uptakes

Uptake, with the plural form uptakes, is the process by which substances are absorbed into an organism, tissue, cell, or compartment. The term covers a broad range of mechanisms that move materials from the external environment into biological systems, including nutrients, water, gases, drugs, and radiotracers.

Cellular uptake occurs through multiple pathways. Passive processes such as diffusion move molecules down concentration or electrochemical gradients. Facilitated diffusion uses specific transport proteins. Active transport requires energy to move substances against gradients. Endocytosis, including phagocytosis and pinocytosis, internalizes larger particles or fluids via vesicle formation.

Plants, microbes, and animals depend on uptake to acquire essential resources. In plants, root uptake transports minerals such as nitrate, phosphate, and potassium through membrane transporters, with rates shaped by soil chemistry, moisture, pH, and symbiotic associations. In microbes, uptake mechanisms enable acquisition of nutrients from the surrounding environment, often adapting to nutrient availability. In animals, intestinal uptake of nutrients and water is similarly governed by transporter activity and regulatory signals.

In medicine and research, uptake describes how substances such as radiotracers, drugs, or nutrients enter tissues. Radiotracer uptake is measured in imaging techniques like PET to assess metabolic activity, while drug uptake influences pharmacokinetics and tissue distribution. Uptake kinetics are commonly modeled with concentration-time data and, for transporter-mediated processes, Michaelis-Menten or similar frameworks.

Factors influencing uptake include concentration gradients, membrane potential, transporter expression, temperature, pH, and substrate competition. Disruptions or alterations in uptake patterns can indicate health conditions, such as reduced intestinal uptake in malabsorption or elevated tracer uptake in cancerous tissue.