Cell Membrane and Transport Flashcards
What is the cell membrane?
Forms the boundary between the internal environment of the cell - the cytoplasm - and its external environment.
What are the functions of the cell membrane?
Functions include the recognition of other cells, the transportation of materials into and out of the cell, the provision of attachment sites for enzymes and hormones added nerve cells the transmission of neural impulses.
What are 2 properties/structure of the cell membrane?
- It is selectively permeable meaning that it is able to control the movement of substances into and out of the cell and it is able to exclude unwanted substances.
- It is a flexible structure.
What are the membranes of organelles like?
Organelle membranes have the same general structure as cell membranes.
Describe the fluid mosaic model.
The fluid mosaic model describes membranes as a phospholipid bilayer, with the ability to flow and change shape, like a two dimensional fluid. Specialised protein molecules are embedded in the lipid in various patterns, like a mosaic. Some of the proteins can move laterally and others are fixed in position. Both proteins and phospholipids help take control the exchange of materials between the internal an external environments.
What is the fluid part of the fluid mosaic model?
Fluid refers to the flexible fluid bilayer of phospholipids that enable the membrane to expand and contract.
What is the mosaic part of the fluid mosaic model?
Mosaic refers to the mosaic of components including cholesterol protein and carbohydrates.
What do transport proteins do?
They allow interaction and communication between cells and exchange of substances between cells and the external environment.
What are the 2 main types of transport proteins?
- Channel proteins (ion channels)
- Carrier proteins (transporters)
What do channel proteins do?
Catalyse the movement of specific ions and some super molecules such as water down each substances own electrochemical gradient. They help move these substances across the membrane via passive transport in a process called facilitated diffusion.
Give an example of a channel protein.
Channel proteins that facilitate the transport of water are called aquaporins they selectively allow water to pass along its concentration gradient.
What do carrier proteins do?
Have to change shape to pass a molecule across the membrane. Many use ATP to transport specific small molecules or ions against their concentration gradient. Some carrier proteins can move ions or molecules for example glucose along their concentration gradient through passive transport.
Give an example of a carrier protein.
The sodium potassium pump maintains the electrochemical gradient and the correct concentrations of sodium and
potassium ions in cells.
What do adhesion proteins do?
Link cells together to maintain both 3 dimensional structure and the normal functioning of tissues.
What do receptor proteins do?
Bind hormones and other substances that cause changes to cells activities. Different types of cells have different receptor proteins, enabling them to respond to only certain signals and so carry out specific functions.
What are the 2 types of transports that materials can be moved across a cell membrane with?
Active and passive transport.
What is the difference between active and passive transport?
Active transport processes require energy (ATP), passive transport processes do not.
What are the different types of active transport?
- Active transport
- Endocytosis
- Exocytosis
What are the different types of passive transport?
- Simple diffusion
- Facilitated diffusion
- Osmosis