Cell Physiology AQ Flashcards
Why do cells require a large surface area to volume ratio to exist?
The large ratio enhances a cells ability to exchange information. The larger this ratio is, the more plasma membrane there is, relative to cytosol volume, to facilitate communication between the interior of the cells and the environment.
Some nerves are a meter long. Do these cells defy this requirement and therefore have a low surface area to volume ratio?
Neurons still have a high SA/V ratio. Their large plasma membrane surface area results from their very long length.
Wha’s the difference in resolution between your eye and a typical laboratory compound light microscope?
The human eye resolution (200 um) vs. a compound light microscope (0.24 um) = 1000x = 1000 fold = 3 orders of magnitude.
What is the difference in resolution between a light microscope and a TEM?
The compound light microscope (0.24 um) vs. a TEM (0.2 nm) = 1000x = 1000 fold = 3 orders of magnitude.
Light micrographs are obtained by directing photons through a specimen. In general, how are TEMs and SEMs obtained?
TEMs fire electrons through tissues and SEMs fire electrons at the surface of tissues
What’s the fundamental difference in the images obtained from these two different types of microscopes?
The main difference is that TEMs show the ultrastructure of a specimen (for example, the organelles within a cell) whereas SEMs provide a topographical view of the specimen (for example, the surface of a cell).
What’s the name of the cell that can increase blood calcium levels?
Osteoclast.
What’s the alternate name for an erythroctye?
Red blood cell (RBC).
What’s the name of the cell that contains a brush border?
Enterocyte.
What’s the name of the cell that makes connective tissue in your body?
Fibroblast.
98% of a plasma membrane is lipid (most of which are phospholipids) and 2% protein. However, 50% of the weight of a plasma membrane is lipid and 50% is protein. What does this latter fact say about proteins in the membrane?
Membrane proteins are very large and heavy molecules compared to membrane lipids
How does cholesterol in the membrane affect membrane fluidity?
Cholesterol resists phase transitions. It helps to prevent the membrane from becoming too fluid in warm conditions, where phospholipids tend to spread apart, and helps to prevent the membrane from becoming too rigid in cold conditions, where phospholipids tend to pack tightly together.
If cholesterol is so important in maintaining the integrity of membranes, why is it often seen as bad for you?
Cholesterol is often erroneously mistaken for lipoproteins such as HDL and LDL, which are merely carriers for cholesterol. Since high levels of LDL are bad for cardiovascular health, it is often assumed that cholesterol is bad too. Too much cholesterol is indeed bad for you, but not enough cholesterol is just as bad.
What is the difference between an integral membrane protein and a peripheral membrane protein?
Integral membrane proteins span the entire membrane and have polypeptide segments that are exposed on both the p- and e-faces of the membrane. Peripheral membrane proteins are on either the e- or p- (mostly P) face of the membrane and have polypeptide segments that are partially inserted into the membrane to tether them to the membrane.
How does a carrier protein differ from a channel protein?
Carrier proteins bind a solute on one side of the membrane, which triggers a conformational change, allowing them to release the solute to the other side of the membrane. Channel proteins are hydrophilic pores in the membrane that are highly selective for a specific solute or ion.
What are the 3 different ways in which channels are gated in the human body?
Ligand-gated channels, voltage-gated channels, and mechanically-gated channels.
How is a plasma membrane, solely constituted of phospholipids, is inherently semipermeable?
The plasma membrane is inherently semipermeable due to its hydrophobic interior and hydrophilic surfaces (i.e., p- and e-faces). The plasma membrane is permeable to small, nonpolar substances and gases, but is impermeable to polar/charged molecules/ions.
What two things are required for anything to cross the plasma membrane?
: A pathway and an energy source
How do distance, size of solute, steepness of gradient, temperature and electrical forces influence the rate of diffusion?
Concentration gradients dissipate (or get less steep) with increasing distance; larger solutes diffuse slower than smaller solutes; the steeper the gradient, the faster the rate of diffusion; higher temperatures increase the rate of diffusion; electrical forces influence the rate of diffusion if the diffusing solute is polar or charged. For example, if Na+ is diffusing into the cell, it has both a chemical gradient (more Na+ on the outside of the cell than the inside) and an electrical gradient (the inside of the cell is negative and Na+ is positive).
What is the primary mechanism by which water crosses the lipid bilayer?
Through aquaporins
What are a few good examples of molecules that freely can pass the lipid bilayer?
Lipids and gases. In general, small, hydrophobic molecules.
What is the difference between active and passive transport?
Active transport utilizes the energy of ATP. Passive transport utilizes the energy of a concentration gradient.
What is the difference between simple diffusion and facilitated diffusion?
In simple diffusion, molecules cross the membrane on their own (i.e., the plasma membrane itself is the pathway). In facilitated diffusion, molecules require a transport protein to assist their movement across the bilayer (i.e., the transport protein is the pathway). In both circumstances, a concentration gradient is required as the energy source.
A cell is hypertonic to its environment. Will the cell crenate or swell?
: If a cell is hypertonic to its environment, the cell will swell up, and potentially lyse.
Which has a lower osmotic potential, the cytosol of the cell or the interstitial fluid?
The cytosol of the cell has lower osmotic potential (i.e., more dissolved solute).
You are a cell and on a diet. Your friend tells you that there’s this new fad diet that really helps you drop the water weight. It’s all about how much solute you eat they say. Is this diet designed for you to eat more or less solute?
Less.
