Ch. 6 A Tour of the Cell #2
Ribosomal subunits are manufactured by the _____.
nucleolus Ribosomes are manufactured by the nucleolus.
Which structure is not part of the endomembrane system?
chloroplast
_____ aid in the coordination of the activities of adjacent animal cells.
Gap (communicating) junctions Gap junctions allow for the passage of material between cells, thus facilitating communication between these cells.
Which statement about extracellular structures (plant cell walls and the extracellular matrix of animal cells) is correct? See Concept 6.7
Information can be transmitted from these extracellular structures to the cytoplasm. Extracellular structures provide mechanical and chemical signals that are transmitted across the plasma membrane to the interior of the cell.
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?
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.
Can you match these prefixes, suffixes, and word roots with their definitions?
thread: mito- true, good: eu- cell: -cyte (or cyto-) without, lack of, not: a- (or an-) green: chloro- inside, inner: endo- out of: ex-
Which of these cell junctions form a barrier to the passage of materials?
tight junctions Tight junctions form a barrier that prevents fluids from moving between cells.
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.
The cellular organization and extracellular environments of plants and animals are very different.
1. Membrane protein complexes that strengthen the adhesion between adjacent cells, like rivets, to protect against pulling forces structure: desmosomes; animal 2. Small channels that form across the plasma membranes of adjacent cells; especially important in intercellular communication structure: gap junctions; animal 3. Membrane proteins that create a watertight seal between cells structure: tight junctions; animal 4. Small channels between cells that are otherwise surrounded by walls; enable movement of water and solutes between cells structure: plasmodesmata; plant 5. A polysaccharide that is used to synthesize cell walls, which protect cells and help maintain their shape structure: cellulose; plant 6. Long fibers of protein found in the extracellular matrix that provide structural support for cells structure: collagen; 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.
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.
Which of these structures stores, modifies, and packages products?
A The Golgi apparatus modifies, stores, and packages products of the ER.
_____ is/are identical in structure to centrioles.
Basal bodies Basal bodies and centrioles have identical structures.
Which of the following are common traits of chloroplasts and mitochondria? See Concept 6.5
Both have their own DNA
Choose the letter that indicates the organelle that contains most of a cell's DNA.
C The nucleus contains most of a cell's DNA.
Many cellular structures and molecules have specific locations within the cell to perform their functions.
Cytoplasm: - ribosome - phosphofructokinase Internal membrane of mitochondrion and/or chloroplast: - ATP synthase - photosystem I Stroma (chloroplast): - rubisco Matrix (mitochondrion): - isocitrate dehydrogenase
Which of these provides the cell with structural support?
D Microfilaments are a component of the cytoskeleton.
Which of these is the double membrane that encloses the nucleus?
E This is the nuclear envelope.
Which of these are hollow rods that shape and support the cell?
Microtubules are rods that also play a role in organelle movement.
Which of the following functions is NOT associated with the cytoskeleton in eukaryotic cells? See Concept 6.6
Movement of RNA molecules from the nucleus to the cytoplasm
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.
Peripheral protein: NADP+ reductase Peripheral protein: Pc Integral protein: ATP synthase Integral protein: Photosystem II Free protein: Rubisco
Which of these organelles produces H2O2 as a by-product?
Peroxisomes produce hydrogen peroxide as a by-product of their metabolic processes.
Mitochondria are found in _____. See Concept 6.5
Plant and animal cells
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.
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 - Chloroplast - Central vacuole Animal cell only: - Centriole Both: - Nucleus - Plasma membrane - Mitochondrion - Cytoskeleton - Endoplasmic reticulum - Golgi apparatus 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.
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.
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: 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.
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.
SER: synthesizes lipids nucleus: assembles ribosomes cytoskeleton: defines cell shape RER: produces secretory proteins golgi: modifies and sorts proteins lysosomes: digests proteins mitochondria: 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.
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.
Which statements are true for chloroplasts?
They are the sites of reactions that convert solar energy into chemical energy. They contain the green pigment chlorophyll. They have membranous sacs called thylakoids that are surrounded by a fluid called stroma. 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.
Can you match these prefixes, suffixes, and word roots with their definitions?
below, less than: hypo- leaf: -phyll same: sym- eat: phago- formed substance: -plasm above, greater than: hyper- small: micro-
The _____ is composed of DNA and protein.
chromatin Chromatin is composed of DNA and protein.
Can you match these prefixes, suffixes, and word roots with their definitions?
color: chrom- across: trans- body: -some (or soma-) water: aqu- (or aqua-) little, small: -elle two: bi- between: inter-
The primary role of _____ is to bind animal cells together.
desmosomes The primary role of desmosomes (anchoring junctions) is to bind cells together.
The cilia and flagella of eukaryotic cells are composed of _____.
microtubules
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
mitochondria
Which structure is common to plant and animal cells?
mitochondrion
Which of these organelles carries out cellular respiration?
mitochondrion Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP.
Which cell would be best for studying lysosomes?
phagocytic white blood cell
The _____ is a selective barrier, regulating the passage of material into and out of the cell.
plasma membrane The plasma membrane regulates the passage of material into and out of the cell.
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?
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.
Which of the following is present in a prokaryotic cell?
ribosome
Cellular structures and molecules vary greatly in size, number, and distribution. rank from large to small
ribosome ATP synthase rubisco phosphofructokinase tRNA
_____ are the sites of protein synthesis.
ribosomes Ribosomes are the site of protein synthesis.
Which of these organelles manufactures proteins bound for secretion out of the cell?
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.
Where is calcium stored?
smooth endoplasmic reticulum In addition to storing calcium, the smooth ER also plays a role in detoxification and lipid synthesis.