Cell membrane and transport Flashcards
What processes are responsible for the transport of individual molecules or ions across cell membranes?
Diffusion, osmosis, and active transport.
What is bulk transport?
The transport of larger volumes of materials into or out of cells.
What are examples of larger quantities of materials that might need to cross the membrane?
Large molecules such as proteins or polysaccharides, parts of cells, and whole cells (e.g., bacteria).
What is bulk transport into cells called?
Endocytosis.
What is bulk transport out of cells called?
Exocytosis.
Do bulk transport processes require energy?
Yes, they require energy input and are therefore forms of active transport.
What is endocytosis?
Endocytosis is the process by which the cell surface membrane engulfs material, forming a small sac (or ‘endocytic vacuole’) around it.
What are the two forms of endocytosis?
The two forms of endocytosis are phagocytosis and pinocytosis.
What is phagocytosis?
Phagocytosis is the bulk intake of solid material by a cell.
What are cells that specialize in phagocytosis called?
Cells that specialize in phagocytosis are called phagocytes.
What are the vacuoles formed during phagocytosis called?
The vacuoles formed are called phagocytic vacuoles.
Can you give an example of phagocytosis?
An example is the engulfing of bacteria by phagocytic white blood cells.
What is pinocytosis?
Pinocytosis is the bulk intake of liquids.
What is micropinocytosis?
If the vacuole (or vesicle) that is formed is extremely small, then the process is called micropinocytosis.
What is exocytosis?
Exocytosis is the process by which materials are removed from, or transported out of, cells (the reverse of endocytosis).
What substances are released during exocytosis?
Substances such as enzymes, hormones, or cell wall building materials are released.
How are substances packaged for exocytosis?
They are packaged into secretory vesicles formed from the Golgi body.
What happens to the secretory vesicles during exocytosis?
The vesicles travel to the cell surface membrane.
What occurs when vesicles reach the cell membrane?
They fuse with the cell membrane and release their contents outside of the cell.
Can you provide an example of exocytosis?
An example is the secretion of digestive enzymes from pancreatic cells.
Functions of receptor molecules [3]
1) Cell recognition/ antigens
2) Cell adhesion
3) Form hydrogen bonds with water to stabilise the membrane
What role does cholesterol play in membrane fluidity?
Cholesterol regulates the fluidity of the membrane.
How does cholesterol affect phospholipid packing at low temperatures?
Cholesterol prevents phospholipids from packing too closely together when temperatures are low.
What is the effect of cholesterol on membranes at higher temperatures?
Cholesterol stabilises the cell membrane at higher temperatures by stopping it from becoming too fluid.
