membrane structure
Key points
Hydrophilic: water lovers
Hydrophobic: water haters
The functions of membrane proteins are:
1. Hormone binding sites: allows for one specific hormone to bind
2. Enzymes: catalyze reactions inside or outside the cell
3. Electron carriers: they are arranged in chains so that the electrons are able to pass from one carrier to another
4. Channels for passive transport: allow one specific substance to pass through
5. Pumps for active transport: release energy from ATP and use it to move specific substances across the membrane
- Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules.
Hydrophilic: water lovers
Hydrophobic: water haters
- Membrane proteins are diverse in terms of structure, position in the membrane and function.
The functions of membrane proteins are:
1. Hormone binding sites: allows for one specific hormone to bind
2. Enzymes: catalyze reactions inside or outside the cell
3. Electron carriers: they are arranged in chains so that the electrons are able to pass from one carrier to another
4. Channels for passive transport: allow one specific substance to pass through
5. Pumps for active transport: release energy from ATP and use it to move specific substances across the membrane
- Cholesterol is a component of animal cell membranes.
phospholipids
•Flexible, adaptable, in motion
•Selectively permeable
–“Controlled entry”
–Small, hydrophobic
•Hydrophobic fatty acid tails repel water and form the middle layer
•Hydrophilic phosphate heads attract water and form outer layers
•Selectively permeable
–“Controlled entry”
–Small, hydrophobic
•Hydrophobic fatty acid tails repel water and form the middle layer
•Hydrophilic phosphate heads attract water and form outer layers
proteins
They are a major components of the cellular membrane. There are two types of proteins:
- Integral Proteins: have hydrophobic and hydrophilic regions. They completely penetrate the lipid bilayer and control the entry and exit of specific molecules from the cells
- Peripheral Proteins: they remain bound to the surface of the membrane. Attached to them are glycoproteins which control the recognition of substances or materials that are going to pass through the cell.
- Integral Proteins: have hydrophobic and hydrophilic regions. They completely penetrate the lipid bilayer and control the entry and exit of specific molecules from the cells
- Peripheral Proteins: they remain bound to the surface of the membrane. Attached to them are glycoproteins which control the recognition of substances or materials that are going to pass through the cell.
Why are membranes important?
•Membranes define compartments
•Membrane proteins control traffic
•Membranes are fluid
•Membrane proteins control traffic
•Membranes are fluid
source: Biology Class.
THEORY OF KNOWLEDGE
- The explanation of the structure of the plasma membrane has changed over the years as new evidence and ways of analysis have come to light. Under what circumstances is it important to learn about theories that were later discredited?