4. Cell Membranes And Transport Flashcards
why is the fluid mosaic model membrane described as “fluid”
because phospholipids and proteins can move around via diffusion
why is the fluid mosaic membrane described as “mosaic”
because the scattered pattern produced by the proteins within the phospholipid bilaterally looks like a mosaic when viewed from above.
what are the three types of lipids in the cell membrane
phospholipid
cholesterol
glycolipids
what are the two types of protein in the cell membrane
glycoprotein
transport proteins (carrier and channel)
what are the three main receptor types
signaling receptors for hormones and neurotransmitters
receptors involved in endocytosis
receptors involved in cell adhesion
cell marker/antigen for cell to cell recognition
what are the stages of a pathway in cell signaling
-a stimulus is received by a receptor
-signal is converted to a ‘message’ that can be passed on
-‘message’ is transmitted to a target
What is diffusion
The net movement of molecules from a region of its higher concentration to a region of its lower concentration as a result of their random movement
What is facilitated diffusion
Certain substances cannot move through the phospholipid bilayer without the help of certain proteins like channel and carrier proteins.
What is osmosis
The net movement of water molecules from, a region of higher water potential to a region of lower potential through a partially permeable membrane
What is active transport
The movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
Requires carrier proteins
What is meant by endocytosis
The bulk movement of Particles or molecules into the cell.
The cell membrane engulfs material to form a small vesicle.
Describe the steps in endocytosis
Phagocytosis- the bulk uptake of solid material
The vacuoles are called phagocytic vacuoles.
Eg engulfing of bacteria by white blood cells.
Pinocytosis- the bulk uptake of a liquid
The vesicles are often very small in which case the process is called micropinocytosis.
What is exocytosis
The reverse of endocytosis.
Process by which materials are removed from cells by the fusion of vesicles containing the substance with the cell membrane
Explain what happens during exocytosis
Secretory vesicles from the Golgi apparatus carry the enzymes to the cell surface and release their contents.
