Chapter 1-6: Cellular Transport, Endocytosis, and Organelles

A set of practice flashcards covering active transport, endocytosis, vesicular trafficking, ER/Golgi function, organelles, cytoplasm, and cell extensions as described in the lecture notes.

What is the function of the Na+/K+ ATPase (sodium–potassium pump) and why is it essential for the resting membrane potential?

It hydrolyzes ATP to move Na+ out and K+ into the cell against their gradients, maintaining the electrochemical gradient; without it, leakage would destabilize the resting membrane potential.

Name the two main types of solute pumps mentioned.

Antiporters and symporters.

What are leakage channels and what is their role at rest?

Always-open channels that allow Na+ to enter and K+ to exit along their gradients, sustaining the resting membrane potential in conjunction with the Na+/K+ pump.

What is endocytosis and what are its major forms?

Process by which the cell takes in material via vesicles; major forms include phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Describe phagocytosis and the cells that perform it predominantly.

Endocytosis of large particles by phagocytes (macrophages); forms a phagosome that fuses with a lysosome for digestion.

What is pinocytosis and how does it differ from phagocytosis?

Non-specific uptake of extracellular fluid and solutes via tiny vesicles; broad sampling rather than targeted ingestion.

What is receptor-mediated endocytosis and what structures are involved?

Ligand binding to specific receptors triggers endocytosis via clathrin-coated pits (and caveolae in some cases).

What is exocytosis and the role of SNARE proteins?

Vesicles fuse with the plasma membrane to release contents; SNARE proteins mediate docking and fusion.

What is transcytosis?

Movement of endocytosed vesicles across the cell to the opposite membrane for exocytosis.

Where are proteins synthesized and how are they prepared for transport?

Synthesis occurs in the rough endoplasmic reticulum; proteins are packaged into transport vesicles and sent to the Golgi for sorting.

What are the three Golgi pathways for processed proteins?

A) Secretion via secretory vesicles; B) Insertion into the plasma membrane; C) Storage/holding for future use (or lysosomal targeting).

What is the role of lysosomes in digestion and recycling?

Lysosomes contain digestive enzymes; they degrade damaged organelles and pathogens and recycle components.

What distinguishes rough endoplasmic reticulum from smooth endoplasmic reticulum?

RER has ribosomes and synthesizes proteins; SER lacks ribosomes and is involved in lipid metabolism (SER in skeletal muscle is the sarcoplasmic reticulum, handling Ca2+).

In skeletal muscle, what is the smooth endoplasmic reticulum called and what is its key function?

The sarcoplasmic reticulum; stores and releases Ca2+ for muscle contraction.

What is autophagy and how are damaged organelles dealt with?

Damaged organelles are degraded in lysosomes and their components recycled by the cell.

What is mitochondrial fusion and why is it important?

Damaged mitochondria can fuse to form a healthy mitochondrion; fusion is a quality-control mechanism.

What is the cytoplasm and what are cytosolic inclusions?

The cytoplasm is the intracellular fluid; inclusions are insoluble components like glycogen granules, pigments (e.g., melanin), lipids, or crystals (e.g., otoliths) depending on the cell.

What are cilia, microvilli, and flagella and their functions?

Cilia: short projections that move substances across the cell surface; Microvilli: increase surface area for absorption; Flagella: enable cell movement (e.g., sperm).

What is the difference between chemical-gated channels and second messenger systems?

Chemical-gated channels open directly in response to ligand binding; second messenger systems trigger intracellular signaling cascades (via G proteins, cAMP) without immediate channel opening.

What role do cell adhesion molecules (CAMs) play in the plasma membrane?

CAMs mediate contact signaling, anchor cells to the extracellular matrix, and facilitate cell–cell interactions and immune surveillance.

Why does osteoporosis risk increase after menopause according to the notes?

Loss of estrogen leads to increased bone resorption by lysosomes releasing calcium, weakening bone.

What is the difference between endocytosis and exocytosis?

Endocytosis brings material into the cell via vesicles; exocytosis releases material from the cell by vesicle fusion with the plasma membrane.