Review Questions Chp 4 (KEY)[1]

8/14/2019 Review Questions Chp 4 (KEY)[1]

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Review Questions - Chapter 4

Cell Structure and Function

1.

Be able to list the three generalizations that together constitute the cell theory.

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.

2.

List and describe the three major regions that all cells have in common.

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 ornuc leoid region localizes thehereditary material, which can be copied and

read.

3. The cytoplasm contains membrane systems,

particles (including ribosomes), filaments (the

cytoskeleton), and a semifluid substance.

3.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.

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 ProteinsMembrane Proteins

Proteinpump across

bilayer

Proteinchannel

across bilayer

Protein pump

Recognitionprotein

Receptorprotein

extracellularenvironment

cytoplasm

lipid bilayer

Figure 4.4

Page 57

6.

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

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.

7.

Cell size is necessarily limited because its volume increases with the

___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,

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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 EMs.

These use a beam of photons and quantum physics to see down

to the atomic realm.

Transmission electron microscopes: Use electrons and electro-

magnets . The latter focus the beam of electrons through a thin,

metal stained sample and form a picture of the cells interior. Upto 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.

10.In eukaryotic cells, __organelles_______ separate different incompatiblechemical 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

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filaments, which anchor the DNA molecules and

keep them organized.

3. The outer surface is studded with ribosomes.

12.____Nucleoli______ are sites where the protein and RNA subunits of ribosomes

are assembled. [pp. ]

13.

___Chromatin_______is the cell's collection of DNA molecules and associatedproteins; a __chromosome________ is an individual DNA molecule and associated proteins. [p. ]

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.

Explain how the endoplasmic reticulum (rough and smooth types), peroxisomes, Golgi

bodies, lysosomes, and a variety of vesicles function together as the cytomembranesystem.

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 Reticulum1. 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 wayto 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.

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.

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.

Endocytic vesicles move packaged goods (various biochemicals)through out the cytoplasm.

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.__Lysosomes________ are organelles of intracellular digestion that bud from Golgimembranes 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,

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hydrogen peroxide, which is then converted to water.

18

.

Within __mitochondria________, energy stored in organic molecules is releasedby enzymes and used to form many ATP molecules in the presence of oxygen.

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.

Describe the detailed structure of the chloroplast, the site of photosynthesis (include

grana and stroma).

Chloroplasts are oval or disk shaped, bounded by adouble 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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20

.

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

Chloroplasts: Site of photosynthesis

Chromoplasts store red and brown pigments that give color topetals, fruits, and roots.

Colorless amyloplasts store starch granules.

21.

Elements of the __cytoskeleton________give eukaryotic cells their internalorganization, 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 movementduring cell division; others are permanent, such as

microfilaments operational in muscle

contraction. Intermediate filaments are alsopermanent structures in some animal cells. They

provide structure for these cells.

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.

Describe the general functions of motor proteins and crosslinking proteins.

Motor proteins: Type of protein (e.g., myosin) attached tomicrofilaments 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.

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KinesinKinesin

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

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.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 todivide or change shape.

Secondary cell wall: Of older plant cells no longer growing butin need of structural support, a wall on the inner surface of theprimary wall. Contains lignin in older cells of woody plants.

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28

.

Describe the location and function of plasmodesmata.

In plants tiny channels called plasmodesmata cross

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 otherorgans subjected to stretching; __gap________ junctions link the cytoplasm ofneighboring cells. [p ]

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Review Questions Chp 4 (KEY)[1]