Ch 4 - Membrane Structure and Function
Our body recognizes the foreign nature of a parasite or disease agent and we soon build up antibodies. A few parasites can change their identity to evade our immune system. How could cells do this on a regular basis?
New glycoproteins are produced in the cell and moved into the plasma membrane.
Radioactive isotopes are used to tag proteins in the cell membranes of mouse cells. These cells are then fused with human cells in cultures. What is the likely consequence of the tagged mouse proteins?
The tagged proteins DRIFT ACROSS cell membranes and are soon found dispersed across both human and mouse cell membranes.
In the Malpighian tubules of an insect (blind, threadlike excretory tubule attached to the gut of an insect), salt molecules are actively transferred from body fluids to the inside of the tubule. Which of the following is NOT true? ( ) Water is also "pulled" by osmosis into the Malpighian tubule. ( ) The concentration of salt is normally higher in the body fluids than it is inside the tubule. ( ) The process decreases the salt concentration of the body fluids. ( ) Insects must excrete excess salt through the Malpighian tubules. ( ) The tubules have the same tonicity as the body fluids.
The tubules have the same tonicity as the body fluids.
Carrier molecules are required for
both facilitated diffusion AND active transport.
Which of the following is NOT true regarding active transport? ( ) moves molecules or ions against their concentration gradient ( ) involves protein pumps ( ) is associated with large numbers of mitochondria ( ) is associated with nerve and muscle cells ( ) cannot be done by animal cells
cannot be done by animal cells
Which of the following molecules add stiffness and strength to the plasma membrane? ( ) glycoproteins ( ) cholesterol ( ) phospholipids ( ) enzymatic proteins ( ) phosphate groups
cholesterol
Molecules such as glucose and amino acids are NOT lipid soluble and therefore they
combine with carrier proteins and pass across by facilitated transport.
Once a solute and a solvent are evenly distributed in a solution, they will
continue to move about but with no net movement to higher concentration.
A student sitting on the back row opened a bottle of foul-smelling perfume and dabbed it on her wrists. One-by-one (beginning from the back of the room) the students began to cough due to the foul smell. This phenomena was due to
diffusion
Which membrane transport process can continue whether the cell is alive or dead?
diffusion
The definition of osmosis is the
diffusion of water across a selectively permeable membrane.
Which is a correct association of protein types?
enzymatic proteins - carry out metabolic reactions directly
Which of the following refers to materials only leaving the cell? ( ) diffusion ( ) exocytosis ( ) endocytosis ( ) pinocytosis ( ) phagocytosis
exocytosis
A cell placed in a hypotonic solution will
gain water.
Which intercellular junction allows for the rapid movement of small molecules or ions to flow from one animal cell to the next?
gap junctions
If you have a 10% sugar solution and a 35% sugar solution how does the 10% solution compare to the 35% solution?
hypotonic
An isotonic solution means that the solute concentration outside the cell
is the same as inside the cell.
The cell membrane is composed of
lipids and proteins.
A differentially permeable membrane separates a molasses solution from distilled water. Over time, the
molasses will become more dilute.
Red blood cells come in many blood types including A, B, AB and type O (lacking proteins A and B), Rh positive, Rh negative (lacking Rh+), and many others. If blood is transfused, the recipient detects any new or foreign proteins. The blood type proteins are
on the outer surface of the red blood cell membrane.
The pressure that is generated when water flows through a differentially permeable membrane is termed
osmotic pressure.
Macrophages, a type of white blood cells, are able to remove bacteria from our bloodstream and tissues by
phagocytosis.
When an intestinal cell ingests substances inside very small vesicles that can only be seen with an electron microscope, this is
pinocytosis.
When a plant cell is placed in a hypotonic solution, the cell wall prevents
the cell from bursting.
In the emergency room, saline solutions are often run into a person's vein. The saline solution must be
0.9% NaCl
If 0.9% NaCl were isotonic to a cell, then
1.0% would be hypertonic.
Which component of the extracellualr matrix is responsible for forming proteoglycans?
Amino sugars
When blood supplies oxygen and food to a cell surface and these molecules diffuse across, we might expect some "resting time." However, if we inspected most cell membranes in a living human body, we would find a nearly continuous flow of substances back-and-forth across the plasma membrane. Which of the following is NOT a reason why? ( ) Cell metabolism is constantly using up oxygen and raw materials; this lowers their concentration so more will diffuse into the cell. ( ) Cell metabolism is constantly producing waste molecules; this increases their concentration so more will diffuse out of the cell. ( ) Cells produce useful secretions; this increases their concentration and more will diffuse out of the cell. ( ) Cell metabolism constantly produces carbon dioxide in respiration; this increases its concentration so more will diffuse out of the cell. ( ) Cells are living entities and in order to live can never "rest".
Cells are living entities and in order to live can never "rest".
Exocytosis and endocytosis are carried out by proteins in the cell membrane. True or False?
False
Oxygen leaves the alveoli in the lungs and enters the capillaries by endocytosis. True or False?
False
The same signaling molecule that binds to the receptor on the outside of the cell is used to alter gene expression in the nucleus. True or False?
False
The inside and outside of the plasma membrane are
IDENTICAL in phospholipid bilayer but have cytoskeletal filaments on the INSIDE and carbohydrate chains of glycolipids and proteins on the OUTSIDE.
Which of the following factors could cause the cell membrane to become less permeable? ( ) If the channel proteins were to denature and become inactive ( ) If the molecules trying to enter the cell were decreased in size ( ) If the hydrophilic head of the phospholipids were to become hydrophobic while the hydrophobic tails become hydrophilic ( ) If the size of the protein channel was to increase ( ) All of these choices would cause the cell membrane to become less permeable
If the channel proteins were to denature and become inactive
What will happen to the water level in Figure 4.1? {image of U shaped tube with 20% protein & 80% water on side A & 100% water on side B with a differentially permeable membrane between the sides}
It will rise in side A.
Which is true of facilitated transport by carrier proteins? ( ) Facilitated transport only applies to small and lipid soluble molecules. ( ) It is represented by the glucose carrier that can transport hundreds of molecules a second. ( ) After a carrier has transported a molecule, it is unable to transport any more. ( ) Facilitated transport requires expenditure of chemical energy and is therefore active transport. ( ) One carrier protein can carry a variety of different molecules
It is represented by the glucose carrier that can transport hundreds of molecules a second.
What will happen to the protein solution of side A in Figure 4.1? {image of U shaped tube with 20% protein & 80% water on side A & 100% water on side B with a differentially permeable membrane between the sides}
It will become less concentrated since water passes from B to A.
Which statement is FALSE concerning movement of molecules across the cell membrane? ( ) Water and gas molecules have no difficulty ( ) Small uncharged molecules pass through easily ( ) Large molecules do not pass through easily ( ) Charged molecules do not pass through easily ( ) Lipid molecules do not pass through easily
Lipid molecules do not pass through easily
What two components are commonly found in the extracellular matrix that help resist stretching and provide resilience? ( ) proteins & polysaccharides ( ) proteins & phospholipids ( ) polysaccharides & phospholipids ( ) amino acids & phospholipids ( ) nucleic acids & proteins
PROteins & POLYsaccharides
Which of the following is not a function of the cell membrane? ( ) It provides mechanical strength to the cell ( ) It gives shape to the cell ( ) It regulates passage of molecules into and out of the cell ( ) It is largely responsible for cellular homeostasis ( ) Serves as a site for protein synthesis
Serves as a site for protein synthesis
A cell is placed in a solution of large nutrient molecules tagged with a red dye. Soon the cell is dark red, showing a concentration of the nutrient much higher than the external solution. We add a reagent that blocks the use of ATP. What result would you expect from this experiment? ( ) The nutrient would continue to rapidly enter the cell by diffusion because as a nutrient it is constantly being used in cell metabolism, so the cell will get redder ( ) The color will remain the same since all future transfer will stop ( ) The color will fade as the import of the nutrient stops and diffusion evens the concentrations ( ) The cell will continue to get darker since the import of the nutrient does not involve ATP ( ) The cell will die without access to ATP
The color will remain the same since all future transfer will stop. I said E but whatever.
If the proteins forming the cell junctions within the stomach were denatured, what is a likely consequence?
The desmosome junctions would not hold together causing the cells in the stomach to pull apart.
The extracellular matrix is responsible for which of the following features?
The extracellular matrix does all of these: helps the cell resist stretching; enables adherence to neighboring cells; plays a role in cell signaling; and acts as a structural feature.
Kidney dialysis relies on diffusion of various dissolved waste molecules (solutes) across a non-living semipermeable membrane. If the concentration of solutes in the blood increases over time before dialysis is administered, what will happen to the rate of dialysis when it occurs?
The rate will speed up since the concentration gradient is higher.
How can marine animals such as sharks live in a salt water?
They increase OR decrease the amount of urea in their blood until the blood is ISOTONIC with the environment.
What will happen to dye crystals if placed in the bottom of a beaker of water over a long period of time?
They will diffuse equally throughout the beaker.
If a particular molecule is brought into the cell by receptor-medicated endocytosis, then changing the receptors will change the molecule that is being transported. True or False?
True
One way to determine whether something is being actively transported across a membrane, is to compare its rate of transport with and without a chemical that blocks ATP production. True or False?
True
Which is a correct example of tonicity? ( ) Water is hypertonic to red blood cells ( ) Turgor pressure is created when a plant cell swells in a hypotonic solution ( ) Plasmolysis results from plant cells in hypotonic solutions. ( ) Crenated red blood cells result when they are placed in a hypotonic solution. ( ) If a cell is placed in a hypertonic solution, water enters the cell.
Turgor pressure is created when a plant cell swells in a hypotonic solution
A membrane sac filled with large molecules of potassium is suspended in a beaker of water. What will happen?
Water will enter the sac and it will swell.
In certain cancerous cells, the cell divides continuously even in the absence of a growth factor (signaling molecule) that indicates the cell should divide. Which of the following could NOT explain this? ( ) a receptor molecule that is always turned off ( ) a receptor molecule that is always activated ( ) a transduction pathway that is always turned on ( ) a target protein that is always activated ( ) a gene for cell division that is expressed when it should not be
a RECEPTOR molecule that is always turned OFF
Of the following conditions, which is absolutely necessary for diffusion to take place? ( ) a differentially permeable membrane ( ) a true solution ( ) a concentration difference ( ) a non-permeable membrane ( ) a living cell
a concentration difference
Oxygen diffuses into the capillaries of the lungs because there is
a higher concentration of O2 in the alveoli than the capillaries.
The term hypertonic means
a higher solute concentration.
When you cut into most active plant tissue, water appears almost immediately because plant cells are in
a hypotonic solution that produces turgor pressure.
The number of mitochondria in a cell would be a general indicator of the extent of
active transport.
When a substance moves from an area of low concentration to an area of high concentration while using energy, the process is termed
active transport.
Which is the most common type of intercellular junction between skin cells?
adhesion junctions
Which components of a cell membrane are used for cell-to-cell recognition? ( ) phospholipids ( ) proteins ( ) glycolipids ( ) cholesterol molecules
proteins
According to the fluid-mosaic model of membrane structure,
proteins float inside or within the phospholipid bilayer.
Which function does the lipid bilayer component of the plasma membrane NOT provide for the cell? ( ) defines a permeable boundary between the organized interior and the chaotic external environment ( ) provides an impermeable, self-sealing membrane that keeps all internal living processes sealed inside ( ) controls the exchange of molecules between one cell and adjacent cells or the environment ( ) provides a fluid and flexible boundary that insulates the interior from the variations in humidity, food, and other external conditions ( ) provides a matrix for proteins that regulate the exchange of molecules between the inside and outside of the cell
provides an impermeable, self-sealing membrane that keeps all internal living processes sealed inside
Which type of membrane protein will be used to bind to hormones? ( ) channel proteins ( ) carrier proteins ( ) cell recognition proteins ( ) receptor proteins ( ) enzymatic proteins
receptor proteins
Receptor-mediated endocytosis involves all of the following EXCEPT ( ) receptor proteins to bind to specific molecules ( ) a coated pit due to a layer of fibrous protein on the cytoplasmic side of the membrane ( ) various outcomes from destruction of the vesicle to restoration of the surface configuration ( ) the mechanism for regulating exchange between a mother and fetus ( ) secretion of materials from a cell
secretion of materials from a cell
Osmosis can occur when a membrane is
semipermeable.
If a cell lacks ATP, which of the following processes would cease to operate immediately? ( ) diffusion ( ) sodium/potassium pump ( ) facilitated diffusion ( ) osmosis ( ) tonicity
sodium/potassium pump
When you add sugar to your coffee or tea, the sugar is the
solute
Permeability refers to
the extent to which a membrane allows a substance to pass through.
In the new procedures developed to clone a mammalian cell, the nucleus is removed from an egg cell and the nucleus from the adult to be cloned is injected inside this cell. If we did this process with a basketball, we would permanently damage the shell. What property of the cell repairs this damage?
the fluid-mosaic nature of the membrane
Insulin formed by the Golgi apparatus in insulin-producing cells leaves those cells by
the insulin-filled vesicles fusing with the cell membrane and spilling their contents externally.
Certain individuals with a Y chromosome develop into females because testosterone is not able to induce the formation of male sexual characteristics. This is most likely due to a defect in
the receptor
When water enters a plant cell
the vacuole becomes enlarged.
Proteins do NOT pass through cell membranes because
they are very large molecules. (membrane is made of proteins but this doesn't explain why they can't pass through)
What property of phospholipids make them suitable for the formation of the double layer found in membranes?
they have both a hydrophobic and a hydrophilic end
If a molecule crosses a plasma membrane faster than it diffuses in water, then the process is likely to involve active transport.
true
Dead plants seen alongside a salted roadway died because the saline solution caused the cells to
undergo plasmolysis