Biology test

What is the basic unit of life?

Cells

What are the similarities and differences between the structures of centrioles and flagella?

Centrioles and flagella are made of microtubules but show different arrangements.

Which of the following structures is not found in prokaryotic cells?

Chloroplast

How do cilia and flagella differ?

Cilia are short. There can be many or few on the cell surface, whereas flagella are long and never numerous.

In individuals with normally functioning CFTR protein, which substances are transported via active transport?

Cl−

Some animal cells produce an extensive extracellular matrix. You would expect their ribosomes to synthesize large amounts of which of the following proteins?

Collagen

Identify the principal driving movement in diffusion, such as depicted here.

Concentration gradient

With which cellular structure does the extracellular matrix interact?

Cytoskeleton

One type of mutation in the CFTR protein prevents the transport of chloride ions through the channel. Which of the following is most likely to be observed in the lungs of patients with this mutation?

Dehydrated mucus

What process is used by prokaryotes to obtain some materials and remove waste?

Diffusion

Which of the following explains why active movement of molecules across membranes must function continuously?

Diffusion allows movement down the concentration gradient to maintain equilibrium.

Radioactive amino acids are fed to a cell in culture for a short amount of time. This is called a pulse. You follow the appearance of radioactive proteins in the cell compartments. In which organelles and in what order does radioactivity appear?

Endoplasmic reticulum - vesicles - Golgi body - vesicles - extracellular region

You are looking at a sample under a light microscope and observe a new type of cell. You come to the conclusion that it is a bacterium and not a eukaryotic cell. What would you observe to come to this conclusion?

Endoplasmic reticulum - vesicles - Golgi body - vesicles - extracellular region

If a doctor injected a patient with what was labeled as an isotonic saline solution, but then the patient died, and an autopsy revealed that several of the patient's red blood cells had burst, such as in the image on the right, would it be true that the injected solution was really isotonic? Why or why not?

False, the solution was hypotonic.

Which structure or structures allow bacteria to move about?

Flagella only

The fluid mosaic model described the plasma membrane, seen here, as a mosaic of components. Why is it advantageous for the plasma membrane to be fluid in nature?

Fluidity allows greater flexibility to the cell and motion of membrane components required for transport.

Water moves via osmosis across plasma cell membranes in which direction?

From an area with a high concentration of water to one of lower concentration

An experiment was set up to determine the movement of molecules through a dialysis-tubing bag into water. A dialysis-tubing bag containing ​​​5\%​​​ lactose and ​​​5\%​​​ fructose was placed in a beaker of distilled water, as illustrated. After four hours, fructose is detected in the distilled water outside of the dialysis-tubing bag, but lactose is not. What conclusions can be made about the movement of molecules in this experiment?

Fructose, being a monosaccharide, diffused through the dialysis bag into the distilled water. However, lactose, being a disaccharide, could not diffuse through the dialysis bag.

How does the structure of a plasmodesma differ from that of a gap junction?

Gap junctions are essential for transportation in animal cells and plasmodesmata are essential for the movement of substances in plant cells.

How would an organism maintain membrane fluidity in an environment where temperatures fluctuated from very high to very low?

Greater proportion of unsaturated phospholipids in membranes.

Where would you find DNA, the genetic material, in an animal cell?

In the mitochondria and the nucleus

Both of the regular intravenous solutions administered in medicine, normal saline and lactated Ringer's solution, are isotonic, such as seen in the middle image here. Why is this important?

Isotonic solutions maintain equilibrium and avoid the exchange of materials to or from the blood.

In what important way does receptor-mediated endocytosis differ from phagocytosis?

It brings in only a specifically targeted substance.

What happens to the membrane of a vesicle after exocytosis?

It fuses with and becomes part of the plasma membrane.

Discuss why the following affect the rate of diffusion: molecular size, temperature, solution density, and the distance that must be traveled.

Larger molecules move slower than lighter molecules. Increasing or decreasing temperature increases or decreases the energy in the medium, affecting molecular movement. Density is inversely proportional to molecular movement. Greater distance slows the diffusion.

Pictured are two cells along with their radius. What does cell B likely have when compared to cell A?

Larger surface area-to-volume ratio

Macrophages ingest and digest many pathogens. Which organelle plays a major role in the activity of macrophages?

Lysosome

Which of the following is surrounded by two phospholipid bilayers?

Lysosomes

Cells lining the intestine absorb a lot of nutrients. How did those cells adapt to their function?

Membrane folds called microvilli increase the surface area.

Which components of the cytoskeleton are responsible for the contraction of muscles?

Microfilaments

Which of the following will disassemble and reform quickly when white blood cells need to move quickly to the site of an infection?

Microfilaments and microtubules

Which organelles would be present in high numbers in the leg muscles of a marathon runner?

Mitochondria

Mitochondria are observed in plant cells that contain chloroplasts. Why do you find mitochondria in photosynthetic tissue?

Mitochondria are required to break down sugars and other materials for energy.

Which of the following produces the energy needed for protein synthesis in the endomembrane system?

Mitochondrion

If protein synthesis on the ribosome is interrupted, what is the next step that cannot occur?

Modification in the endoplasmic reticulum

Eukaryotic cells contain complex organelles that carry out their chemical reactions. Prokaryotic lack many of these complex organelles, although they have a variety of unique structures of their own. However, most prokaryotic cells can exchange nutrients with the outside environment faster than eukaryotic cells. Why is this so?

Most prokaryotic cells are smaller and have a higher surface area-to-volume ratio than eukaryotic cells.

In which human tissues would you find desmosomes? Think of tissues that undergo strong mechanical stress and must be held together with some flexibility.

Muscle cells and skin cells

Mast cells produce signals that activate inflamation. Neutrophils are phagocytic white blood cells. Monocytes are the largest type of white blood cell that engulf phathogens. Based on the information provided, which cell types are most likely to contain clathrin?

Neutrophils and monocytes

Mast cells produce signals that activate inflamation. Neutrophils are phagocytic white blood cells. Monocytes are the largest type of white blood cell that engulf phathogens. Based on the information provided, which cell types produce endosomes?

Neutrophils and monocytes

Which of the following observations contributed to cell theory?

Non-living material cannot give rise to living organisms

Which of the following do not play a role in intracellular movement?

Only intermediate filaments

Which of the following statements appropriately describe the role of clathrin in neutrophils based on your understanding of phagocytosis?

Opsonin marks the antigen for phagocytosis by the neutrophils, whereas clathrin stabilizes the inward-facing surface of the plasma membrane, which engulfs the antigen.

Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane such as the lipid-bilayer sphere, single-layer lipid sphere, and lipid-bilayer sheet?

Phospholipids are amphipathic molecules. The polar head faces towards water and the nonpolar fatty acid tails face towards other fatty acid tails.

List four components of a plasma membrane and explain their function.

Phospholipids: form the bilayer; Carbohydrates: help in adhesion; Cholesterol: provide flexibility; Integral proteins: form transporters; Peripheral proteins: part of the cell's recognition sites.

Who was the first to clearly identify and name individual cells?

Robert Hooke

Paramecia are unicellular protists that have contractile vacuoles to remove excess intracellular water. In an experimental investigation, Paramecia were placed in salt solutions of increasing osmolarity. The rate at which a Paramecium's contractile vacuole contracted to pump out excess water was determined and plotted against osmolarity of the solutions, as shown in the graph. Which of the following is the correct explanation for the data?

The contraction rate increases as the osmolarity decreases because the amount of water entering the paramecium by osmosis increases.

What do double bonds in phospholipid fatty acid tails contribute to?

The fluidity of membranes

Inhibitors of microtubule assembly, vinblastine for example, are used for cancer chemotherapy. How does an inhibitor of microtubule assembly affect cancerous cells?

The inhibitors restrict the separation of chromosomes, thereby stopping cell division.

Which of the following is an example of passive transport across a membrane?

The movement of water from the descending loop of a nephron into the interstitium

Is the nuclear membrane part of the endomembrane system? Why or why not?

The nuclear membrane is part of the endomembrane system as it is continuous with the rough endoplasmic reticulum.

In addition to a plasma membrane, a eukaryotic cell has organelles, such as mitochondria, that also have membranes. In which way would these membranes differ?

The proportions of proteins, lipids, and carbohydrates will vary.

What happens to the proteins that are synthesized on free ribsomes in the cytoplasm? Did they go through the golgi appartus?

The proteins do not go through the Golgi apparatus and remain free in the cytosol.

What is most likely to happen if Paramecia, pictured here, are moved from a hypertonic solution to solutions of decreasing osmolarity?

The rate of contraction would increase with decreasing osmolarity because more salt diffuses into the paramecium.

. Why does the structure of the cytoplasmic membrane point to a common ancestor of all life?

The similar arrangement of phospholipids and proteins points to common ancestry.

How does the sodium-potassium pump contribute to the net negative charge of the interior of the cell?

The sodium-potassium pump forces out three (positive) Na+Na+ ions for every two (positive) K+K+ ions it pumps in, thus the cell loses a net positive charge of one at every cycle of the pump.

Which of the following is true regarding the surface-to-volume ratios of the cube and the sphere when the diameter of the sphere is equal to the side of the cube?

The sphere will have a higher surface area-to-volume ratio than the cube.

Bacteria do not have organelles; yet, the same reactions that take place on the mitochondria inner membrane, the phosphorylation of ADP to ATP, and chloroplasts, photosynthesis, take place in bacteria. Where do these reactions take place?

These reactions occur on the plasma membrane of bacteria.

Thiomargarita namibiensis is a large single cell organism, which can reach lengths of 700μm. The cell is classified as a bacterium. What is the main argument to justify the classification?

This organism does not show presence of any cell organelles and is thus classified as a bacterium.

What type of junctions prevent the movement of chemicals between two adjacent animal cells?

Tight junctions

Which characteristic of a phospholipid, shown here, increases the fluidity of the membrane?

Unsaturated fatty acid tail

In plant cells, the function of the lysosomes is carried out by what?

Vacuole

Which of the following questions can be asked about organisms that live in fresh water?

Will their bodies take in too much water?

What problem is faced by organisms that live in fresh water?

Without compensating mechanisms, their bodies tend to take in too much water.

If there is a mutation in the gene for collagen, such as the one involved in Ehlers-Danlos syndrome, and the individual produces defective collagen, would it affect coagulation? Why or why not?

Yes. The syndrome affects the clotting factors and platelet aggregation.

Which of the following structures has the same general structure in Archaea, Bacteria, and Eukarya, pointing to a common origin?

cytoplasmic membrane

Consider the shapes. The diameter of the sphere is equal to 1mm and the side of the cube is also equal to 1mm. Which has a greater volume? Which has a greater surface area?

1 : 1

Which of the following is most likely to have the greatest concentration of smooth endoplasmic reticulum (SER)?

A cell that makes steroid hormones

In what situation would the use of a light microscope be ideal? Why?

A standard light microscope is used to view living organisms with little contrast to distinguish them from the background, which would be harder to see with the electron microscope.

Which of the following could most effectively be visualized with a scanning electron microscope?

A three-dimensional view of the surface of a membrane

When bacteria lack fimbriae, what are they less likely to do?

Adhere to cell surfaces

What are the advantages and disadvantages of light microscopes? What are the advantages and disadvantages of electron microscopes?

Advantage: In light microscopes, the light beam does not kill the cell. Electron microscopes are helpful in viewing intricate details of a specimen and have high resolution. Disadvantage: Light microscopes have low resolving power. Electron microscopes are costly and require killing the specimen.

Which element of the cell theory has practical applications in health care because it promotes the use of sterilization and disinfection?

All cells arise from pre-existing cells.

Which of the following statements is part of the cell theory?

All living organisms are made of cells.

Given that primitive Earth was high in inorganic molecules, but low in oxygen, which of the following organisms would we expect to appear first in the fossil record?

Archaea

Arsenic poisoning disrupts ATP production by inhibiting several of the enzymes in the oxidative phosphorylation pathway. Some of the symptoms of arsenic poisoning are similar to cystic fibrosis (difficulty breathing and frequent lung infections). Explain what impact arsenic poisoning may have on components of the plasma membrane and transport that result in CF like symptoms.

Arsenic poisoning disrupts ATP production, leading to a decreased transport of Cl− ions by epithelial cells. This leads to decreased electrolyte concentration in the mucus and retention of water into the cells. The mucus becomes dehydrated, as in CF.

Why is it challenging to study the biochemistry of bacterial fossils and determine if the fossils are members of the domain archaea, rather than bacteria?

Bacteria have rigid structures, but their fossil impression is scarce.

The major role of the cell wall in bacteria is protecting the cell against changes in osmotic pressure, pressure caused by different solute concentrations in the environment. Bacterial cells swell, but do not burst, in low solute concentrations. What happens to bacterial cells if a compound that interferes with the synthesis of the cell wall is added to an environment with low solute concentrations?

Bacterial cells may burst due to the influx of water.

What is a difference between prokaryotic and eukaryotic​ cells?

Both cells have cytoplasm but prokaryotic cells lack a nucleus.

How does the sodium-potassium pump make the interior of the cell negatively charged?

By expelling more cations than it takes in

According to the fluid mosaic model of the plasma cell membrane, what is the location of carbohydrates in the cell membranes?

Carbohydrates are present only on the exterior surface of a membrane.

Which of the following is found in both eukaryotic cells and prokaryotic cells?

Ribosomes

Choose the statement that describes processes of receptor-mediated endocytosis, exocytosis, and the changes in the membrane organization.

Receptor-mediated endocytosis involves the binding of a ligand to its receptor, resulting in the formation of a clathrin-coated vesicle that enters the cell. In exocytosis, waste material is enveloped in a vesicle that fuses with the interior of the plasma membrane via attachment proteins.

Which of these is a possible explanation for the presence of a rigid cell wall in plants?

Plants are subjected to osmotic pressure and a cell wall helps them against bursting or shrinking.

Describe the process of potocytosis and explain how it differs from pinocytosis.

Potocytosis is a form of receptor-mediated endocytosis where molecules are transported via caveolae-coated vesicles. Pinocytosis is a mode of endocytosis used for absorption of extracellular water.

What is the difference between primary and secondary active transport?

Primary active transport is directly dependent on ATP, while secondary active transport is indirectly dependent on ATP.

Peroxisomes got their name because hydrogen peroxide is ______.

Produced during their oxidation reactions

Gap junctions are formed by ________.

Protein complexes that form channels between cells

Which plasma membrane component can be either found on its surface or embedded in the membrane structure?

Proteins

Which of the following molecules will be affected if the extracellular matrix of a cell begins to break down?

Proteoglycans

What are the structural and functional similarities and differences between mitochondria and chloroplasts?

Similarities: double membrane, inter-membrane space, ATP production, contain DNA. Differences: mitochondria have inner folds called cristae, chloroplast contains accessory pigments in thylakoids, which form grana and a stroma.

When viewing a specimen through a light microscope, what is a method that scientists use to make it easier to see individual components of cells?

Special stains

What determines the upper limit of cell size?

Surface area-to-volume ratio. Some organisms, such as slime molds, get around this by instead of having separate cells having a branching cytoplasm with a high surface area-to-volume ratio.

The sodium-potassium ​​​(\text{Na}^{+}/\text{K}^{+})​​​ pump functions like an anti-porter transporting ​​​\text{Na}^{+} \!​​​ and ​​​\text{K}^{+} {\!}​​​ across membranes using ATP. This protein spans the membrane with intracellular and extracellular domains. It has a binding site for ​​​\text{Na}^{+} {\!}​​​, ​​​\text{K}^{+} {\!}​​​, and ATP. An experiment was conducted to determine the locations of these binding sites. Artificial cells were created and incubated in buffers containing ATP, ouabain (or oubain), ​​​\text{Na}^{+} {\!}​​​, and ​​​\text{K}^{+} {\!}​​​ in varying combinations inside and outside of the cell as indicated in the chart. The transport of ​​​\text{Na}^{+} {\!}​​​ and ​​​\text{K}^{+} {\!}​​​ was measured to determine activity of the ​​​\text{Na}^{+}/\text{K}^{+} {\!}​​​ pump. Which of the following conclusions is supported by the data?

The ATP binding site of the Na+ /K+ pump is located on the intracellular domain of the pump.

Describe the Na+/K+ pump, labeling the binding sites for Na+, K+, and ATP. Explain how the data indicates the location of the binding sites for Na+ and K+ on the pump. Based on the data, choose the correct statement describing the location of the binding sites for Na+ and K+ on the pump.

The binding of K+ occurs on the outer surface of the cell, and its transportation is blocked when ouabain is present outside the cell. The binding of Na+ occurs on the inner surface of the cell, and its transportation is blocked by the presence of ouabain.

This figure shows the relative sizes of microbes on a logarithmic scale. What is the major consideration in setting the lower limit of cell size?

The cell size must be small as to fit all the processes and structures to support life.

Potassium is a necessary nutrient in order to maintain the function of our cells. What would occur to a person that is deficient in potassium?

The cell would not be able to get rid of extra sodium.