Cell Physiology (Ch. 3)

What are the three main parts of a cell?

Plasma membrane, cytoplasm, organelles (including nucleus)

What does the plasma membrane do?

Acts as the boundary, separates inside (ICF) from outside (ECF)

What is the role of receptors on the plasma membrane?

Bind to external chemicals and influence cell activity

What does selective permeability mean?

Only certain molecules can cross the membrane; small/nonpolar pass easily, others need proteins

How do cells recognize each other?

Through surface markers (antigens) on the membrane

What is a gradient?

A difference across the membrane (chemical = concentration difference, electrical = charge difference)

What is membrane potential?

Stored energy across the membrane due to ion differences

What is the resting membrane potential (RMP)?

-90 mV, inside of the cell is negative compared to outside

What ions are key to RMP?

Potassium (K⁺) leakage channels

What is passive transport?

Movement across membrane without ATP, driven by gradients

What is simple diffusion?

Small molecules move freely from high to low concentration

What is facilitated diffusion?

Molecules move through carrier or channel proteins

What is osmosis?

Movement of water from high to low concentration through aquaporins

What is osmolarity?

Measure of solute concentration that draws water

What is hydrostatic pressure?

The pushing force of water against the cell wall/membrane

What is osmotic pressure?

The pulling force of solutes that draws water in

What happens in an isotonic solution?

Equal solute levels, cell stays the same

What happens in a hypertonic solution?

More solutes outside, water leaves, cell shrinks (crenates)

What happens in a hypotonic solution?

Fewer solutes outside, water enters, cell swells (may burst)

What is active transport?

Movement against gradient, requires ATP

What is the Na⁺/K⁺ pump?

Moves 3 Na⁺ out and 2 K⁺ in per ATP; important for nerves and muscles

What is secondary active transport?

Uses ion gradients made by primary active transport

What is a symporter?

Transports 2 substances in the same direction

What is an antiporter?

Transports substances in opposite directions

What is bulk (vesicular) transport?

Movement of large molecules or quantities using vesicles and ATP

What is exocytosis?

Vesicles fuse with the membrane to release material outside the cell

What is endocytosis?

Cell brings material inside using vesicles

What is phagocytosis?

"Cell eating" - engulfs solids (e.g. pathogens, debris)

What is pinocytosis?

"Cell drinking" - engulfs extracellular fluid

What is receptor-mediated endocytosis?

Specific molecules are taken in after binding to receptors