2.1.5 Biological Membranes – Roles of Membranes Flashcards
(6 cards)
1
Q
Why do cells need membranes?
A
- To act as a partially permeable barrier between a cell and its environment
- To act as a partially permeable barrier between an organelle and the cytoplasm
- As the site of chemical reactions
- As the site of cell-cell communication (aka cell signalling)
2
Q
What are the roles of plasma membranes within cells?
A
- Form compartments around organelles e.g. mitochondria, RER, SER, nucleus, lysosomes, golgi, chloroplast (a.k.a. compartmentalisation)
- Isolate substances/reactions e.g. hydrolytic enzymes
- Site for attachment of other molecules e.g. ribosomes on RER, enzymes on mitochondria/chloroplast
- Creation of specific environments/concentration gradients e.g. mitochondria, chloroplasts
3
Q
What is meant by cell signalling?
A
When cells communicate with each other by releasing chemicals which bind to receptors on another cell’s plasma membrane.
4
Q
Why may some chemicals, e.g. the hormone testosterone, not need a receptor in the membrane and instead be able to move directly into the cell through the phospholipids?
A
It is both small and lipid soluble.
5
Q
What type of molecule would be a receptor for cell signalling?
A
A protein or glycoprotein
6
Q
What must be true about the shapes of the chemical messenger and receptor?
A
They must be complementary shapes.
