Cell Structure (Chapter 4)

Question 1

Robert Hooke

Answer 1

first scientist to see cell walls with microscope in 1665

Question 2

light microscope

Answer 2

visible light is passed through the specimen and then glass lens

lenses refact the light to magnify the image

maximum magnification is ~1000x

maximum resolution is about 0.2 micrometer

Question 3

electron microscope

Answer 3

developed in the 1950s

focuses beam of electrons through specimen or on its surface

100x better than light microscope

Question 4

transmission electron microscope (TEM)

Answer 4

aims electron beam through thin section of a specimen

specimen is stained with atoms of a heavy metals

electrons passing through are scattered more in dense areas

Question 5

scanning electron microscope (SEM)

Answer 5

electron beam scans the surface of the sample

beam excites the electrons on the surface

secondary electrons are detected by a device

Question 6

cell fractionalization

Answer 6

process of placing broken up cells in centrifuge

largest cell components settle to the bottom

enables researchers to use biochemical tests on specific cell parts and organelles

Question 7

features common to all cells

Answer 7

plasma membrane: selective barrier

cytosol: semifluid, jellylike substance
chromosomes: carry genes in the form of DNA
ribosomes: tiny complexes that make proteins

Question 8

eukaryotic cell characteristics

Answer 8

DNA in a nucleus with a double membrane

cytoplasm is the only region between nucleus and membrane

variety of organelles

tend to be larger

Question 9

prokaryotic cell characteristics

Answer 9

DNA concentrated in nucleoid not bounded by membrane

Question 10

factors affecting cell size

Answer 10

requirement for cellular metabolism sets lower bound on cell size

ratio of surface area to volume of cell sets upper bound on cell

volume grows proportionally bigger than surface area

Question 11

composition of membranes

Answer 11

double layer of phospholipids and other lipids

proteins are embedded in lipid bilayer

lipids and proteins are suited to membrane functions

Question 12

plasma membrane

Answer 12

membrane enclosing the cell

Question 13

cytoskeleton

Answer 13

reinforces cell’s shape

functions in cell movement

components are made of protein

types are microfilaments, intermediate filaments, microtubules

Question 14

flagellum

Answer 14

motility structure present in some animal cells

composed of a cluster of microtubules within an extension of the plasma membrane

Question 15

nuclear envelope

Answer 15

double membrane enclosing the nucleus

each membrane is a lipid bilayer with associated proteins

seperated by a space of 20-40 nm

perforated by pores that are 100 nm in diameter

continuous with the ER

Question 16

nucleolus

Answer 16

non-membranous structure involved in production of ribosomes

ribosomal RNA (rRNA) is synthesized

proteins from cytoplasm assembed with rRNA into ribosomes

nucleus has one or more nucleoli

Question 17

chromatin

Answer 17

material consisting of DNA and proteins

appears as diffuse mass

visible in a dividing cell as individual condensed chromosomes

Question 18

ribosomes

Answer 18

complexes that synthesize proteins

free in cytosol or bound to rough ER or nuclear envelope

bound ribosomes make proteins for:

insertion in membranes

packaging within certain organelles such as lysosomes

export from the cell (secretion)

Question 19

golgi apparatus

Answer 19

organelle active in synthesis, modification, sorting, and secretion of cell products

consists of flattened membranous sacs called cisternae

golgi stack has distinct structural directionality: cis face receives, trans face ships

manufactures some macromolecules

Question 20

lysosome

Answer 20

digestive organelle where macromolecules are hydrolyzed

acidic environment that is not ctive in cytosol

only in animal cells

Question 21

mitochondrion

Answer 21

organelle where cellular respiration occurs and most ATP is generated

Question 22

peroxisome

Answer 22

organelle with various specialized metabolic functions

produces hydrogen peroxide as a by-product then converts it to water

Question 23

microvilli

Answer 23

projections that increase the cell’s surface area

Question 24

centrosome

Answer 24

region where the cell’s microtubules are initiated

contains a pair of centrioles

only in animal cells

Question 25

endoplasmic reticulum

Answer 25

network of membranous sacs and tubes active in membrane synthesis and other synthetic and metabolic processes has rough (ribosome studded) and smooth regions (lacks ribosomes)

Question 26

centrole vacuole

Answer 26

prominent organelle only in older plant cells functions include storage, breakdown of waste products, hydrolysis of macromolecules enlargement of vacuole is a major mechanism of plant growth only in plant cells

Question 27

chloroplast

Answer 27

photosynthetic organelle converts energy of sunlight to chemical energy stored in sugar molecules only in plant cells

Question 28

plasmodesmata

Answer 28

channels through cell walls that connect the cytoplasms of adjacent cells only in plant cells

Question 29

cell wall

Answer 29

outer layer that maintains cell's shape and protects the cell from mechanical damage made of cellulose, other polysaccharides, and protein primary cell wall and secondary cell wall only in plant cells

Question 30

nucleus

Answer 30

contains most of the genes in the eukaryotic cell most conspicuous cell; averages 5 µm in diameter includes nuclear envelope, pore complex, nuclear lamina, chromosomes, chromatin, nucleolus

Question 31

pore complex

Answer 31

protein structure that lines each pore regulates entry and exit of proteins and RNAs

Question 32

nuclear lamina

Answer 32

lines nuclear side of nuclear envelope netlike array of protein filaments that maintain shape of nucleus

Question 33

chromosomes

Answer 33

discrete unit of DNA in the nucleus carry genetic information each contains one long DNA molecule associated with proteins

Question 34

messenger RNA (mRNA)

Answer 34

sythesized by the nucleus transported to cytoplasm translated by ribosomes into specific polypeptides

Question 35

functions of smooth ER

Answer 35

synthesis of lipids including oils, phospholipids, steroids detoxify drugs and poisons especially in liver cells detoxification involves adding hydroxyl groups to drugs stores calcium ions

Question 36

functions of rough ER

Answer 36

secretes proteins (glycoproteins) produced by ribosomes attached to rough ER polypeptide chain grows from a bound ribosome chain is threaded into the ER lumen through a pore polypeptide folds into its functional share

Question 37

phagocytosis

Answer 37

process of surrounding smaller organism

Question 38

autophagy

Answer 38

recycle cell's own organic mateiral

Question 39

contractile vacuole

Answer 39

pump excess water out of the cell maintain suitable conditions for ions and molecules common in freshwater protists

Question 40

endosymbiont theory

Answer 40

early ancestor of eukaryotic cells engulfed energy using non-photocynthetic prokaryotic cell eventually becomingendosymbiont (cell within another cell) consistent with characteristics: two membrans, contain ribosomes and DNA

Question 41

mitrochondrial matrix

Answer 41

enclosed by inner membrane of mitochondria contains many different enzymes and mitochondrial DNA catalyze some of the steps of cellular respiration large surface area of inner membrane increases productivity

Question 42

thylakoids

Answer 42

membrane system inside the chloroplast flattened, interconnected sacs granum: stacks of thylakoids stroma: fluid outside the thylakoid containing chloroplast DNA

Question 43

types of plastids

Answer 43

chloroplast amyloplast: colorless organelle that stores starch chromoplast: pigments in fruits and flowers

Question 44

peroxisomes

Answer 44

specialized metabolic compartment bounded by a single membrane

Question 45

microtubules

Answer 45

hollow rods constructed from globular portein called tubulin tubulin protein is a dimer -- molecule made of two subunits serves as track for organelles with motor proteins grow out from centrosomes and centrioles

Question 46

cilia and flagella

Answer 46

microtubule-containing extensions of some cells flagella drive the cell through liquid cilia can drive the cell or move objects along surface of cell

Question 47

9+2 pattern

Answer 47

nine doublets of microtubules are arranged in a ring two single microtubules in the center

Question 48

9+0 pattern

Answer 48

nine doublets of microtubules are arranged in ring no microtubules in center non-motile primary cilia

Question 49

basal body

Answer 49

anchors the cilium or flagellum in the cell

Question 50

dyneins

Answer 50

large motor proteins that cause bending two feet walk along the microtubule one foot maintains contact while the other moves

Question 51

microfilaments

Answer 51

thin solid rods built from actin moelcules, granular protein bear tension and support muscle contraction

Question 52

intermediate filaments

Answer 52

larger than microfilaments, smaller than microtubules maintain cell shape anchor nucleus and othe organelles formation of nuclear lamina

Question 53

extracellular matrix (ECM)

Answer 53

made of glycoproteins and other carbohydrate containing molecules collegen is one of most abundant glycogens forms strong fibers outside the cell

Question 54

integrins

Answer 54

membrane proteins with two subunits bind to the ECM on one side and to associated proteins attached to microfilaments

Question 55

fibronectin

Answer 55

attaches the ECM to integrins embedded in the plasma membrane

Question 56

collagen

Answer 56

fibers are embedded in a web of proteoglycan complexes

Question 57

plasmodesmata

Answer 57

type of cell junction in plant cells perforates cell walls membrane lined channel filled with cytosol joins adjacent cells and unifies plant into single organism water and small solutes can pass freely

Question 58

tight junction

Answer 58

plasma membrane of neighboring cells are very tightly pressed together bound together by specific proteins and forming a continuous seal

Question 59

desmosomes

Answer 59

funtion like rivets to fasten cells together in strong sheets intermediate filaments made of strudy keratin proteins anchor desmosomes attach muscle cells to each other muscle

Question 60

gap junction

Answer 60

provide cytoplasmic channels from one cell to an adjacent cell consist of membrane proteins that surround a pore ions, sugars, amino acids and other small molecules can pass