Question 1

You are studying life-forms in extreme environments, and you have discovered a microorganism with cardiolipin, hopanoids, and ester linkages in the membrane. It also has teichoic acids, galactans, and phenolic glycolipids in the cell wall. In addition, it is a porin similar to OmpA. This microorganism is most likely related to

Accepted Answer

Mycobacteria have complex cell walls with components like mycolic acids, galactans, and phenolic glycolipids, and they can have porins similar to OmpA. The presence of these features, along with cardiolipin and hopanoids, suggests a relation to mycobacteria.

Question 2

The proteins embedded in a membrane require that region to be

Accepted Answer

Proteins embedded in membranes require a hydrophobic environment since the membrane itself is made up of a phospholipid bilayer, which has hydrophobic fatty acid tails facing inward and hydrophilic heads facing outward. Therefore, proteins with hydrophobic regions can easily interact with the membrane, making them stable and functional.

Question 3

Which of the following reinforces and stiffens membranes in bacteria?

Accepted Answer

Hopanoids are a type of lipid found in bacterial membranes that help to reinforce and stiffen the membrane, similar to the function of sterols in eukaryotic cell membranes. Polyamines, peptidoglycans, and lipids do not have the same function in reinforcing and stiffening bacterial membranes.

Question 4

Specific membrane components, particularly ________, determine which substances are transported across the membrane.

Accepted Answer

Proteins, such as transporters and channels, play a critical role in determining which substances are transported across the membrane. They provide specific pathways and binding sites for certain molecules to pass through the membrane. While phospholipids make up the bulk of the membrane structure, they do not play as direct a role in determining which substances are transported. Ions may be transported through specific channels or transporters, but they are not membrane components themselves. Polysaccharides and leaflets are not directly involved in membrane transport.

Question 5

E. coli and Sinorhizobium cell-surface proteins enable colonization of ________ and ________, respectively.

Accepted Answer

E. coli is known for its ability to colonize the human intestinal epithelium, while Sinorhizobium species are recognized for their role in colonizing legume plants, where they form symbiotic relationships and assist in nitrogen fixation.

Question 6

The molecule shown below is ________ and may play a role in ________.

Accepted Answer

The answer of The molecule shown below is ________ and...

Question 7

In the figure below, which of the four fatty acids adds fluidity to a membrane, and what type of bond allows this to happen?

Accepted Answer

The fatty acid in D has a double bond (cis) in its carbon chain, which creates a bend or kink in the molecule, making it harder for the fatty acids to pack tightly together. This increases the fluidity of the membrane.

Question 8

Polyamines are ________ charged when the pH is near neutral.

Accepted Answer

Polyamines are positively charged when the pH is near neutral. This is because they contain multiple amine groups (NH2) which can be protonated (pick up a hydrogen ion) and become positively charged in acidic conditions. When the pH is near neutral, these groups are not protonated, but still carry a positive charge due to the presence of the amine groups.

Question 9

Which of these experiments would NOT be a reason to fractionate bacterial cells?

Accepted Answer

The answer of Which of these experiments would NOT be...

Question 10

All of the statements about genetic analysis of cells complementing cell fractionation are true EXCEPT that it

Accepted Answer

The statement that genetic analysis has never been used to study FtsZ is false. FtsZ is a commonly studied protein involved in cell division and has been studied using genetic analysis methods.

Question 11

Extreme thermophiles have ________ chains in their membrane in order to maintain membrane stability.

Accepted Answer

Extreme thermophiles have terpenoid chains in their membrane in order to maintain membrane stability at high temperatures. Terpenoids are hydrocarbon chains with multiple isoprene units, which give them a high degree of saturation and rigidity, making them ideal for use in high-temperature environments. Lipoprotein, cholesterol, hopanoid, and cardiolipin are found in other types of membranes, but not specifically adapted for extreme thermophiles.

Question 12

A medically important example of active transport is that of drug ________ proteins powered by the hydrogen ion gradient.

Accepted Answer

Active transport is the movement of molecules across a membrane against their concentration gradient and requires energy input. Efflux proteins are a type of active transporter that pump drugs and other molecules out of cells, often as a defense mechanism against toxins or antibiotics. The energy for this transport is provided by the hydrogen ion gradient, which is maintained by the action of other membrane proteins such as ATPases or proton pumps. Therefore, choice A is the correct answer. Porins are passive channels that allow the diffusion of molecules across the membrane, and membrane-permeant molecules can cross the membrane without any assistance. Diffusion is a passive transport process that does not require energy input, and lysis refers to the breaking down of cells, which is not related to transport mechanisms.

Question 13

Which of the following types of molecules may passively diffuse across a membrane?

Accepted Answer

Small uncharged molecules, such as water, are capable of passive diffusion across a membrane.

Question 14

Mary Jane Osborn discovered that inner and outer membranes are different in density by using

Accepted Answer

Ultracentrifugation is the method used to separate and distinguish the components of a mixture based on their different densities. In this case, Mary Jane Osborn could have used ultracentrifugation to separate the inner and outer membranes of the cell, and determine their different densities.

Question 15

We cannot see the molecules within a cell, but ________ and ________ analysis generate a remarkably detailed view.

Accepted Answer

Microscopy and subcellular analysis are the most appropriate choices as they allow visualization of the internal structures within a cell. Chemical and genetic analysis can provide information about the components and functions of these structures but do not directly reveal their physical characteristics. Structural analysis could be an option, but microscopy and subcellular analysis are more specific and commonly used methods for visualizing cellular components. Therefore, option D is the best choice for this question.

Question 16

Cells must be broken open in order to then fractionate the components. Each of the following can be used in bacterial cell breakage EXCEPT

Accepted Answer

Ultracentrifugation is not a method for cell breakage, but rather a method for separating components based on their density. The other choices, French press, lysozyme, mild detergent, and ultrasonic vibration, are all methods for breaking open bacterial cells.

Question 17

The z-ring is

Accepted Answer

The z-ring is controlled by a nutrient-dependent regulator, which is crucial for its role in bacterial cell division. It is not made of actin-like polymers, nor is it involved in nucleoid segregation, replication, or transcription prevention.

Question 18

The capsule polysaccharides form a slippery mucous layer that inhibits

Accepted Answer

Capsule polysaccharides form a slippery mucous layer that inhibits phagocytosis, i.e., the activity of engulfing and destroying foreign particles by white blood cells. This helps pathogens to evade the host's immune system.

Question 19

You study a bacterium that grows in very low-nutrient aqueous environments. Which type of transport mechanism is required to deliver nutrients from these environments where they are at a lower concentration than inside the cell?

Accepted Answer

Active transport is required to move nutrients into the cell against their concentration gradient from low-nutrient aqueous environments where they are at a lower concentration than inside the cell. This process requires energy in the form of ATP.

Question 20

Some bacterial cells are inedible for humans because of the

Accepted Answer

Humans cannot efficiently metabolize nucleic acids, leading to the production of uric acid, which can be harmful in high amounts.

Quiz 3: Cell Structure and Function