Review Questions Chp 4 (key)[1]

Review Questions - Chapter 4

Cell Structure and Function Be able to list the three generalizations that together constitute the cell theory.

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1. All organisms are composed of one or more cells. 2. The cell is the smallest unit having the properties of life. 3. The continuity of life arises directly from the growth and division of single cells. List and describe the three major regions that all cells have in common.

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1. A plasma membrane separates each cell from the environment, permits the flow of molecules across the membrane, and contains receptors that can affect the cell's activities. 2. A nucleus or nuc leoid region localizes the hereditary material, which can be copied and read. 3. The cytoplasm contains membrane systems, particles (including ribosomes), filaments (the cytoskeleton), and a semifluid substance.

Cytoplasm is everything between the plasma membrane and the region of ____nucleus______. [p. ] 4. A __prokaryotic________ cell lacks a nucleus. [p. ] 5. Describe the lipid bilayer arrangement for the plasma membrane. 3.

1. The lipid bilayer of plasma membranes forms a boundary between inside and outside of the cell, subdivides the cytoplasm into compartments, and regulates the entry/exit of substances. The hydrophobic tails face each other while the hydrophilic heads face outward and inward. 2. Proteins positioned in the plasma membrane

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serve as channels, pumps, or receptors.

Membrane Proteins Recognition protein

Receptor protein

extracellular environment

lipid bilayer cytoplasm Protein pump across bilayer

Protein channel across bilayer

Protein pump Figure 4.4 Page 57

Describe and list the function(s) of the following membrane proteins: transport, receptor, recognition, and adhesion.

Transport: Passive or active (require ATP to function. This are channel type or “pumps” Receptor: Modified to interact with biochemicals (hormones etc); these signal the cell to act in certain ways (turn on male genes in 6. the case of testosterone) Recognition: These are modified to determine whether or not a cell or a biochemical in a part of the organism (allow cells to stick together, likes to likes, also very important n the immune system. Adhesion: These “stick together” like kind cells such as skin cells. Cell size is necessarily limited because its volume increases with the 7. ___cube_______ but surface area increases only with the __square (of the cell edge)________. [p. ] 8. Briefly describe the operating principles of light microscopes, phase-contrast microscopes, scanning tunneling microscopes, transmission electron microscopes, 2

and scanning electron microscopes.

Light microscopes: Use glass lens to focus photons. Limited to about 2000x Phase-contrast microscopes: Use two contrasting light phases to to elucidate cell interiors with out killing the cells. Scanning tunneling microscopes: Most powerful types of EM’s. These use a beam of photons and quantum physics to “see” down to the atomic realm. Transmission electron microscopes: Use electrons and “electromagnets” . The latter focus the beam of electrons through a thin, metal stained sample and form a “picture of the cell’s interior. Up to 100,000x and more. Scanning electron microscopes: These EMs reflect beams of electrons off the surface of targeted metal coated objects to form a 3D image. Up to 250,000x.

9. Briefly describe the cellular location and function of the organelles typical of most eukaryotic cells: nucleus, ribosomes, endoplasmic reticulum, Golgi body, various vesicles, mitochondria, and the cytoskeleton.

Nucleus: The nucleus controls access to DNA and permits

easier packing of DNA during cell division; it is embedded with in the cytoplasm.

Ribosomes: Ribosomes , either "free" or attached to membranes, are the assembly sites of polypeptide chains.

Endoplasmic reticulum: The endoplasmic reticulum (ER) modifies proteins and is also involved with lipid synthesis. Located within the cytoplasm.

Golgi body: Golgi bodies also modify proteins, sort and ship

proteins, and play a role in the biology of lipids for secretion

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or internal use. Located within the cytoplasm.

Various vesicles: Various vesicles transport, store, and digest

various materials within the cell. Located within the cytoplasm.

Mitochondria: Mitochondria have enzymes responsible for ATP formation. Located within the cytoplasm.

Cytoskeleton: The cytoskeleton determines cell shape and

internal organization; it also provides for motility. Located within the cytoplasm.

In eukaryotic cells, __organelles_______ separate different incompatible chemical reactions in space and time. [p. ] 11. Describe the nature of the nuclear envelope and relate its function to its structure. 1. The nuclear envelope consists of two lipid bilayers with pores. 2. The inner surface has attachment sites for protein 10.

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filaments, which anchor the DNA molecules and keep them organized. 3. The outer surface is studded with ribosomes.

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____Nucleoli______ are sites where the protein and RNA subunits of ribosomes are assembled. [pp. ]

___Chromatin_______ is the cell's collection of DNA molecules and associated 13 . proteins; a __chromosome________ is an individual DNA molecule and associated proteins. [p. ] 14 Explain how the endoplasmic reticulum (rough and smooth types), peroxisomes, Golgi . bodies, lysosomes, and a variety of vesicles function together as the cytomembrane system. A. The endomembrane system is a series of organelles in which lipids are assembled and new polypeptide chains are modified into final proteins. B. Endoplasmic Reticulum 1. The endoplasmic reticulum is a collection of interconnected tubes and flattened sacs that begins at the nucleus and winds its way through the cytoplasm. 2. Two kinds of ER may be found in a cell: a. Rough ER consists of stacked, flattened sacs with many ribosomes attached; oligosaccharide groups are attached to polypeptides as they pass through on their way to other organelles or to secretory vesicles. b. Smooth ER has no ribosomes; it is the area from which vesicles carrying proteins and lipids are budded; it also inactivates harmful chemicals.

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C. Golgi Bodies 1. A Golgi body consists of flattened sacs--resembling a stack of pancakes--whose edges break away as secretory vesicles. 2. Here proteins and lipids undergo final processing, sorting, and packaging.

D. A Variety of Vesicles 1. Lysosomes are vesicles that bud from Golgi bodies; they carry powerful enzymes that can digest the contents of other vesicles, worn-out cell parts, or bacteria and foreign particles. 2. Peroxisomes are small vesicles that contain enzymes using oxygen to degrade fatty acids and

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amino acids, forming a harmful byproduct, hydrogen peroxide, which is then converted to water.

Describe the function of exocytic vesicles; also describe the function of endocytic vesicles.

Exocytic vesicles export materials out of cells via the cell membrane. These vesicles actually fuse with the cell membrane to release the material.

15 . Endocytic vesicles move “packaged goods” (various biochemicals)

through out the cytoplasm.

16 __Lysosomes________ are organelles of intracellular digestion that bud from Golgi . membranes of animal cells and some fungal cells. [p. ] 17 Define and describe the function of peroxisomes. . Peroxisomes are small, membrane bound vesicles that contain enzymes using oxygen to degrade fatty acids and amino acids, forming a harmful byproduct, 7

hydrogen peroxide, which is then converted to water. Within __mitochondria________, energy stored in organic molecules is released by enzymes and used to form many ATP molecules in the presence of oxygen. 18 .

19 Describe the detailed structure of the chloroplast, the site of photosynthesis (include . grana and stroma). Chloroplasts are oval or disk shaped, bounded by a double membrane, and are critical to the process of photosynthesis. a. In the stacked disks (grana), pigments and enzymes trap sunlight energy to form ATP. b. Sugars are formed in the fluid substance (stroma) surrounding the stacks. c. Pigments such as chlorophyll (green) confer distinctive colors to the chloroplasts.

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Give the general function of the following plant organelles: chloroplasts, chromoplasts, amyloplasts, and the central vacuole.

Chloroplasts: Site of photosynthesis 20 . Chromoplasts store red and brown pigments that give color to petals, fruits, and roots. Colorless amyloplasts store starch granules. 21 Elements of the __cytoskeleton________ give eukaryotic cells their internal . organization, overall shape, and capacity to move. [p. ] 22 List the three major structural elements of the cytoskeleton and give the general . function of each. 1. The main components are microtubules, microfilaments, and intermediate filaments--all assembled from protein subunits. 2. Some portions are transient, such as the "spindle"

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microtubules used in chromosome movement

during cell division; others are permanent, such as

microfilaments operational in muscle contraction. Intermediate filaments are also permanent structures in some animal cells. They provide structure for these cells.

23 Describe the general functions of motor proteins and crosslinking proteins. .

Motor proteins: Type of protein (e.g., myosin) attached to microfilaments and microtubules; used in cell movements (e.g., contraction).

Cross linking proteins: Proteins that join various cytoskeletal elements to form “mesh-like” structures such as the cell cortex. 10

Kinesin

http://fondazione-elba.org/nsito/abstract/37.htm

24 Amoeba proteus, a soft-bodied protistan, crawls on __pseudopods________. [p. ] . 25 Both cilia and flagella have an internal microtubule arrangement called the "______9 . + 2_______" array. [p. ] 26 A centriole remains at the base of a completed microtubule-producing center where it . is often called a _basal body_________ __________. [p. ] 27 Distinguish a primary cell wall from a secondary cell wall in leafy plants. .

Primary cell wall: A thin, flexible plant cell wall of cellulose, polysaccharides, and glycoproteins; allows growing cells to divide or change shape. Secondary cell wall: Of older plant cells no longer growing but in need of structural support, a wall on the inner surface of the primary wall. Contains lignin in older cells of woody plants.

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Describe the location and function of plasmodesmata. In plants tiny channels called plasmodesmata cross 28 the adjacent primary walls and connect the cytoplasm . of adjacent cells. 29 ___Tight_______ junctions link the cells of epithelial tissues; . __adhering________ junctions join cells in tissues of the skin, heart, and other organs subjected to stretching; __gap________ junctions link the cytoplasm of neighboring cells. [p ]

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30 Describe the structure of a generalized prokaryotic cell. Include the bacterial flagellum, . nucleoid, pili, capsule, cell wall, plasma membrane, cytoplasm, and ribosomes. A. Bacteria are some of the smallest and simplest cells. 1. Bacterial flagella project from the membrane and permit rapid movement. 2. A somewhat rigid cell wall supports the cell and surrounds the plasma membrane, which regulates transport into and out of the cell. 3. Ribosomes, protein assembly sites, are dispersed throughout the cytoplasm. 4. Pilus: A fine filamentous appendage,

somewhat analogous to the flagellum, that occurs on some bacteria. Also called fimbria. 5. Cell membrane; structural and functional boundary between cytoplasm and the fluid outside the cell 6. Cytoplasm: All cell parts, particles, and semifluid substances between the plasma membrane and the nucleoid. 7. Nucleoid: Portion of bacterial cell interior in which the DNA is physically organized but not enclosed by a membrane.

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List the two kingdoms of prokaryotic cells. 31 .

Archebacteria (Archea) and Eubacteria (Bacteria)

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