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Biology 100 > Chapter 6: A Tour of the Cell > Flashcards

Chapter 6: A Tour of the Cell Flashcards

1
Q

What is cell fractionation?

A

separating organelles by breaking components of cell apart (ex. grinding up or osmotic shock) then blend to homogenate, then centrifuge

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2
Q

Three key differences between prokaryotes and eukaryotes

A

euks larger
prokaryotes have nucleoid, euks have nucleus
euks have distinct organelles

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3
Q

Name the three reasons cells are small

A

need appropriate surface to volume ratio
rate of movement into cell
local concentration of cell contents is maintained

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4
Q

large cells have a ___ surface to volume ratio than smaller cells

A

smaller

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5
Q

The more cell surface area available, the more

A

nutrients you can absorb

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6
Q

What is the endomembrane system?

A

consists of organelles that help regulate protein function

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7
Q

The components in the endomembrane system are connected via transfer by

A

vesicles

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8
Q

What are the two regions of the ER?

A

Rough and Smooth

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9
Q

Describe characteristics of the smooth ER

A

lack ribosomes
contains enzymes in lipid based rxn
stores intercellular calcium

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10
Q

Describe characteristics of rough ER?

A

Has membrane bound sacs and ribosomes
ribosomes generate polypeptides within endomembrane system

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11
Q

What occurs in golgi apparatus?

A

where proteins are packaged and shipped

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12
Q

What is a lysosome?

A

Membranous sac of hydrolytic enzymes that can digest large molecules, think of as recycle center

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13
Q

What is the purpose of the proton pumps on surface of lysosomes?

A

Maintains pH

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14
Q

What are vacuoles?

A

Plant cell lysosome
stores pigments, toxins

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15
Q

Mitochondrial DNA are ___ chromosomes

A

linear

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16
Q

Mitochondria and chloroplasts share some similarities with bacteria. What are they?

A

Enveloped by double membrane
free ribosomes and circular DNA
produced somewhat independently in cells

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17
Q

What occurs on peroxisomes?

A

Reduction and oxygenation reactions

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18
Q

What is the cytoskeleton?

A

Network of fibers that organizes structures and activities in cell

19
Q

cell crawling is made possible by ____

A

actin filaments

20
Q

The most abundant compoennt of the ECM in animal cells is

A

collagen

21
Q

True or False: the cell wall is considered an extracellular component

A

True

22
Q

What are tight junctions?

A

when a cell attachment is adjacent to proteins in another cell. Forms a tight seal that prevents fluid from leaking out

23
Q

What are desmosomes?

A

proteins found in membrane that form bridges between anchoring proteins and adjacent
intermediate filaments reinforce desmosomes by attaching to proteins

24
Q

What are gap junctions

A

provide a means of cell communication

channels in adjacent cells that allow small molecules from one cell to next
allow for rapid communication

25
Q

What are plasmodesmata?

A

cell junctions that occur in regions where there are holes in the cell wall

26
Q

Describe the molecular composition of nucleoli and explain their function.

A

Nucleoli consist of DNA and the ribosomal RNAs (rRNAs) made according to its genes in the DNA, as well as proteins imported from the cytoplasm. Together, the rRNAs and proteins are assembled into large and small ribosomal subunits. (These are exported through nuclear pores to the cytoplasm, where they will participate in polypeptide synthesis.)

27
Q

Describe the structural and functional distinctions between
rough and smooth ER.

A

The primary distinction between rough and smooth ER is the presence of
bound ribosomes on the rough ER. Both types of ER make phospholipids, but membrane proteins and secretory proteins are all produced by the ribosomes on the rough ER. The smooth ER also functions in detoxification, carbohydrate metabolism, and storage of calcium ions.

28
Q

Imagine a protein that functions in the ER but requires modification in the Golgi apparatus before it can
achieve that function. Describe the protein’s path through the cell, starting with the mRNA molecule that specifies the protein.

A

The mRNA is synthesized in the nucleus and then passes out through a nuclear pore to the cytoplasm, where it is translated on a bound ribosome, attached to the rough ER. The protein is synthesized into the lumen of the ER and may be modified there. A transport vesicle carries the protein to the Golgi apparatus. After further modification in the Golgi, another
transport vesicle carries it back to the ER, where it will perform its cellular
function

29
Q

A classmate proposes that mitochondria and chloroplasts should be classified in the endomembrane
system. Argue against the proposal

A

Mitochondria and chloroplasts are not derived from the ER, nor
are they connected physically or via transport vesicles to organelles of the endomembrane system. Mitochondria and chloroplasts are structurally quite different from vesicles derived from the ER, which are bounded by a single membrane

30
Q

Do plant cells have mitochondria? Explain

A

Yes. Plant cells are able to make their own sugar by photosynthesis, but mitochondria in plant cells are the organelles that are able to generate
ATP molecules to be used for energy generation from sugars, a function required in all cells

31
Q

In what way are the cells of plants and animals structurally
different from single-celled eukaryotes?

A

The most obvious difference is the presence of direct cytoplasmic connections between cells of plants (plasmodesmata) and animals (gap junctions). These connections result in the cytoplasm being continuous between adjacent cells.

32
Q

If the plant cell wall or the animal extracellular
matrix were impermeable, what effect would this have on
cell function?

A

The cell would not be able to function properly and would probably soon die, as the cell wall or ECM must be permeable to allow the exchange of matter between the cell and its external environment.

33
Q

_____ guide vesicles from the ER to the Golgi apparatus and
from the Golgi to the plasma membrane.____ are
also involved in the separation of chromosomes during cell
division,

A

microtubules

33
Q

In animal cells, microtu-
bules grow out from a_____ a region that is often located near the nucleus. These microtubules function as
compression-resisting girders of the cytoskeleton

A

centrosome

33
Q

True or False: Like microtubules, microfilaments seem to be present in all eukaryotic cells

A

True

33
Q

Within the
centrosome is a pair of _____,each composed of nine
sets of triplet microtubules arranged in a ring

A

centrioles

34
Q

the structural role of microfilaments in the cytoskeleton is to

A

bear tension

35
Q

Describe the role of myosin and microfilaments in muscle motility

A

The ”walking” of
myosin projections (the so-called heads) drives the parallel myosin and
actin filaments past each other so that the actin filaments approach each
other in the middle (red arrows). This shortens the muscle cell. Muscle
contraction involves the shortening of many muscle cells at the same
time (TEM)

36
Q

True or False: intermediate filaments are found in other cells with the same frequency as microfilaments

A

false they are only found in some animals

37
Q

Compare intermediate filaments to microfilaments and microtubules

A

Intermediate filaments are more permanent fixtures of cells than are microfilaments and microtubules, which are often disassembled and reassembled in various parts
of a cell.

38
Q

Describe tight junctions

A

tight junctions, the plasma
membranes of neighboring cells are
very tightly pressed against each
other, bound together by specific
proteins. Forming continuous seals
around the cells, tight junctions
establish a barrier that prevents
leakage of extracellular fluid across a
layer of epithelial cells (see red
dashed arrow). For example, tight
junctions between skin cells make
us watertight.

39
Q

Describe desmosomes

A

Desmosomes (one type of anchor-
ing junction) function like rivets,
fastening cells together into strong
sheets. Intermediate filaments
made of sturdy keratin proteins an-
chor desmosomes in the cytoplasm.
Desmosomes attach muscle cells
to each other in a muscle. Some
“muscle tears” involve the rupture
of desmosomes.

40
Q

Describe gap junctions

A

Gap junctions (also called com-
municating junctions) provide
cytoplasmic channels from one
cell to an adjacent cell and in this
way are similar in their function to
the plasmodesmata in plants. Gap
junctions consist of membrane pro-
teins extending from the mem-
branes of the two cells. These
proteins create pores through
which ions, sugars, amino acids,
and other small molecules may
pass. Gap junctions are necessary
for communication between cells in
many types of tissues, such as heart
muscle, and in animal embryos

Biology 100 (27 decks)

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