Most Repeated MDCAT Biology: Cell Structure and Function MCQs

Explanation

The function of the nucleolus is to make ribosomes. The nucleolus is a distinct subcompartment within the cell nucleus, and it plays a vital role in ribosome biogenesis, which is the process of producing ribosomes, the cellular machinery responsible for protein synthesis. The nucleolus is responsible for making ribosomes by transcribing, processing, and assembling the components of ribosomes before exporting them to the cytoplasm, where they perform their crucial role in protein synthesis. Ribosomes are essential cellular structures involved in protein synthesis.

Explanation

The correct answer is Cristae, which are the finger-like infoldings of the inner membrane of mitochondria. These structures are critical for the mitochondria's function, as they increase the surface area available for the electron transport chain, thereby enhancing ATP production.In contrast, Ribosomes are involved in protein synthesis and do not relate to mitochondrial structure. The Matrix refers to the space within the mitochondria, but it does not describe any infoldings. Porin is a type of protein that allows for the transport of substances across membranes and is not an infolding structure.

Explanation

The percentage of water in both bacterial and mammalian cell is 70%.Hence, this option is correct.

Explanation

On the cristae of mitochondria are located enzymes and coenzymes by means of which carbohydrates (starch), fatty acids (lipids), and amino acids (lipids) are metabolized to CO₂ and H₂O. Energy in the form of ATP is released in this process, which is stored within mitochondria. ATP is an energy-rich compound, and it provides energy for various cellular activities. Hence, "mitochondria" is known as the "powerhouse" of the cell. Hence, this option is correct.

Explanation

The plasma membrane performs several functions but the main and the most important functions are protection of cell cytoplasm to regulate the flow of solutions and material in an out of the cell with certain limitation. These limitations or checkin lowacross the membrane is called differential or selective permeability. Therefore, plasma membrane is called semipermeable membrane.

Explanation

Fluid mosaic model: According to the fluid mosaic model, the lipid bilayer is retained as the core of the membrane. The structure and arrangement of membrane proteins in the fluid-mosaic model are like icebergs in the sea. The proteins occur as a 'mosaic' of discontinuous particles that penetrate deeply into and even completely through the lipid sheet. Hence, this option is correct.

Explanation

Lysosomes contain enzymes that break down cellular waste, damaged organelles, and macromolecules. This makes them the main organelles responsible for intracellular digestion.

Explanation

A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism. No cells in the human body have a cell wall, hence liver cells will not have one either. Plant cell walls are primarily made of cellulose, which is the most abundant macromolecule on Earth. The cell wall is a characteristic structure of fungi and is composed mainly of glucans, chitin, and glycoproteins.

Explanation

The fungal cell wall is primarily made of chitin, a strong polymer that provides rigidity and protection. It also contains glucans and glycoproteins. Hence, this option is correct.

Explanation

Bacterial cell walls are primarily composed of peptidoglycan, which is a unique macromolecule consisting of both sugars (polysaccharides) and amino acids. This gives bacterial cell walls their rigidity and shape.

Explanation

The correct answer is facilitated diffusion. This process involves the passive movement of molecules across the cell membrane via specific transport proteins. It does not require energy, which is consistent with the observation that no ATP was used. Large molecules typically cannot pass through the membrane without assistance, which is why facilitated diffusion is necessary. Active transport is incorrect because it requires ATP to move molecules against their concentration gradient. Simple diffusion is not suitable for large molecules as it involves the movement of small or non-polar molecules directly through the lipid bilayer.

Explanation

Ultra centrifuge is not an organelle; it is a very fast centrifuge used to precipitate large biological molecules from solution or separate them by their different rates of sedimentation.