Chapter 5 - Structure And Function Of Plasma Membranes Flashcards
What are on plasma membranes that allow for cell to cell communication and connections?
Surface markers
-these allow for the immune system to determine self from non self for example autoimmune disease’s
How does the plasma membrane transmit information?
It allows proteins to transmit complex signals from extracellular input receivers to intracellular processing activators such as hormones and growth factors
What bad things can happen to plasma membranes if other pathogens take them over?
They can be hijacked or mutated leading to disease states
When was the plasma membrane (PM) identified? And when were the chemical components determined?
Identified in 1890s and determined its chemical components in 1915
-initially various theories proposed a sandwich like structure of proteins and lipids
Singer and Garth theorized what in 1972?
The fluid mosaic model
The fluid mosaic model states what?
The model is that of a semiliquid phospholipid bilayer with cholesterol, proteins, and carbohydrates floating in and around the bilayer
What are phospholipids composed of?
A phosphate head, a glycerol, and two fatty acid tails
What is in between the phospholipids in the PM that stabilize them?
Cholesterol
A typical human cell is composed of what percentage of the 3 main macromolecules? (By mass)
50 percent protein, 40 percent lipid, and 10 percent carbs (by mass)
Percentage of macromolecule makeup of cells can vary. Explain the differences between myelin sheaths of nerve tissue and the inner mitochondrial membrane
Myelin sheaths of nerve tissue is mostly lipids and some protein and even fewer carbs while the inner mitochondrial membrane is mostly proteins and some lipids with virtually no carbs
Where is the only place carbohydrates can be found on the PM and in what form?
They can only be found on the PMs external surface in the form of glycoproteins or glycolipids
The interactions between the nonpolar fatty acid tails interacting with one another and the polar phosphate head of phospholipids effectively seperates what?
The serious solution inside the cell (cytoplasm) from the cells exterior (interstitial fluid)
The polar heads of phospholipids can form what bonds with other molecules (especially water)?
Hydrogen bonds
Phospholipids are known to spontaneously form what shapes and structures?
Spheres and bilayers
What are integral proteins
Those that are embedded into the phospholipids Hydrophobic region
How many a-a do single pass integral proteins usually have?
20-25
Some integral proteins extend through both layers and some only one layer of the PM, those that are large can have up to how many protein segements?
12, which are extensively folded and embedded in the PM
Integral proteins have hydrophobic and hydrophilic regions where?
The hydrophobic region is at the center and mildly hydrophilic regions at their peripheries that contact the cytoplasm or the extracellular fluid
Pertaining to the secondary protein structure how many conformations can integral proteins have?
They can have one or more alpha helixes or multiple beta sheets
Where are peripheral proteins found?
Only on the PM’s exterior or interior surfaces and can be attached to the phospholipid bilayer or to integral proteins
What can peripheral proteins be? What types of proteins?
Enzymes, structural components, or receptors (often referred to as cell-specific proteins)
Where are carbohydrates found on the PM? And in what form?
Only on the PM’s outer surface and are either in the form of glycoproteins or glycolipids
The carbohydrate components can be straight or branched on the PM and are usually how many monosaccharides pollysaccharides?
2-60
The carbohydrate components on the PM are vital for what?
Cell recognition, which is especially important in immunity including allowing cells to differentiate self from non self
-viruses and other antigens are identified by these components of the PM on immune cells, viruses are experts at changing their glycolipid and glycoprotein surfaces
What is the term used to describe the PM’s carbohydrate components?
Glycocalyx
The glycocalyx has to do what with polarity and what?
It is highly hydrophilic (polar) attracting water to these cells outer surfaces
Describe the plasma membrane’s fluidity and how it withstands punctures?
The lipid and protein components of the PM float in the bilayer however the PM is rather rigid, and has the property of allowing a very fine needle to penetrate it and withdraw without bursting the cell
How does the fatty acids chemical composition on the phospholipid tails make the plasma membrane more rigid?
The fatty acid risks are fully saturated and therefore are very straight and rigid, if they were unsaturated it would contain double bonds which would bend the fatty acids and have less rigidity
Some species have cells with more unsaturated fatty acids, this allows them to live in environments that are what?
Cold, helps them to remain flexible in cold temeratures
Plasma membranes have what type of permeability?
They are selectively permeable
Most plasma membrane transport is what type?
Passive transport
How do materials move through a concentration gradient?
ALWAYS down a concentration gradient (under normal conditions)
What is the main difference between passive and active transport?
Passive transport requires no energy (ATP) while active transport does not
E.g. for active transport is the sodium potassium pump
-most of a cells energy is used in this process
In terms of polarity what passes through the PM easily? And what does not?
Non-polar and lipid soluble materials with low molecular weight can pass through the bilayers hydrophobic core easily, polar substances cannot pass through the PM’s lipid core
What types of vitamins, drugs, molecules, and common molecules can pass right through the PM? List a few
Vitamins A,D,E,K along with fat soluble drugs, hormones, oxygen, and carbon dioxide all pass through the PM by simple diffusion
Even though polar substances do not pass through the PM’s lipid core it connects easily to what?
The cells exterior
What types of molecules and atoms cannot pass through the lipid core?
Ions, along with sugars and amino acids
Instead what do these ions, sugars, and amino acids need to get into the PM?
They need help from protein channels to get through
What type of process is diffusion in terms of energy?
A passive process, expends no energy
In diffusion how do substances move in the gradient?
It moves from high to low concentration (down a concentration gradient)