Lec 2: Cellular Level of Organization and Transport (copy)

Chemical Level

The most fundamental level comprising atoms (C, H, O, N, P) that combine to form essential biological molecules, such as DNA.

Cellular Level

Molecules assemble to form cells, which are the basic structural and functional units of living organisms.

Tissue Level

Groups of specialized cells and their surrounding extracellular materials work together to perform specific functions.

Organ Level

Structures composed of two or more distinct tissue types that possess specific functions and recognizable shapes.

System Level

Collections of related organs that cooperate to accomplish a common physiological objective.

Organismal Level

The highest organizational level, where all organ systems function synergistically to maintain a living human individual.

Plasma Membrane

The dynamic, selectively permeable outer boundary wall that defines the physical border of the cell.

Nucleus

The membrane-enclosed control center containing hereditary genetic material (DNA).

Cytoplasm

The cellular contents located between the plasma membrane and the nucleus, consisting of fluid cytosol and functional organelles.

Intracellular Fluid (ICF)

The fluid medium contained entirely within the cell (cytosol).

Extracellular Fluid (ECF)

The fluid located outside the cell, surrounding tissues.

Osmosis

The process of water movement across a semipermeable membrane due to differences in solute concentration.

Isotonic Environment

Solution where solute concentration in ECF equals that in ICF, resulting in no net movement of water.

Hypertonic Environment

Solution where solute concentration in ECF is greater than in ICF, leading to cell shrinkage as water moves out.

Hypotonic Environment

Solution where solute concentration in ECF is lower than in ICF, causing cell swelling as water moves in.

Facilitated Diffusion

Passive movement of polar or charged molecules down their concentration gradient mediated by transmembrane helper proteins.

Active Transport

Movement of substances against a concentration or electrical gradient, requiring cellular energy (ATP) expenditure.

Sodium-Potassium Pump (Na+/K+ ATPase)

Primary active transport mechanism that expels sodium ions and imports potassium ions against their concentration gradients.

Endocytosis

Active transport mechanism that internalizes extracellular substances by forming new vesicles from the plasma membrane.

Exocytosis

Active secretion process that transports intracellular materials out of the cell into the extracellular fluid.

Lysosomes

Spherical, membrane-bound vesicles containing digestive enzymes, functioning as cellular demolition sites.

Mitochondria

Organelles that generate cellular energy in the form of ATP, known as the "powerhouse of the cell."