Membrane Transport

What is the definition of passive transport?

does not require energy; solutes move from high to low concentration.

What is the significance of selectively permeable membranes?

control what enters and exits the cell.

What are the types of passive transport?

Simple diffusion, facilitated diffusion, and osmosis.

What does simple diffusion entail?

Solutes move through the phospholipid bilayer without assistance.

What types of molecules typically undergo simple diffusion?

Hydrophobic, non-polar molecules like steroid hormones, O2, CO2, and urea.

What is facilitated diffusion?

Movement of solutes across the membrane with the help of specific proteins.

What are channel proteins?

Proteins that provide tunnels through which ions can pass without changing shape.

Give examples of channel proteins.

Na+, K+, Ca2+, Cl-, and aquaporins.

What are carrier proteins?

Proteins that change shape to transport solutes across the membrane.

What types of substances do carrier proteins typically transport?

Glucose, amino acids, and small-ish molecules.

What is osmosis?

The movement of water across a membrane from low to high solute concentration.

How does water move during osmosis?

Water moves towards higher solute concentration.

What is the primary energy source for active transport?

ATP is the most common energy source.

What is the key difference between active transport and passive transport?

Active transport requires energy and moves substances against their concentration gradient, passive transport does not require energy

What is the function of the Na+/K+ pump?

It moves sodium outside and potassium inside the cell against their gradients

What is primary active transport?

Transport that directly uses ATP to move solutes against their gradient.

Define secondary active transport.

It uses the concentration gradient of one solute to drive the transport of another solute.

What is bulk or vesicular transport?

Transport of large molecules via vesicles which requires energy.

What is exocytosis?

Process where a vesicle fuses with the plasma membrane to release contents outside the cell.

What occurs during endocytosis?

A vesicle forms from the plasma membrane to intake substances into the cell.

What is pinocytosis?

Random uptake of fluids and dissolved solutes by forming vesicles.

What is receptor-mediated endocytosis?

Specific uptake of solutes through membrane protein receptors.

What is phagocytosis?

Process of 'cell eating' where large particles are engulfed by the cell.

Provide examples of cells that use phagocytosis.

Amoeba, macrophages, and neutrophils in humans.

What are phagosomes?

Food vesicles that fuse with lysosomes for digestion.

What occurs when vesicles fuse with the plasma membrane?

It increases the surface area of the plasma membrane.

What effect does active transport have on concentration gradients?

It increases the concentration of solutes on one side of the membrane.

What role do protein helpers play in transport?

They assist in moving solutes through the membrane during active transport.

What is the role of ATPases?

They are pumps that hydrolyze ATP to provide energy for transport.

Identify one reason why cells need to control their internal environment.

To maintain homeostasis and proper functioning.

Why is water movement critical in biological systems?

It influences cell shape, nutrient transport, and waste removal.