Week 1 Flashcards
How does the structure of cell membranes differ from that of organelle membranes?
There are variations in both membrane-associated proteins and phospholipids. And some organelles have membranes with two lipids bilayers.
Name two types of phosphoglycerides found in the cell membrane.
Phosphatidylcholine and Phosphatidylserine
What describes membrane lipids derived from Sphingosine?
Sphingolipids
There are five major phospholipids distributed asymmetrically within the cell membrane bilayer, some live predominantly in the outer leaflet and some in the inner leaflet. Where do each of these live?
Outer leaflet: Phosphatidylcholine, Sphingomyelin
Inner Leaflet: Phosphatidylethanolamine, Phosphatidylserine, and Phosphatidylinositol.
What happens when Phosphatidylserine, traditionally an intracellular phospholipid, flips its position to join the outer leaflet?
The lipid is recognized by immune cells and is quickly eliminated, marked for destruction. “Danger signal”
True/False: Cholesterol is a five-ring structure, in which it is oriented parallel to the phospholipid tails so the hydroxyl group of cholesterol can interact with the phospholipid head groups.
False, because Cholesterol is actually a four-ring structure not five.
How are Phospholipids amphipathic?
Phospholipids contain a hydrophilic polar phosphate head group and two hydrophobic non polar fatty acid tails, making them amphipathic.
There two main types of membrane proteins: _____ and _____. Some may be anchored to the membrane via GPI (also define this) or lipid anchors.
1) Peripheral 2) Integral proteins
GPI - Glycophosphatidylinositol
Peripheral membrane proteins are exactly what they sound, as far staying “outside” of the membrane, what are some of the functions a peripheral membrane protein may have?
Function as electron carrier, cytoskeletal elements or intracellular secondary messengers.
Integral membrane proteins are _____ within the lipid bilayer. What do they function as?
Anchored.
Function as membrane receptors, enzymes, cell adhesion molecules, signal transduction proteins, and transporters.
What are peripheral membrane proteins?
Peripheral membrane proteins are those that are noncovalently bound to other membrane proteins.
Three types of transporters for proteins in the transmembrane.
1) Uniporter 2) Symporter 3) Antiporter
What are the three factors that influence membrane fluidity?
1) Temperature 2) Saturation of phospholipid fatty acid tails 3) Cholesterol
Will decreased saturation increase or decrease membrane fluidity?
Decreased saturation, meaning increased number of double bonds within fatty acid tails, will INCREASE membrane fluidity.
What effect does cholesterol have on membrane fluidity as temperature increases or decreases?
Temp Increases: Cholesterol will decrease fluidity
Temp Decreases: Cholesterol will increase fluidity
What is cell Polarity?
A property in which cell membranes exhibit spatial differences in shape, structure, and function within one cell type.
What can Glycocalyx be thought of? Its functions: attachment, antigen-binding, cell-cell recognition, and protection from injury.
“Cell coat” - located on the outer surface of the plasma membrane and is the sum of the sugars associated with every proteoglycan on the cell surface.
Where would you usually find lipid rafts? What do they help with?
You would find them in localized regions with elevated cholesterol and glycosphingolipid content in the cell membrane. More so where fatty acid tails are highly saturated (low fluidity).
Mostly, lipid rafts will help among the chaos, signal transduction.
What are the major functions of the cytoskeleton?
Cytoskeleton supports cell structure, cell and organelle movement, and cell division.
Which of the three types of protein filaments is the smallest?
Microfilaments (7nm)
In respect to the cell, where would you find microfilaments?
Abundant in eukaryotic cells, yes, are found especially at the cell periphery.
In what way do actin microfilaments display polarity?
In their assembly and disassembly, which occur at the positive (+) end where G actin is bound to ATP.
Where would you find intermediate filaments in a cell?
Located throughout the cytoplasm.
Do Intermediate filaments have polarity?
NO, and they do not require ATP for assembly.
Desmin, a type of intermediate filament, is found where?
Skeletal, cardiac, and smooth muscle. Framework lining the myofibrils and myofilaments. Desmin = muscle
Which type of intermediate filament, is found in glial cells of the brain, providing structural support to these cells in the nervous system?
Glial fibrillary acidic protein (GFAP)
Which type of intermediate filament is found in neurons, providing structural support for axons and dendrites, important for signaling?
Neurofilaments
If a patient’s tumor is GFAP positive, what cell type must this cancer originate from?
Neuroglia, because GFAP is the intermediate filament of neuroglial cells.
Is it Microfilaments or Microtubules that form cell appendages like cilia and flagella?
Microtubules do! In fact, they are larger than microfilaments made up of alpha and beta tubular structures.
Do microtubules have polarity?
Yes! Each tubulin within binds two GTP molecules, forming the positive end, while the non-GTP binding end forms the negative end.
How can you remember whether it’s the positive or negative end of microtubules that reaches toward the periphery or toward the nucleus?
Mnemonic: Negative end Near Nucleus
Positive end Points to Periphery.
Microtubules also bind motor proteins necessary for transportation of vesicles. (It’s used kind of like a highway) What are the names of the motor proteins? Do they use ATP?
Kinesin and Dynein
Both use ATP
Which direction do these motor proteins move in the cell?
Dynein is retrograde transport (from periphery to nucleus)
Kinesin is anterograde transport (From nucleus to periphery)
Can Cilia be nonmotile?
Yes, it can motile or nonmotile
What is the microtubule structure of motile cilia?
Motile cilia have a 9 + 2 microtubule arrangement, with 9 doublets surrounding 2 singlets
Oh the ways a cell can get injured! Let’s think of one example, what happens there is decreased ATP production?
Without ATP cell swells. Without ATP, the Na+/K+ pumps are unable to function. What usually would maintain fluid homeostasis, does not, and water will follow salt, causing the cell swelling.
Another way a cell can be injured/die, what happens when Calcium pumps also fail? What organelles rely on the function of Calcium pumps?
Low Calcium pump function due to low ATP causes the buildup of Calcium in the cytosol, which activates specific mediators of apoptosis, initiating the cell-death process.
Two organelles: ER, Mitochondria
An irreversible type of damage that causes inflammation, as well as spilling lytic enzymes into the cytoplasm is due to ______.
Membrane damage, especially here lysosomal membrane damage.
One way to injure the cell again, messes with the cell’s ability to transcribe and translate information. How it is released is from a damaged mitochondria. What are they?
Reactive Oxygen Species (ROS)
True/False: Necrosis is pathologic.
True
There are 6 different types of necrosis
Coagulative, liquefactive, gangrenous, caseous, fat, and fibrinoid
When apoptosis occurs, is there an inflammatory response?
No inflammatory reaction
True/False: Apoptosis is the only one out of the two death pathways that uses Caspase activation.
True.
Under what circumstance is apoptosis a physiologic process?
When embryogenesis occurs and certain cells must die to shape a particular anatomic structure such as fingers.
What circumstance would apoptosis use a pathologic process?
If they detect fatal DNA damage or irreparable problems of protein mis-folding.
In the Intrinsic Pathway, how does the cell undergo apoptosis this way?
What are the important proteins that kickstart this process?
The cell will basically kill itself.
The two pro-apoptotic proteins are (BAX/BAK), they overcome the anti-death proteins (Bcl-2), imitating the apoptosis cascade. Cytochrome C is also a factor, as it also activates the Caspase cascade, leading to cell death.
In the Extrinsic Pathway, what are the important receptors and proteins that play here?
First of all, extrinsic is activated by an external stimulus…by Fas/FasL receptor or cytotoxic T cell. Then executioner caspases finish the job.
The Eukaryotic postal service consists of what two organelles?
Rough Endoplasmic Reticulum and the Golgi Apparatus
What about the Smooth endoplasmic reticulum? Does it also take part in sorting and packaging and shipping of proteins?
No, not really, but it is important for detoxification and steroid hormone production.
Where is RER placed in the cell?
It’s located throughout the cell, but is most concentrated right around the nucleus and near the Golgi Apparatus.
In RER, where there are studded ribosomes, what is the job of the ribosomes?
Involved in protein translation.
What is the RER analogous to, when its job is to fold, modify, and package proteins? Where does it send the proteins next?
Analogous to a warehouse.
Next, it’ll send the proteins to the Golgi Apparatus for further processing.
Where would there be a lot of RER? In what type of cell?
Cells that make a lot of secretory proteins, such as antibody-secreting plasma cells, are rich in RER, making them appear darker on staining.
The Smooth Endoplasmic Reticulum is responsible for:
Synthesizing ______ and ______ hormones. Fatty Acids and _______.
________ drugs and metabolites
Releasing ___ ions for muscle contraction.
Steroids, and steroid hormones, fatty acids, and phospholipids.
Detoxifying drugs and metabolites.
Releasing Calcium ions for muscle contraction.
Where would you find a lot of SER?
Ex: Hepatocytes, because one of their main roles is detoxification.
Where does the Golgi Apparatus sit in the cell?
Located close to the nucleus and the RER.
The Golgi apparatus is supported by cytoplasmic microtubules. What happens clinically if there is a deficiency of these microtubules?
Clinically, it will result in a type of achondrogenesis, a rare skeletal disorder characterized by short trunk, small limbs and narrow chest. (Fun fact, don’t really have to know)
