Question

question #26
to maintain homeostasis, materials have to move across cell membranes. some examples of these movements are listed below. select the three processes that require the cell to expend energy.
a amoeba consuming a bacterium
b pancreatic cell secreting insulin into the blood
c brain neuron taking up glucose from the blood
d somatic cell absorbing cholesterol from the blood
e paramecium absorbing water from its surroundings

Explanation:

• A (amoeba consuming a bacterium): This is phagocytosis (a form of endocytosis). Endocytosis is an active - transport process. The cell membrane engulfs the bacterium, forming a vesicle. This requires energy as the cell has to change the shape of its membrane and move substances against the concentration gradient (in a sense, as it is taking in a large particle).
• B (pancreatic cell secreting insulin into the blood): This is exocytosis. The cell packages insulin in vesicles and fuses these vesicles with the cell membrane to release insulin. This process requires energy for vesicle formation, movement, and fusion with the membrane.
• C (brain neuron taking up glucose from the blood): Glucose uptake by neurons (and many cells) can occur through active transport. In some cases, especially when the concentration of glucose inside the cell is higher than in the blood (or against the concentration gradient), the cell uses carrier proteins and energy (in the form of ATP) to take up glucose. For example, in the sodium - glucose linked transporter (SGLT) system, energy from the sodium gradient (which is maintained by the sodium - potassium pump, an energy - consuming process) is used to transport glucose into the cell.
• D (somatic cell absorbing cholesterol from the blood): Cholesterol is absorbed via receptor - mediated endocytosis. Receptor - mediated endocytosis is an active process. The cell has receptors for cholesterol - carrying lipoproteins. Once bound, the cell forms a vesicle to internalize the cholesterol - lipoprotein complex. This requires energy for receptor - ligand binding, vesicle formation, and movement within the cell.
• E (paramecium absorbing water from its surroundings): This is osmosis. Osmosis is the movement of water across a semi - permeable membrane from an area of lower solute concentration (higher water concentration) to an area of higher solute concentration (lower water concentration). It is a passive process and does not require the cell to expend energy.

Answer:

A. amoeba consuming a bacterium, B. pancreatic cell secreting insulin into the blood, C. brain neuron taking up glucose from the blood