bio 2.9

These flashcards cover the key concepts related to mechanisms of transport across cell membranes, including diffusion, facilitated diffusion, active transport, endocytosis, and exocytosis.

What is diffusion in the context of transport across cell membranes?

The movement of molecules from a high concentration to a low concentration.

Which type of molecules can pass freely across the cell membrane?

Small, non-polar molecules such as nitrogen, oxygen, and carbon dioxide.

What is facilitated diffusion?

The movement of molecules from a high concentration to a low concentration through transport proteins.

Which type of transport proteins do large polar molecules and charged ions require to move across the membrane?

Channel proteins.

How does water move through the cell membrane in large quantities?

Via aquaporins.

What is osmosis?

The diffusion of water across a membrane.

What is the primary characteristic of active transport?

It moves molecules or ions against their concentration gradient from low concentration to high concentration.

What type of proteins are used in active transport?

Protein pumps.

What is endocytosis?

The process by which the cell uses energy to take in macromolecules and other matter by forming new vesicles from the plasma membrane.

What are the three types of endocytosis?

Phagocytosis, pinocytosis, and receptor-mediated endocytosis.

What is exocytosis?

The process by which internal vesicles use energy to fuse with the plasma membrane and secrete large macromolecules out of the cell.

What is the net movement direction in passive transport?

From a high concentration to a low concentration without direct input of energy.

How are sodium ions maintained at high concentration outside the cell?

They are actively transported from inside of the cell to the outside through a membrane protein.

What energy source is required for active transport?

Metabolic energy, such as ATP.

What is a key takeaway regarding large molecules moving into and out of the cell?

Large molecules are moved into the cell by endocytosis and out of the cell by exocytosis.