2B | Cell Membranes Flashcards
What is a cell-surface membrane?
Cell-surface membranes are partially permeable barriers between the cell and its environment, controlling which substances enter and leave the cell.
How can a substance enter the cell-surface membrane?
A substance can enter the cell-surface membrane by diffusion, osmosis or active transport.
Cell membranes have a structure named as what?
Fluid-Mosaic
The Cell Membrane’s structure is described as ‘Fluid-Mosaic’.
Describe why it is considered fluid.
The cell membrane is ‘fluid’ as the phospholipids which form a bilayer are constantly moving.
In a cell surface membrane, where is Cholesterol located?
Cholesterol molecules are present within the bilayer.
The Cell Membrane’s structure is described as ‘Fluid-Mosaic’.
Describe why it is considered mosaic.
The cell membrane is ‘mosaic’ as the proteins present in the cell membrane’s phospholipid bilayer are scattered through it, like tiles in a mosaic.
Give 2 types of proteins present on a Cell Membrane.
Extrinsic Protein
Intrinsic Protein
What is an Extrinsic Protein?
Extrinsic proteins are proteins that are confined to the inner or outer surface of the cell membrane - they do not span the entire length of the membrane.
What is an Intrinsic Protein? Give 1 example.
intrinsic proteins are proteins that are present on cell membranes which span the entire length of the cell membrane.
As a result, carrier and channel proteins are seen as intrinsic.
What is a channel protein?
Channel proteins are intrinsic proteins present on the cell surface membrane which allow ions. which are water-soluble, to pass through the membrane.
What is a carrier protein?
Carrier proteins are intrinsic proteins present on the cell surface membrane which allow large molecules, such as glucose, to pass through the membrane.
Why can’t a large molecule like glucose pass directly through the cell surface membrane?
It is too large to travel through the phospholipid bilayer.
Why can’t an ion pass directly through the cell surface membrane?
Ions are water-soluble, and as a result, they are not able to pass through the phospholipid bilayer as the fatty acid tails which are found past the glycerol molecules are hydrophobic - they repel water.
Water soluble molecules must go through the cell membrane by what process?
Facilitated diffusion
How do Ions and other water soluble molecules pass through the cell surface membrane?
Ions and other water soluble molecules pass through the cell membrane through facilitated diffusion with the help of a channel protein.
Large molecules must go through the cell membrane by what process?
Facilitated diffusion
How do large molecules pass through the cell surface membrane?
Large molecules, like glucose, are too large to fit through the phospholipid bilayer and as a result they must go through the cell surface membrane by a process called facilitated diffusion through a carrier protein.
Cell membranes have receptor proteins.
Name each one.
Glycolipid
Glycoprotein
What is the function of receptor proteins on cell membranes?
Receptor proteins on the cell surface membrane allow the cell to detect chemicals released from other cells.
The chemicals signal to the cell to respond in some way, for example, the hormone insulin binds to receptor proteins on liver cells to tell them to absorb glucose.
Some proteins have a polysaccharide chain attached. What are they called?
Glycoproteins
Some lipids have a polysaccharide chain attached.
What are they called?
Glycolipids
What is a Glycoprotein?
A glycoprotein is a receptor protein that is present on the surface of cell surface membranes. It is a protein that has a polysaccharide chain attached.
What is a glycolipid?
A glycolipid is a receptor protein that is present on the surface of cell surface membranes. It is a lipid that has a polysaccharide chain attached.
Label A to F:
https://media.discordapp.net/attachments/352951793187029005/828707346380357642/unknown.png
A = Extrinsic protein B = cholesterol C = Intrinsic protein D = Phospholipid Bilayer E = Glycolipid D = Glycoprotein