Plasma membranes Flashcards
True or False.
Plasma membranes only surround cells.
- False.
- Plasma membranes also surround membrane- bound organelles (ie. mitochondria/ nucleus.)
-note: membrane of any organelles of eukaryotes
Why are plasma membranes described as a “fluid mosaic model?”
- Mosaic: due to the mixture of molecules/ proteins found (vary in shape and size. )
- Fluid: The proteins, phospholipids, glycoproteins, glycolipids can move around.
How are molecules (ie glycoproteins, channel proteins, glycolipids) arranged in the phospholipid bi- layer ? What does this create?
- They are either within or on the outside of the bi- layer.
- Creates the partially- permeable membrane (only certain molecules can pass through other molecules in bi- layer. )
What does an unsaturated fatty acid chain look like in comparison to a saturated fatty acid?
- It has a kink ( bends) due to the double bond between carbon atoms.
What is the role of cholesterol in plasma membranes?
- Restricts movement of other molecules (making up membrane.)
- Makes plasma membrane more rigid.
What 4 molecules are found in plasma membranes that can move?
1.) Phospholipids
2.) Proteins (ie. channel/ carrier.)
3.) Glycoproteins
4.) Glycolipids.
What are the 2 types of proteins in plasma membranes? What is the difference between the two?
- Intrinsic: proteins that span across from one side of the bi- layer to the other.
- Extrinsic: Do not extend completely across/ through the membrane.
What are extrinsic proteins used for in the plasma membrane?
- Provide mechanical support or they are connected to proteins or lipids to make glycoproteins/ glycolipids.
- Function of glycoproteins/ glycolipids —> cell recognition (ie. receptors. )
In what case is it useful for cholesterol to make plasma membranes more rigid/ less fluid?
- Useful: makes membrane less fluid at high temperatures and prevents water/ dissolved ions from leaking out of the cell (could cause dehydration/ cells bursting.
(more fluid membrane is = more gaps in membrane.)
() - extra info for clarification.
What are intrinsic proteins used for in the plasma membrane?
- Protein carriers/ channel proteins involved in transport of molecule across the membrane.
What sort of molecules are transported by channel proteins?
- Water/ amino acids/ potassium/ sodium.
How exactly do carrier proteins transport molecules into the cell?
- Larger molecules will bind to the carrier protein.
- The carrier protein will change shape to transport molecules to other side of membrane.
What are the molecules that can pass easily through the plasms membrane? Give examples?
- Lipid-soluble substances (ie. hormones.)
- Non-polar, very small molecules (ie. O₂, CO₂,)
What molecules cannot pass through the plasma membrane by simple diffusion? Give examples?
- Polar molecules (water)
- And large molecules (glucose.)
- Water-soluble substances (ie. sodium/ potassium/ amino acids.)
If you have more unstaured fatty acids in a plasma membrane, what does this do to the membrane?
- More unssaturated fatty acids = increase in fluidity/ flexibility/ lower melting point.