Chapter 4: Cell Exchange Materials
Structure of cell membrane
Functions of Cell Membrane
Diffusion
Carrier-mediated Transport
Vesicular Transport
Cell requirements
Physical barrier: separates cytoplasm from extracellular fluid
Regulation of the passage of materials: controls the movement of materials into and out to cell
Sensitivity: first part of cell affected by any changes in the extracellular
Support: internal part of cell membrane is attached to the microfilaments of cell's cytoplasm, giving support to whole cell
The spreading out of particles so they are evenly distributed over the space available
Follows concentration gradient: difference in concentration on each side (high to low)
Includes: oxygen, carbon dioxide. Alcohol, steroids, fat-soluble substances can diffuse through the lipid portions of the membrane
Proteins in cell membrane bind to molecules to be transported and help them pass across membrane
carrier proteins are specific to one particular molecule
carriers can become saturated (when all carriers are occupied rate of movement cannot increase)
carrier activity is regulated by substances such as hormones
2 main types: facilitated diffusion and active transport
Movement of substances across the cell membrane in membranous bag called vesicles
Active process as energy from the cell is needed
Endocytosis: taking liquids or solids into the cell
Exocytosis: contexts of a vesicle inside the cell are passed to the outside
Cells in body in stable environment; must have continual supply and removal of materials
Osmosis: net diffusion of water
All cells need oxygen for respiration which is the process that releases the energy needed for the cell's activities. Need glucose as well
Each cell is surrounded by cell membrane which separates cell contents from external environment.
Important in determining which substances will get into and out of a cell
"fluid mosaic model": "fluid" because molecules of the membrane are constantly changing position and "mosaic" because it is composed of many different kinds of molecules
Each molecule has hydrophilic head and hydrophilic tail
Main structure is phospholipid molecules that are arranged in two layers: bilayer