Mastering Biology Chp. 4 HW

What is the approximate volume of the budding cell?

14 µm^3

You have a distant cousin, age 4, who is always tired and fatigued and is not able to play games and sports like other healthy children. He most likely has an enzyme deficiency or defect associated with which intracellular organelle?

Mitochondria

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

gap junctions

3) Membrane proteins that create a watertight seal between cells

light junctions

Which organelle plays a role in intracellular digestion?

lysosome (The prefix "lyso-" means decomposition)

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.

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.)

Approximately how much additional cytoplasm will the budding cell have to synthesize as it grows to the size of the mature cell?

19 µm^3

Approximately how much additional area of plasma membrane will the budding cell have to synthesize as it grows to the size of the mature cell?

22 µm^2

What is the approximate surface area of the budding cell? (Remember that you approximated the diameter of the budding cell to be 3 µm.)

28 µm^2

What is the approximate diameter of the budding cell?

3 µm

The shape of a yeast cell can be approximated by a sphere, so you can calculate the volume of each cell using the formula for the volume of a sphere: A sphere with the radius and diameter shown V=(4/3)πr^3 Note that π (the Greek letter pi) is a constant with an approximate value of 3.14, and r stands for radius, which is half the diameter. What is the approximate volume of the mature parent cell?

33 µm^3

Note that the scale bar under the photo is labeled 1 μm (micrometer). The scale bar works the same way as a scale on a map, where, for example, 1 inch equals 1 mile. In this case the bar represents a much smaller distance. What is the approximate diameter of the mature parent cell?

4 µm

As the new cell grows, its plasma membrane needs to expand to contain the increased volume of the cell. Calculate the surface area of each cell using the formula for the surface area of a sphere: A=4πr^2 What is the approximate surface area of the mature parent cell? (Remember that you approximated the diameter of the mature parent cell to be 4 µm.)

50 µm^2

The cellular organization and extracellular environments of plants and animals are very different. (1-6 below)

A primary distinction between plant cells and animal cells is the fact that plant cells are surrounded by cell walls. If it were not for plasmodesmata, the cell walls would essentially imprison the plant's cells, making intercellular communication and the distribution of nutrients nearly impossible. Animal cells have a variety of intercellular junctions, including tight junctions, desmosomes, and gap junctions. The gap junctions of animal cells are most similar to the plasmodesmata of plants. Gap junctions tend to be limited to tissues that require rapid and coordinated signal relay systems, such as heart muscle; they play no role in nutrient distribution.

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?

ER protein lysosomal enzyme 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)

Flagella are found in both eukaryotic cells and prokaryotic cells. Despite the functional similarities of all flagella, scientists suspect that eukaryotic and prokaryotic flagella have evolved independently. Why don't they think there is a common evolutionary origin for prokaryotic and eukaryotic flagella?

Eukaryotic flagella undergo an undulating motion and are covered by a plasma membrane; prokaryotic flagella move by rotating and lack a plasma membrane.

What is the function of the nuclear pore complex that is found in all eukaryotes?

It regulates the movement of all molecules into and out of the nucleus.

Plant cells and animal cells share many of the same structures, but each type of cell also has unique structures. In this activity, you will indicate which cell structures are found only in plant cells, only in animal cells, or in both plant and animal cells.

PLANT CELL ONLY: cellulose cell wall central vacuole chloroplast ANIMAL CELL ONLY: centriole BOTH: cytoskeleton plasma membrane nucleus mitochondrion Golgi apparatus endoplasmic reticulum (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.

PROKARYOTIC ONLY: nucleoid EUKARYOTIC ONLY: nucleolus lysosomes mitochondria BOTH: 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.

PROTEIN SYNTHESIS A) ER 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.

SMOOTH ER: lipid synthesis calcium ion storage poison detoxification ROUGH ER: protein synthesis GOLGI APPARATUS: protein modification and sorting cisternal maturation LYSOSOMES: macromolecule digestion autophagy (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)

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.

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.

When the budding cell matures, it will be approximately how many times greater in volume and how many times greater in surface area than its current size?

The new cell will be approximately 2.4 times its current volume and 1.8 times its current surface area.

The structure of a chloroplast is closely tied to its function as the site of photosynthesis. Diagram showing chloroplast structure. Some of the following statements are true for chloroplasts; others are true for mitochondria.

They have membranous sacs called thylakoids that are surrounded by a fluid called stroma. They are the sites of reactions that convert solar energy into chemical energy. They contain the green pigment chlorophyll. (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.)

All of the following are part of a prokaryotic cell except

an endoplasmic reticulum.

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

cellulose

6) Long fibers of protein found in the extra cellular matrix that provide structural support for cells

collagen

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

desmosomes

The cilia and flagella of eukaryotic cells are composed of _____.

microtubules (Eukaryotic cilia and flagella are composed of microtubules)

Researchers tried to explain how vesicular transport occurs in cells by attempting to assemble the transport components. They set up microtubular tracks along which vesicles could be transported, and they added vesicles and ATP (because they knew the transport process requires energy). Yet, when they put everything together, there was no movement or transport of vesicles. What were they missing?

motor proteins

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?

phagocytosis (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)

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

plasmodesmata

Which structure is the site of the synthesis of proteins that may be exported from the cell?

rough ER

Which of the following is a major cause of the size limits for certain types of cells?

the need for a surface area of sufficient area to support the cell's metabolic needs