Cell Transport

Flashcards about Cell Transport

What is the purpose of cell transport?

Cells need a constant flow of nutrients and material in order to function, and they must be able to excrete waste and products, being selective about what enters and leaves.

What are the two major ways that cells can transport molecules?

Passive and Active Transport

What does passive transport mean for molecules flowing through the cell membrane?

No energy is required; it utilizes diffusion.

Define diffusion.

The movement of molecules from an area of high concentration to an area of low concentration.

What increases the rate of diffusion?

The greater the concentration difference.

What happens when the concentration of both sides of a membrane is the same?

Molecules will continue to freely move back and forth, however, there is no longer a net change in concentration.

What is it called when there is no longer a net change in concentration, even though molecules are still moving?

Dynamic equilibrium.

What are the three ways that cells can utilize diffusion for passive transport?

Simple Diffusion, Osmosis, and Facilitated Diffusion

What is simple diffusion?

Very small and non-polar substances can diffuse straight through the cell membrane without any assistance.

What kind of molecules cannot use simple diffusion to cross the membrane?

Large polar molecules and charged ions.

What is Osmosis?

The flow of water in and out of the cell through simple diffusion.

How does water flow in osmosis?

From an area of high-water concentration (low solute) to an area of low-water concentration (high solute).

What does osmosis determine about the cell?

The shape of its cell.

What are the three possible results of osmosis?

Hypotonic, Hypertonic, and Isotonic.

What is Facilitated Diffusion?

Diffusion that receives some assistance from special membrane proteins.

In what two ways can proteins assist with diffusion?

Channel proteins and carrier proteins.

What do channel proteins do?

Form hydrophilic (polar) tunnels through the membrane that allow water and ions to pass through.

What do carrier proteins do?

They form a passageway through the membrane, binding to molecules, changing shape, and releasing the molecule on the other side of the cell.

What is Active Transport?

Requires the use of energy to transport molecules against the concentration gradient (low → high concentration).

What are the four ways cells use active transport?

Primary Active Transport, Secondary Active Transport, Exocytosis, and Endocytosis.

What do primary active transport pumps do?

Move cations such as H+, Ca2+, Na+, and K+ to areas of high concentration, and are powered by ATP.

How do secondary active transport pumps work?

They use the energy from the electrochemical gradient created by primary active transport pumps.

What are the two types of secondary active transport pumps?

Symport and Antiport.

What is symport?

When the molecule travels in the same direction as the ions.

What is antiport?

When the molecule travels in the opposite direction as the ions.

What are Exocytosis and Endocytosis?

Ways of actively transporting molecules in bulk in (endocytosis) and out (exocytosis) of the cell.

What is exocytosis?

Substances exit the cell

What is endocytosis?

Substances enter the cell

What are the three categories of endocytosis?

Pinocytosis, receptor-mediated endocytosis, and phagocytosis.

What happens in pinocytosis (cell drinking)?

The plasma membrane forms a pit-like depression that traps the desired substances along with the extracellular fluid, then pinches off, forming a vesicle.

What happens in receptor-mediated endocytosis?

Molecules to be taken in bind to highly specific receptor proteins, which collect in a depression in the membrane, pinching off and forming a vesicle.

What happens in phagocytosis (cell eating)?

A cell engulfs large undissolved particles such as pathogenic bacteria or viruses.