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BIO112 > Unit 2 Chapter 7: Cells > Flashcards

Unit 2 Chapter 7: Cells Flashcards

1
Q

What are chromosomes (in prokaryotes)

A
  • the most prominent structure in bacterial cells

- usually have 1 circular one (large DNA molec with some proteins)

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2
Q

How does DNA fit into small cells

A

DNA double helix coils on itself with the help of enzymes to form the highly compacted “super coil structure”

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3
Q

Where are bacterial chromosomes found

A

in the nucleoid (usually in center/20% of cells volume)

NOTE: nucleoid is enclosed by a membrane

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4
Q

What are plasmids (prokaryotes)

A

small, circular, usually super-coiled DNA molecs found in bacteria that contain genes but are physically independent of the main circular chromosome
-can be considered auxiliary genetic elements as the genes inside them are not usually required

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5
Q

What are ribosomes

A
  • structures that manufacture proteins

- in bacteria they contain RNA and proteins

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6
Q

Describe the photosynthetic membranes in prokaryotes

A
  • contain the enzymes and pigment molecs required for photosynthesis to occur and develop as infoldings of the plasma membrane
  • sometimes vesicles pinch off as membrane folds in
  • sometimes flattened stacks of photosyn membrane form the infolds in the plasma membrane
  • large surface area allows for more reactions to occur
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7
Q

What are 4 key tasks of bacterial organelles

A
  1. storing calcium ions or other key molecs
  2. holding magnetite crystals which act as a compess and sense a magnetic field and swim in a directed way
  3. organizing enzymes in charge of making carbon compounds from CO2
  4. hiding enzymes that generate chemical energy from ammonium ions
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8
Q

What is the cytoskeleton (prokaryotes)

A

long thin fibres made of long polymers of globular proteins that serve as structural support
-responsible for shape, cell division, transport of plasmids and organization of cell interior

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9
Q

What are flagella (prokaryotes)

A
  • enable species to swim by rotating like a propeller
  • tail-like structure
  • few in # and located on cell surface
  • made of flagellin
  • no membrane
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10
Q

Describe the structure and function of the cell wall in prokaryotes

A
  • structure: tough, fibrous layer that surrounds the plasma membrane
  • resists pressure that is exerted due to inward water flow from osmosis. protects cell and gives it shape and rigidity
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11
Q

Why is compartmentalization beneficial?

A
  • incompatible chem reactions can be separated

- chemical reactions become more efficient

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12
Q

What is the nucleus

A
  • brain of cell
  • contains chromosomes and is the info storage and processing centre
  • enclosed by a DOUBLE membrane
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13
Q

What is the nuclear envelope

A

double membrane that encloses nucleus and is studded with openings/inside surface is linked to fibrous proteins that form a sheet called the nuclear lamina
-continuous with endomembrane system

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14
Q

What does the nuclear lamina do

A

stiffens structure and maintains shape

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15
Q

Do chromosomes float freely in the nucleus

A

no, each has a distinct spot and is attached nuclear lamina in at least one spot

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16
Q

What is the nucleolus

A

distinct region in nucleus where RNA found in ribosomes are made and small ribosomal subunits are assembled

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17
Q

What is the ER

A

extensive series of membrane bound sacs extending from nuclear envelope into cytoplasm

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18
Q

What is the difference between smooth and rough ER

A

rough=has attached ribosomes that make proteins to be inserted into the plasma membrane, secreted to the outside of the cell or shipped to an organelle; rough ER products are packaged into vesicles and transported

smooth=no ribosomes, contains enzymes that catalyze lipid reactions, manufactures phospholipids, reservoir for Ca ions (signalling)

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19
Q

What is the golgi apparatus

A

flattened membranous sacs (cisterna) which are stacked

  • organizes, packages and ships proteins (processing and sorting)
  • cis-faces ER
  • trans-faces membrane
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20
Q

What does the cis side of the golgi body do

A

receives products from rough ER

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21
Q

What dies the trans side of the golgi body do

A

ships the products away towards cell surface

22
Q

What are ribosomes (eukaryotes)

A

made of 4 rRNAs and 80 proteins, make proteins, NOT classified as an organelle because not surrounded by a membrane

23
Q

What are peroxisomes

A

globular organelles: contain enzymes, centres for oxidation reactions, have a single membrane and originate as buds from the ER

24
Q

What are lysosomes

A

digestive centres

25
Q

What is autophagy

A
  • a damaged organelle is brought in and delivered to a lysosome
  • its digested
  • small molecs from the digestion are released into the cytosol
26
Q

What is phagocytosis

A

cell eating

  • plasma membrane detects a cell or particle and engulfs it creating a phagosome
  • delivered to lysosome and digested
  • small molecs from the digestion are released into the cytosol
27
Q

What is pinocytosis

A

cell drinking

  • fluid brought into cell via tiny vesicles that form infoldings of plasma membrane
  • fluid used elsewhere in cell
28
Q

What is receptor mediated endocytosis

A

think claw machine

  • molec binds to membrane proteins that act like receports
  • membrane folds off and pinches in to form an early endosome
  • endosome undergoes processing ie;. activation of proton pumps that lower pH
  • early endosome matures into a late one and recieves digestive enxymes from golgi body
  • late endosome turns into lysosome
29
Q

What are vacuoles

A

large storage depot usually for water or ions

30
Q

What is the mitochondria

A

powerhouse of cell

  • has 2 membranes
  • contains DNA (chromosomes) which allows them to make some of their own proteins
  • have own ribosomes
  • plastids
  • have cristae which increase SA to fill membrane with proteins and make ATP
31
Q

What are chlroroplasts

A
  • has DNA
  • in plants, mature form of plastids, convert solar energy into chemical energy for photosynthesis
  • has a double membrane
  • thylakoids stacked into grana which are all in stroma
  • larger than mitochondria
32
Q

What is lignin

A

forms a branching cave like network that is impossible for enzymes to attack
in the secondary cell wall that some plants produce

33
Q

Why are cells small

A

surface area to volume ratio, most reactions require diffusion and diffusing molecules don’t travel long distances due to their random walk

34
Q

What is included in the endomembrane system

A

ER, golgi body, vesicles, nuclear and cell mebranes

35
Q

What happens in the nucleus

A

DNA is replicated, DNA is transcribed in to mRNA and rRNA, mRNA is translated rRNA is not

36
Q

Why is rRNA not translated

A

it directly folds into a 3D structure

37
Q

What does the animal pancreatic cell do

A

exports digestive enzymes

38
Q

What does the animal testis cell do

A

exports lipid soluble signals

39
Q

What is the evidence that mitochondria and chloroplasts are descendants of bacteria (endosymbiont theory)

A
  1. double membrane
  2. own genome
  3. own ribosomes more similar to eubacteria
  4. genes more similar to eubacteria genes
40
Q

What was the Pulse-Chase experiment

A

used to research the secretory path way:
pulse=expose exp. cells to a high concentration of a labelled molec for a short time
chase=larger amounts of unlabelled version of the same molec for a longer time

results support the secretory path way that proteins move from ER to golgi to secretetion

41
Q

What is the signal hypothesis

A
  1. ribosome synthesizes ER signal sequence
  2. signal sequence binds to a signal recognition particl:SRP
  3. ribosome+SRP+ signal sequence attaches to SRP receptor in ER membrane
  4. once receptor and SRP connect, SRP is released
  5. signal sequence removed and protein synthesis is completed
42
Q

What are the possible “fates” for proteins

A

stay in endomembrane system, sent to lysosomes, plasma membrane for exocytosis or outside of the cell

43
Q

What are actin filaments and what is their function

A

-microfilaments
-made of actin
-polar, has a + and - end
-treadmilling=the addition or subtracting of actin molecs to each end (tend to grow at + end)
-structure resembles two long strands coiled around eachother
Function: structural support, cell shape by resisting tension, movement (myosin head binds to actin for movement), divide cells, move organelles

44
Q

What are intermediate filaments and what is their function

A
  • non-polar
  • fibres wound into thicker cables
  • purely for structure: resist tension (pull), anchor nucleus and organelles
  • made of keratin, vimentin or lamin
45
Q

What are microtubules

A
  • hollow tubes of alpha and beta tubulin
  • largest cytoskeletal components
  • polar, usually grow at their + end
  • originate from MTOC, which contains centrosome that contain 2 bundles of microtubules called called centrioles
  • provide stability + movement via flagella/cilia, resist compression, move chromosomes during division, move organelles, intracellular transport, formation of cell plate in plant division
46
Q

What happens if microtubules are prevented from forming

A

ER no longer assembles in its normal network-like config

47
Q

What is kinesin

A

like actin it is a motor protein, which acts like a delivery truck to move transport vesicles down the microtubule tracks
-it “walks” along the tracks when it’s head region binds to ATP

48
Q

What are flagella (eukaryotes)

A
  • made of microtubules
  • move cell by whipping back and forth
  • plasma membrane
  • evolved independently from bacteria flagella
  • closely related to cilia
49
Q

What is dynein

A

-a motor protein
-changes shape when phosphate from ATP binds to it
-change in shape moves molecule along microtubule
-when dynein reattaches it has succeeded in walking a step along the microtubule doublet
(allows microtubule doubles to slide past eachother)
-walks in opposite direction of kinesin
-bends cilia and flagella

50
Q

What allows microtubules/axonemes to bend

A

if dynein arms on one side of axoneme walk and cause some doublets to slide while those on the other side are at rest
-in cilia/flagella this causes swimming

51
Q

How are molecular postal codes read

A

they bind to receptor proteins

52
Q

Where does translation always begin

A

in the cytosol

BIO112 (19 decks)

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