AP Biology, Chapter 4

What are the main functions of the smooth endoplasmic reticulum?

Synthesizes carbohydrates, lipids (phospholipids & cholesterol), and steroid hormones. Also stores calcium in muscle cells.

We have discussed the upper limits of cell size; yet, there is a lower limit to cell size. What determines how small a cell can be?

The cell should be able to accommodate all the structures and metabolic activities necessary to survival.

What is most likely to have the greatest concentration of smooth endoplasmic reticulum (SER)? 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). Steroid-secreting cells are characterized by abundant SER. For example, cells in the gonads and the adrenal gland have an extensive network of SER because they synthesize cholesterol as a precursor for steroid hormones or take up this substrate from plasma lipoproteins. Many of the enzymes for sterol and steroid synthesis are localized in the SER.

Cells lining the intestine absorb a lot of nutrients. How did those cells adapt to their function? A Cells use cilia to move nutrients to their surface. B Cells grow much larger than adjacent cells to increase intake. C Cells are flat and thin to absorb more nutrients. D Membrane folds called microvilli increase the surface area.

(D). The microvilli are the cellular membrane protrusions of the intestinal membrane, which increase the surface area for maximum absorption.

In plant cells, what carries out the function of the lysosomes? A) Nuclei B) Peroxisomes C) Ribosomes D) Vacuole

(D). The vacuole plays a role similar to lysosomes and fulfills many functions. It contains digestive enzymes, isolates harmful materials, stores waste products and secondary compounds such as pigments in petals, latex, and alkaloids that deter predators. It helps maintain the pressure within a cell by changing its content of water, contributes to the balance of pH, exports products, and stores proteins for seed germination.

Do mitochondria and chloroplasts have... - A double membrane? - Produce ATP? - Have DNA? - Have thylakoids and grana?

- Yes - Yes - Yes - Only chloroplsts.

Explain the process of cell communication from the extracellular matrix all the way down to the nucleus.

1) On the outside surface of their cells, cells have protein receptors. 2) A molecule from the extracellular matrix will bind with the receptor, and the microfilaments within the cell will adjust their structure. 3) The microfilaments adjustments of structure sends a chemical signal to the nucleus to turn "on" or "off" the transcription of specific sections of DNA.

What are the similarities and differences between the structures of centrioles and flagella? A Centrioles and flagella are made of microtubules but show different arrangements. B Centrioles are made of microtubules, but flagella are made of microfilaments, and both show the same arrangement. C Centrioles and flagella are made of microfilaments. Centrioles have a 9 + 2 arrangement. D Centrioles are made of microtubules, flagella are made of microfilaments, and both have different structures.

A

Which element of the cell theory has practical applications in health care because it promotes the use of sterilization and disinfection?A) All cells come from preexisting cells.B) All living organisms are composed of one or more cells.C) A cell is the basic unit of life.D) A nucleus and organelles are found in prokaryotic cells.

A) All cells come from preexisting cells. If all microorganisms are removed or killed, then the environment, medical devices, or other items are sterile or, at least, have fewer potential pathogens.

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, how would it affect coagulation? A The syndrome affects the clotting factors and platelet aggregation. B The syndrome leads to hypercoagulation of blood. C Coagulation is not affected because collagen is not required for coagulation. D The syndrome occurs due to the breakdown of platelets.

A. Collagen is a structural protein of the blood vessel wall, which is normally concealed beneath the cells that line the blood vessel inner walls. When the blood vessel becomes injured, collagen is exposed and attracts cells called platelets from the blood which causes blood clotting.

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

Adhere to cell surfaces.

Why does the immune system attack a transplanted organ? A) Glycoproteins and glycolipids on the surface of the organ are similar to those found on pathogens. B) Glycoproteins and glycolipids on the surface of the organ are not recognized by the immune system. C) Glycoproteins and glycolipids on the surface of the organ are toxic to the body. D) Glycoproteins and glycolipids on the surface of the organ are similar to those found on immune cells.

B) Glycoproteins and glycolipids on the surface of the organ are not recognized by the immune system.

Gap junctions are formed by — A gaps in the cell wall of plants B protein complexes that form channels between cells C tight, rivet-like regions in the membranes of adjacent cells D a tight knitting of membranes

B. Gap junctions develop when a set of six proteins in the plasma membrane arrange themselves in an elongated donut-like configuration called a connexon. When the pores of connexons align, a channel between the two cells form.

Which components of the cytoskeleton are responsible for the contraction of muscles? A Intermediate filaments B Microfilaments C Microtubules

B. Microfilaments are also the narrowest portion of the cytoskeleton. Microfilaments are made up of a protein called actin which serves as a track for a motor protein called myosin. When a muscle contracts, actin and myosin filaments slide past each other.

What are the two domains of prokaryotic cells?

Bacteria and Archaea

Why is it challenging to study bacterial fossils and determine if the fossils are members of the domain Archaea rather than Bacteria?

Bacteria lack rigid structures, thus do not form fossils....Bacteria do not easily form fossils because they lack rigid structures such as shells or skeletons. It is hard to identify the biochemical features that differentiate archaea from bacteria in fossils.

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...The cells will burst because of the movement of water inside the cell because there is no cell wall protection against bursting. Important antibiotics such as penicillin kill bacteria by interfering with the cell wall synthesis.

What has the ability to disassemble and reform quickly? A Intermediate filaments and microtubules B Microfilaments and intermediate filaments C Microfilaments and microtubules D Only intermediate filaments

C

Which sequence correctly lists in order the steps involved in the incorporation of a protein within a cell membrane? A) Synthesis of the protein on the ribosome; modification in the Golgi apparatus; packaging in the endoplasmic reticulum; modification in the vesicle B) Synthesis of the protein on the lysosome; modification 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; modification in the endoplasmic reticulum

C

Where would you find DNA, the genetic material, in an animal cell? A) In the centriole. B) Only in the mitochondria. C) In the nucleus and mitochondria.

C) In the nucleus and mitochondria.

Eukaryotic cells contain complex organelles that carry out their chemical reactions. Prokaryotes 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 most eukaryotic cells. Why is this so? A) Most prokaryotic cells are smaller, and have a higher surface-to-volume ratio, than eukaryotic cells. B) Most prokaryotic cells are larger, and have a higher surface-to-volume ratio than eukaryotic cells. C) Most prokaryotic cells are smaller, and have a lower surface-to-volume ratio than eukaryotic cells. D) Prokaryotic cells are larger and have a lower surface-to-volume ratio than eukaryotic cells.

C. Most prokaryotic cells are smaller, and have a lower surface-to-volume ratio than eukaryotic cells

Peroxisomes got their name because hydrogen peroxide is...(Also explain the peroxisomes main function in the cell.) A) A cofactor for the organelles' enzymes. B) Incorporated into their membranes C) Produced during their oxidation reactions. D) used in their detoxification reactions.

C. Produced during their oxidation reactions. Peroxisomes carry out oxidation reactions which break down amino acids and fatty acids.

Picture: One cell with a radius of 3 micrometer, and another cell with the radius of 3,000 micrometers. What does cell B likely have when compared to cell A?

Cell B has a larger surface area to volume ration. Khan Academy has a great video on this: Cell Size.

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

Cytoplasmic membrane

Which structure has the same general structure in the domains Archaea, Bacteria, and Eukarya, pointing to a common origin and why does it point towards a common ancestor?

Cytoplasmic membrane, because of its similar arrangement of phospholipids and proteins.

What does NOT play a role in intracellular movement? A Intermediate filaments and microtubules B Microfilaments and intermediate filaments C Microfilaments and microtubules D Only intermediate filaments

D, Recall that intermediate filaments provide the cell its shape and help in fastening organelles in place.

What are desmosomes and where do you find them? A Bone cells and cartilage cells. B Muscle cells and skin cells C Nerve cells and muscle cells D Secretory cells and muscle cells

Desmosomes occur when short proteins (called cadherins) in the plasma membranes of each cell connect to the intermediate filaments and connect the two cells together. Unlike tight junctions, the gap is not so tight that substances cannot flow between cells, however. B

In order to obtain some materials and remove waste, what process is used by prokaryotes?

Diffusion. The changes in the concentration help the movement of the particles and waste across the plasma membrane. This process is known as diffusion, where molecules move from high to low concentration.

Which structure or structures allow bacteria to move about? Flagella or fimbriae, or pili, or all?

Flagella only. Fimbriae and pili are the same thing, and they only attach to surfaces.

What is the similarity between the surface area to volume ratios learned about in lesson 2 of this chapter, and the anatomy of the cortex?

Form follows function in biology. We see this by cells staying small in order to have a small surface area to volume ratio. We see this same thing with the folds of the cortex. If the cortex was stretched out, it would be meters long, but it is folded.

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

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.

Eukaryotic cells contain complex organelles that carry out their chemical reactions. Prokaryotes 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 most eukaryotic cells. Why is this so?

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

Do prokaryotic cells have membrane bound organelles, ribosomes, DNA, a nucleus, a plasma membrane, a cell wall, or polysaccharide capsules?

No, yes, yes, no, yes, no , yes. All prokaryotes have plasma membranes, cytoplasm, ribosomes, and DNA that is not membrane-bound. Most have peptidoglycan cell walls and many have polysaccharide capsules

Which of the following is surrounded by two phospholipid bilayers? A) Lysosome B) Ribosome C) Nucleolus D) Nucleus

Nucleus

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

Peroxisomes have a byproduct of hydrogen peroxide during its break down due to the enzyme catalase while lysosomes do not. Lysosomes. Lysosomes are part of two processes called autotrophy (self eating) and crinophagy (break down of excess stuff). Macrophages ingest viruses and go to the lysosome to be broken down. Lysosomes break down things into its building block constituents (often macromolecules) and release them back into the cell.

Who was the first scientist to correctly point out an individual cell?

Robert Hooke

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? A) The cell has a cell wall. B) The cell has a flagellum. C) The cell does not have a nucleus. D) The cell is small.

Some eukaryotic cells have a cell wall. Some eukaryotic cells have flagellum. All cells are "small." So, C is the answer because prokaryotes never have membrane bound organelles including a nucleus.

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. Special stains are used to enhance visualization of the cell or certain cellular components under a microscope. Cells may also be stained to highlight metabolic processes or to differentiate between live and dead cells in a sample.

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

The similar arrangement of phospholipids and proteins points to common ancestry...The similar arrangement of macromolecules, phospholipids, and embedded proteins in the lipid bilayer makes it a primitive trait. Archaea, Bacteria, and Eukarya display a closely related general architecture of the plasma membrane.

Inhibitors of microtubule assembly, vinblastine for example, are used for cancer chemotherapy. How does an inhibitor of microtubule assembly affect cancerous cells? A The inhibitors restrict the separation of chromosomes by the mitotic spindle. B The inhibition of microtubules interferes with the synthesis of proteins. C The inhibitors bind the microtubule to the nuclear membrane. D The inhibitors interfere with energy production.

The solution is (A). Cancerous cells divide rapidly. By inhibiting microtubules' movement, cell division stops because the chromosomes cannot be separated by the centrioles.

Some animal cells produce an extensive extracellular matrix. You would expect their ribosomes to synthesize large amounts of which proteins? A Actin B Collagen C Myosin D Tubulin

The solution is (B). Collagen is interwoven with proteoglycans, and collectively these molecules form the extracellular matrix. Actin, myosin, and tubulin are found inside the cells and are part of the cytoskeleton.

Which statement is a possible explanation for the presence of a rigid cell wall in plants? A Plants remain exposed to changes in temperature and thus require rigid cell walls to protect themselves. B Plants are subjected to variations in osmotic pressure, and a cell wall helps them against bursting or shrinking. C Plant cells have a rigid cell wall to protect themselves from grazing animals. D Plant cells have a rigid cell wall to prevent the influx of waste material.

The solution is (B). Plant cells are subject to extreme changes in osmotic pressures. The rigid cell wall protects tissues against excessive shrinking or bursting of cells. * Osmosis is defined as the process of going from an area of lower concentration of solvent to an area of higher concentration of solvent. * Osmotic pressure occurs in plant cells where the inside of the cell is pushing against the cell wall while it is being attracted to the area of higher concentration of solvent on the outside.

What happens to the proteins that are synthesized on free ribosomes in the cytoplasm? Do they go through the Golgi apparatus? A These proteins move through the Golgi apparatus and enter in the nucleus. B These proteins go through the Golgi apparatus and remain in the cytosol. C The proteins do not go through the Golgi apparatus and move into the nucleus for processing. D The proteins do not go through the Golgi apparatus and remain free in the cytosol.

The solution is (D). Most of the proteins synthesized on free ribosomes stay in the cytosol. They do not go through the Golgi apparatus to be tagged for export or integration in membranes.

What type of junctions prevents the movement of chemicals between two adjacent animal cells? A Desmosomes B Gap junctions C Plasmodesmata D Tight junctions

The solution is (D). Tight junctions composed of occludins and claudins are essential for forming an impermeable barrier to fluids. They are typically found in cells of the epithelial tissues that line exposed internal and external surfaces in animal bodies. For example, cells in the intestinal mucosa are joined by tight junctions to prevent leakage of intestinal content directly into the underlying tissues.

Why did electron microscopes provide such a breakthrough in the study of cells?

They can magnify up to 100,000 times. They make it possible for scientists to see the internal structures of a cell.

Thiomargarita namibiensis is a large single-cell organism, which can reach lengths of 700 μm. 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...Like the other prokaryotes, Thiomargarita namibiensis does not possess a nucleus or any other organelles thus is classified as a bacterium.

You are a scientist looking at a novel cell, how would you differentiate between whether the cell you are observing is a prokaryotic or eukaryotic cell?

You would first look to see if the cell has a true nucleus. Then, you would look for other membrane bound organelles. Size could also help to determine since prokaryotes are typically smaller.