DLA #1: Cellular Organization Flashcards
Describe Eukaryotic Cells.
Comprised of multiple membrane-enclosed organelles.
Describe Prokaryotic Cells.
Comprised of a single compartment surrounded by plasma membrane.
Explain the functional significance of organelles as they pertain to the cell.
Organelles carry out specific function within the cell. The functions they carry out produce products that are then transferred throughout the cell in a complex network.
Name two important properties of the phospholipid bilayer (plasma membrane).
1) Fluidity
2) Selective permeability
Describe fluidity in regards to the plasma membrane.
Plasma membrane is comprised of 50/50 proteins and lipids. These proteins and lipids are mobile. Hence => “Fluidity”
Why is cholesterol considered an important lipid in the plasma membrane.
Because it stabilizes the fluidity of the membrane.
Ex) 1) At high temp. => fluidity of pm goes up. Cholesterol will then stabilize the structure from dissociating by increasing the melting point.
2) At low temp. => fluidity of pm decreases and the phospholipids begin to cluster. Cholesterol are found b/w phospholipids and prevent their collapse.
What two important molecules comprise the plasma membrane structure:
Proteins and Lipids
**Ratio => 50/50
Describe the polarity of a phospholipid structure
Hydrophilic Head and a Hydrophobic Tail
What are the three major classes of lipids in the pm
1) Phospholipids
2) Cholesterol
3) Glycolipids
Synonym for hydrophobic.
Nonpolar
Synonym for hydrophillic.
Polar
Water is a _____ molecule.
Polar
What are the two major classes of proteins.
1) Integral 2) Peripheral
What are integral proteins.
Proteins embedded into the lipid bilayer
What are peripheral proteins
Associate with integral membrane proteins
Rank the abundance of lipids associated with the pm
Phospholipids > Cholesterol > Glycolipids
Where are glycolipids (glycocalyx) found and why are they important
Glyclolipids are located on the outer leaflet of the phospholipid bilayer Important in cell recognition **Very prominent in rbc’s
What is the structure and function of phospholipids.
Structure: The pm is comprised mainly of p.lipids. They aid in forming the inner and outer leaflet. The head of the p.lipid is polar and the tail is nonpolar. Function: Form the cells protective barrier and allow for selective permeability.
Why is the plasma membrane important.
Creates a barrier from the extracellular to the intracellular environment
Describe why the pm is referred to as the “fluid mosaic” model.
Mosaic => made of multiple different units.
Fluid => all the components associated with the membrane are dynamic and can freely move along the membrane.
Different categories of integral proteins
1) Pumps/carriers/Transporters
2) Channels
3) Receptors
4) Linkers
5) Enzymes
6) Structural Proteins
Describe what kinds of compounds are “freely” permeable to the pm
Hydrophobic, non-polar, and uncharged compounds. Ex) O2, CO2, other gases
Describe what kinds of compounds are “less” permeable to the pm
Small, polar, and uncharged compounds Ex) H20
Describe what kinds of compounds are “highly” impermeable to the pm
Charged, polar, large
Hydrophilic heads of the p.lipid bilayer face _____ and _____.
Exterior and cytosol
The hydrophobic core of the p.lipid bilayer is formed by the:
Fatty acid tails
Phosphatidylserine
Type of phospholipid found at the inner leaflet of the bilayer.
Transferred by enzymes to outer leaflet during programmed cell death.
Allows the human body to remove dying cells.
Describe Glycocalyx and its function.
Carbohydrate rich zone on the cell surface.
Important for cell protection, recognition, and cell to cell interaction.
***Glycocalyx is a layer of glycolipids, glycoproteins and proteoglycans
Explain linker proteins.
Linker proteins are a type of integral protein that associate with the pm. They do not completely go through the pm BUT they interact with other proteins that do completely pass through. In a diagram, the linker protein does have some “slight” attachment to the pm and is bound another protein embedded through the membrane.
*** AT FIRST GLANCE THEY LOOK LIKE PERIPHERAL PROTEINS => THEY ARE NOT
Structural proteins
Type of integral proteins that interacts with the extracellular environment and creates cell adhesion.
When a substance exits the cell by the fusion of a vesicle w/ a plasma membrane we call the process_______.
Exocytosis
When a substance enter the cell by a vesicle formed from the plasma membrane we call this process_______.
Endocytosis
Name the three types of Endocytosis:
1) Pinocytosis
2) Phagocytosis
3) Receptor Mediated
Describe pinocytosis:
- “Cell drinking”
- Cell uses a structure (invagination) to take in aqueous environment to bring in solutes to a membrane bound vesicle.
- Way in which cell can take in stuff that it needs.
- Engulfs small particles
- Fusion into endosome then into lysosome
Pinocytosis is NON-SPECIFIC and CLATHRIN-INDEPENDENT
Phagocytosis
- “Cell eating”
- Cell uses pseudopodia (finger like projection) to engulf large substances into the vesicles within the cell.
- Phagocytosis is ACTIN-DEPENDENT and CLATHRIN-INDEPENDENT
- Bacterium is engulfed into a phagosome and transfered into an endosome. Then sent into a lysosome
Pinocytosis is regarded as a _____ process meaning it occurs all the time.
Constitutive (no one has to tell the cell to initiate this process)
Specialized examples of phagocytes
Macrophages and Neutrophils
During phagocytosis, what are examples of particles you expect to be taken up
-Microorganisms -Apoptotic cells -Non-biological materials
Describe the story of when a phagocyte cell engulfs particles
Antibodies bind to a bacterium => bacterium + antibodies bind to receptors (Fc) on pm => pseudopodia engulfs the bacterium creating a phagosome => phagosome fusion with lysosome => formation of residual bodies.
Describe receptor-mediated endocytosis
- Cargo-specific
- Clathrin-dependent
- Utilization of adaptin
- Vesicle binds to endosome and then lysosome
Describe exocytosis
Fusion of secretory vesicles w/in the plasma membrane
Exocytosis is regarded as a _______ process.
Constitutive
How is exocytosis regulated within the cell
Requires a stimulus of Ca2+ influx
What is an endosome
Membrane enclosed structure formed as a result of endocytosis. Later it matures into a lysosome.
During development of the endosome what can be said about its pH during maturation.
Becomes more acidic due to H+ influx
List the three pathways to lysosomal digestion
1) Phagocytosis 2) Endocytosis 3) Autophagy
Describe autophagy
- “self-eating”
- lysosomes entrap degrading material and the enzymes necessary to break that material down.
- during autophagy, a lysosome will fuse with a autophagosome.
- content degradation, recycling and reuse occurs.
At what state is autophagy most frequently occurring.
During a fasting state.
What is a proteasome.
A protein complex that degrades proteins. This complex is ATP dependent.
Why are proteasomes so unique.
They do not require lysosomes to aid in the degradation of proteins.
How does a proteasome know which protein to destroy.
Via polyubiquitination. (Ubiquitin tags a protein)
Proteasome inhibitors are commonly used in what clinical situation
Cancer patients
Explain vesicle targeting.
Vesicle targeting is a form of endocytosis very similar to receptor-mediated endocytosis.
Event is exhibited b/w rER and Golgi
Lysosomal Storage diseases worth knowing:
THERE IS A WORD DOC ON THE COMPUTER QUICKLY GOING OVER LTPs and ENDOSOMES. GIVE THAT A QUICK READ BEFOREHAND.
READ DOC
