Cells- Biological membranes Flashcards
(20 cards)
What are the membranes that surround cells and organelles composed of ?
A sea of phospholipids with protein molecules between the phospholipid molecules.
What is the fluid mosaic model?
The name of the structure of the membrane. The membrane is fluid, with a mosaic arrangement of proteins.
What are the functions of the cell membrane?
- Controlling substances in and out of the cell
- Contains receptors for other molecules e.g. hormones
- Enables adjacent cells to stick together.
Can lipid or water soluble molecules diffuse through the cell membrane?
Lipid soluble.
Why can lipid soluble molecules pass through the membrane, but not water soluble molecules?
The membrane is comprised of phospholipids with hydrophilic heads that point outwards and hydrophobic heads that point inwards. This means that the membrane is flexible and self-sealing.
What are the other components of cell membranes?
Proteins, cholesterol, glycolipids, and glycoproteins.
What are intrinsic proteins?
Proteins within the cell membrane- includes carrier proteins.
What are extrinsic proteins?
Proteins on the outside of the cell membrane.
What is the function of the proteins in the cell membrane?
- Aid movement across the cell membrane.
- Provide mechanical support.
- Act in conjunction with glycolipids as receptors.
What is the function of cholesterol in the cell membrane?
- Make the membrane more rigid and reduce the lateral movement of the phospholipids.
- To prevent the leakage of water and dissolved ions as it is hydrophobic.
What is the function of the glycolipids in the cell membrane?
- Act as cell surface receptors.
- Allow cells to adhere to one another and form tissues.
What is the function of the glycoproteins in the cell membrane?
- Act as cell surface receptors and neurotransmitters.
- Allow cells to recognise one another.
- Allow cells to attach to one another to form tissues.
How does diffusion occur in the cell membrane?
Small, non-polar, lipid soluble molecules such as carbon dioxide and oxygen passively diffuse from a high to a low concentration. The molecules move through the phospholipid bilayer.
How does facilitated diffusion occur in the cell membrane?
Polar, charged, and water soluble molecules diffuse through a channel protein.
How does osmosis occur in the cell membrane?
Water molecules diffuse from an area of high concentration to an area of low concentration.
How does active transport occur in the cell membrane?
All types of molecules are transported up the concentration gradient through a channel protein. Requires ATP.
How does exocytosis occur in the cell membrane?
Vesicles containing large particles are fused with cell surface membrane and released from the cell.
How does endocytosis occur in the cell membrane?
Large particles are enclosed in vesicles made from the cell membrane and transported into the cell.
How does co-transport occur in the cell membrane?
Ions are used to move substances in and out of cells, for example
What increases the rate of diffusion?
- Surface area increasing
- Diffusion distance decreasing
- Concentration gradient becoming steeper
- The temperature increases.
