Active transport, endocytosis and exocytosis Flashcards
What is active transport?
Active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. During active transport, a cell uses energy to move substances against a concentration gradient.
What do active transport proteins use to move a substance against a concentration gradient?
They use chemical energy. Most active transport proteins use energy from a molecule called ATP, either directly or indirectly.
For what do cells use energy?
A cell may use energy to move a large substance or a large amount of a substance in vesicles. Transport in vesicles lets substances enter or exit a cell without crossing through the membrane.
What is endocytosis?
Endocytosis is the process of taking liquids or fairly large molecules into a cell by engulfing them in a membrane. During endocytosis, the cell membrane folds inward and fuses together, surrounding the substance in a pocket. The pocket pinches off inside the cell, forming a vesicle. The vesicle fuses with a lysosome or a similar vesicle, where enzymes break down the membrane and its contents.
What are enzymes?
Enzymes are substances produced by a living organism, which act as catalysts to bring about a specific biochemical reaction. A catalyst is a substance that causes or accelerates a chemical reaction without itself being affected.
What is phagocytosis?
Phagocytosis is a type of endocytosis in which the cell membrane engulfs large particles. Phagocytosis plays a key role in your immune system. Some white blood cells called macrophages help our body fight infection. They find foreign materials, such as bacteria, and engulf and destroy them.
What is exocytosis?
Exocytosis, the opposite of endocytosis, is the release of substances out of a cell by the fusion of a vesicle with the membrane. During this process, the cell forms a vesicle around material that needs to be removed or secreted. The vesicle is transported to the cell membrane. The vesicle membrane fuses with the cell membrane and releases the contents.
REMEMBER!
Cells use energy to transport materials that cannot diffuse across a membrane!
Proteins can transport materials against a concentration gradient!
Endocytosis and exocytosis transport materials across the membrane in vesicles!
