Lab Textbook Chapter 4- The Cell: Anatomy and DIvision

Question 1

Nucleus

Answer 1

• Contains the genetic material, DNA
• Often described as the control center of the cell, the nucleus is necessary for cell reproduction
• Chromatin (genetic material in a threadlike form) is present when the cell isn’t dividing
• When the cell is in the process of dividing, the chromatin coils and condenses to form rod like bodies called chromosomes
• Nucleus also contains one more more small round bodies called nucleoli, composed primarily of proteins and RNA
• The nucleus is bound by a double layed porous membrane, the nuclear envelope

Question 2

Nuclear Envelope

Answer 2

• The nuclear envelope is distinguished by its large nuclear pores.
• They are spanned by protein complexes that regulate what passes through and permit easy passage of protein and RNA molecules

Question 3

Plasma Membrane

Answer 3

• The plasma membrane separates cell contents from teh surrounding environment
• Its main structural building blocks are phsopholipids (fats) and globular protein molecules
• Selective permeability - Plays an active role in determining which substances may enter or leave the cell and in what quantity

Question 4

Ribosomes

Answer 4

• Are densely staining, roughly spherical bodies composed of RNA and protein
• They are the actual sites of protein synthesis
• They are seen floating free in the cytoplasm or attached to a membranous structure (rough ER)

Question 5

Endoplasmic Reticulum (ER)

Answer 5

• Is a highly foled system of membranous tubules and cisterns (sacs) that extends throughout the cytoplasm
• The ER is continuous with the nuclear envelope, forming a system of channles for transport of cellular subsances (primarily proteins) from one part of the cell to another
• Rough ER - studded with ribosomes; its cisterns modify and store the newly formed proteins and dispatch them to other areas of the cell; external face synthesizes phospholipids and cholesterol
• Smooth ER - has no function in protein synthesis, is a site of steroid and lipid synthesis, lipid metabolism, and drug detoxication

Question 6

Golgi Apparatus

Answer 6

• Stack of flattened sacs with bulbous ends and associated small vesicles; found close to the nucleus
• Plays a role in packaging proteins or other substances for export form the cell or incorporation into the plasma membrane and in packaging lysosomal enzymes

Question 7

Lysosomes

Answer 7

• Various sized membranous sacs containing digestive enzymes including acid hydrolases
• Functionto digest worn out cell organelles and foreign substances that enter the cell
• Have the capacity of total cell destruction if ruptured

Question 8

Peroxisomes

Answer 8

• Small lysosome like membranous sacs containing oxidase enzymes that detoxify alcohol. hydrogen peroxide, and other harmful chemicals

Question 9

Mitochondria

Answer 9

• Generally rod-shaped bodies with a double-membrane wall
• Inner membrane is thrown into folds, or cristae; contain ezymes that oxidize foodstuffs to produce cellular energy (ATP)
• Often referred to as “powerhouses of the cell”

Question 10

Centrioles

Answer 10

• Paired, cylindrical bodies lie at right angles to each other, close to the nucleus
• As part of the centrosome, they direct the formation of the mitotic spindle during cell division
• Form the bases of cilia and flagella

Question 11

Cytoskeletal elements; microfilaments, intermediate filaments and microtubules

Answer 11

• Provide cellular support; function in intracelluar transport
• Microfilaments are formed largely of actin, a contractile protein, and thus are important in cell mobility, particularly in muscle cells
• Intermediate filaments are stable elements composed of a variety of proteins and resist mechanical forces acting on cells
• Microtubules form the internal structure of the centrioles and help determine cell shape

Question 12

Cell Division: Mitosis and Cytokinesis

Answer 12

• Mitosis is the division of the copied DNA of the mother cell to two daughter cells
• Cytokinesis is the division of the cytoplasm
• Phases of mitosis: Prophase, metaphase, anaphase and telophase
• Interphase is often included in discussions of mitosis but is not part of mitosis
• Interphase- G1-The centrioles begin replicating; S- DNA is replicated; G2- Final preparations for mitosis are completed and centrioles finish replicating
• Prophase- chromatin condenses and becomes chromosomes; nucleoli disappear; the two centrosomes separate from each other; nuclear envelope breaks up; allowing spindle to interact with the chromosomes; growing spindle microtubules attach to kinetochores (special protein structures at each chromosomes’s centromere)
• Metaphase- two centrosomes are at opposite poles of the cell; chromosomes cluster at the midline of the cell (metaphase plate); enzymes act to separate the chromatids from each other
• Anaphase - shortest phase; begins abruptedly as the centromeres of the chromosomes split simultaneously
• Telophase- begins as soon as chromosomal movement stops (prophase in reverse); identical sets of chromosomes at opposite poles uncoul and become chromatin; a new nuclear envelope forms around each chromatin mass; nucleoli reappear within the nuclei, spindle breaks down and disappears; mitosis has ended, the cell if (for a brief period) binucleate (has two nuclei)
• Cytokinesis- begins in late anaphase continues beyond telophase; a contractile ring of actin microfilaments forms the cleavage furrow and pinches the cell apart