Cell Physiology Flashcards
What molecules make up the plasma membrane?
- Phospholipid bilayer
- Steroids (cholesterol)
- Glycolipids
- Membrane proteins (intrinsic, extrinsic, and glycoproteins)
What is the basic structure of the plasma membrane?
phospholipid bilayer with differing ratios of proteins and steroids dispersed throughout
Describe
Phospholipid
a lipid containing a phosphate group in its molecule; polar head group with non-polar tails
Describe
Plasma Membrane Steroids
In particular cholesterol; amphiphatic molecules that maintain proper membrane fluidity
There is one molecule of cholesterol for each molecule of phospholipid
How is the structure of the phospholipid bilayer formed?
Spontaneously; the polar heads face the aqueous enviornment while the nonpolar tails form the hydrophobic core
Describe
Glycolipids
Lipids with CHO chain attached that are found on the outer leaflet of plasma membrane
* Amphipathic
* Form glycocalyx
Describe
Integral (intrinsic) Proteins
- Amphipathic – inserted into phospholipid bilayer of plasma/cell membrane and partially span membrane or are transmembrane proteins (completely cross phospholipid bilayer of membrane)
- Comprise the majority (70%) of all proteins
- Examples: transporters or channels
Describe
Peripheral (extrinsic) Proteins
- a class of membrane proteins that attach to the lipid bilayer, acting on the lipid-water interface
- NOT amphipathic
- on the inner/outer surface of membrane
Describe
Glycoproteins
- Protein with attached carbohydrates
- Extracellular surface of plasma membrane (forms glycocalyx)
What are the three types of cell junctions?
- Desmosomes
- Tight Junctions
- Gap Junctions
What are the components of desmosomes?
- Adhering junctions
- Plaques
- Cadherins
- Intermediate filaments
Describe
Adhering junctions
- Anchor cells together in tissues subject to considerable stretching
- Structural integrity to tissues
Describe
Plaques
Component of adhering junctions
* Cytoplasmic
* Anchoring points for cadherins
Describe
Cadherins
Component of adhering junctions
* Links cells together
Describe
Intermediate filaments
Component of adhering junctions
* Anchor cytoplasmic surface of desmosomes to cell components
* Structural support
Where are tight junctions found?
In epithelial tssue specialized for molecular transport (ex. covering of the body’s internal and external surfaces)
What are occludins?
Component found in tight junctions
* Form nearly impermeable junctions
* Link adjacent cells together
* Limit movement of molecules between cells (they pass through cells)
* Limit movement of integral membrane proteins and lipids
What is the function of tight junctions?
Fuse the plasma membranes of adjacent cells together tightly in order to limit the leakage of various substances between the two cells
Where are desmosomes found?
In tissue that experience intense mechanical stress (ex. cardiac muscle tissue, bladder tissue, gastrointestinal mucosa, and epithelia)
What is the function of desmosomes?
Desmosomes form links between cells, and provide a connection between intermediate filaments of the cell cytoskeletons of adjacent cells
Where are gap junctions found?
Found between all cells that are directly touching other cells (everything except ex. RBC and sperm)
What is the function of gap junctions?
To connect cells together so that molecules may pass from one cell to the other. This makes it so that molecules can directly enter neighboring cells without having to go through the extracellular fluid surrounding the cells
Why are gap junctions called “communicating junctions”?
They electrically and metabolically couple cells which allows small molecules and ions to move quickly between cells (e.g. cells get messages quicker)
Describe
Glycocalyx
a dense, gel-like meshwork that surrounds the cell, constituting a physical barrier for any object to enter the cell
What is the purpose of cell junctions?
Stabilize interactions between cells and promote communication
What is the difference between tight junctions and desmosomes?
A tight junction is a watertight seal between two adjacent cells, while a desmosome acts like a spot weld which strengthens the tissue (ex. allows skin to stretch and stay together)
What is the function of the nucleus?
Transmission of genetic material and storage of information for protein synthesis
What are the components of the nucleus?
- Chromatin
- Nuclear envelope
- Nuclear pores
- Nucleolus
Describe
Chromatin
DNA associated with proteins (condenses to form chromosomes during cell division)
Describe
Nuclear envelope
Double-layered porous membrane of the nucleus
Describe
Nuclear pores
Allows selective movement of molecules in and out of the nucleus
Describe
Nucleolus
Inner core of nucelus where synthesis of ribsomal RNA occurs
What is the structure of the nucleus?
Which cells have no nucleus?
Red Blood Cells
What cells have multiple nuclei?
Skeletal muscle cells
Do ribosomes have membranes?
They are non-membrane bound
Describe the subunits of ribosomes
- One is small and one is large
- Each subunit composed of proteins and ribsomal RNA (rRNA)
- Subunits “join” prior to protein synthesis: functional ribosomes
What are the two major types of functional ribosomes?
- Free ribosomes in cytoplasm
- Ribosomes bound to endoplasmic reticulum
