Chapter 6

Front 1

The study of cell structure

Back 1

Cytology

Front 2

Two basic types of microscopes

Back 2

Light Microscope

Electron micro

Front 3

Light Microscope

Back 3

Visible light is passed through a specimen and then through glass lenses Resolution: 0.2um

Front 4

Electron microscope

Back 4

electromagnets focus an electron beam Resolution: 0.2nm

Front 5

the ratio of an objects image size to its real size

Back 5

magnification

Front 6

the measure of the clarity of the image or the minimum distance of two distinguishable points

Back 6

resolution

Front 7

visible difference in parts of the sample by staining or labeling

Back 7

Contrast

Front 8

LMs can magnify effectively to about ___ times the sisze of the actual specimen

Back 8

1000

Front 9

Electron microscopes cannot

Back 9

study live cells

Front 10

scanning electron microscopes

Back 10

focus a beam of electrons onto the surface of a specimen 3d images

Front 11

transmission electron microscopes

Back 11

focus beam of electrons through specimen

Front 12

TEMs are used mainly to study

Back 12

the internal structures of cells

Front 13

takes cells apart and separates the major organelles from one another

Back 13

cell fractionation

Front 14

_____ fractionate cells in to their component parts

Back 14

Centrifuges

Front 15

Cell fractionation enables scientists to

Back 15

determine the functions of organelles

Front 16

Cell fractionation is used to isolate/fractionate cell components based on

Back 16

size and density

Front 17

Basic features of all cells

Back 17

-plasma membrane

-semifluid substance called cytosol

-chromosomes (carry genes)

-ribosomes (make proteins)

Front 18

prokaryotic cells are characterized by having :

Back 18

-no nucleus

-dna in an unbound region called the nucleoid

-no membrane-bound organelles

-cytoplasm bound by the plasma membrane

Front 19

eukaryotic cells are characterized by having

Back 19

-dna in a nuclus that is bound by a membranous nuclear envelope

-membrane-bound organelles

-cytoplasm in the region between the plasma membrane and nucleus ; within the cytoplasm, suspended in cytosol, are varie

Front 20

____ is a selective barrier that allows sufficient passage of oxygen nutrients and waste to service the volume of every cell

Back 20

Plasma membrane

Front 21

The general structure of a biological membrane is a

Back 21

double layer of phospholipids

Front 22

plasma membranes and organelle membranes participate directly in metabolism because

Back 22

many enzymes are built right into the membranes

Front 23

The ___ contains most of the DNA in a eukaryotic cell

Back 23

Nucleus

Front 24

_____ use the information from the DNA to make proteins

Back 24

Ribosomes

Front 25

____contains most of the cell's genes (some in mitochondria and chloroplasts) and is usually the most conspicuous organelle

Back 25

Nucleus

Front 26

The _____ encloses the nucleus separating it from the cytoplams

Back 26

Nuclear envelope

Front 27

____ regulate entry and exit of molecules from the nucleus

Back 27

Pores

Front 28

The shape of the nucleus is maintained by the ____ which is composed of protein

Back 28

nuclear lamina

Front 29

_____, a framework of protein fibers extending throughout the nuclear interior

Back 29

Nuclear matrix

Front 30

In the nucleus, DNA is organized into discrete units called

Back 30

chromosomes

Front 31

Each chromosom is composed of

Back 31

a single DNA molecule associated with proteins

Front 32

The DNA and proteins of chromosomes are together called

Back 32

Chromatin

Front 33

The ____ is located within the nucleus and is the site of ribosomal RNA synthesis and ribosome assembly

Back 33

Nucleolus

Front 34

Ribosomes are particles made of

Back 34

ribosomal RNA and protein

Front 35

Ribosomes carry out protein synthesis in 2 locations:

Back 35

-cytosol (free ribosomes)

-Outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

Front 36

Components of the endomembrane system:

Back 36

-nuclear envelope

-endoplamic reticulum

-golgi apparatus

-lysosomes-vacuoles

-plasma membrane

Front 37

Two distinct regions of ER:

Back 37

-Smooth ER: lacks ribosomes

-Rough ER: surface is studded with ribosomes

Front 38

Smooth ER

Back 38

-synthesizes lipids including oils, phospholipids and steroids (sex hormones and adrenal glands steroids); testes and ovaries rich in SER

-metabolizes carbohydrates

-detoxifies drugs and poisons especially in liver cells by adding hydroxyl groups

-stores calcium ion (muscle contraction)

Front 39

Rough ER

Back 39

-Bound ribosomes which secrete proteins (insulin)

-most secretory proteins are glycoproteins (proteins covalently bonded to carbohydrates)

-distribute transport vesicles, proteins surrounded by membranes

-membrane factory for the cell; grows in place by adding membrane proteins and phospholipids to its own membrane

-makes membrane phospholipids

Front 40

_____ consists of flattened membranous sacs called cisternae looking like a stack of pita bread (extensive in cells specialized for secretion)

Back 40

Golgi apparatus

Front 41

Functions of Golgi apparatus

Back 41

-modifies products of the ER during transit from cis to trans region, glycoproteins formed in the ER have their carbohydrates modified first in ER and then in Golgi (remove some sugar monomers and substitute others)

-membrane phospholipids may be altered

-manufactures certain macromolecules (pectins)

-sorts and packages materials into transport vesicles; molecular identification tags such as phosphate groups are added

-cisternal maturation model

Front 42

____ is a membranous sac of hydrolytic enzymes that can digest macromolecules and are made by Rough ER and transfered to golgi for processing

Back 42

Lysosomes

Front 43

Lysosomal enzymes can

Back 43

hydrolyze proteins, fats, polysaccharides, and nucleic acids

-work best in the acidic environment inside the lysosome

Front 44

Some types of cell can engulf another cell by ____ this forms a food vacuole; macrophages defend the body by engulfing and destroying bacteria and other invaders

Back 44

phagocytosis

Front 45

lysosomes fuse with the food vacuole and

Back 45

digest the molecules

Front 46

Lysosomes also use enzymes to

Back 46

recycle the cell's own oragnelles and macromolecules, a process called autophagy

Front 47

A plant cell or fungal cell may have one or several

Back 47

vacuoles derived from endoplamic reticulum and golgi apparatus

Front 48

vacuolar membrane is

Back 48

selective in transporting solute

Front 49

Food vacuoles are formed by

Back 49

phagocytosis

Front 50

contractile vacuoles

Back 50

found in many freshwater protist, pump excess water out of cells

Front 51

smaller vacuoles can

Back 51

hold reserves of imp organic compounds

-protect the plant against herbivores

-contain pigments to attract pollinating insects

Front 52

central vauoles (solution inside is called as cell sap)

Back 52

foind in many mature plant cells, hold organic compounds, inorganic ions K & Cl ion and water

Front 53

_____ are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP

Back 53

Mitochondria

Front 54

_____ found in plants and algae are the sites of photosynthesis

Back 54

Chloroplast

Front 55

______ are oxidative organelles

Back 55

Peroxisomes

Front 56

_____ are not part of the endomembrane system

Back 56

Mitochondria, chloroplast and peroxisomes

Front 57

Mitochondira and chloroplast have similarities with bacteria:

Back 57

-enveloped by double membrane

-contain free ribosomes and circular DNA molecules

-grown and reproduce somewhat independently in cells

Front 58

Endosymbiont theory

Back 58

-early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host

-host cell and endosymbiont merged into a single organism, eukaryotic cell with a mitochondria

-at least one of the cells may have taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplast

Front 59

Mitochondria

Back 59

-are in nearly all eukaryotic cells

-have smooth outer membrane and an inner membrane folded into cristae

-inner membrane creates 2 compartments:

-intemembrane space

-mitochondrial matrix

-some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix

-cristae present a large surface area for enzymes that synthesize ATP

Front 60

Chloroplast contain the green pigment _____

Back 60

chlorophyll as well as enzyme and other molecules that function in photosynthesis

Front 61

Choloropplast are ____ organelles found in leaves and other green organs of plants and in algae

Back 61

Lens-shaped

Front 62

Chloroplast structure includes:

Back 62

-Thylakoids: membranous sacs, stacked to form granum

-Stroma internal fluid

Front 63

______ are specialized metabolic compartments bounded by a single membrane

Back 63

peroxisomes

Front 64

peroxisomes produce

Back 64

hydrogen peroxide and convert it to water

Front 65

peroxisomes perform reaction with many different funtions:

Back 65

use oxygen to break fatty acids, in liver detoxify alcohol

Front 66

Specialized peroxisomes called glyoxisomes are found in

Back 66

the fat-storing tissue of plant seeds

Front 67

______ is a network of fibers extending throughout the cytoplasm

Back 67

cytoskeleton

Front 68

Cytoskeleton is composed of 3 types of molecular structures

Back 68

-microtubules

-microfilaments

-intermediate filaments

Front 69

the cytoskeleton roles:

Back 69

to support the cell and maintain its shape

-provides anchorages for many organelles and even cytisolic enzymes

-interacts with motor proteins to produce motility. motor proteins bring about bending of cilia/flagella, cytoplasmic streaming and muscle contraction

-vesicles can travel along monorails provided by the cytoskeleton

-manipulates the plasma membrane to form food vacuole

-evidence suggest that the cytoskeleton may help regulate biochemical activities

Front 70

____ are the thickest of the 3 components of the cytoskeleton

Back 70

microtubules

Front 71

____ are the thinnest components of the cytoskeleton

Back 71

microfilaments also called actin filaments

Front 72

____ are the fibers with diameters in a middle range

Back 72

intermediate filaments

Front 73

Microtubules ( Tubulin Polymer)

Back 73

Structure: holow

D:25nm

Protein subunits: tubulin, a-tubulin and b-tubulin

Function: -maintenance of cell shape

-cell motility

-chromosome movements in cell division

-organelle movements

-guide secretory vesicles from golgi apparatus to plasma membrane

Front 74

Microfilaments (Actin filaments)

Back 74

Structure: two interwined strands of actin, each a polymer of actin subunits

D:7nm

Protein subunits: Actin

Main function: -maintenance of cell shape (tension bearing elements)

-changes in cell shape

-muscle contraction

-cytoplasmic streaming

-cell motility

-cell division (cleavage furrow formation)

Front 75

Intermediate Filaments

Back 75

Structure: fibrous proteins supercoiled into thicker cables

D:8-12nm

Protein subunits: one of several different proteins (such as keratin) depending on cell type

Main functions:-maintenance of cell shape (tension-bearing elements)

-anchorage of nucleus and certain other organelles

-formation of nuclear lamina

Front 76

in many cells, microtubules grow out from a _____ near the nucleus

Back 76

centrosome

Front 77

The centrosome is a

Back 77

"microtubule-organizing center"

Front 78

in animal cells, the centrosome has a pair of ____, each with nine triplets of microtubules arranged in a ring

Back 78

centrioles

Front 79

plant cells lack centrosomes with

Back 79

centrioles but have well-organized microtubules

Front 80

Microtubules controls the beating of

Back 80

cilia and flagella, locomotor appendages of some cells

Front 81

Cilia and flagella share a common structure

Back 81

-A core of microtubules sheathed by the plasma membrane

-A basal body that anchors the cilium or flagellum

-A motor protein called dynein, which drives the bending movements of cilium or flagellum

Front 82

How dynein "walking" move flagella and cilia

Back 82

-dynein arms alternately grab, move, and release the outer microtubules

-protein cross-links limit sliding

-forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum

Front 83

Microfilaments structure role is

Back 83

to bear tension, resisting pulling forces within the cell

Front 84

Microfilaments form

Back 84

3D netwrk called the crotex just inside the plasma membrane to help support the cell's shape

Front 85

Microfilaments that function in cellular motility contain the protein

Back 85

myosin in addition to actin

Front 86

______ extend and contract trough the reversible assembly and contraction of actin subunits into microfilaments

Back 86

Pseudopodia (cellular extensions)

Front 87

________ is circular flow of cytoplasm within cells

Back 87

cytoplasmic streaming

Front 88

____ are more permanent cytoskeleton fixtures than the other two classes holding nucleus & nuclear lamina

Back 88

intermediate filaments

Front 89

Extracellular structures include:

Back 89

-cell walls of plants

-the extracellular matrix (ECM) of animal cells

-intercellular junctions

Front 90

_____ is an extracellular structure that distinguishes plant cells from animal cells

Back 90

Cell wall

Front 91

Prokaryotes, fungi and some protist also have

Back 91

cell walls

Front 92

Plant cell walls may have multiple layers:

Back 92

-primary cell wall: relatively thin and flexible

-middle lamella: thin layer between primary walls of adacent cells; pectins

-secondary cell wall: added between the plasma membrane and the primary cell wall

Front 93

_____ are channels between adjacent plant cells

Back 93

Plasmodesmata

Front 94

Animal cells lack cell walls but are covered by an elaborate _____

Back 94

extracellular matrix (ECM)

Front 95

ECM is made up of

Back 95

glycoproteins such as collagen, proteoglycans, and fibronectin

Front 96

ECM proteins bind to receptor proteins in the plasma membrane called

Back 96

integrins

Front 97

Functions of the ECM:

Back 97

-support

-adhesion

-movement

-regulation

Front 98

Intercellular junctions (facilitate contact):

Back 98

-plasmodesmata

-tight junctions

-desmosomes

-gap junctions

Front 99

______ are channels that perforate plant cell walls, water and small solutes(sometimes proteins and RNA) can pass from cell to cell

Back 99

Plamodesmata

Front 100

_____ membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

Back 100

At tight junctions

Front 101

_______ fasten cells together into strong sheets

Back 101

Desmosomes (anchoring junction)

Front 102

_______ provide cytoplasmic channels between adjacent cells

Back 102

Gap junctions (communicating junction)