Ch 6. A Tour of the Cell

Question 1

why are there upper and lower limits to cell size?

Answer 1

-surface area increases slower than volume. more volume = more food needed & more waste generated, but a lower S.A. = less room for food to enter and waste to leave

Question 2

what are the four main differences between prokaryotic and eukaryotic cells?

Answer 2

1. size = prokaryotes are smaller than eukaryotes
2. nucleus = prokaryote has no nucleus
3. membrane-bound organelles = prokaryotes have none
4. organism size = prokaryotes are 1 cell organisms, eukaryotes are uni/multicellular

Question 3

what are the main benefits of compartmentalization in eukaryotic cells?

Answer 3

-improves the efficiency of cellular functions by allowing many things to occur in one space
-concentrates molecules [eg - digestive enzymes in lysosomes]
-have more membranes for membrane-bound pathways [ETC]

Question 4

what is the mathematical relationship between diameter, volume, and surface area?

Answer 4

as diameter increases…
-volume goes up by D^3
-surface area goes up by D^2

ex. a diameter increase of 5x = 125x volume but only 25x surface area

Question 5

what does the cytoplasm consist of?

Answer 5

cell organelles + cytosol (jelly the organelles float in) + cytoskeleton

Question 6

what is the structure of the nucleus?

Answer 6

-round, central organelle of the cell with:
1. double membrane
2. nuclear pores (holes)
3. nuclear lamina

Question 7

what is the function of the nucleus?

Answer 7

-enclose and protect genetic material
-transcribe DNA to RNA

Question 8

what is the difference between cytosol and cytoplasm?

Answer 8

cytosol = the fluid part of the cytoplasm
cytoplasm = organelles / cytoskeleton, which float in the cytosol

Question 9

what is the structure of ribosomes and what are the two kinds?

Answer 9

structure: 2 subunits of RNA and protein
1. bound = “stuck” to ER, make proteins for secretion
2. free = loose in cytosol, make proteins for inside the cell

Question 10

what is the function of a ribosome?

Answer 10

to translate mRNA to make proteins

Question 11

what are the broad components of the endomembrane system?

Answer 11

-endoplasmic reticulum (rough & smooth)
-golgi apparatus
-lysosomes
-vacuoles
-central vacuole [plants only]

Question 12

what is the structure of the endoplasmic reticulum?

Answer 12

-a membranous maze of tubules and cisterna, continuous with the nucleus

Question 13

what is the function of both kinds of endoplasmic reticulum?

Answer 13

rough: has ribosomes attached to it, so makes membrane proteins & phospholipids for use outside cell

smooth: lipid synthesis, detoxification, calcium storage in muscle cells

Question 14

what is the structure of the golgi apparatus (what are the two ends?)

Answer 14

cis end = receives vesicles
trans end = ships out modified vesicles

Question 15

what is the function of the golgi apparatus?

Answer 15

-synthesizing polysaccharides
-modifying carbohydrates
-sending previously made products to right destination

Question 16

what is the structure of a lysosome?

Answer 16

-a membrane bound sac with a low pH and a bunch of digestive enzymes

Question 17

what is the function of a lysosome?

Answer 17

-digesting foreign particles
-removing dead cell debris

Question 18

what is the structure & function of vacuoles?

Answer 18

structure: membrane bound sacs
function: mostly food storage & contraction

Question 19

what is the structure & function of central vacuoles? [plants only]

Answer 19

structure: sacs enclosed by a tonoplast membrane
function: storing wastes, proteins, and pigments

Question 20

what is the structure of mitochondria?

Answer 20

-double membrane with an inner and outer
-membranes have an intermembrane space + a matrix
-has its own DNA and ribosomes

Question 21

what is the function of mitochondria?

Answer 21

cellular respiration

Question 22

what are plastids? what are the three kinds?

Answer 22

plastids are double membrane organelles found in photosynthetic organisms
-consist of chloroplasts, amyloplasts, and chromoplasts

Question 23

what is the structure of chloroplasts?

Answer 23

-are plastids [double membrane organelles]
-have inner sacs called thylakoids stacked like pancakes called grana
-external space is called stroma

Question 24

what is the function of chloroplasts?

Answer 24

photosynthesis

Question 25

what do amyloplasts and chromoplasts store?

Answer 25

amyloplasts = store starch and amylase to break down starch
chromoplasts = store pigments

Question 26

what is the evidence that mitochondria and chloroplasts were once their own organelles?

Answer 26

-both are very similar genetically to bacteria
-both have their own, separate DNA
-have cell membranes similar to bacteria

Question 27

what is the structure of peroxisomes?

Answer 27

-peroxisomes are a single membrane compartment

Question 28

what is the function of peroxisomes?

Answer 28

-detoxification of free radicals (atoms with unpaired electrons that can damage cells)

Question 29

what are the components of the cytoskeleton?

Answer 29

-actin filaments / microfilaments
-intermediate filaments
-microtubules, which include cilia and flagella

Question 30

what is the structure & function of actin filaments?

Answer 30

structure: thin, long fibers
function: allow for muscle stretch and contraction by changing cell shape

Question 31

what is the structure and function of intermediate filaments?

Answer 31

structure: intermediate width fibers, diff. types in each cell type
function: maintaining cell shape

Question 32

what is the structure of microtubules?

Answer 32

-a thick, hollow cylinder composed of repeating tubulin proteins

-can work alone or be grouped together to make larger structures

Question 33

what is the function of lone microtubules [NOT grouped]?

Answer 33

-cell support
-organization & movement of vesicles
-cell division [mitotic spindle]

Question 34

what is the function of grouped microtubules [what 3 structures do they make]?

Answer 34

can make larger structures…
1. flagella = whiplike tails that move sperm
2. cilia = hairlike cell projections that move mucus
3. centrioles = organize loose microtubules during cell division

Question 35

in what kind of organisms are cell walls found?

Answer 35

plants, fungi, algae, protists, prokaryotes

Question 36

what are the functions of the cell wall?

Answer 36

-protection of the cell from external environment
-maintaining cell shape
-regulating fluid intake

Question 37

what is the structure of the cell wall?

Answer 37

-thick cellulose embedded in a matrix, 3 walls:
1. primary wall = furthest from cell membrane
2. middle lamella = contains pectin which acts as a glue
3. secondary wall = closest to cell membrane

Question 38

what are the components of the extracellular matrix / ECM?

Answer 38

-glycoproteins
-proteoglycans
-fibronectin / integrins

Question 39

what are glycoproteins?

Answer 39

-proteins with carbohydrate chains attached, such as collagen
-work to provide structure & bind tissues together [muscle-skin, skin-bone, muscle-bone]

Question 40

what are proteoglycans?

Answer 40

carbohydrates with some protein
-work as shock absorbers [GAGs]

Question 41

what is fibronectin and integrin?

Answer 41

integrin = connects proteins inside cell with fibronectin outside cell

-allows cell to react to external conditions

Question 42

what are the four kinds of intercellular junctions?

Answer 42

1. plasmodesmata [plants ONL]
2. tight junctions
3. desmosomes
4. gap junctions

Question 43

what are plasmodesmata?

Answer 43

-channels connecting plant cells
-allows water and nutrients to flow from roots to leaves

Question 44

what are tight junctions?

Answer 44

-fused membranes that prevent fluid leakage
-found in the bladder & stomach primarily

Question 45

what are desmosomes?

Answer 45

-spot welds that fasten cells together
-found in skin & cardiac muscle cells

Question 46

what are gap junctions?

Answer 46

-channels between cells that allow them to communicate [NEURONS]