Cellular Structures Flashcards
1
Q
Plasma Membrane Composition: Lipids and Proteins
A
- Phospholipids → Hydrophilic head and Hydrophobic Tail
- The heads make up the majority of inner and outer surface of the plasma membrane
- The tails make up the majority of the inside of the membrane
2
Q
Sphingolipids
A
- First category of special fats
- Atypical since they are created from “sphingo-seen” which is a large amino alcohol
3
Q
Cholesterol
A
- Second category of special fats
- maintains membrane fluidity
- When too cold, cholesterol is there to get between phospholipids and keep them from clumping and freezing together
- When too hot it keeps the molecules more packed together so it doesn’t get too “goopy”
4
Q
Waxes
A
- Third category of special fats
- Lot fatty acid chain reacted with a long alcohol to form a double long chain
- Their job is to give stability to the hydrophobic region of the membrane
- Waxes are pretty rare in mammals and are mostly found in plants
- These three different lipids found in the plasma membrane blend together like the strands of polyester and nylon giving the membrane bilayer special hydrophobic properties on the inside and hydrophilic properties on the outside
5
Q
Integral Proteins
A
- Associated with the internal portion of the lipid bilayer
- Integral proteins that pass all the way through the bilayer are transmembrane proteins
-
Examples:
- Auquaporins or water channels
- Allow water molecules to pass in and out of the cell
- Auquaporins or water channels
-
Examples:
- Another type of integral proteins are embedded proteins
- These are located just within the inner our our outer surface of the plasma membrane
- Inner ones are referred to as cytoplasmic
- Outer ones are referred to as extracellular
-
Examples:
- Extracellular Hormone receptor proteins on the surface
- Cytoplasmic farnesyl
- An enzyme involved in making terpenes. terpenoids, and sterols on the interior of the plasma membrane
6
Q
Peripheral Proteins
A
- Bound to the lipid bilayer through electrostatic interactions and can be easily removed or attached back onto our plasma membrane
-
Examples:
- G-Proteins
- Found in G-coupled receptors
- G-Proteins
7
Q
Passive Diffusion
A
- Molecules move from higher concentration to lower concentration
- In passive process, entropy increases as molecules move down their concentration gradient
- This increase in entropy supplies the energy for passive diffusion
8
Q
Facilitated Diffusion
A
- Occurs when molecules that can’t normally pass through the membrane are able to move down their concentration gradient due to the presence of a membrane protein channel or transporter that helps move them along
9
Q
Osmosis
A
- Facilitated diffusion that is specific to water through the help of transmembrane proteins, Aquaporins
- When solutes are present in equal amounts, but different concentrations on either side of a semi-permeable membrane, water can move or osmose across the membrane towards the side with higher solute concentration to decrease the concentration gradient.
10
Q
Primary Active Transport
A
- Use ATP of another energy molecule as a power source to move things through the membrane
- Example:
- Sodium-potassium pump
- Three sodium molecules first bind to the transmembrane protein pump
- Then an ATP molecule comes along and bind to the pump
- When the high energy of ATP phosphate bond is broken, the energy is harvested by the sodium-potassium pump releasing sodium into the extracellular space of the membrane against its concentration gradient, while also leaving behind an ADP which is still attached to the pump, and a free-floating inorganic phosphate molecule.
- Two potassium molecules take advantage of the pumps new altered shape with ADP attached to it and hop in from the extracellular space
- This triggers another change in the pump to release the ADP, forcing the potassium molecules into the cell
- Sodium-potassium pump
11
Q
Secondary Active Transport
A
- Harness the energy released by one particle going down its electrochemical gradient to drive a different particle up against its gradient
- Symport: Particles are moving in the same direction
- Antiport: Particles flow in opposite direction
12
Q
Endocytosis
A
- Cell membrane invagenates (turning inside out) and pinches to a vesicle
- The vesicles contains the extracellular fluid as well as whatever solute the cell wanted to bring in
12
Q
Endocytosis
A
- Cell membrane invagenates (turning inside out) and pinches to a vesicle
- The vesicles contains the extracellular fluid as well as whatever solute the cell wanted to bring in
13
Q
Exocytosis
A
Takes the vesicle containing material, merges with the plasma membrane and expels the material into the extracellular fluid
- Neurons use excotysis to release neurotransmitter into the synaptic cleft
14
Q
Cell Junctions
A
- A class of cellular structures consisting of multiprotiens complexes that provide contact of adhesions between neighbouring cells or between a cell and extracellular matrix in animals
- Gap Junctions
- Desmosomes
- Tight Junctions
15
Q
Gap Junctions
A
- Little tubes that allow for direct communication
- Made up of six little connexions , which are just gap proteins that team up to make one big connexon
- They can open or close to let in water or other molecules either between cells or from a cell to the extracellular space.
16
Q
Desmosomes
A
- Main job is to bind adjacent cells by grabbing onto the next cell cytoskeleton
- Hold all epithelial tissue, particularly in the skin together
- They work by tying together the filaments from two transmembrane proteins on two adjacent cells
17
Q
Tight Junctions
A
- Keep epithelial cells close together, so that nothing can leak between them
- Form a tight physical chain on the outermost later of cells in the epithelium acting like a giant rubber band that stops fluids and ions from leaking out into the space between the cell.
