chapter 4 questions

Question 1

which type of microscope would you use to study a)the changes in shape of a living human white blood cell b)the finest details of surface texture of a human hair c)the detailed structure of an organelle in a liver cell?

Answer 1

a)light microscope b)scanning electron microscope c)transmission electron microscope

Question 2

to convince yourself that a small cell has more surface area relative to volume than a large cell, compare the surface-to-volume ratios of the large cube and one of the small cubes in figure 4.2A

Answer 2

large: 54/27 = 2; small cube: 6/1 = 6 (surface area is 1 x 1 x 6 sides = 6 units2; volume is 1 x 1 x 1 unit3)

Question 3

list 3 features that are common to prokaryotic and eukaryotic cells. list 3 features that differ.

Answer 3

both types cells have plasma membranes, chromosomes containing DNA, and ribosomes. prokaryotic cells are smaller, do not have a nucleus that houses their DNA or other membrane enclosed organelles, and have smaller, somewhat different ribosomes.

Question 4

which of the following cellular structures differs from the others in the list: mitochondria, chloroplast, ribosome, lysozome, vacuole? how does it differ?

Answer 4

ribosome, because it is the only structure in the list that is not bounded by a membrane

Question 5

what are the main functions of the nucleus?

Answer 5

to house and copy DNA and pass it on to daughter cells in cell division; to build ribosomal subunits; to transcribe DNA instructions into RNA and thereby control the cell’s functions

Question 6

what role do ribosomes play in carrying out the genetic instructions of a cell?

Answer 6

ribosomes synthesize proteins according to the instructions carried by messenger RNA from the DNA in the nucleus

Question 7

which structure includes all others in the list: rough ER, smooth ER, endomembrane system, nuclear envelope?

Answer 7

endomembrane system

Question 8

explain why we say that the endoplasmic reticulum is a biosynthetic factory?

Answer 8

the ER produces a huge variety of molecules, including phospolipids for cell membranes, steroid hormones, and proteins (synthesized by bound ribosomes) for membranes, other organelles, and secretion by the cell.

Question 9

what is the relationship of the golgi apparatus to the ER in a protein-secreting cell?

Answer 9

the golgi receives transport vesicles that bud from the ER and that contain protein synthesized by ribosomes attached to the ER. the golgi finishes processing the proteins and then dispatches transport vesicles that secrete the proteins to the outside of the cell

Question 10

how is a lysozome like a recycling centre?

Answer 10

it breaks down damaged organelles and recycles their molecules

Question 11

is a food vacuole part of the endomembrane system?

Answer 11

yes; it forms by pinching in from the plasma membrane, which is part of the endomembrane system

Question 12

how do transport vesicles help tie together the endomembrane system?

Answer 12

transport vesicles move membranes and substances they enclose between components of the endomembrane system

Question 13

what is cellular respiration?

Answer 13

a process that converts the chemical energy of sugars and other food molecules to the chemical energy of ATP

Question 14

which membrane in a chloroplast appears to be the most extensive? why?

Answer 14

the thylakoid membranes are the most extensive, providing a large area of membrane that contains chlorophyll for photosynthesis

Question 15

all eukaryotes have mitochondria, but not all eukaryotes have chloroplasts. can you propose an evolutionary explanation for this observation?

Answer 15

the first endosymbiotic event would have given rise to eukaryotic cells containing mitochondria. at least one of these cells may have then taken up a photosynthetic prokaryote, giving rise to eukaryotic cells that contain chloroplasts in addition to mitochondria

Question 16

which component of the cytoskeleton is most important in a)holding the nucleus in place within the cells; b) guiding transport vesicles from the golgi to the plasma membrane; c) contracting muscle cells?

Answer 16

a) intermediate filaments b)microtubules c) microfilaments

Question 17

compare and contrast cilia and flagella.

Answer 17

both cilia and flagella have the same 9+2 pattern of mmicrotubuoles and mechanism for bending. cilia are shorter, more nutritious, and beat in a coordinated oar-like pattern. the longer flagella which are limited to one or a few per cell, undulate like a whip

Question 18

why does a lack of dyenein proteins affect the action of both cilia and flagella?

Answer 18

both cilia and flagella have the same arrangement of microtubuole doublets with attached dyenein motor proteins that cause them to bend

Question 19

a muscle tear injury would probably involve the rupture of which type of cell junction?

Answer 19

anchoring junction

Question 20

which animal cell junction is analogous to a plasmodesma?

Answer 20

a gap junction

Question 21

how do mitochondria, sooth ER, and the cytoskeleton all contribute to the contraction of a muscle cell?

Answer 21

mitochondria supply energy in the form of ATP. the smooth ER helps regulate contraction by the uptake and release of calcium ions. microfilaments function in the actual contractile apparatus