Chapter 6: A Tour of The Cell 2

Question 1

Mitochondria

Answer 1

sites of cellular respiration. 1-10 um. mobile.

Question 2

chloroplasts

Answer 2

sites of photosynthesis. 3-6 um. mobile.

Question 3

endosymbiont theory

Answer 3

early ancestor of eukaryotic cells engulfed prokaryote.
- mitochondria and chloroplasts have a double membrane (possibly like ancestral prokaryote)
- both have DNA and ribosomes
- both are somewhat autonomous

Question 4

cristae

Answer 4

infoldings of inner membrane of mitochondrion. increases surface area of inner mitochondrial membrane

Question 5

mitochondrial matrix

Answer 5

second compartment of mitochondrion enclosed by inner membrane. its enzymes catalyze some steps for cellular respiration.

Question 6

thylakoids

Answer 6

flattened, interconnected sacs within chloroplasts

Question 7

grana

Answer 7

stacks of thylakoids

Question 8

stroma

Answer 8

fluid outside thylakoids. contains DNA and ribosomes and membranes

Question 9

Plastids

Answer 9

family of plant organelles (including chloroplasts).

Question 10

amyloplast

Answer 10

colorless plastid that stores starch (amylose), particularly in roots and tubers

Question 11

chromoplast

Answer 11

plastid that stores pigments (orange hue for fruits/flowers)

Question 12

Peroxisome

Answer 12

single membrane organelle whose removes hydrogen from substrate and transfers it to O2 to form H2O2 (hydrogen peroxide). an enzyme can convert the h2o2 to h20. it can break down fatty acids (with oxygen) or detoxify alcohol/substances (remove hydrogen)

Question 13

glyoxysome

Answer 13

specialized peroxisomes in plant seeds. converts fatty acids to sugar. (energy for seedling)

Question 14

cytoskeleton

Answer 14

dynamic network of fibers extending throughout cytoplasm. supports shape and organizes structures + activities of cells.

Question 15

Motor proteins

Answer 15

assists with cell motility.

Question 16

microtubules

Answer 16

structure: hollow tubes; 13 columns of tubulin dimers
diameter: 25 nm with 15 nm lumen
subunits: a tubulin and b tubulin
functions: maintenance of cell shape (compression-resisting), cell motility (cilia/flagella), chromosome/organelle movements

Question 17

microfilaments

Answer 17

structure: two intertwined strands of actin
diameter: 7 nm
subunits: actin
functions: maintenance of cell shape (tension-bearing) changes in cell shape, muscle contraction, cytoplasmic streaming, cell motility (pseudopodia), cell division (cleavage furrow)

Question 18

intermediate filaments

Answer 18

structure: fibrous proteins supercoiled into thicker cables
diameter: 8-12 nm
subunits: one of several different proteins (depends on cell type)
functions: maintenance of cell shape (tension-bearing), anchorage of nucleus and certain other organelles, formation of nuclear lamina

Question 19

microtubule structure

Answer 19

two slightly different ends (because of orientation of tubulin dimers). one end accumulates/releases tubulin dimers faster (plus end).

Question 20

centrosome

Answer 20

microtubule-organizing center for animal cells. (compression resisting)

Question 21

centrioles

Answer 21

9 sets of triplet microtubules arranged in a ring. a pair for each centrosome.

Question 22

flagella

Answer 22

undulating motion. 10-200 um length, 0.25 um diameter. 1-2 per cell.

Question 23

cilia

Answer 23

back and forth motion. 2-20 um length. 0.25 um diameter. several motile cilia per cell, one primary cilia (9+0 pattern) per cell (recieves signals).

Question 24

cilia/flagella strucure

Answer 24

nine doublets of microtubules arranged in a ring. two single microtubules in the center. sheathed in plasma membrane extension.

Question 25

Basal body

Answer 25

anchors cilia/flagella. similar structure to centriole

Question 26

cross-linking proteins

Answer 26

connects outer doublet microtubules in flagella + motile cilia.

Question 27

dyneins

Answer 27

large moter proteins between the outer doublet microtubules. walks along the doublets (held in place by cross-linking proteins), making them curve/bend.

Question 28

actin

Answer 28

globular protein.

Question 29

cortex

Answer 29

outer cytoplasmic layer of cell. supported by microfilaments, and has semisolid gel consistency

Question 30

myosin

Answer 30

motor protein for actin.

Question 31

pseuodopodia

Answer 31

cellular extensions that undergo localized contractions due to actin/myosin

Question 32

cytoplasmic streaming

Answer 32

circular flow of cytoplasm within cells

Question 33

cell wall

Answer 33

extracellular plant cell structure. thicker than plasma membrane, made up of microfibrils of cellulose

Question 34

primary cell wall

Answer 34

first layer of cell wall. relatively thin and flexible.

Question 35

cell wall formation.

Answer 35

cellulose synthase makes cellulose microfibrils, oriented at right angles to direction of cell expansion. microtubules guides cellulose synthase as it deposits cellulose.

Question 36

middle lamella

Answer 36

between primary walls. thin layer with lots of pectin (sticky polysaccharide).

Question 37

secondary cell wall

Answer 37

several laminated layers, strong and durable matrix.

Question 38

ECM

Answer 38

present in animal cells. made mostly of glycoproteins

Question 39

collagen

Answer 39

most abundunt ECM glycoprotein. forms strong fibers outside the cells.

Question 40

proteoglycans

Answer 40

small core protein with several carbohydrate chains attached. network of ECM

Question 41

fibronectin

Answer 41

glycoprotein that attaches cells to ECM

Question 42

integrins

Answer 42

cell-surface receptor proteins that span the plasma membrane and bind on cytoplasmic side to associated microtubule proteins. attaches to fibronectin and other ECM proteins. transmits signals between ECM and cell.

Question 43

plasmodesmata

Answer 43

membrane lined channels filled with cytoplasm in cell walls. joins plant cells.

Question 44

tight junctions

Answer 44

animal cells. plasma membranes of cells pressed very tightly together and bound by specific proteins. prevents leakage of extracellular fluid across layer of epithelial cells

Question 45

desmosomes

Answer 45

animal cells. fastens cells together (ex: muscle cells). intermediate filaments of keratin anchor desmosomes in cytoplasm.

Question 46

gap junctions

Answer 46

animal cells. membrane protein surrounding a pore. provide cytoplasmic channels from one cell to an adjacent cell.