Cell Membrane Transport - Term 1 Flashcards
Week 2
How do cells exchange materials?
Cells must exchange materials like nutrients and gases with their environment by allowing them to pass through their environment.
What types of molecules can pass through the lipid bilayer of a cell membrane?
The lipid bilayer is permeable to a few small uncharged molecules such as oxygen and carbon dioxide
Why can’t polar and ionic compounds pass directly through the cell membrane?
The cell membrane is impermeable to polar and ionic compounds, these substances must enter and exit the cell differently
What are the functions of the cell membrane?
It serves as a physical barrier, regulates the passage of materials, is sensitive to changes and provides support.
What is the purpose of a physical barrier in the cell membrane?
It separates the cytoplasm from the extracellular fluid around it.
How does the cell membrane regulate the passage of materials?
Regulates the movement of ions and nutrients into the cell, controls the removal of wastes, and facilitates the release of secretions
How is the cell sensitive?
- It detects any changes in the extracellular environment.
- It has receptors that can detect specific molecules around it.
Give an example of how the cell membrane is sensitive
An increase of glucose in the blood.
How does the cell membrane provide support?
It’s attached to the cytoskeleton which supports cell structure. Cells are attached to one another via the cell membrane giving rise to tissues.
What is the fluid mosaic model?
It explains the structure and function of the cell membrane
Why is the membrane said to be fluid?
Because the molecules of which it is made are constantly changing positions.
Why is the membrane said to be a mosaic?
Because it’s composed of many different kinds of molecules.
Describe the structure of a phospholipid
- Arranged in a bilayer (two layers)
- All have a hydrophilic head and hydrophobic tails.
- Heads on the outside and tails on the inside
Which two proteins do cell membranes contain?
Integral and peripheral proteins
What are integral proteins?
- Located through the membrane
- Responsible for transporting ions and small molecules across the membrane
- Can be polar in nature when moving against their concentration gradient
What is peripheral proteins?
- Proteins that are attached to one side of the membrane only.
What are the proteins included in the cell?
- Receptor, channel, carrier and cell-identity markers.
What are receptor proteins?
- Limited in the cell membrane
- Certain molecules outside of the cell bind to receptor proteins which influences changes within the cell.
- Site-specific
Describe the function of a channel protein
Found in the cell membrane and allows substances to pass in/out of the cell.
What substances can pass the cell through channel proteins?
Water-soluble substances (ions, sodium, calcium, and chlorine) can enter and leave the cell through the channels if they are small enough to fit through.
What substances can’t pass through the cell through channel proteins?
Large molecules like glucose can’t pass. They must pass via facilitated diffusion which is a passive process.
Describe the function of a carrier protein
- They bind to molecules (glucose) so they can be transported across the cell membrane and into the cytoplasm.
- The number of carrier proteins available limits the intake of molecules into the cell.
Describe the function of a cell identity-marker proteins
Serves as recognition markers for the body’s immune system.
The immune system recognises these cells and therefore will not be destroyed.
