Fundamentals 1- Membranes and Cytoplasm

• Integral proteins:
• 1. span the entire length of the membrane completely (20AA)
• 2. Removed by Detergent

• Periphral Proteins:
• 1.Ionicly bind to lipids or other proteins and do not penetrate the bilayer
• 2. Removed with high salt (1mol NaCl)
• 3. located on both extracellular(made in ER and secreted) and intracellular (made in cytoplasm)

1. Transmembrane proteins- a-helix domain completly spans the membrane and can make a single pass or multiple passes

• 2. Partially penetrating proteins- all the protein is on the same side of the membrane
• ex: Caveolin caveolae

3. Covalently tethered proteins- are covalently linked to the membrane through glycolipids or phospholipids

All are integral proteins because all of them are removed using detergent.

1. Fat droplet- found in adipocytes, adrenal cortex cells, liver cells.

2. Glycogen granules- storage sites for glucose found mainly in the liver cells

3. Lipofucin granules- in aged, non-dividing cells like neurons and muscle cells. usually golden brown in colors and can be membrane bound because they start as lysosomes but cannot break down any more.

An inclusion is something in the cell usually non-membrane bound with the exception of lipofuscin granules that have no function in the cell and are accumulated metabolites.

• The Bacteral have a different structures that are unique to it and not found in eukayotic cells
• 1. Ribosomes-the 30S and 50S units are targets for certain antibiotics and inhibiting these they inhibit the protien synthesis and kill the bacteria

2. Cell wall- eukayotes do no have a cell wall so targeting this will kill the bacteria because it has no barriers ex- vancomycin and penicillin

Antibiotic- a soluble substance that is derived from a mold or bacterium that inhibits the growth of other microorganisms

• The Mitochondrial Origin Theory
• Mitochondria were bacteria that were engulfed by the cell in the very beginning. Mitochondria were aerobic and used the O2 of the cell to make ATP so it adapted to living with the cell.

The mitochondria encodes for its own ribosomes of 30S and 50S the same as the bacteria.

The antibiotics that target these in bacteria can leak through the double membrane in small quantities and destroy our own ATP making mitochondria which can make us feel unwell and out of energy.

1. Phospholipids- polar head (hydophilic) and non-polar tails (hydrophobic) create a bilayer for protection and regulation of what goes in and out of the cell

2. Cholesterol- Helps maintain the fluidity of the membrane. Increased colesterol --> less fluid the membrane and harder for things to get in and out of the cell

3. Proteins- integral and peripheral proteins that are in a mass ratio of 1:1 to phospholipids

• 1.Glycerol backbone
• 2. 2 non-polar fatty acid hydrocarbon chains
• 3.the phosphate containing polar group

• 1. phosphatidylcholine
• 2. phosphatidylserine
• 3. phosphatidylethanolamine
• 4. phosphatidylinositol

Phosphatidylethanolamine is neg charged and is found on the inner membrane of the cell

• steriod
• lipid-soluble
• found in both leaflets of the membrane
• amphiphilis- OH forms the polar head
• synthesized in the ER
• Can flip easily in the membrane unlike phospholipids because of its small polar head group

• Functions:
• 1. they keep the structure of the hydrocarbons of the phospholipids so a cell wall is not needed

2. they make the membrane less soluble to small water molecules

3. they prevent crystalization of hydrocarbons when lowering the temp which doesnt happen in the body

Phospholipids can move laterally and can rotate in a circular motion, flex, but cannot flip to the other leaflet because their polar heads are large. Therefore they are asymetrical in the leaflets of the membrane. what is on one leaflet is not on the other

Cholesterol flips easy because it has a small polar head group. Therefore the cholesterol is 50/50 on inner and outer membrane leaflets

about 10 seconds to diffuse throughout the membrane

If the tails are saturated that means there are no double bonds in the hydrocarbons and that they are closely packed together and are ridgid

If the tails are unsaturated that means there are double bonds are there are kinks in the hydrocarbons making the membrane more fluid.

• It can elicit a conformational change in the protein on the opposite end of the binding.
• ex: if insulin binds to the receptor on the extracelular side of the protein, it can then have a conformational change in the protein on the intracellular side to elicit a responce

This is called the 2nd messenger pathway

• glycoprotein= carbohydrate+protein
• glycolipid= carbodydrate + lipid

when lipids and proteins are being sythesized in the ER sometimes carbohydrates can attach to them during the process

carbohydrates are always located on the extracellular leaflet of the bilayer

The membrane functions as not only structure but protection and a regulatory site.

It gives the cell a way to monitor what comes in and out of the cell

The cell can also create its own microenvironments and compartmentalize its functions (organelles)

each of the organelles has a specific function and only specific molecules need to be involved to make the cell more efficent.

The resting membrane potential of a cell is usually around -60mV.

It is negitive because of the ion concentrations on both sides of the membrane

Na, K, Cl and Ca are the 4 main ions that contribute to this negitive charge inside the cell

Both inside and outside the membrane has the same ions but in different concentrations

Bacteria- forms large aggregates

Humans- they are hooked on the something outside the cell : Extracellular matrix, inside the cell: cytoplasmic matrix, or they can be hooked on proteins of other cells around it.

an area of the membrane in which it has thickend and more sphingomyelin and cholesterol and some proteins have concentrated

only specific and longer transmembrane protiens can accumulate here.

they also can form plasma membrane organelles called caveolae

nucleus, mitochondria