PSL app Ques 3 cellular and tissue levels

Can you explain the process by which cholesterol enters your body cells

Cholesterol enters into cells via receptor-mediated endocytosis. During this process the LDL receptors in the cell membrane will recognize and bind LDL. The plasma membrane will invaginate forming a vesicle that contains the LDL molecules. Cholesterol will then be released into the cytosol of the cells from the LDL molecules.

What is the difference between an integral membrane protein and a peripheral membrane protein? How does a carrier protein differ from a channel protein? What are the 3 different ways in which channels are gated in the human body

.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. b.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 a highly selective for a specific solute or ion. c. Ligand-gated channels, voltage-gated channels and mechanically-gated channels

What are the three germ layers of an embryo and which of the four principal tissue types do each give rise to

1.Ectoderm → external lining of the body (i.e., the skin) and the nervous system.2.Mesoderm → muscle tissue, connective tissue and the inside lining of bloodvessels (endothelium).3.Endoderm → internal linings of the body

What two things are required for anything to cross the plasma membrane

A pathway and an energy source

What is the difference between a primary lysosome and a secondary lysosome? What is difference in hydrogen ion concentration between a lysosome and the cytosol ofthe cell?

A primary lysosome is a vesicular organelle formed by the Golgi. It contains acid hydrolases but they are not functional as the pH of the primary lysosome is too high. A secondary lysosome is formed by the fusion of a primary lysosome and an endosome or a phagosome A secondary lysosome has a pH of 5. The acid hydrolases are functional in a secondary lysosome as they work most optimally at pH 5.b.Cytosol ( ~7) vs. lysosome (~ 5). 10 x 10 = 100x = 100 fold = 2 orders of magnitude.

What literally are ABO blood group antigens? How does A differ from B, AB and O

ABO blood group antigens are sugars (from glycoproteins and glycolipids) on thesurface of red blood cells.b.i.A: has the antigen N-acetylgalactosamine.ii.B: has the antigen galactoseiii.AB: has both antigens: N-acetylgalactosamine and galactoseiv.O: has no antigens

How are intermediate filaments involved in cell-cell attachment?

Cells are connected to one another via interactions between their respective integral membrane proteins. These integral membrane proteins are also tetheredto intermediate filaments within each cell's cytoplasm.

Why are virtually all cells of the human body within 20 μm of a capillary

Because diffusion is distance limited.

How is it that all cells of your body (except gametes) have the same DNA yet there are approximately 200 different types of cells?

Differential gene expression. In other words, a cheek cell has the same genes asa liver cell, but the two cells are very different from one another. They are different because each cell has a different set of genes turned on/off

What are the two components of the cytoplasm? What is the difference between intracellular fluid and extracellular fluid? What is the difference between extracellular fluid and interstitial fluid?

Cytosol and organelles.b.Intracellular fluid (ICF) is the fluid inside cells while extracellular fluid (ECF) is thefluid outside of cells (this includes interstitial fluid (IF) and intravascular fluid (IVF)).c.IF is just the fluid between cells, and ECF is IF plus the fluid (plasma) inside the cardiovascular system (IVF).

.In terms of quantity, 98% of a plasma membrane is lipid (most of which are phospholipids) and 2% is protein. However, 50% of the weight of a plasma membrane islipid 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

Are gap junctions part of a junctional complex? What is their function?

No, gap junctions are pores that let ions and small molecules move between cells. They are often referred to as communicating junctions

Cigarette smoking can decrease the motility of cilia in the respiratory tract. What complications could this cause?

This can cause mucus accumulation and can lead to the restriction of airflow andrespiratory infections.

The pump-leak leak model is an extraordinarily important process in the human body. Can you explain the pump-leak model and its fundamental utility in the human body?

The pump-leak model essentially says that whatever is pumped out of the cell leak back in. When Na+ leaks back into cells like muscle cells, they contract. Often, when an ion leaks back in, it drags another solute into the cell against its concentration gradient. This is seen with the SGLT

What are the three components of the cytoskeleton? What are the subunits that comprise each? Which cytoskeletal filaments support microvilli? Cilia? Which are responsible for mediating pseudopodial movement?

a. Actin filaments (microfilaments), intermediate filaments and microtubules. b. Actin: G-actin monomers (globular actin) form dimers that assemble as two strings of beads, forming long filaments referred to as F-actin (filamentous actin). c. Actin (microfilaments). d.Microtubules. e. Actin (microfilaments)

What's the name of the cell that can increase blood calcium levels? What's the name of the cell in which the entire bicarbonate buffer system works inside its cytoplasm? What's the name of the cell that contains a brush border? What's the name of the cell that makes connective tissue in your body?

a. Osteoclast.b. Red blood cell (RBC).c. Enterocyte. d. Fibroblast

Peroxisomes produce antioxidants. Where are the oxidants generated that these antioxidants combat? Why are oxidants (or free radicals) so dangerous to the human body? What is a good example a vital function of free radicals in the body

a. Oxidants (free radicals) are generated by reactions such as cellular respiration (i.e., the oxidation of fuels).b.Oxidants are dangerous because they can steal electrons from molecules that make up the cells and tissues of your body. Ultimately, bonds are broken, and cells and tissues are damaged leading to disease.c.Free radicals (such as superoxide anion or hydroxyl radical) can be used in the body by phagocytes to destroy pathogens. Free radicals (such as nitric oxide) vasodilate blood vessels which helps maintain proper blood flow

What is the stoichiometry (i.e., numbers and direction of ions transported) of the Na+/K+ pump? Can you provide a detailed explanation of secondary-active transport

a.3 Na+ out and 2 K+ in.b.Secondary transport occurs due to a chemical gradient that is generated by primary active transport. One example of this is the entrance of glucose into the small intestine. The entrance of glucose into intestinal cells is coupled with the entrance of Na+ ions into the cells. SGLTs are the transporters. So, the concentration gradient of Na+ (created by the actions of the Na+/K+ pump - a primary active transporter) drags glucose into the cell. Since the SGLT does not directly use the energy of ATP, but rather the gradient of Na+ created by Na+/K+pump, it is considered to be a secondary-active transporter.

What is the difference between active and passive transport? What is the differencebetween simple diffusion and facilitated diffusion?

a.Active transport utilizes the energy of ATP. Passive transport utilizes the energy of a concentration gradient. b.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

What is the difference between a resting membrane potential (RMP) and a transmembrane potential (TMP)? What is the primary mechanism responsible for a RMP?

a.An RMP is the transmembrane potential at which the cell is at rest.b.K+ leaks channels are primarily responsible for establishing a RMP

What is the primary mechanism by which water crosses the lipid bilayer? What are a few good examples of molecules that freely can pass the lipid bilayer?

a.Aquaporins.b.Lipids and gasses. In general, small, hydrophobic molecules

How does cholesterol in the membrane affect membrane fluidity? If cholesterol is so important in maintaining the integrity of membranes, why is it often seen as bad for you?

a.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. b.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

Can you explain how distance, size of solute, steepness of gradient, temperature and electrical forces can influence the rate of diffusion?

a.Concentration gradients dissipate (or get less steep) with increasing distance.b.Larger solutes diffuse slower than smaller solutes.c.The steeper the gradient, the faster the rate of diffusion.d.Higher temperatures increase the rate of diffusion.e.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 a brush border? Where would you expect to see a brush border in the body? What is a brush border enzyme?

a.Cytoplasmic projections of microvilli on the apical surface of a cell that help to increase surface area of the cell. These microvilli collectively look like the bristlesof a brush, hence "brush border."b.Wherever absorption occurs (i.e., in the small intestine).c.An enzyme located in the brush border that catalyzes reactions on the E face of the cell (e.g., sucrase, lactase and maltase).

What are the two main types of microtubule-associated proteins (MAPs)? If a cell makes a protein near the nuclear membrane and needs to transport this protein towardsthe plasma membrane, which of these two MAPs would mediate this transport

a.Dynein and kinesin.b.This is anterograde movement, so kinesin

A cell is hypertonic to its environment. Will the cell crenate or swell? Which has a lower osmotic potential, the cytosol of the cell or the interstitial fluid?

a.If a cell is hypertonic to its environment, the cell will swell up, and potentially lyse.b.The cytosol of the cell has lower osmotic potential (i.e., more dissolved solute).

What is the most abundant extracellular cation? Intracellular cation? Is Cl- more abundant intracellularly or extracellularly? What are the anions inside the cell

a.Na+.b.K+.c.Extracellularly.d.Negatively charged cytosolic proteins, DNA and RNA

What cells that you are born with essentially never divide again throughout life? How can you prove this?

a.Neurons, muscle cells and fat cells.b.Places you would never get cancer, such as your heart, biceps, etc

Are ribosomes membranous or nonmembranous organelles? What is the differencebetween fixed and free ribosomes? What are the structural and functional differences between smooth and rough endoplasmic reticulum

a.Nonmembranous organelles.b.Fixed ribosomes are attached to the RER and they produce the proteins that aredestined to become membrane proteins, part of an organelle or exported from the cell. Free ribosomes are freely-floating in the cytoplasm and synthesize proteins that are destined to remain within the cytosol of the cell.c.The RER is organized as several elongated sacs of membrane. It synthesizes cytoplasmic, membranous and organelle proteins. The SER is organized as small elliptical spheres of membrane. It aids in lipid biosynthesis, protein transport, drug detoxification and calcium storage. It does not do protein synthesis

What does is mean that a cell is polarized? Depolarized? Can you explain a few ways in which a cell could become depolarized? Hyperpolarized

a.Polarized cells are more negative on the inside than on the outside.b.Cells become depolarized when ions such as Na+ or Ca2+ flow into the cell and make the cell less negative on the inside, and therefore less polarized.c.Cells become hyperpolarized when ions such Cl- enter the cell or when K+ leaves the cell

Light micrographs are obtained by directing photons through a specimen. In general, how are TEMs and SEMs obtained? What's the fundamental difference in the images obtained from these two different types of microscopes?

a.TEMs fire electrons through tissues.b.SEMs fire electrons at the surface of tissues.c.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)

Taxol is a long-standing treatment for cancer. How does it work? What are its drawbacks? What would be a better way to treat cancer?

a.Taxol works by binding to microtubules and freezing the mitotic spindle apparatus, thus the cancer cells cannot divide.b.The problem with this chemical is that it targets any dividing cell, including healthy ones.c.A better way to treat cancer would to be able to directly identify and target cancerous as opposed to merely targeting any dividing cell of the body

What is the function of the Golgi apparatus? Are all proteins that leave the Golgi destined to leave the cell? If not, what are all of the potential fates of proteins that leave Golgi?

a.The Golgi apparatus modifies, sorts, packages and distributes proteins it receives from the RER. b.Not all proteins leaving Golgi are destined to leave the cell. c.Some proteins go to lysosomes or to the plasma membrane becoming membrane proteins).

With an understanding of the central dogma of life, can you explain how elucidating the sequence of the protein insulin allowed scientists to ultimately clone the human insulin gene?

a.The central dogma of life = DNA → RNA → Protein Using this, scientists were able to deduce the sequence of the RNA from the sequence of the protein, and then the sequence of the DNA from the RNA. The sequence of the DNA is the gene for insulin. This gene can be spliced out of human cells and spliced into the DNA of bacterial cells or yeast cells, which then make the human insulin protein.

Can you explain how the mitochondria in your cells were once free-living bacteria? What are the lines of evidence that support the endosymbiotic theory

a.The endosymbiotic theory proposes that purple non-sulfur bacteria were taken in by a larger host cell and they co-evolved together. b.Mitochondria have a double membrane, their own circular DNA, their own ribosomes and can divide on their own as well. They are also susceptible to antibiotic therapy just like bacteria.

What's the difference in resolution between your eye and a typical laboratory compound light microscope? Between a light microscope and a TEM

a.The human eye resolution (200 um) vs. a compound light microscope (0.24 um) = 1000 x = 1000 fold = 3 orders of magnitude. b.The compound light microscope (0.24 um) vs. a TEM (0.2 nm) = 1000 x = 1000 fold = 3 orders of magnitude.

Why do cells require a large surface area to volume ratio to exist? Some neurons are a meter long. That's a lot of cytoplasm! Do these cells defy this requirement and therefore have a low surface are to volume ratio?

a.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.b.Neurons still have a high SA/V ratio. Their large plasma membrane surface area results from their very long length.

Can you explain how a plasma membrane, solely constituted of phospholipids, is inherently semipermeable

a.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 gasses, but is impermeable to polar/charged molecules/ions.

What are the three components of a junctional complex? Which one is most apically located? Which one involves actin filaments? Which is primarily involved in preventing things from moving through the intercellular space

a.Tight junctions (or occluding junctions). These are the most apical junctions of the junctional complex and prevent things from moving through the intercellular space.b.Adhering junctions (or belt junctions) are associated with actin filaments. c.Desmosomes are associated with intermediate filaments

Is a glucose transporter (GLUT) a uniporter, symporter or antiporter? How does glucose enter your body cells? How does it enter the cells lining your small intestine

a.Uniporter.b.GLUTs.c.Sodium-glucose transporters (SGLTs).

Do bacterial cells living on and in your body outnumber your own cells? If bacteria are so bad, why are they "part of" us?

a.Yes.b.The bacteria living in and on our body are "good bacteria." They are referred to as our normal flora. These bacteria, in general, cover the surfaces (internal and external) of our body and, therefore, reduce the likelihood that "bad bacteria" can infect us. Our normal flora serve many other roles as well. For example, bacteria in our digestive tract aid in our digestive processes.