Plasma Membrane & Organelles (L4) Flashcards
What are the main functions of a cell?
Manufacture cellular materials/obtain raw materials, remove waste, generate energy, regulate processes
What is a plasma membrane? What does it do?
A plasma membrane is a semipermeable barrier (made of phospholipid bilayer) that allows only some substances/molecules to pass through the cell.
- allows passage of like molecules
- controls movement of substances in and out of cell
What are the benefits of a small cell having a greater surface to volume ratio?
Because smaller cells are able to survive more effectively.
As the area inside the cell gets bigger, it makes it harder for the cell to stay alive. (the organelles get bigger, and it makes it harder for it to get through plasma membrane)
What does it mean when the plasma membrane isn’t static?
It means that everything embedded on the plasma membrane is constantly moving. This movement is measured by fluidity.
Fluidity of the plasma membrane is influenced by three factors.
Saturation. Temperature. Cholesterol.
Saturation - loosely/tightly packed
Temperature - hot/cold
Cholesterol - stabilises fluidity of substances by sitting in between phospholipids to ensure that not too much/scarce fluidity
These determine the function of the membrane.
Proteins
What are the functions of proteins?
Cell recognition. Signal transduction. Intercellular linking/joining (in between cells. Extracellular linking (in between organelles/protein structures). Cellular transport.
A type of transport where no energy is needed. Molecules move down a concentration gradient.
Passive transport.
Energy is needed, where molecules move against their concentration gradient.
Active transport.
What is the difference between diffusion and facilitated diffusion.
Both move down their concentration gradients and require no energy. However ,diffusion is when molecules permeable to a membrane move in passively. Facilitated diffusion is the movement of impermeable molecules through channels and barriers passively (through aquaporins - in osmosis)
Indirect active transport, where one substance is pumped across the membrane to establish a concentration gradient that will power the movement of a second substance against its concentration gradient.
-ATP is used to produce a concentration gradient.
Co-transport.
Why are organelles membrane bound?
To allow different processes in diff. conditions to occur at the same time within the cell.
How is water transported across the membrane?
Through aquaporins via diffusion
