MasteringBiology Ch)4

Which molecules do not normally cross the nuclear membrane?

DNA All processes involving DNA take place in the nucleus

What is the function of a bacterium's capsule?

protection

Select the correct statement describing cellular structure or function.

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

Choose the best description of the cell cytoskeleton.

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.

Identify the correct statement about differences between rough and smooth endoplasmic reticulum (ER).

The outer surface of smooth ER lacks ribosomes, whereas the outer surface of rough ER has ribosomes. Review this structural difference between smooth and rough ER.

The structure that regulates the passage of material into and out of this bacterial cell is indicated by the letter _____.

The plasma membrane is selectively permeable.

True or false? Large proteins containing a nuclear localization signal (NLS) bind to the nuclear pore and enter the nucleus without any expenditure of energy.

False Cytoplasmic proteins called importins bind to large proteins containing an NLS and mediate their transport across the nuclear membrane through an active transport (energy-requiring) process.

_____ are surface appendages that allow a bacterium to stick to a surface.

Fimbriae

Which statement correctly describes an endomembrane function?

Products of the ER are usually modified during their transit from the cis to the trans region of the Golgi apparatus. 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.

The primary role of _____ is to bind animal cells together. a.) tight junctions b.) gap (communicating) junctions c.) desmosomes d.) the cytoskeleton e.) plasmodesmata

The primary role of desmosomes (anchoring junctions) is to bind cells together.

Tour of a Plant Cell: Structures and Functions (BioFlix tutorial) Part C - Structure and function of the mitochondria

Their matrix contains enzymes that function in cellular respiration. They are the sites of reactions that convert chemical energy from food molecules to ATP. Their inner membrane has infoldings called cristae.

What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?

cell wall

Which organelle plays a role in intracellular digestion?

lysosome The prefix "lyso-" means decomposition

Tour of a Plant Cell: Structures and Functions (BioFlix tutorial) Part B - Plant organelle functions

plant cell wall - strong protective stucture made from cellulose fibrils central vacuole - regulates cytoplasm composition, creates internal pressure, and stores cell compounds chlorplast - makes sugar by converting light energy into chemical energy. mitochondrion - produces chemical energy (ATP) that can power the cell Golgi apparatus - modifies and packages protiends 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.

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?

1000 : 1 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.

_____ aid in the coordination of the activities of adjacent animal cells. a.) Plasmodesmata b.) Keratin fibers c.) Gap (communicating) junctions d.) Desmosomes e.) Tight junctions

Gap junctions allow for the passage of material between cells, thus facilitating communication between these cells.

Tour of a Plant Cell: Structures and Functions (BioFlix tutorial) Part C - Structure and function of the chloroplast The structure of a chloroplast is closely tied to its function as the site of photosynthesis.

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

Which of these cell junctions form a barrier to the passage of materials? a.) desmosomes (anchoring junctions) b.) gap (communicating) junctions c.) keratin fibers d.) plasmodesmata e.) tight junctions

Tight junctions form a barrier that prevents fluids from moving between cells.

In experiments to test whether a protein can enter the nucleus, why would proteins be labeled with fluorescent molecules?

To make the proteins easy to see Fluorescent tags make the location of the proteins easy to visualize.

Tour of an Animal Cell: Structures and Functions (BioFlix tutorial) Part A - Animal cell structures and functions 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. smooth ER - synthesizes lipids b. nucleolus - assembles ribosomes c. defines cell shape d. rough ER - produces secretory proteins e. golgi apparatus - modifies and sorts proteins f. - digests proteins g. mitochondrion - 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.

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

microtubules Eukaryotic cilia and flagella are composed of microtubules.

Tour of a Plant Cell: Structures and Functions (BioFlix tutorial) Part A - Comparing plant cells and animal cells 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. 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.

plant cell only - cellulose cell wall, central vacuole, chloroplast. animal cell only - centriole BOTH - mitochondrion. nucleus, Golgi apparatus, endoplasmic reticulum, plasma membrane, cytoskeleton 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.

Tour of an Animal Cell: Structures and Functions (BioFlix tutorial) Part C - Role of the eukaryotic cytoskeleton 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 intermidiate 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 microfililaments. 5. The only cytoskeletal fibers not associated with intracellular movement or whole cell locomotion are the intermidiate filaments . 6. During muscle contractions, myosin motor proteins move across tracks of microfililaments. 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.

Tour of an Animal Cell: Structures and Functions (BioFlix tutorial) Part B - Comparing eukaryotic and prokaryotic 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.

Which of the following statements about the nuclear envelope is false? The nuclear envelope is continuous with the Golgi apparatus. The nuclear envelope is composed of two lipid bilayers. Nuclear pores are made up of a group of proteins that are collectively called the nuclear pore complex. Molecules pass into and out of the nucleus through nuclear pores.

The nuclear envelope is continuous with the Golgi apparatus.

In a bacterium, where are proteins synthesized?

ribosomes

steps leading to the synthesis of a polypeptide is _________.

transferring of information from DNA to messenger RNA --> RNA leaves Nucleus and carries information to ribosomes --> translation of an RNA nucleotide sequence into a sequence of amino acids --> linking of nucleotides to form a polypeptide