Q1 You got this!!! Flashcards
What is the difference between prokaryotes and eukaryotes?
Prokaryotes do not contain internal membranes while eukaryotes have internal membranes.
Are viruses alive? Why or why not?
Viruses are NOT alive because they are not able to reproduce on their own. They hijack the cellular machinery in cells in order to reproduce.
Describe how eukaryotes developed from prokaryotes (i.e. endosymbiotic theory).
There were two different stages in the development of prokaryotes to eukaryotes. 1. plasma membranes folded inward to create internal membranes. 2. the consumption and integration of other bacteria, like aerobic and photosynthetic bacteria.
What allows certain molecules to pass through the plasma membrane and prevents others from diffusing?
Molecules are able to pass based on their size and charge. Large molecules and charged molecules are unable to diffuse across the membrane.
What is the difference between the following types of proteins/membrane proteins: transporters and channels, sensors and receptors, enzymes, and anchors?
Transporters and channels are involved with the import and export of materials across the membrane, sensors and receptors play a role with cellular signals and information transmission, enzymes assist in the catalysis of reactions, anchors bind cytoskeletal structures and proteins to membranes.
Describe the structure of an individual phospholipid, glycolipid, and cholesterol.
All three have a hydrophobic tail region as well as a hydrophilic head, meaning that these lipids are amphipathic. Phospholipids have a phosphate/alcohol head, glycolipids have a sugar head, and cholesterol has an alcohol head. Phospholipids and glycolipids have two fatty acid tails while cholesterol has a single tail with a steroid region as well as a fatty acid region.
What factors influence membrane fluidity?
Temperature, tail properties, lipid composition
How does the plasma membrane differ between colder and warmer temperatures
In colder temps, the lipids of the membrane are more unsaturated, have shorter tails, and more cholesterol. In warmer temps, the lipids are more saturated, have longer tails, and have less cholesterol.
How does cholesterol assist in membrane fluidity in cold temperatures?
When there is cholesterol present in cold temperatures, the cholesterol prevents the solidification of the lipid bilayer as well as tight packing.
What is the process by which new phospholipids are added to the ER?
New phospholipids are added to the cytosolic side of the ER membrane. ER scramblase then randomly rearranges lipids between the monolaters. This results in symmetric growth of the bilayer.
How are lipids involved in addition to the golgi as well as the creation of vesicles?
After phospholipid membranes, created from the ER, are added to the golgi membrane, flippases move phospholipids from the golgi lumen face to the cytosolic face. This results in asymmetry between the monolayers that results in the eventual pinching off of a vesicle.
What are two types of asymmetry in the membrane and why are they important?
The first type of asymmetry involves the proteins present on each face. Because there are different molecules on each face, it is important to have different proteins and lipids on each face. The second form of asymmetry is in respect to the monolayers of the golgi membrane. This asymmetry aids in the pinching off of vesicles.
What are the functions of glycolipids and where are they located?
Glycolipids are located on the non-cytosolic face and play a role in cell recognition/information transmission.
What face are inositol phospholipids on and how are they involved in cell signaling? What does this process look like?
Inositol phospholipids are present on the cytosolic face. When a signal is received by a protein on the non-cytosolic face, the signal is relayed on the interior of the cell. One of these interior receptors is phospholipase, so when the signal reaches this protein, an inositol phospholipid is hydrolyzed, resulting in the cleavage of IP3. IP3 is a signal that can trigger other mechanisms within the cell.
How are lipid rafts different from other regions of the membrane? What important process is concentrated here?
Lipid rafts are more tightly packed than other regions of the membrane because they contain more cholesterol and sphingolipids. They contain many proteins involved with cell signaling as well as anchors. One type of phospholipid in this region are inositol phospholipids.
What are two types of folding for transmembrane proteins?
alpha helix and beta sheets
How are detergents similar to lipids? What a structure do they form with each other? with transmembrane proteins?
Detergents are similar to lipids in the sense that they are both amphipathic. They form micelles alone, and with transmembrane proteins, they can protect the hydrophobic region of the protein.
What is the cortex? Where is it located? What are five functions of the cortex? What does the lattice structure of the cortex comprised of?
The cortex is the region right “beneath” the membrane, on the cytosolic face. It aids in mechanical strength, shape changes, movement, restriction of domains, adsorption
What is the glycocalyx? What are some of its functions and what two molecules make up this layer?
The glycocalyx is also known as the carbohydrate layer “beneath” the membrane on the cytosolic face. The glycocalyx is important for cell protection, lubrication, and adhesion/recognition. There are two general molecules: proteoglycans (with a long sugar chain) and glycoproteins (with a short sugar chain).
Describe the process by which the neutrophils migrate from the blood to infected tissues.
When there is infected tissues, the epithelial cells express a protein called lectin. Neutrophils have carbohydrates on their cell surface that are able to bind to these molecules, allowing them to roll along the endothelial cells until they reach a point of exit.
Why does a cell have specific membrane domains constraining proteins? How does this occur?
Cells have different domains because they must maintain different asymmetries. This can occur by proteins binding to the cortex, extracellular matrix, surface proteins, or by acting as diffusion barriers.
What are similarities between transporters, pumps, and channels? Differences?
All are involved in the movement of molecules across membranes. Transporters and pumps undergo conformational changes while channels do not. Pumps require energy in order to perform active transport while the transporters and channels are utilized for passive transport.
Describe the difference between passive and active transport.
Passive transport flows down the concentration gradient and does not require energy. Active transport flows against the concentration gradient and does require energy.
What are the different types of concentrated solutions? When a cell is placed in these solutions, how is the cell affected?
Hypotonic: Low concentration of solutes in solution compared to the cell. Water will flow into the cell and eventually cause lysing. Isotonic: Equal concentrations of solutes in solution compared to the cell. Water will flow both in and out of the cell. Hypertonic: High concentrations of solutes in solution compared to the cell. Water will flow out of the cell and cause cell shriveling.
What channel protein is responsible for the transport of water in and out of the cell? How is this protein selective for water?
Aquaporins are the channel protein responsible for the movement of water. The channel is narrow to prevent large molecules from passing and the channel also has asparagines that prevent charged species from passing through.
What ions are high in concentration inside and outside the cell? What ion is low in concentrations both inside and outside the cell?
Potassium is high in concentration inside the cell. Sodium and chlorine are high in concentration outside the cell. Calcium is almost non existent within the cell and in low concentrations outside the cell.
Approximate the resting membrane potential of a cell. Using your understanding of ion concentrations in and out the cell, describe how these charges are balanced.
The membrane potential is ~70 mV. Sodium and chlorine outside the cell balance each other’s charge. Potassium inside the cell is balanced by nucleic acids, proteins, and cell metabolites.
Describe how passive transport of charged solutes is affected by the electrochemical gradient.
The electrochemical gradient can be split into the concentration gradient and the electrical gradient. When these flow in the same direction, there’s high diffusion. When they flow in opposite directions, there’s low diffusion. The concentration gradient is more influential than the electrical gradient.
Describe the homeostasis of blood sugar levels.
When there is high blood sugar levels, the pancreas releases insulin. This stimulates the conversion of glucose into glycogen in the liver as well as uptake of sugars in the blood by cells/tissues. This in turn lowers the blood sugar. When there is low blood sugar levels, glucagon is released by the pancreas. This stimulates the conversion of glycogen to glucose in the liver and raises blood sugar levels.
What is the difference between symports and antiports?
Symports transport two particles in the same direction while antiports move two particles in opposite directions.
How does the sodium/potassium pump function?
The sodium/potassium pump is a form of active transport. The process begins when 3 sodium ions bind to the protein. ATP is hydrolyzed, resulting in the protein phosphorylating and changing conformations. The sodium leaves and is replaced with 2 potassium ions. This binding results in the release of the phosphate and the pumps return to its original conformation, where potassium is then released.
Why does calcium have a low cytosolic concentration?
Calcium has a low cytosolic concentration because it is most often used as a signal or trigger.
How does calcium ATPase function?
When calcium binds to the protein, ATP hydrolyzes to cause a conformational change. the calcium is released on the other side of the membrane.
What are the ratios for the following transporters: Na+/K+, Na+/Ca2+, Na+/glucose.
Na+/K+ —> 3:2
Na+/Ca2+ –> 3:1
Na+/glucose –> 2:1
