Week 2 Lab

What is the primary function of the plasma membrane's selective permeability?

It allows nutrients to enter the cell while keeping out undesirable substances, and it keeps valuable cell proteins and other substances within the cell while allowing waste to pass to the exterior.

What are the two basic ways transport occurs through the plasma membrane?

Active transport (cell provides energy/ATP) and passive transport (driven by particle concentration or pressure).

What are the two types of passive transport?

Diffusion and filtration.

Where does filtration occur in the body?

Filtration occurs only across capillary walls.

How is diffusion defined in the context of cellular transport?

The movement of molecules from an area of higher concentration to an area of lower concentration.

What is a concentration gradient?

The difference in concentration.

What is the driving force for diffusion?

The kinetic energy of the molecules themselves.

What factors influence the rate of diffusion?

Molecule size, temperature, and the steepness of the concentration gradient.

How do small molecules, high temperature, and a steep concentration gradient affect the diffusion rate?

They result in an increased diffusion rate.

Under what conditions do molecules generally transport passively through the plasma membrane?

If they are small enough to pass through the pores or if they can dissolve in the lipid portion of the membrane.

What is simple diffusion?

The diffusion of solutes through a semipermeable membrane.

What is a solute?

A substance that gets dissolved in a solution.

What is osmosis?

The diffusion of water through a semipermeable membrane.

What is dialysis?

A purification process that separates small molecules (e.g., urea) from large molecules (e.g., blood) by passing them through a semipermeable membrane.

What are the characteristics of substances moved by active transport?

They are usually unable to pass through diffusion, not lipid soluble, too large, or move against the concentration gradient.

What are the two types of active processes?

Active transport and vesicular transport.

What is required for active transport to occur?

It requires carrier proteins to combine specifically with the transported substance and the use of ATP energy.

Which substances are moved into the cell by carrier proteins via active transport?

Amino acids and sugars, which are both insoluble in lipid and too large to pass through the membrane.

How are Na+ ions moved across the cell membrane?

They are ejected from cells by active transport.

What are the two directions of movement in vesicular transport?

Endocytosis (into the cell) and exocytosis (out of the cell).

What is phagocytosis?

A type of endocytosis ('cell eating') where the cell engulfs solid particles like bacteria by wrapping around them to form a phagosome, which then fuses with a lysosome to digest the material.

What is pinocytosis?

A type of endocytosis ('cell drinking') where the cell takes in liquids and small dissolved particles through vesicle formation.

What is a vesicle?

A small membrane-bound sac that transports substances within or outside the cell.