (A) leaves out R, and options (B) and (D) include the false statement S.
KEY IDEA
Serum supplies growth factors (P), attachment factors such as fibronectin (Q), and hormones, minerals and trace elements (R). The pH of the culture is controlled by the medium's buffer (bicarbonate with incubator , or HEPES), not by serum.
WATCH OUT FOR
Choosing (D) because serum proteins buffer a little. That small buffering effect is not what serum is added for. The bicarbonate and system (or HEPES) maintains pH 7.4, and serum-free media hold that pH without any serum.
From the GATE 2019 BT paper. Every question of this paper · Download the full paper · All 5 Animal cell culture questions, with notes
