Anatomy #2: The Cell

Question 1

Cytology

Answer 1

Study of cells.

Question 2

Plasma Mebrane

Answer 2

Forms the outer, limiting barrier separating the internal contents of the cell from the external environment.

It’s structure is a phospholipid bilayer containing cholesterol and proteins (integral and peripheral) and some carbohydrates (externally).

It also contains receptors for communication, forms intracellular connections, and regulates material movement in and out of cell.

Question 3

Cytoplasm

Answer 3

A general term for all the cellular contents located between the plasma membrane and the nucleus. Three components of the cytoplasm are cytosol (a viscous fluid), inclusions (nonfunctional, temporary structures that store cellular products), and organelles.

It is the place of many metabolic processes of the cell; stores nutrients and dissolved solutes.

Question 4

Nucleus

Answer 4

Surrounded by double membrane nuclear envelope (each membrane is a phospholipid bilayer); contains nucleolus and chromatin.

Cell’s control center. Controls all genetic information. Site of ribosome subunit assembly.

Question 5

Cytosol

Answer 5

Viscous fluid medium with dissolved solutes. Provides support for organelles and serves as viscous medium through which diffusion occurs.

Many cytoplasmic proteins are the enzymes that act as catalysts in cellular reactions. The cytosol’s carbohydrates and lipids serve as an energy source for the cell. Many of the small molecules in the cytosol are the building blocks of large macromolecules.

Question 6

Organelles

Answer 6

Membrane-bound and non-membrane-bound structures that have unique functions and activities.

Question 7

Inclusions

Answer 7

Large and diverse group of chemical substances that these cells store temporarily. Droplets of melanin, protein, glycogen granules, or lipid. Usually non-membrane bound.

It stores materials.

Question 8

Nuclear Envelope

Answer 8

Double membrane boundary between cytoplasm and nuclear contents. Each layer in the nuclear envelope is a phospholipid bilayer.

Pores in envelope regulate exchange of materials with the cytoplasm.

Question 9

Nuclear Pores

Answer 9

Openings through the nuclear envelope.

Allows for passage of materials between nucleus and cytoplasm.

Question 10

Nucleolus (or nucleoli)

Answer 10

Spherical, dark-staining, dense granular region in the nucleus. Made up of RNA, enzymes, and other proteins.

Synthesizes rRNA and assembles ribosomes in the nucleus.

Question 11

Chromatin and Chromosomes

Answer 11

Filamentous association of DNA and histone proteins.

Site of gens in the DNA.

Question 12

Smooth Endoplasmic Reticulum

Answer 12

Interconnected network of membrane tubules and vesicles; no ribosomes.

Synthesizes, transports, and stores lipids; metabolizes carbohydrates; detoxifies drugs, alcohol, and poisons.

The amount of smooth ER is greater in cells that synthesize steroid hormones. In addition,t he liver contains abundant amounts of smooth ER to process digested nutrients and detoxify drugs and alcohol.

Question 13

Rough Endoplasmic Reticulum

Answer 13

Flattened intracellular network of membrane sacs called cisternae; ribosomes attached on cytoplasmic surface.

Synthesizes proteins for secretion, new proteins for the plasma membrane, and lysosomal enzymes; transports and stores molecules.

Ribosomes on this are called fixed ribosomes because they’re attached to the membrane surface of the ER, forming the rough ER. As new proteins are synthesized by the fixed ribosomes, they pass through membrane of the rough ER and enter its cisternae, where their original structure changes by either adding other molecules or removing part of what was originally synthesized. These modified proteins packaged into transport vesicles. They shuttle proteins from the rough ER to the Golgi apparatus for further modification.

The amount of rough ER is greater in cells producing large amounts of protein for secretion, such as a cell int he pancreas that secretes enzymes for digesting materials in the small intestine.

Question 14

Golgi Apparatus

Answer 14

Also called golgi complex. Stacked series of flattened, smooth membrane sacs with associated transport vesicles (also called shuttle vesicles) Composed primarily of a series of cisternae. The edges of each sac bulge, and many small transport vesicles are clustered around the expanded edges of the individual sacs. The vesicles concentrated at the periphery of the Golgi apparatus are active in transporting and transferring material between the individual sacs as well as between the Golgi apparatus and other cellular structures.

Modifies, packages, and sorts newly synthesized proteins for secretion, inclusion in new plasma membrane, or lysosomal enzyme synthesis from the rough ER in transport vesicles.

Especially extensive and active in cells specialized for secretion.

The Golgi apparatus exhibits a distinct polarity: The membranes of the cisternae at opposite ends of a stack differ in thickness and molecular composition. These two poles are called the receiving region and the shipping region. The diameter of the flattened sac is larger in the receiving region. THe products of the rough ER go from receiving to shipping region.

Question 15

Lysosomes

Answer 15

Membrane sacs with digestive enzymes. Formed by Golgi apparatus.

Digest materials or microbes ingested by the cell, and also waste products; remove old/damaged organelles; self-destruct (autolyze), They also break down large molecules, like proteins, fats, polysaccharides, and nucleic acids.

Question 16

Proxisomes

Answer 16

Membrane-enclosed sacs; usually contain large amounts of specific enzymes to break down harmful substances.

Convert hydrogen peroxide formed during metabolism to water.

Question 17

Mitochondria

Answer 17

Double membrane structures with cristae; fluid matrix contents at center.

Synthesize most ATP during cellular respiration: “powerhouse of cell”.

Number of mitochondria in cell depends on cell’s energy needs. Because mitochondria can self-replicate, the number of mitochondria are greater in cells that have a high energy demand. Like muscle cells.

They contain a small unique fragment of DNA. It contains genes for producing mitochondrial proteins.

Question 18

Ribosomes

Answer 18

Dense cytoplasmic granules with two subunits (large and small); may be free in cytoplasm (free ribosomes) or bound to rough ER (fixed ribosomes).

Synthesize proteins for:

1) use in the cell (free ribosomes)
2) secretion, incorporation into plasma membrane, or lysosomes (fixed ribosomes)

Question 19

Cytoskeleton

Answer 19

Organized network of protein filaments or hollow tubules throughout the cell.

Provides structural support; facilitates cytoplasmic streaming, organelle and cellular motility, transport of materials, and chromosomal movement and cell division.

Question 20

Microfilaments

Answer 20

Actin protein monomers formed into filaments.

Maintain cell shape; aid in muscle contraction and intracellular movement; separate dividing cells.

Question 21

Intermediate Filaments

Answer 21

Various protein components.

Provide structural support; stabilize cell junctions.

Question 22

Microtubules

Answer 22

Hollow cylinders of tubulin protein; able to lengthen and shorten.

Support cell; hold organelles in place; maintain cell shape and rigidity; direct organelle movement within cell and cell motility as cilia and flagella; move chromosomes at cell division.

Question 23

Centrosome

Answer 23

Amorphous region adjacent to nucleus; contains a pair of centrioles.

Organizes microtubules; participates in spindle formation during cell division.

Question 24

Centrioles

Answer 24

Paired perpendicular cylindrical bodies; composed of microtubule triplets.

Organize microtubules during cell division for movement of chromosomes.

Question 25

Cilia

Answer 25

Short, membrane-attached projections containing microtubules; occur in large numbers on exposed membrane surfaces.

Move fluid, mucus, and materials over the cell surface.

Question 26

Flagellum

Answer 26

Long, singular membrane extension containing microtubules.

Propels sperm cells in human male.

Question 27

Microvilli

Answer 27

Numerous thin membrane folds projecting from the free cell surface.

Increase membrane surface area for increased absorption and/or secretion.

Question 28

Glycocalyx

Answer 28

An external carbohydtate (sugar) coat the plasma membrane has.

The glycocalyx (the carbohydrate portion of the glycolipid molecule) helps these molecules participate in cell-cell recognition, intracellular adhesion, and communication.

Question 29

Lipids

Answer 29

Materials that are insoluble in water; examples are fats and oils, as well as steroids. The insolubility of the lipids within the plasma membrane ensure that the membrane will not simply “dissolve” when it comes in contact with water. The three types of lipids int he plasma membrane are phospholipids, cholesterol, and glycolipids.

Question 30

Phospholipids

Answer 30

Contain both water-soluble and water-insoluble regions as well as the element phosphate. These molecules are called polar, meaning that a charge is distributed unevenly through the molecule so that one region has a positive charge and another region has a negative charge. Often these molecules are portrayed int he membrane as a balloon with two tails. The balloonlike, polar “head” is charged and hydrophillic. The two “tails” are uncharged, nonpolar, and hydrophobic. Because all phospholipid molecules have these two regions with different water association properties, they readily associate to form two parallel sheets of phospholipid molecules lying tail-to-tail. The hydrophobic tails form the internal environment of the membrane, and their polar heads are directed outward. This basic structure of the plasma membrane is called the phospholipid bilayer. It ensures that intracellular fluid (ICF) remains inside the cell, and extracellular fluid (ECF) remains outside.

Question 31

Interstitial Fluid

Answer 31

Thin layer of fluid that bathes the external surface of a cell.

Question 32

Cholesterol

Answer 32

A type of lipid called a steroid, amounts to about 20% of the plasma membrane lipids. Cholesterol is scattered within the hydrohpbic regions of the phospholipid bilayer, where it strengthens the membrane and stabilizes it at temperature extremes.

Question 33

Glycolipids

Answer 33

Lipids with attached carbohydrate groups (glucocalyx), form about 5-10% of the membrane lipids. They’re located only on the outer layer of the membrane, where they’re exposed to the extracellular fluid.

Question 34

Proteins

Answer 34

Complex, diverse molecules composed of chains of smaller molecules called amino acids. Proteins play various structural and functional roles within the cell and within the body. They make up about half of the plasma membrane by weight. Most of the membrane’s specific functions are determined by its resident proteins. Plasma membrane proteins are of two types: integral and peripheral.

Question 35

Integral Proteins

Answer 35

Are embedded within, and extend across, the phospholipid bilayer. Some species of integral proteins act as membrane channels, providing a pore (hole) in the membrane through which specific substances pass.

Question 36

Receptors

Answer 36

Other integral proteins. Serve as binding sites for molecules outside of the cell. Hydrophobic regions within the integral proteins interact with the hydrophobic interior of the membrane. In contrast, the hydrophilic regions of the integral proteins are exposed to the aqueous environments on either side of the membrane.

Question 37

Peripheral Proteins

Answer 37

Not embedded in the phospholipid bilayer. They’re attached loosely to either the external or internal surface of the membrane, often to the exposed parts of the integral proteins. Peripheral proteins can “float” and move about the bilayer, much like a beach ball floating on the surface in a swimming pool.

Question 38

Enzymes

Answer 38

Also called catalysts. Enzymes are molecules that are important for functional or metabolic activities in the cell because they change the rate of a reaction without being affected by the reaction itself. An enzyme is the equivalent of an electric starter for a barbecue grill; the starter can repeatedly ignite the fire in the grill because it’s unchanged by the fire itself.

Question 39

Glycoproteins

Answer 39

Proteins with attached carbohydrate groups. They form about 90% of all the membrane molecules that have carbohydrates attached to their external surface. Together, the carbohydrate groups attached to both glycoproteins and the previously mentioned glycolipids form the fuzzy glycocalyx on the external surface of the plasma membrane.

Question 40

Transport

Answer 40

A transmembrane protein spans the plasma membrane completely. It has an internal hydrophobic region and hydrophilic regions at both the internal and external membrane surfaces. This protein assists the movement of a particular substance across the membrane. Sometimes the transport of material across the membrane requires cellular energy. A molecule called ATP provides the energy for that transport. ATP releases energy when the bond that attaches its third phosphate to the rest of the molecule is broken.

Question 41

Intracellular Connection

Answer 41

Junctions form between some neighboring cells when proteins in the membranes of each cell attach. These junctions secure the cells to each other.

Question 42

Anchorage for the Cytoskeleton

Answer 42

Cell shape is maintained by the attachment of structural proteins inside the cell (the cytoskeleton) to membrane proteins.

Question 43

Enzyme Activity

Answer 43

Some membrane proteins are catalysts that change the rates of some metabolic reactions. The plasma membrane in most cells contains enzymes that increase the rate of ion movement across the membrane. Examples of such catalytic proteins are ion pumps, described later in this chapter.

Question 44

Cell-Cell Recognition

Answer 44

The carbohydrate components of both glycoproteins and glycolipids usually act as identification molecules that are specifically recognized by other cells.

Question 45

Signal Transduction

Answer 45

Signal transduction is the transmission of a message from a molecule outside the cell to the inside of the cell. The cell then responds by changing its internal activities.

Question 46

Transport Proteins

Answer 46

Special integral membrane proteins attract specific molecules in both the internal and external environments of the cell and assist their transport across the membrane. For example, some transport proteins (also called carrier proteins) bind to specific carbohydrates and help them move across the membrane.

Question 47

Plasma Membrane Structure Transport

Answer 47

Differences in the membrane phospholipids (both int he composition of the polar head and the length and composition of the tails) affect the ability of some molecules to cross that membrane. For example, because polar molecules such as water are small and able to interact with the phospholipid bilayer rapidly, while other polar molecules, such as simple sugars, cannot pass through the bilayer.

Question 48

Concentration Gradient

Answer 48

Materials tend to move more rapidly when their concentrations are significantly different between two compartments. For example, if the intracellular fluid had a low concentration of a permeable substance, and the extracellular fluid had a high concentration of that substance, this substance would more easily pass through the membrane into the cell.

Question 49

Ionic Charge

Answer 49

An ion may either be repulsed or attracted to the membrane structures. This ionic charge influences molecular movement across the membrane. For example, if the inside of the cell has a negative charge, a negative ion outside might be repelled, while a positive ion might be attracted.

Question 50

Lipid Solubility

Answer 50

Materials that are lipid-soluble easily dissolve through the phospholipid bilayer. Thus, lipid-soluble molecules can pass through the membrane more easily than non-lipid-soluble molecules can.

For example, small nonpolar molecules called fatty acids readily move through the hydrophobic interior of the phospholipid bilayer and enter the cytoplasm of the cell, whereas larger, charged polar molecules, such as simple sugars or amino acids, are prevented from moving through the hydrophobic region of the plasma membrane.

Question 51

Passive Transport

Answer 51

Substances move across a plasma membrane without need of energy by the cell. Materials move along a concentration gradient.

Question 52

Simple Diffusion

Answer 52

Occurs when substances move across membranes unaided because they are either small or nonpolar, or because they are both. As a result, a net movement of specific molecules or ions takes place from a region of their higher concentration to a region of their lower concentration. This net movement continues until all of those molecules are evenly distributed in the environment.

Question 53

Osmosis

Answer 53

Special type of diffusion where water diffuses from one side of the selectively permeable membrane to the other. The net movement of water across a semipermeable membrane continues from a region of high water concentration to a region of low water concentration until equilibrium is established.

Question 54

Facilitated Diffusion

Answer 54

Requires the participation of specific transport proteins that help specific substances move across the plasma membrane. These substances are either large molecules or molecules that are insoluble in lipids. The molecule to be moved binds to the transport protein in the membrane. This binding helps alter the shape of both the transport protein and the molecule to be moved, thus permitting it to pass across the membrane. This diffusion is aided by a specific transport protein.

Moves compounds across the cell membrane in a concentration-dependent manner.

Question 55

Bulk Filtration

Answer 55

Or bulk movement. Involves the diffusion of solvents and solutes together across the selectively permeable membrane. Solvents are liquids that have substances called solutes dissolved in them. For example, water can be a solvent if it has a solute such as salt or sugar dissolved in it. An example of bulk filtration is when fluid and certain solutes are transported from the blood into the extracellular fluid. Bulk filtration works in this way.

Hydrostatic pressure (fluid pressure exerted by blood pushing against the inside wall of a blood vessel) forces both water and small solutes from the blood across the plasma membranes of cells lining the capillaries. Only smaller molecules and ions can be forced across membrane by hydrostatic pressure.

Question 56

Active Transport

Answer 56

The movement of a substance across a plasma membrane against a concentration gradient, so materials must be moved from an area of low concentration to an area of high concentration. Active transport is similar to swimming upstream against a current, where you must exert energy (swim) to move against the water flow. To move materials against their concentration gradient, active transport requires cellular energy int he form of ATP and sometimes a transport protein as well. ATP is continually synthesized by mitochondria. Active transport methods include ion pumps and several processes collectively known as bulk transport.

Question 57

Ion Pumps

Answer 57

Active transport processes that move ions across the membrane are called ion pumps. Ion pumps are a major factor in a cell’s ability to maintain its internal concentrations of ions. One type of ion pump is the sodium-potassium pump. This transport mechanism is specifically called an exchange pump, because it moves on ion into the cell while simultaneously removing another type of ion from the cell.

Question 58

Bulk Transport

Answer 58

Macromolecules cannot move across the plasma membrane via ion pumps or even with normal transport proteins. Instead, larger molecules move across membrane via exocytosis and endocytosis.

Question 59

Exocytosis

Answer 59

Large molecules are secreted from the cell. Typically, the material for secretion is packaged within intracellular transport vesicles, which move toward the plasma membrane. When the vesicle and plasma membrane come into contact, the lipid molecules of the vesicle and plasma membrane bilayers rearrange themselves so that the two membranes fuse. The fusion of these lipid bilayers requires the cell to expend energy. Following fusion, the vesicle contents are released to the outside of the cell. An example of this process occurs int he pancreas, where cells release digestive enzymes into a pancreatic duct for transport to the small intestine.

Question 60

Endocytosis

Answer 60

Large macromolecules being taken into the cell. The steps are similar to exocytosis, only in reverse. Extracellular macromolecules and large particulate matter are packaged in a vesicle that forms at the cell surface for internalization into the cell. A small area of plasma membrane folds inward to form a pocket, or invagination, which deepens and pinches off as the lipid bilayer fuses. This fusion of the lipid bilayer is the energy-expending step. A new intracellualr vesicle is formed containing material that was formerly outside the cell. There are 3 types of encocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis.

Question 61

Phagocytosis

Answer 61

Means “cellular eating.” It’s a nonspecific process that occurs when a cell engulfs or captures a large particle external to the cell by forming membrane extensions called pseudopodia, or false feet, to surround the particle. Once the particle is engulfed by the pseudopodia, it’s packaged within an enclosed membrane sac. If large enough, this sac is classified as a vacuole. The contents of the vacuole are broken down chemically after it fuses with a lysosome, which contains enzyme,es that split large molecules into smaller ones. Only few types of cells can perform phagocytosis.

Question 62

Pinocytosis

Answer 62

Known as “cellular drinking.” This process occurs when the cell internalizes a very small droplet of extracellular fluid into tiny internal vesicles. This process is nonspecific because all solutes dissolved in the droplet are taken into the cell. Most cells perform this type of transport across the membrane. Pinocytosis is similar to bulk filtration in that both types of transport move similar to materials. However, it differs from bulk filtration because pinocytosis moves materials against a concentration gradient. An example of pinocytosis occurs within cells that form a capillary wall, where vesicles fill with a fluid droplet containing small solutes from the blood, carry this droplet to the other side of the cell, and then expel its contents outside the capillary wall.

Question 63

Receptor-Mediated Endocytosis

Answer 63

The movement of specific molecules from the extracellular environment into a cell by way of a newly formed vesicle. This process begins when molecules in the extracellular fluid bind to their specific integral membrane protein receptors. This process is different from the nonspecific transport mechanisms discussed earlier. It’s considered a specific mechanism because the endocytosis is stimulated by the binding of the specific molecules to their specific membrane receptors. The receptor proteins then cluster in one region of the membrane to begin the process of endocytosis. The plasma membrane housing the bound specific molecules from the extracellular fluid folds inward to form a pocket, or invagination. This membrane pocket deepens and pinches off as the lipid bilayers fuse. The fusion of these lipid bilayers requires the cell to expend energy in the form of ATP.

An example of this occurs when human cells contain receptors that bind and internalize cholesterol, which is required for new membrane synthesis. Cholesterol travels in our blood bound to proteins called low-density lipoproteins (LDLs). LDL particles bind to LDL receptors in the membrane. Receptor-mediated endocytosis enables the cell to obtain bulk quantities of specific substances, even though those substances may not be very concentrated in the extracellular fluid.

Question 64

Melanin

Answer 64

A stored pigment in some skin, hair, and eye cells. Protects the body from the sun’s ultraviolet light.

Question 65

Glycogen

Answer 65

A polysaccharide that is stored primarily in the liver and skeletal muscle cells.

Question 66

Membrane-bound Organelles

Answer 66

Or membranous organelles. Similar to plasma membrane surrounding cell that is composed of a phospholipid bilayer with diverse associated proteins.

Note that every membrane exhibits a unique protein-lipid composition, which confers a unique function(s) to that membrane.

Question 67

Transport Vesicles

Answer 67

Small, enclosed membrane sacs.

Question 68

Materials Moving Through GOlgi Apparatus

Answer 68

1) Newly synthesized proteins int he rough ER cisternae are sequestered into a transport vesicle.
2) The vesicle pinches off the ER and travels to the Golgi apparatus.
3) Newly arrived transport vesicles fuse with the receiving region of the Golgi apparatus.
4) Protein modification occurs as the proteins are moved by transport vesicles sequentially through the Golgi apparatus cisternae from the receiving region to the shipping region.
5) Modified proteins are packaged in secretory vesicles.
6) Vesicles leaving the shipping region became (a) lysosomes, which contain proteins called digestive enzymes, (b) secretory vesicles that undergo exocytosis, or (c) new parts of the plasma membrane.

Question 69

Autophagy

Answer 69

Process of removing old organelles.

Question 70

Autolysis

Answer 70

When a cell is damaged or dies, enzymes from all lysosomes are released into the cell, resulting in the rapid digestion of the cell itself.

Question 71

Peroxisomes

Answer 71

Membrane-enclosed sacs that are usually smaller in diameter than lysosomes. Formed by pinching off vesicles from the rough ER. Use oxygen to catalytically detoxify specific harmful substances either produced by the cell or taken into the cell.

For example, the peroxisome is able to convert hydrogen peroxide (a toxic compound) that’s sometimes produced by cells into water before it can damage the cell. It does this using the enzyme catalase, which is a component of the peroxisome.

Peroxisomes are most abundant in liver cells, where they break down fatty acids and detoxify some toxic materials, such as alcohol, that are absorbed in the digestive tract.

Question 72

Cristae

Answer 72

The second inner membrane of the mitochondria that is folded internally into the space at the center of the organelle. They increase the surface area that is exposed to the internal fluid contents, termed the matrix. Inner membrane proteins are on the cristae.

Question 73

Free Ribosomes

Answer 73

Those that float freely in the cytosol. Responsible for synthesis of proteins that remain in cytosol.

Question 74

Fixed Ribosomes

Answer 74

Those attached to the endoplasmic reticulum. Produce proteins that are exported out of the cell, incorporated into the plasma membrane, or housed an enzymes within a new lysosome.

Question 75

Deoxyribonucleic Acid (DNA)

Answer 75

Enormous macromolecule that contains the genetic material of the cell. Housed by nucleus. The DNA within the nucleus, termed nuclear DNA, is much more complex than the DNA in mitochondria.

DNA is organized into discrete units called genes.

Question 76

Genes

Answer 76

Provide the instructions for the production of specific proteins, and thereby direct all of the cell’s activities.

Question 77

Nucleotides

Answer 77

Building blocks that form the DNA double helix. It contains a sugar (called a deoxyribose sugar), a phosphate molecule, and a nitrogen-containing base.

There are four different types of nucleotides, each having one of four different bases: adenine, cytosine, guanine, and thymine.

Question 78

Histones and Nucleosome

Answer 78

The long DNA double helix winds around a cluster of special nuclear proteins called histones, forming a complex known as a nucleosome. The degree of coiling of the DNA around the histole proteins ultimately determines the length and thickness of the chromosome.

Question 79

Mitosis

Answer 79

The cell division process that takes place in somatic cells, which are all of the cells in the body EXCEPT the sex cells.

Question 80

Interphase

Answer 80

Most cells in interphase during majority of their lives. It’s a time when cell appears to be resting because no overt activity is observed. However, while the cell carries on its normal activities, it may also be preparing for division.

Interphase is a time for growth and making new cellular parts, replicating DNA and centrioles, and producing the proteins, RNA< and organelles needed for cell division. Interphase has three phases, G1, S, and G2.

Question 81

G1 Phase

Answer 81

First growth phase: Protein synthesis and metabolic activity occur; new organelles are produced; centriole replication begings at the end of this phase.

Question 82

S Phase

Answer 82

Nuclear DNA is replicated.

Question 83

G2 Phase

Answer 83

Second growth phase: Brief growth period for production of cell division enzymes; centriole replication finishes; organelle replication continues.

Question 84

Prophase

Answer 84

Chromatin threads appear due to coiling and condensation; elongated duplicated chromosomes consisting of identical sister chromatids become visible.

Nuclear envelope disappears at the end of this stage.

Nucleolus disappears.

Microtubules begin to form mitotic spindle.

Centrioles move toward opposing cell poles.

Question 85

Metaphase

Answer 85

Chromosomes line up at the equatorial plate of the cell.

Microtubules from the mitotic spindle attach to the centromeres of the chromosomes from the centrioles.

Question 86

Anaphase

Answer 86

Centromeres that held sister chromatid pairs together separate; they are now single-stranded chromosomes.

Identical pairs of single-stranded chromosomes are pulled toward opposite ends of the cell.

Question 87

Telophase

Answer 87

Chromosomes arrive at cell poles and stop moving.

Nuclear envelope reappears, mitotic spindle disintegrates, chromosomes uncoil, disappear and become thin chromatin threads within boundary of the new nuclear envelope.

Nucleoli reappear.

Question 88

Cytokinesis

Answer 88

Usually begins in late anaphase and ends after telophase ends; cleavage furrow is formed from a contractile ring of microfilaments; cytoplasm divides, completeing the formation of two daughter cells.

Question 89

Necrosis

Answer 89

Process where cells are killed by harmful agents or mechanical damage. The damage is irreversible and there is an inflammatory response.

Question 90

Apoptosis

Answer 90

Process of programmed cell death where the cell is induced to commit suicide. Cells is apoptosis exhibit nuclear changes (chromatin degradation), shrikage in volume, and abnormal development in both organelle and plasma membrane structure.

Question 91

Anaplasia

Answer 91

Obvious loss of cellular or structural differentiation and change in cells’ orientation to each other and to blood vessels; seen in most malignant neoplasms.

Question 92

Dysplasia

Answer 92

Abnormal development of a tissue; a pathologic condition resulting in a change in the shape, size, and organization of adult cells; development of cellular and tissue elements that are not normal.

Question 93

Hyperplasia

Answer 93

Increase in the normal number of cells within a tissue or organ; an excessive proliferation of normal cells; doesn’t include tumor formation.

Question 94

Hypertrophy

Answer 94

Generalized increase in the bulk or size of a part of an organ, not as a consequence of tumor formation.

Question 95

Malignant Tumor

Answer 95

An abnormal growth of cells that invades surrounding tissues.

Question 96

Metaplasia

Answer 96

Abnormal transformation of a fully differentiated adult tissue into a differentiated tissue of another kind.