Mastering Biology Ch 06

Many cellular structures and molecules have specific locations within the cell to perform their functions. Sort the structures and molecules according to where they are found in the cell.

Cytoplasm: phosphofructokinase, ribosome Internal membrane of mitochondrion and/or chloroplast: photosystem I, ATP synthase Stroma (chloroplast): rubisco Matrix (mitochondrion): isocitrate dehydrogenase

Which of these is the double membrane that encloses the nucleus? a. B b. A c. E d. C e. D

c. E - This is the nuclear envelope.

Can you match these prefixes, suffixes, and word roots with their definitions? -plasm hypo- phago- -phyll sym- hyper- micro-

small: micro- below, less than: hypo- formed substance: -plasm same: sym- eat: phago- above, greater than: hyper- leaf: -phyll

The nuclear pore complex regulates molecular traffic in and out of the nucleus. Which molecules and cellular components pass through the nuclear pore during normal cellular activity? Select all that apply. - nucleosomes - DNA - ribosomal subunits - mRNA

- ribosomal subunits - mRNA Ribosomal subunits (made from rRNA and protein) and mRNA are synthesized within the nucleus for use in the cytoplasm. The gateway between the nucleus and the cytoplasm is the nuclear pore.

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. Word Bank: - intermediate filaments - microtubules - microfilaments

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.

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

C. The plasma membrane is selectively permeable.

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.

The DNA-containing region of this bacterial cell is indicated by the letter _____. A. B. C. D. E.

D. The nucleoid region contains DNA.

Cellular proteins may be embedded within a cellular membrane (integral protein), loosely bound to the surface of a cellular membrane (peripheral protein), or not associated with a membrane at all (free protein). Identify the types of proteins shown in the figure below, which shows an internal chloroplast membrane. Match the type of protein on the left with the examples on the right. Terms may be used once, more than once, or not at all.

Free Protein: Rubisco Peripheral Protein: NADP+ reductase, Pc Integral Protein: ATP synthase, Photosystem II

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: chloroplast, central vacuole, cellulose cell wall Animal Cell only: centriole Both: mitochondrion, nucleus, plasma membrane, cytoskeleton, 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.

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, poison detoxification, calcium ion storage 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.

Choose the letter that indicates the organelle that contains most of a cell's DNA. a. C b. A c. B d. D e. E

a. C - The nucleus contains most of a cell's DNA.

Motor proteins are responsible for moving vesicles and organelles within the cell. Motor proteins move along protein "tracks." In the example shown in the Visualizing figure, what are those tracks made of? a. actin b. receptor proteins c. transport proteins d. tubulin

a. actin As they move vesicles and organelles within the cell, the motor proteins shown in the Visualizing figure are "walking" along microfilaments made of actin.

Which of these organelles produces H2O2 as a by-product? a. peroxisome b. mitochondrion c. centrioles d. flagellum e. nucleus

a. peroxisome Peroxisomes produce hydrogen peroxide as a by-product of their metabolic processes.

The _____ is the bacterial structure that acts as a selective barrier, allowing nutrients to enter the cell and wastes to leave the cell. a. plasma membrane b. nucleoid region c. ribosome d. pili e. cell wall

a. plasma membrane The plasma membrane is selectively permeable.

In a bacterium, where are proteins synthesized? a. ribosomes b. nucleus c. peroxisome d. nucleoid region e. capsule

a. ribosomes Ribosomes are involved in the manufacture of polypeptides (proteins).

_____ are the sites of protein synthesis. a. ribosomes b. mitochondria c. peroxisomes d. microfilaments e. Golgi apparatuses

a. ribosomes Ribosomes are the site of protein synthesis.

Where is calcium stored?

a. smooth endoplasmic reticulum In addition to storing calcium, the smooth ER also plays a role in detoxification and lipid synthesis.

What is a function of a bacterium's capsule? a. propulsion b. DNA storage c. protection d. protein synthesis

c. protection A bacterium's capsule has a protective role.

Can you match these prefixes, suffixes, and word roots with their definitions? -some (or soma-) chrom- -elle inter- aqu- (or aqua-) bi- trans-

across: trans- water: aqu- (or aqua-) color: chrom- two: bi- between: inter- little, small: -elle body: -some (or soma-)

Which of these structures stores, modifies, and packages products? a. B b. A c. C d. E e. D

b. A - The Golgi apparatus modifies, stores, and packages products of the ER.

Which of these are hollow rods that shape and support the cell? a. microfilaments b. plasma membrane c. chloroplasts d. peroxisomes e. microtubules

e. microtubules Microtubules are rods that also play a role in organelle movement.

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? - lysosomal enzyme - insulin - actin - ribosomal protein - DNA polymerase - ER protein

lysosomal enzyme, insulin, ER protein 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.

Can you match these prefixes, suffixes, and word roots with their definitions? endo- mito- eu- chloro- -cyte (or cyto-) ex- a- (or an-)

true, good: eu- out of: ex- cell: -cyte (or cyto-) without, lack of, not: a- (or an-) thread: mito- inside, inner: endo- green: chloro-

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 solar energy into chemical energy. - They are the sites of reactions that convert chemical energy from food molecules to ATP. - They have membranous sacs called thylakoids that are surrounded by a fluid called stroma. - They contain the green pigment chlorophyll. - Their inner membrane has infoldings called cristae.

- 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 - 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.

The cellular organization and extracellular environments of plants and animals are very different. Determine the type of structure for each one and if the cell is plant or animal. 1) Membrane protein complexes that strengthen the adhesion between adjacent cells, like rivets, to protect against pulling forces. 2) Small channels that form across the plasma membranes of adjacent cells; especially important in intercellular communication. 3) Membrane proteins that create a watertight seal between cells. 4) Small channels between cells that are otherwise surrounded by walls; enable movement of water and solutes between cells. 5) A polysaccharide that is used to synthesize cell walls, which protect cells and help maintain their shape. 6) Long fibers of protein found in the extracellular matrix that provide structural support for cells.

1.) Structure: Desmosome, Type: Animal 2.) Structure: Gap Junctions, Type: Animal 3.) Structure: Tight Junctions, Type: Animal 4.) Structure: Plasmodesmata, Type: Plant 5.) Structure: Cellulose, Type: Plant 6.) Structure: Collagen, Type: Animal 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.

Cellular structures and molecules vary greatly in size, number, and distribution. Use the enlargements in the figure to rank the following structures and molecules from largest to smallest. - ATP synthase - Rubisco - Ribosome - tRNA - Phosphofructokinase

Largest structure or molecule to Smallest: Ribosome, ATP synthase, Rubisco, Phosphofructokinase, tRNA

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: nucleolus, lysosome, mitochondria Both: flagella, plasma membrane, ribosomes 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.

Starts at protein synthesis: a. endoplasmic reticulum b. cis Golgi cisternae c. medial Golgi cisternae d. trans Golgi cisternae e. plasma membrane Ends in 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.

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.

_____ is/are identical in structure to centrioles. a. Mitochondria b. Basal bodies c. Microfilaments d. Chromatin e. Nuclear envelopes

b. Basal bodies Basal bodies and centrioles have identical structures.

Which of these organelles carries out cellular respiration? a. chromatin b. mitochondrion c. nucleolus d. smooth endoplasmic reticulum e. ribosomes

b. mitochondrion Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP.

Ribosomal subunits are manufactured by the _____. a. rough endoplasmic reticulum b. nucleolus c. lysosome d. smooth endoplasmic reticulum e. peroxisome

b. nucleolus Ribosomes are manufactured by the nucleolus.

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. Time ER Golgi Cytoplasm Lysosomes Extracellular space 3 min 162 7 21 5 4 20 min 73 88 17 10 8 60 min 9 35 14 112 13 120 min 11 23 18 151 10 Based on these data, what is the most likely function of the cells in this experiment? a. secretion b. phagocytosis c. detoxification d. muscle contraction

b. 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.

Which of these organelles manufactures proteins bound for secretion out of the cell? a. lysosomes b. rough endoplasmic reticulum c. nucleolus d. Golgi apparatus

b. rough endoplasmic reticulum The ribosomes associated with the rough ER synthesize secretory proteins bound for the exterior of the cell. Further processing and packaging occurs in the Golgi apparatus.

What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?\ a. capsule b. pili c. cell wall d. flagella e. nucleoid region

c. cell wall The cell wall is a rigid supporting structure.

Where is a bacterial cell's DNA found? a. ribosomes b. nucleus c. peroxisome d. nucleoid region e. capsule

d. nucleoid region Bacteria lack a nucleus; their DNA is found in the nucleoid region.

The _____ is a selective barrier, regulating the passage of material into and out of the cell. a. nucleus b. chloroplast c. lysosome d. plasma membrane e. nuclear envelope

d. plasma membrane The plasma membrane regulates the passage of material into and out of the cell.

Which of these provides the cell with structural support? a. A b. C c. B d. E e. D

e. D - Microfilaments are a component of the cytoskeleton.

_____ are surface appendages that allow a bacterium to stick to a surface. a. Flagella b. Cell walls c. Mitochondria d. Ribosomes e. Fimbriae

e. Fimbriae Fimbriae enable bacterial cells to stick to a surface.

The _____ is composed of DNA and protein. a. mitochondrion b. centriole c. ribosome d. flagellum e. chromatin

e. chromatin Chromatin is composed of DNA and protein.

The cilia and flagella of eukaryotic cells are composed of _____. a. tonofilaments b. pili c. microfilaments d. intermediate filaments e. microtubules

e. microtubules Eukaryotic cilia and flagella are composed of microtubules.