Cellular Process Flashcards

What is the primary function of the phospholipid bilayer in the cell membrane?

Answer: Formation of a selective barrier for molecules

The primary function of the phospholipid bilayer in the cell membrane is to form a selective barrier that controls the movement of molecules into and out of the cell. Its hydrophobic interior prevents the free passage of most polar molecules, while its overall structure maintains cellular integrity and homeostasis. This selectivity is vital for cell function.

Which of the following best describes passive transport?

Answer: Diffusion of molecules down their concentration gradient without energy input

Passive transport describes the movement of substances across a cell membrane down their concentration gradient, meaning from an area of higher concentration to an area of lower concentration. This process does not require the cell to expend metabolic energy (ATP) because it is driven by the natural tendency of molecules to spread out. Examples include simple diffusion and facilitated diffusion.

During the signal transduction process, what role does a second messenger, such as cAMP, play?

Answer: Amplifies and transmits the signal inside the cell

In signal transduction, a second messenger like cAMP amplifies and transmits the signal received by a cell surface receptor to various target molecules inside the cell. It acts as an intracellular relay, propagating the initial signal throughout the cytoplasm and initiating a cascade of biochemical events. This amplification ensures a robust and coordinated cellular response to external stimuli.

In oxidative phosphorylation, ATP synthesis is powered by:

Answer: A proton gradient across the mitochondrial inner membrane

During oxidative phosphorylation, ATP synthesis is powered by a proton gradient established across the mitochondrial inner membrane. The electron transport chain pumps protons into the intermembrane space, creating an electrochemical gradient. Protons then flow back into the matrix through ATP synthase, and the energy released drives the phosphorylation of ADP to ATP.

Which of the following processes requires energy input in the form of ATP?

Answer: Active transport

Active transport is the process that requires energy input in the form of ATP to move molecules across a cell membrane. Unlike passive transport, active transport moves substances against their concentration gradient, from an area of lower concentration to an area of higher concentration. This energy-dependent process is crucial for maintaining specific ion concentrations and nutrient uptake.