Mastering Biology CH. 4

Which cell would be best for studying lysosomes? A. phagocytic white blood cell B. bacterial cell C. nerve cell D. muscle cell

A.

Which structure-function pair is MISMATCHED? A. microtubule; muscle contraction B. Golgi; protein trafficking C. ribosome; protein synthesis D. nucleolus; production of ribosomal subunits

A.

The diameter of a typical eukaryotic cell is approximately ten times the diameter of a typical prokaryote. What is the ratio of the volume of typical eukaryotic:prokaryotic cells? A. 100:1 B. 10:1 C. 1000:1

C. As the diameter of a cell increases, other dimensions also change. For two cells of approximately equivalent shape but different diameters, surface area increases as the square of diameter, and volume increases as the cube of diameter. Thus, if a eukaryotic cell is ten times the diameter of a prokaryote, its surface area will be one hundred (102) times that of the prokaryote and its volume will be one thousand (103) times that of the prokaryote.

Which of the following correctly matches an organelle with its function? A. ribosome ... manufacture of lipids B. nucleus ... cellular respiration C. mitochondrion ... photosynthesis D. lysosome ... movement E. central vacuole ... storage

E. But remember, plant cells have a central vacuole, whereas most animal cells have several smaller vacuoles located throughout the cytoplasm.

Which of the following functions is NOT associated with the cytoskeleton in eukaryotic cells? A. determining the shape of animal cells B. the contraction of muscle cells in animals C. the beating of cilia or flagella D. maintaining the position of the nucleus in the cell E. movement of RNA molecules from the nucleus to the cytoplasm

E. RNA molecules exit the nucleus via nuclear pores, and the cytoskeleton is not involved.

Which of the following clues would tell you if a cell is prokaryotic or eukaryotic? A. the presence or absence of ribosomes B. the presence or absence of a rigid cell wall C. whether or not the cell carries out cellular metabolism D. whether or not the cell contains DNA E. whether or not the cell is partitioned by internal membranes

E. Prokaryotic cells lack any internal membranous compartmentalization.

Drag each cell structure to the appropriate bin. If a structure is found in both plant cells and animal cells, drag it to the "both" bin. A: Chloroplasts B: Cellulose Cell Wall C: Central Vacuole D: Centriole E: Plasma membrane F: Cytoskeleton G: Mitochondria H: Golgi Apparatus I: ER J: Nucleus

Plant Cells Only: A, B, C Animal Cells Only: D Both: E, F, G, H, I, J Plant cells and animal cells have more in common than they have differences. Nevertheless, plant cells' unique structures play important roles. Photosynthesis occurs in plant cells' chloroplasts. The plant cell's central vacuole takes up most of the space within the cell and serves a variety of functions, including storage and hydrolysis of organic compounds. Plant cell walls, which are composed primarily of cellulose, protect the cells from damage and maintain their shape. Cellulose is the most abundant organic compound on the planet.

Drag the correct description under each cell structure to identify the role it plays in the plant cell.

Plant cell wall- strong, protective structure made from cellulose fibrils Central vacuole-regulates cytoplasm composition, creates internal pressure, and stores cell compounds Chloroplast-makes sugar by converting light energy into chemical energy Mitochondrion-produces chemical energy (ATP) that can power the cell Golgi apparatus-modifies and packages proteins Each organelle in a plant cell carries out a specific function. Mitochondria and the Golgi apparatus serve the same functions in both plant cells and animal cells

Two fundamental types of cells are known to exist in nature: prokaryotic cells and eukaryotic cells (like the one shown in the Tour of an Animal Cell animation). Both prokaryotic and eukaryotic cells carry out all of the processes necessary for life, but they differ in some important ways. In this activity, you will identify which cell structures are found only in prokaryotic cells, only in eukaryotic cells, or in both types of cells. Drag each cell structure to the appropriate bin.

Prokaryotic only: nucleoid Eukaryotic only: Lysosome, Mitochondria, Nucleolus Both: Ribosomes, Plasma membrane, Flagella Only bacteria and archaea have prokaryotic cells, which lack a nucleus and other membrane-enclosed organelles. Prokaryotic cells are smaller and, at the level of the individual cell, are generally less versatile than eukaryotic cells, which compartmentalize many of their metabolic pathways into organelles. Nevertheless, prokaryotes are indispensable in every known ecosystem, and certain species are capable of surviving in some of the harshest and most nutrient-limiting environments on Earth.

Proteins that are secreted from a eukaryotic cell must first travel through the endomembrane system. Drag the labels onto the diagram to identify the path a secretory protein follows from synthesis to secretion. Not all labels will be used

Protein synthesis a. endoplasmic reticulum b. cis Golgi cisternae c. medial Golgi cisternae d. trans Golgi cisternae e. plasma membrane Extracellular space As they are being synthesized, secretory proteins enter the lumen of the endoplasmic reticulum. From the ER, vesicles transport these proteins to the Golgi, where they are sequentially modified and concentrated in a cis-to-trans direction. Secretory vesicles bud from the Golgi and move along cytoskeletal filaments to eventually fuse with the plasma membrane, secreting their protein cargo. Each of these transport steps requires specialized proteins to ensure that the cargo is sent to the proper location and is able to fuse with the target membrane.

The various parts of the endomembrane system serve different functions in the cell. In this activity, you will identify the roles of each part of the endomembrane system. Drag each function to the appropriate bin.

Smooth ER: Lipid synthesis, Calcium ion storage, Poison detoxification Rough ER: Protein synthesis Golgi apparatus: Protein modification and sorting, Cisternal maturation Lysosomes: Autophagy, Macromolecule digestion The endomembrane system is critical for the synthesis, processing, and movement of proteins and lipids in the cell. The smooth ER functions mainly in lipid synthesis and processing. The rough ER is the site of secretory protein synthesis. These proteins are processed further in the Golgi apparatus, from where they are dispatched in vesicles to the plasma membrane. Lysosomes, whose enzymes and membranes are made and processed by the rough ER and Golgi apparatus, function in the hydrolysis of macromolecules, such as in phagocytosis and autophagy.

Structure and function of the chloroplast The structure of a chloroplast is closely tied to its function as the site of photosynthesis. Some of the following statements are true for chloroplasts; others are true for mitochondria. Which statements are true for chloroplasts? Select the three that apply.

Their matrix contains enzymes that function in cellular respiration. They are the sites of reactions that convert chemical energy from food molecules to ATP. x They are the sites of reactions that convert solar energy into chemical energy. x They contain the green pigment chlorophyll. x They have membranous sacs called thylakoids that are surrounded by a fluid called stroma. Their inner membrane has infoldings called cristae. The chloroplast and the chemical reactions associated with it are extremely important for all living things. The photosynthetic reactions are responsible for converting solar energy into chemical energy that is used not only by the cells in which photosynthesis occurs but also by other organisms. For example, all of the foods you eat can be traced back to a plant or other photosynthetic organism. Furthermore, the chloroplast and its reactions have had a profound influence on the constitution of Earth's atmosphere due to the fact that oxygen is a byproduct of photosynthesis.

To understand how cells function as the fundamental unit of life, you must first become familiar with the individual roles of the cellular structures and organelles. Drag the labels on the left onto the diagram of the animal cell to correctly identify the function performed by each cellular structure.

a. synthesizes lipids b. assembles ribosomes c. defines cell shape d. produces secretory proteins e. modifies and sorts proteins f. digests proteins g. generates ATP The eukaryotic cell has well-defined structures that serve discrete functional roles. An organism's ability to perform essential functions such as metabolism, reproduction, and maintaining homeostasis depends on the proper functioning of structures at the cellular level. Although these structures are present in all animal cells, their number or activity level may vary depending on the cell type. For example, cells in the pancreas that produce the hormone insulin have extensive rough endoplasmic reticula, while muscle cells contain numerous mitochondria.

Scientists can track the movement of proteins through the endomembrane system using an approach known as a pulse-chase experiment. This experiment involves • the "pulse" phase: Cells are exposed to a high concentration of a radioactively labeled amino acid for a short period to tag proteins that are being synthesized. • the "chase" phase: Any unincorporated radioactively labeled amino acids are washed away and large amounts of the same, but unlabeled, amino acid are added. Only those proteins synthesized during the brief pulse phase are radioactively tagged. These tagged proteins can be tracked through the chase period to determine their location in the cell. The data below were obtained from a pulse-chase experiment in which cells were examined at different times during the chase period. The numbers represent the radioactivity (measured in counts per minute) recorded at each of the indicated sites. The higher the number, the greater the radioactivity. Based on these data, what is the most likely function of the cells in this experiment?

x phagocytosis muscle contraction detoxification secretion The cells in this experiment were macrophages. These immune system cells have many lysosomes for the destruction of bacteria and other invaders brought into the cell via phagocytosis. The enzymes (hydrolases) that carry out this catabolic activity are synthesized in the endoplasmic reticulum, modified in the Golgi, and transported to the lysosomes.

The cytoskeleton of a eukaryotic cell plays a major role in organizing the structures and activities of the cell. The cytoskeleton consists of three main types of fibers: microfilaments, intermediate filaments, and microtubules. The three types of fiber differ in size, composition, and the functions they perform in the cell. Drag the terms on the left to the appropriate blanks in the sentences on the right. Terms can be used once, more than once, or not at all.

1. In eukaryotic flagella, the fibers that slide past one another due to the activity of dynein proteins are microtubules. 2. Many cell organelles, most notably the nucleus, are anchored by intermediate filaments which are assembled from a diverse class of proteins. 3. Centrosomes are sites where protein dimers assemble into microtubules. 4. The extension of pseudopodia in amoeba is due to the regulated assembly and destruction of microfilaments. 5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermediate filaments. 6. During muscle contractions, myosin motor proteins move across tracks of microfilaments. The eukaryotic cytoskeleton is appropriately named because, at the cellular level, these fibers and their associated motor proteins perform similar roles as an animal's musculoskeletal system. Microfilaments are responsible for cell locomotion and the cell's structural characteristics. Microtubules serve as intracellular highways for transporting vesicles and organelles; they are also required for cellular locomotion via flagella and cilia. Intermediate filaments are rope-like structures that anchor organelles and intercellular junctions called desmosomes. They are specialized for bearing tension.

A cell has formed a food vacuole as it ingested a food particle. Which of the following events is associated with the breakdown of that food particle? A. Digestion of the food particle occurs in a vesicle enclosed by a membrane that separates the digestion from the cytoplasm. B. Proteins for digestion of the food particle were initially processed in mitochondria. C. Enzymes for the breakdown of the food are delivered to the food vacuole from the cytosol. D. Proteins for digestion of the food are made by ribosomes in the Golgi apparatus. E. The membrane of the food vacuole is derived from the cell wall.

A. Digestion occurs within a vesicle. If the digestive enzymes were in the cytosol, they might degrade essential components of the cell.

Which statement about extracellular structures (plant cell walls and the extracellular matrix of animal cells) is correct? A. Information can be transmitted from these extracellular structures to the cytoplasm. B. Proteins and lipids are common components of extracellular structures. C. Extracellular structures store energy in the form of polysaccharides for subsequent metabolism by the cell. D. All extracellular structures form barriers to separate adjacent cells. E. Extracellular structures regulate the passage of water molecules across the cell membrane.

A. Extracellular structures provide mechanical and chemical signals that are transmitted across the plasma membrane to the interior of the cell.

Choose the best description of the cell cytoskeleton. A. The cell cytoskeleton is a dynamic network of fibers that can be quickly dismantled and reassembled to change cell shape and the position of cell components. B. The cell cytoskeleton is similar to an animal skeleton in providing rigid internal support and structure to the cell. C. The cell cytoskeleton serves as permanent scaffolding to anchor cell components into position within the cell cytoplasm.

A. Read about the dynamic nature of the cytoskeleton and the interactions between its network of fibers.

Identify the correct statement about differences between rough and smooth endoplasmic reticulum (ER). A. The outer surface of smooth ER lacks ribosomes, whereas the outer surface of rough ER has ribosomes. B. Rough ER consists of a network of membranous tubules and sacs called cisternae, whereas smooth ER is less complex. C. Smooth ER is part of the endomembrane system of the eukaryotic cell, and rough ER is not.

A. Review this structural difference between smooth and rough ER.

Which of the following are common traits of chloroplasts and mitochondria? A. Both have their own DNA. B. Both are surrounded by a single membrane. C. Both reproduce by meiosis. D. Both are found in plant and animal cells. E. Proteins for both are synthesized on ribosomes in the rough ER.

A. Mitochondria and chloroplasts contain their own DNA and ribosomes.

Which statement correctly describes an endomembrane function? A. The lumen of the endoplasmic reticulum (ER) is continuous with the cell nucleus. B. Products of the ER are usually modified during their transit from the cis to the trans region of the Golgi apparatus. C. Secretory proteins in transit from one part of the cell to another are carried in lysosomes.

B. The cis and trans regions of the Golgi apparatus act as receiving and shipping departments. As molecules move from the cis to the trans face of the Golgi apparatus, they are usually modified.

Select the correct statement describing cellular structure or function. A. Mitochondria and chloroplasts are part of the endomembrane system of the eukaryotic cell. B. Plant and animal cells both carry out cellular respiration, producing ATP. C. Only plant cells contain chloroplasts, and only animal cells contain mitochondria.

B. All plant and animal cells carry out cellular respiration in mitochondria, producing ATP.

Cyanide binds to at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide will be found within the __________. A. lysosomes B. ribosomes C. mitochondria D. peroxisomes

C.

Which of the following is present in a prokaryotic cell? A. mitochondrion B. chloroplast C. ribosome D. nuclear envelope

C.

Which statement correctly describes the nuclear envelope of a eukaryotic cell? A. The nuclear envelope is a single membrane, consisting of a phospholipid bilayer. B. Plasmadesmosomes in the nuclear envelope permit the exchange of macromolecules between the nucleus and the cytoplasm. C. All of the proteins of the cell are synthesized on ribosomes bound on the nuclear envelope. D. The nuclear envelope is continuous with the endoplasmic reticulum. E. The outer layer of the nuclear envelope is coated with laminin.

D.

5. A polysaccharide that is used to synthesize cell walls, which protect cells and help maintain their shape

Structure: cellulose Plant or Animal: plant

6. Long fibers of protein found in the extracellular matrix that provide structural support for cells

Structure: collagen Plant or Animal: animal

1. Membrane protein complexes that strengthen the adhesion between adjacent cells, like rivets, to protect against pulling forces.

Structure: desmosomes Plant or Animal: animal

2. Small channels that form across the plasma membranes of adjacent cells; especially important in intercellular communication

Structure: gap junctions Plant or Animal: animal

4. Small channels between cells that are otherwise surrounded by walls; enable movement of water and solutes between cells.

Structure: plasmodesmata Plant or Animal: plant

3. Membrane proteins that create a watertight seal between cells.

Structure: tight junctions Plant or Animal: animal

All proteins are synthesized by ribosomes in the cell. Some ribosomes float freely in the cytosol, while others are bound to the surface of the endoplasmic reticulum. Most proteins made by free ribosomes function in the cytosol. Proteins made by bound ribosomes either function within the endomembrane system or pass through it and are secreted from the cell. Which of the following proteins are synthesized by bound ribosomes? Select all that apply.

actin x ER protein ribosomal protein DNA polymerase x lysosomal enzyme x insulin Most proteins that function in the cytosol (such as actin) or in the nucleus (such as DNA polymerase) are synthesized by free ribosomes. Proteins that function within the endomembrane system (such as lysosomal enzymes) or those that are destined for secretion from the cell (such as insulin) are synthesized by bound ribosomes. As a protein destined for the endomembrane system is being synthesized by a ribosome, the first amino acids in the growing polypeptide chain act as a signal sequence. That signal sequence ensures that the ribosome binds to the outer membrane of the ER and that the protein enters the ER lumen.