Honors Bio II Test Review: Chapters 4 & 5

Active transport must function continuously because __________. A. plasma membranes wear out B. not all membranes are amphiphilic C. facilitated transport opposes active transport D. diffusion is constantly moving solutes in opposite directions

D. Diffusion is constantly moving solutes in opposite directions

Prokaryotes depend on ________ to obtain some materials and to get rid of wastes. A. ribosomes B. flagella C. cell division D. diffusion

D. Diffusion

Which characteristic of a phospholipid contributes to the fluidity of the membrane? A. its head B. cholesterol C. a saturated fatty acid tail D. double bonds in the fatty acid tail

D. Double bonds in the fatty acid tail

What is the combination of an electrical gradient and a concentration gradient called? A. potential gradient B. electrical potential C. concentration potential D. electrochemical gradient

D. Electrochemical gradient

Which of the following do not play a role in intracellular movement? A. microfilaments and intermediate filaments B. microfilaments and microtubules C. intermediate filaments and microtubules D. only intermediate filaments

D. Only intermediate filaments

Which of the following is found both in eukaryotic and prokaryotic cells? A. nucleus B. mitochondrion C. vacuole D. ribosomes

D. Ribosomes

Which of the following is surrounded by two phospholipid bilayers? A. the ribosomes B. the vesicles C. the cytoplasm D. the nucleoplasm

D. The nucleoplasm

If the nucleolus were not able to carry out its function, what other cellular organelles would be affected?

Free ribosomes and rough endoplasmic reticulum (which contains ribosomes) would not be able to form.

You already know that ribosomes are abundant in red blood cells. In what other cells of the body would you find them in great abundance? Why?

Ribosomes are abundant in muscle cells as well because muscle cells are constructed of the proteins made by the ribosomes.

In your opinion, is the nuclear membrane part of the endomembrane system? Why or why not? Defend your answer.

Since the external surface of the nuclear membrane is continuous with the rough endoplasmic reticulum, which is part of the endomembrane system, then it is correct to say that it is part of the system.

Explain why not all microbes are harmful.

Some microbes are beneficial. For instance, E. coli bacteria populate the human gut and help break down fiber in the diet. Some foods such as yogurt are formed by bacteria.

Prokaryotic cells are much smaller than eukaryotic cells. What advantages might small cell size confer on a cell? What advantages might large cell size have?

Substances can diffuse more quickly through small cells. Small cells have no need for organelles and therefore do not need to expend energy getting substances across organelle membranes. Large cells have organelles that can separate cellular processes, enabling them to build molecules that are more complex.

What are the advantages and disadvantages of each of these types of microscopes?

The advantages of light microscopes are that they are easily obtained, and the light beam does not kill the cells. However, typical light microscopes are somewhat limited in the amount of detail they can reveal. Electron microscopes are ideal because you can view intricate details, but they are bulky and costly, and preparation for the microscopic examination kills the specimen.

Where does the cell get energy for active transport processes?

The cell harvests energy from ATP produced by its own metabolism to power active transport processes, such as the activity of pumps.

Antibiotics are medicines that are used to fight bacterial infections. These medicines kill prokaryotic cells without harming human cells. What part or parts of the bacterial cell do you think antibiotics target? Why?

The cell wall would be targeted by antibiotics as well as the bacteria's ability to replicate. This would inhibit the bacteria's ability to reproduce, and it would compromise its defense mechanisms.

Explain how the extracellular matrix functions.

The extracellular matrix functions in support and attachment for animal tissues. It also functions in the healing and growth of the tissue.

Why is it advantageous for the cell membrane to be fluid in nature?

The fluid characteristic of the cell membrane allows greater flexibility to the cell than it would if the membrane were rigid. It also allows the motion of membrane components, required for some types of membrane transport.

In the context of cell biology, what do we mean by form follows function? What are at least two examples of this concept?

"Form follows function" refers to the idea that the function of a body part dictates the form of that body part. As an example, compare your arm to a bat's wing. While the bones of the two correspond, the parts serve different functions in each organism and their forms have adapted to follow that function.

If the pH outside the cell decreases, would you expect the amount of amino acids transported into the cell to increase or decrease?

A decrease in pH means an increase in positively charged H+ ions, and an increase in the electrical gradient across the membrane. The transport of amino acids into the cell will increase.

In what situation(s) would the use of a light microscope be ideal, and why?

A light microscope would be ideal when viewing a small living organism, especially when the cell has been stained to reveal details.

In what situation(s) would the use of a scanning electron microscope be ideal, and why?

A scanning electron microscope would be ideal when you want to view the minute details of a cell's surface, because its beam of electrons moves back and forth over the surface to convey the image.

In what situation(s) would a transmission electron microscope be ideal, and why?

A transmission electron microscope would be ideal for viewing the cell's internal structures, because many of the internal structures have membranes that are not visible by the light microscope.

Bacteria that lack fimbriae are less likely to ________. A. adhere to cell surfaces B. swim through bodily fluids C. synthesize proteins D. retain the ability to divide

A. Adhere to cell surfaces

What is the primary function of carbohydrates attached to the exterior of cell membranes? A. identification of the cell B. flexibility of the membrane C. strengthening the membrane D. channels through membrane

A. Identification of the cell

Which of the following is not a component of the endomembrane system? A. mitochondrion B. Golgi apparatus C. endoplasmic reticulum D. lysosome

A. Mitochonrion

Which plasma membrane component can be either found on its surface or embedded in the membrane structure? A. protein B. cholesterol C. carbohydrate D. phospholipid

A. Protein

What problem is faced by organisms that live in fresh water? A. Their bodies tend to take in too much water. B. They have no way of controlling their tonicity. C. Only salt water poses problems for animals that live in it. D. Their bodies tend to lose too much water to their environment.

A. Their bodies tend to take in too much water

In plant cells, the function of the lysosomes is carried out by __________. A. vacuoles B. peroxisomes C. ribosomes D. nuclei

A. Vacuoles

The ________ is the basic unit of life. A. organism B. cell C. tissue D. organ

B. Cell

Which of the following have the ability to disassemble and reform quickly? A. microfilaments and intermediate filaments B. microfilaments and microtubules C. intermediate filaments and microtubules D. only intermediate filaments

B. Microfilaments and microtubules

The process by which a cell engulfs a foreign particle is known as: A. endosymbiosis B. phagocytosis C. hydrolysis D. membrane synthesis

B. Phagocytosis

Which transport mechanism can bring whole cells into a cell? A. pinocytosis B. phagocytosis C. facilitated transport D. primary active transport

B. Phagocytosis

Peroxisomes got their name because hydrogen peroxide is: A. used in their detoxification reactions B. produced during their oxidation reactions C. incorporated into their membranes D. a cofactor for the organelles' enzymes

B. Produced during their oxidation reactions

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

Both are similar in that they are enveloped in a double membrane, both have an intermembrane space, and both make ATP. Both mitochondria and chloroplasts have DNA, and mitochondria have inner folds called cristae and a matrix, while chloroplasts have chlorophyll and accessory pigments in the thylakoids that form stacks (grana) and a stroma.

Which of the following is most likely to have the greatest concentration of smooth endoplasmic reticulum? A. a cell that secretes enzymes B. a cell that destroys pathogens C. a cell that makes steroid hormones D. a cell that engages in photosynthesis

C. A cell that makes steroid hormones

How does the sodium-potassium pump make the interior of the cell negatively charged? A. by expelling anions B. by pulling in anions C. by expelling more cations than are taken in D. by taking in and expelling an equal number of cations

C. By expelling more cations than are taken in

The principal force driving movement in diffusion is the __________. A. temperature B. particle size C. concentration gradient D. membrane surface area

C. Concentration gradient

Water moves via osmosis _________. A. throughout the cytoplasm B. from an area with a high concentration of other solutes to a lower one C. from an area with a high concentration of water to one of lower concentration D. from an area with a low concentration of water to one of higher concentration

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

The key components of desmosomes are cadherins and __________. A. actin B. microfilaments C. intermediate filaments D. microtubules

C. Intermediate filaments

In what important way does receptor-mediated endocytosis differ from phagocytosis? A. It transports only small amounts of fluid. B. It does not involve the pinching off of membrane. C. It brings in only a specifically targeted substance. D. It brings substances into the cell, while phagocytosis removes substances.

C. It brings in only a specifically targeted substance

What happens to the membrane of a vesicle after exocytosis? A. It leaves the cell. B. It is disassembled by the cell. C. It fuses with and becomes part of the plasma membrane. D. It is used again in another exocytosis event.

C. It fuses with and becomes part of the plasma membrane.

Which of the following are found only in plant cells? A. gap junctions B. desmosomes C. plasmodesmata D. tight junctions

C. Plasmodesmata

When viewing a specimen through a light microscope, scientists use ________ to distinguish the individual components of cells. A. a beam of electrons B. radioactive isotopes C. special stains D. high temperatures

C. Special stains

Which of the following sequences correctly lists in order the steps involved in the incorporation of a proteinaceous molecule within a cell? A. synthesis of the protein on the ribosome; modification in the Golgi apparatus; packaging in the endoplasmic reticulum; tagging in the vesicle B. synthesis of the protein on the lysosome; tagging in the Golgi; packaging in the vesicle; distribution in the endoplasmic reticulum C. synthesis of the protein on the ribosome; modification in the endoplasmic reticulum; tagging in the Golgi; distribution via the vesicle D. synthesis of the protein on the lysosome; packaging in the vesicle; distribution via the Golgi; tagging in the endoplasmic reticulum

C. Synthesis of the protein on the ribosome; modification in the endoplasmic reticulum; tagging in the Golgi; distribution via the vesicle

Injection of a potassium solution into a person's blood is lethal; this is used in capital punishment and euthanasia. Why do you think a potassium solution injection is lethal?

Cells typically have a high concentration of potassium in the cytoplasm and are bathed in a high concentration of sodium. Injection of potassium dissipates this electrochemical gradient. In heart muscle, the sodium/potassium potential is responsible for transmitting the signal that causes the muscle to contract. When this potential is dissipated, the signal can't be transmitted, and the heart stops beating. Potassium injections are also used to stop the heart from beating during surgery.

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

Centrioles and flagella are alike in that they are made up of microtubules. In centrioles, two rings of nine microtubule "triplets" are arranged at right angles to one another. This arrangement does not occur in flagella.

How do cilia and flagella differ?

Cilia and flagella are alike in that they are made up of microtubules. Cilia are short, hair-like structures that exist in large numbers and usually cover the entire surface of the plasma membrane. Flagella, in contrast, are long, hair-like structures; when flagella are present, a cell has just one or two.

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

Heavy molecules move more slowly than lighter ones. It takes more energy in the medium to move them along. Increasing or decreasing temperature increases or decreases the energy in the medium, affecting molecular movement. The denser a solution is, the harder it is for molecules to move through it, causing diffusion to slow down due to friction. Living cells require a steady supply of nutrients and a steady rate of waste removal. If the distance these substances need to travel is too great, diffusion cannot move nutrients and waste materials efficiently to sustain life.

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

Injection of isotonic solutions ensures that there will be no perturbation of the osmotic balance, and no water taken from tissues or added to them from the blood.

Why do ions have a difficult time getting through plasma membranes despite their small size?

Ions are charged, and consequently, they are hydrophilic and cannot associate with the lipid portion of the membrane. Ions must be transported by carrier proteins or ion channels.

If a peripheral membrane protein were synthesized in the lumen (inside) of the ER, would it end up on the inside or outside of the plasma membrane?

It would end up on the outside. After the vesicle passes through the Golgi apparatus and fuses with the plasma membrane, it turns inside out.

A doctor injects a patient with what the doctor thinks is an isotonic saline solution. The patient dies, and an autopsy reveals that many red blood cells have been destroyed. Do you think the solution the doctor injected was really isotonic?

No, it must have been hypotonic as a hypotonic solution would cause water to enter the cells, thereby making them burst.

Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane?

The hydrophobic, nonpolar regions must align with each other in order for the structure to have minimal potential energy and, consequently, higher stability. The fatty acid tails of the phospholipids cannot mix with water, but the phosphate "head" of the molecule can. Thus, the head orients to water, and the tail to other lipids.

Why is it important that there are different types of proteins in plasma membranes for the transport of materials into and out of a cell?

The proteins allow a cell to select what compound will be transported, meeting the needs of the cell and not bringing in anything else.

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+ ions for every two (positive) K+ ions it pumps in, thus the cell loses a positive charge at every cycle of the pump.

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

They differ because plant cell walls are rigid. Plasmodesmata, which a plant cell needs for transportation and communication, are able to allow movement of really large molecules. Gap junctions are necessary in animal cells for transportation and communication.

Why does water move through a membrane?

Water moves through a membrane in osmosis because there is a concentration gradient across the membrane of solute and solvent. The solute cannot effectively move to balance the concentration on both sides of the membrane, so water moves to achieve this balance.