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z. CELL0007 > Cell Biology > Flashcards

Cell Biology Flashcards

1
Q

What are the 2 functions of the plasma membrane?

What is so useful about membrane-bound organelles in eukaryotes?

What is the most common phospholipid & what is it made up of?

What is the fundamental characteristic of it?

A
  1. Enable composition of cell to differ from its environment
  2. Prevent molecules inside mixing with outside/Separates compartments

Internal membranes around organelles allows difference in composition of organelles & environments to allow different environments & processes

Phosphatidylcholine- 2 hydrocarbon chains, glycerol, hydrophilic head (choline & phosphate)

Amphipathic (polar & non-polar)

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2
Q

What does a hydrophilic substance do in water?

Hydrophobic substance?

What do amphipathic molecules form in water/aq solutions?

A

Forms H bonds & electrostatic attractions with it

Hydrophobic effect- adjacent water molecules form cage-like structure around to maximise hydrogen bonds with eachother- minimises energy to form droplets

Bilayer

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3
Q

Why are planar phospholipid bilayers energetically unfavourable?

What is more favourable?

What is crucial about this?

What different proteins are in the phospholipid membrane?

A

Edges are exposed to water

Forming sealed compartments (bilayers spontaneously close on themselves)

Can’t completely seal (communication, information, expand)- aided with proteins

Transporters, ion channels, anchors, receptors, enzymes

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4
Q

How thick is the lipid bilayer membrane & what percentage of its mass accounts for proteins?

What are the 4 ways a protein can associate with a membrane?

What does a transmembrane cross the layer as and why?

How long does the helix have to be to span the membrane?

A

5nm , 50%

Transmembrane- goes through bilayer
Monolayer associated a-helix-
Lipid linked- proteins with covalently linked lipids
Protein-attached- non cov interactions with membrane

a-helix: polar ends of the peptides allow hydrogen bonds with hydrophilic heads & also exterior hydrophobic side chains surrounded by hydrophobic tails

20AA

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5
Q

What is the Central Dogma of Life & who was it proposed by? What transfers are possible/not?

How did Louis Pasteur prove the Generation of Life that cells arise from all-cells-from-cells hypothesis & not the spontaneous generation hypothesis?

What was Pasteur’s cell theory?

A

DNA -> RNA -> Protein
Transfer of NA to protein is possible
Protein to protein and protein to NA not possible
Francis Crick

Straight neck flask- boiled broth & let sit in open = cells

Swan-neck flask- boiled broth but cells accumulated in condensation in the neck = no cells in broth
- tilted flash microbes from neck enter broth = cells

living organisms are made up of cells with are the unit for all organisms & they come from pre-existing cells & are made through growth & division

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6
Q 
What are the resolutions of:
unaided eye
light microscope
super resolution microscopy
electron/x-ray/cyro-em

E.coli bacteria: what is unique about its genome? Does it have membranes? How large is it?

What types of organisms are e.coli bacteria?

What are the 3 different cells in cyanobacteria & what do they do?

How are these cells separated & why?

What have they evolved & why?

A

0.2mm
200nm/2E-4mm
20nm/2E-5mm
2-0.2nm

circular DNA lies freely in cytoplasm, no internal membranes/compartmentalisation, unicellular & 0.1-1 micrometres

phototrophs & chemolithotrophs

H = heterocyst: fixes atmospheric nitrogen into ammonia
S = spore (resistant & dormant)
V = fixation carbon (light to chemical energy)

H & V separated- nitrogenase sensitive to oxygen in carbon fixation

Thylakoids- large SA for carbon fixation/photosynthesis

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7
Q

What organelles can you see in eukaryotes in light vs electron microscope?

Nucleus:

What is it enclosed in & how does this enable its function?

How is genetic info contained in the nucleus?

What occurs in the nucleolus?

A

Light = nucleus & shapes, electron = organelles (ribosomes, mitochondria etc)

Nuclear envelope with pore- allow transport DNA/RNA in & out of cell

chromatin (associated w/ histones & TFs)

genes transcribe rRNA & assemble ribosomal proteins with ribosomal subunits

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8
Q

What is the ER the site of?

What is the structure of the ER?

What does it store?

What does the RER produce?

What does the golgi apparatus do?

What does the golgi apparatus look like?

A

Protein & lipid synthesis

Labyrinthine space enclosed in a membrane

Calcium ions

Transmembrane proteins & lipids

Receives the lipids & proteins from the ER & modifies them & sends to other organelles

Stacked membranes

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9
Q

What does the cytoplasm contain?

What occurs in the cytosol?

What do the lysosomes receive?

What do lysosomes contain & as a result what is their function?

What do the endosomes receives?

What do endosomes do?

A

Organelles & cytosol

Protein synthesis & chemical reactions

Proteins & lipids from ER

Lysozymes & low pH degrade non-functioning organelles/large particles/endocytosis

Lipids from golgi

Endocytosed material enters & then is delivered to lysosome- as a result has low pH

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10
Q

What are the structural features of the mitochondria?

What is its functions?

In what organisms are chloroplasts found?

What do peroxisomes contain & what is its function?

What other organelles do eukaryotes contain?

A

Surrounded by double membrane, circular mitrochondrial DNA

Oxidise sugar to generate ATP & site of biochem pathways like cell death

Plants & algae

Enzymes for oxidative reactions to inactivate toxic molecules- in lipid metabolism

Ribosomes, transport vesicles (trafficking between organelles), cytoskeleton (utility, transport, cell shape), actin & intermediate filaments

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11
Q

How are organelles without membrane formed and why?

How do these characteristics compare in prokaryotes & eukaryotes:
Nucleus 
Diameter cell
Cytoskeleton
Cytoplasmic organelles
DNA content (bp)
chromosomes
A

Lipid phase separation in situations of stress- they demonstrate a control of gene expression

E = yes, P = no
E = 10-100 micrometre, P = 1micrometre
E = yes P = no
E = yes P = no
E = 1.5E7-5E9, P = 1E6-5E6
E = many linear DNA molecules, P = single circular DNA molecule
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11
Q

How are organelles without membrane formed and why?

How do these characteristics compare in prokaryotes & eukaryotes:
Nucleus 
Diameter cell
Cytoskeleton
Cytoplasmic organelles
DNA content (bp)
chromosomes
A

Lipid phase separation in situations of stress- they demonstrate a control of gene expression

E = yes, P = no
E = 10-100 micrometre, P = 1micrometre
E = yes P = no
E = yes P = no
E = 1.5E7-5E9, P = 1E6-5E6
E = many linear DNA molecules, P = single circular DNA molecule
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12
Q

The Endosymbiotic theory discusses how an archaebacterium develops into an animal cell & plant cell.

How does it form a eukaryotic animal cell?

Plant cell?

What is the evidence to support this theory?

A
  1. Archaebcterium grows & develops infoldings = endomembrane system & membrane around nucleus
  2. Aerobic protobacterium with its own membrane is engulfed by the cell as a parasite & becomes endosymbiont
  3. The bacterium’s use oxygen to produce energy allows host thrive in rich oxygen environment = form mitrochondria

Cyanobacterium/photosynthetic bacteria becomes endosymbiont to form a chloroplast

  1. Chloroplasts & mitochondria are the same size as prokaryotic cells & also divide by binary fission
  2. They both have their own circular DNA
  3. Both have 30S & 50S ribosomes
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13
Q

How is a transmembrane hydrophilic pore different to a transmembrane cross layer?

What is the composition of a bacterial transmembrane filled water channel?

How can membrane proteins be transported out of the golgi with vesicles?

What are the 4 ways lateral mobility of plasma membrane proteins are restricted?

Elaborate on how the 4th one restricts some membrane proteins’ access in the epithelial cell of the gut

A

Aq is on the inside-
5 transmembrane helices form a water filled channel in the bilayer where the hydrophilic side chains are on the inside

16 strand beta sheet curved around itself in the bilayer & porin proteins associate to form a trimer with 3 different channels

Vesicle buds from golgi apparatus membrane with membrane protein inside & forms transport vesicle- then fuses to plasma membrane to release protein extracellularly

  1. Proteins tethered to cell cortex
  2. Proteins bound in extra cellular matrix
  3. Cell-cell interactions
  4. Restricted movement from 1 part of cell to the other by tight junctions

Tight junctions between the epithelial cells stop proteins moving from blood stream into gut lumen & vice versa

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14
Q

What do cytoskeletons do?

What is the diameter of intermediate filaments?

What are they made of?

What do they look like?

What are their characteristics?

What are they used for?

A

Give cell shape, & allow organise internal components & movement

10nm

Fibrous intermediate filament proteins

Rope like structures/fibres

Flexible, strong, deform under stress but don’t rupture

Forms nuclear lamina beneath inner nucleus membranes, span cytoplasm between cell-cell junctions to distribute mechanical stress in epithelial tissue

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15
Q

What is the diameter of a microtubule? What does this say about its characteristics?

What are they made up of?

What are their characteristics?

A

25nm (more rigid intermediate & actin filaments)

Hollow cylinders made of tubulin (protein), long & straight with a centrosome at one end

Rupture when stretched

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16
Q

What are the structures of actin filaments?

What is their diameter?

Where are they found most?

A

Helical polymers of actin- organised into linear bundles, 2D networks or 3D gels- very flexible

7nm

Cortex (layer cytoplasm beneath plasma membrane)

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17
Q

How is a growing intermediate filament formed?

What properties does it have?

Where are the 2 main regions intermediate filaments are found?

What are they used in more specifically? (4)

A
  1. a helical region = monomer
  2. monomer is coiled in pairs to form a dimer
  3. Staggered tetrameter of 2 coiled-coil dimers
  4. then lateral association of 8 tetrameters

Rope like- high tensile strength

Cytoplasm & nucleus

Keratin filaments in epithelial cells
Vimentin & its filaments in connective, muscle & glial tissue
Neurofilaments in nerve cells
Nuclear lamins in all animal cells for shape

18
Q

How is the structure of a microtubule built up?

What is special about a microtubule’s structure?

What are the organising sites microtubules grow from?

How do microtubules grow out of centrosomes? What happens to the centrioles?

What causes dynamic instability in microtubules and what happens?

What do capping proteins do then?

A

1 subunit = tubulin heterodimer is encoded by 2 genes
Tubulin heterodimers make up a protofilament, and 13 of these make 1 microtubule

Has polarity- due to the tubulin dimers being arranged in the same direction means theres a + (top) and - end (bottom)

In dividing cells = centrosome (spindles)
Cilia & flagella = basal (cilia)

Tubulin nucleates out of ring nucleating sites in the centrosome- where - end is anchored and + end grows. Pair of centrioles at right angles inside centrosome

GTP hydrolysis. GTP-tubulin dimers add to the end of a growing microtubule causing + GTP cap. GTP hydrolysis/GDP-tubulin peels away from microtubule wall & released into cytosol causing shrinking microtubule

Stabilise microtubules (prevent shrinking) with +ve capping

19
Q

What 2 microtubule binding proteins are involved in movement? What kind of proteins are they?

Which end of the microtubule do they move towards?

What are their structures?

How does this contribute to their walking movement?

What can they transport with them?

A

Kinesins & dyneins- motorproteins

Kinesins = +
Dyneins = -

Both have globular heads with ATPase activity

ATP hydrolysis results in the heads interacting with the microtubules

On the tails- large protein complexes, vesicles, organelles

20
Q

How are microtubules arranged in cilia/flagella?

How is a powerstroke in cilia caused?

A

9 + 2

Dynein motorproteins move along by 1 microtubule causing it to bend = powerstroke if all the doublets are coordinated

21
Q

What is actin filaments characteristics? (4)

How is polarity caused?

What do many lateral interactions help with?

What is treadmilling? What else can occur due to the hydrolysis of ATP?

What do these processes regulate?

A

Thin, flexible proteins, polarised, 2 stranded helix with twist every 37nm

ATP binding cleft in the actin monomers (+ end has site, - site doesn’t)

Prevents separation

ATP-actin monomers bind to +ve end. Hydrolysis of ATP causes instability due to ADP-bound monomers, so actin at -ve end fall off. Dynamic instability

Polymer length

22
Q

How can actin filaments help with cell movement? in steps

What is myosin?

What is myosin I’s function & how does it move? What is its structure?

myosin V?

myosin II?

muscle cells contain sarcomeres- what are these?

What are the lighter and darker filaments in muscles?

how does an entire muscle contract?

how does muscle relax?

A
  1. Actin polymerises at the +ve end of lamellipodium & attaches to integrins in the focal contact = anchorage
  2. Cell uses anchorage to drag itself forward by contracting at other cell end as myosin motor proteins slide the actin filaments
  3. Repeating cycling = further protrusion

Motor protein that moves along actin filaments due to their globular head with ATPase activity

membrane association & endocytosis
tail anchors plasma membrane & myosins move towards +ve end actin with hydrolysis of ATP as globular heads.
1 head with short tail

2 heads, biggest tail, carries cargo on tail region

muscle contraction, 2 heads & smaller tail than V

2 dimers of myosin II interact between tails to form a bipolar dimer where tails inwards & heads outwards. 2 actin fibres bound either side of 1 myosin, where + faces heads and - faces inner tails.
when myosin active- moves towards the + ends causing actin slide outwards = contraction

+=======–=======+ (actin)
ooo——————ooo (myosin)
+=======–=======+ (actin)

contractile units of microfibrils

dark = myosin II (bound to sarcomere)
light = actin (attached to Z disc)

myosin moves to + end causing actin slide outwards = contraction of sarcomere. if all sarcomeres contract = muscle contracts

myosin stops moving

23
Q

What are the 4 parts of the cell cycle?

What are cyclin-dependent protein kinases Cdpks used for in the cell cycle? What is the enzyme & protein?

How more specifically is the cell cycle activity controlled? e.g activation & inhibition

What Cdks & cyclins control the S phase & M phase?

Where in the cycle are the concentrations of these cyclins highest?

What is it that actually triggers these phases?

A

G1, S (DNA rep), G2, M (mitosis & cytokinesis)

Enzymes that attach phosphates to proteins covalently- can activate or inhibit the proteins hence control the cell cycle
Cdk = enzyme, cyclin = protein

Activation = cdk associate with cyclin
Phosphorylation of Cdk = both activation & inhibition
Inhibition = association with p27 or p21

S-Cdk with S cyclin
M-Cdk with M cyclin

S cyclin is between G1-S and beginning of M
M cyclin is between G2-M and beginning M

Activation of cdks due to the high concentration of the cyclins (low conc inactivates them)

24
Q

How would you halt the G1 to S phase?

Why does this happen?

What does p53 do?

How would you halt the G2 to M phase?

How would you halt the M to G1 phase?

A

S-Cdk already formed- so inhibit with p27/p21 proteins to form inactivated p27-cyclin-Cdk complex

damaged DNA means protein kinases activate p53 by phosphorylation (tumour suppressor/protoncogene)

stimulates transcription p21 gene and induces DNA repair & sometimes activates programmed cell death

M-Cdk already assembled- so kinase phosphorylates Cdk enzyme at its inhibitory site

Cyclin is degraded with ubiquitylation (adding protein tag) & then destruction in proteosome

25
Q

How can you inhibit DNA replication in G1 & S? in 4 steps

what else is S-Cdk useful for?

A
  1. in G1 origin recognition complex ORC assembled on the origin of replication on the DNA
  2. DNA helicase binds so Cdc6 dissociates
  3. prereplicative complex preRC is inactive, but is activated when S-Cdk activity is high at end of G1
  4. S-Cdk activates helicase, pre-RC & DNA polymerase

because it dissociates Cdc6 it prevents re-replication

25
Q

How can you inhibit DNA replication in G1 & S? in 4 steps

what else is S-Cdk useful for?

A
  1. in G1 origin recognition complex ORC assembled on the origin of replication on the DNA
  2. DNA helicase binds so Cdc6 dissociates
  3. prereplicative complex preRC is inactive, but is activated when S-Cdk activity is high at end of G1
  4. S-Cdk activates helicase, pre-RC & DNA polymerase

because it dissociates Cdc6 it prevents re-replication

26
Q

What do cohesin rings do during the S phase? Why?

What do condensin rings do in the M phase? Why?

What is a chromosome made up of?

How are the cytoskeletons recruited in mitosis?

Do plant cells contain these same structures?

A

Tie 2 adjacent sister chromatids in each duplicated chromosome- forms large protein rings to prevent chromatids coming apart

coil each sister chromatid/DNA double helix into smaller & compact structures- so more easily segregated in mitosis

2 sister chromatids with centromere

Microtubules- to separate duplicated chromosomes via pulling chromatids apart as spindles
Contractile rings- actin & myosin filaments that form around the spindles for division

Microtubules but not contractile rings

27
Q

What are the 6 steps for the formation of the mitotic spindles/division of the centrosome & metaphase?

A
  1. Microtubules nucleate from centrosomes
  2. In interphase (animals G1 S G2) centriole pair in centrosome associate with the centrosome matrix so microtubules grow out
  3. Centrosome duplicates at same time as DNA rep in S phase by S-Cdks
  4. Early M phase- centrosome starts divide & nucleate own aster microtubules
  5. Centrosomes move apart & form bipolar mitotic spindles with aster at each pole
  6. Mitotic spindle waits for breakdown of nuclear envelope & then when it does break down- spindle microtubles interact with chromosome
28
Q
  1. What happens in prophase? t=0 of M phase
  2. Prometaphase t=79min
  3. Metaphase t = 250
  4. anaphase t=279
  5. telophase t=315
  6. cytokinesis t=362
A
  1. Chromosomes condense, mitotic spindles assemble between 2 centrosomes & chromosomes have duplicated and start to move apart
  2. Breakdown nuclear envelope so chromosomes attach to spindle microtubules via their kinetochores & move
  3. Chromosomes align equator of spindle between spindle poles & kinetochore of each sister chromatid attach to opposite poles of spindle
  4. chromatids pulled opposite spindle poles = segregation of chromosomes, kinetochores of microtubules get shorter & spindle poles move apart
  5. 2 sets chromosomes arrive poles of spindle & nuclear envelope builds around each set. contractile ring for cytokinesis forms
  6. cytoplasm divides in 2- separation of cytosome & daughter cells where the division is due to contractile ring of actin & myosin perpendicular to spindle
29
Q

Which region of the microtubules binds to the kinetochores?

What are the 3 types of microtubules that make up the mitotic spindle?

A

+ve

aster microtubules, kinetochore microtubules, interpolar (binds to motor proteins)

30
Q

What are the 3 steps for triggering the separation of sister chromatids after metaphase?

What occurs in anaphase A? What is the force driving this?

What are the 2 driving forces in anaphase B?

A
  1. Separase (proteolytic) is inactivated by securin inhibitory protein
  2. APC degrades cohesin when chromosomes aligned properly in metaphase
  3. Separase’s activation means cohesin complex/rings degraded to allow separation chromatids in anaphase (stops this occurring prematurely)

Kinetochore microtubules depolarise while attached to chromosomes- shortening & pulling them to opposite poles. loss tubulin subunits on kinetochore microtubules

interpolar microtubules slide part eachother & pull poles apart by kinesins
dyneins pull poles outwards towards cell cortex

31
Q

How does the nuclear envelope break down in prometaphase?

How does it reform at telophase?

How do plant cells not divide by?

What are plant cells division affected by?

How do plant cells divide?

A

Phosphorylation of nuclear pore proteins & lamin = triggers disassembly of nuclear envelope into small vesicles

dephosphorylation of nuclear pore proteins & lamin = vesicles come together around chromosome & reassemble envelope

contractile rings (only in animals)

cell wall

  1. new cell wall forms inside equator of old spindle after telophase (chromosome segregation)
  2. interpolar microtubules of spindle form a phragmoplast & golgi-derived vesicles fuse at equator (filled with cell wall materials) to form growing cell wall towards cell wall perpendicularly
  3. pre-existing plasma membrane & the membrane surrounding the new cell wall fuse to separate the 2 daughter cells
32
Q

What type of amino acids are present in the following functions of signal sequences:

Import into ER
retention in lumen of ER
import into mitochondria
import into nucleus
import into peroxisomes

By what way do materials enter the nucleus?

A 
hydrophobic & negative charge
polar
positive
positive
positive & 3 AA long

gated transport

33
Q

What are the 4 steps importing cargo protein into the nucleus via gated transport?

Exporting cargo protein? (3)

What converts Ran-GTP into Ran-GDP & where is it found?

What about Ran-GDP to Ran-GTP?

How to nuclear import receptors bind to cargo?

Export receptors?

A
  1. Cargo protein interacts with importers in cytosol with nuclear localisation signal & complex can move in/out pores
  2. Complex diffuses into nucleus & interaction of complex disrupted by binding ran-GTP to importer
  3. Ran-GTP displaces cargo = release cargo & Ran-GTP free to move in/out pore
  4. Ran-GTP enters cytosol- causes conversion to Ran-GDP releasing importer from Ran-GTP so it’s free to bind to cargo
  5. Ran-GTP binds to exporter allows complex move with nuclear export signal so can diffuse in/out cytoplasm
  6. In cytosol: Ran-GTP converted Ran-GDP = disruption & release of cargo
  7. Exporter free in cytoplasm diffuse back into nucleus

GAP (GTP-ase activating protein) found exclusively in cytoplasm

GEF(Guanine nucleotide exchange factor) found in nucleus & bound to chromatin

nuclear localisation signal

nuclear export signal

34
Q

What is transmembrane translocation and in which organelles does it affect?

What kind of translocation is it?

What kind of translocation is it when the proteins are made on the RER?

In post translational translocation in mitochondria:

To what exterior complex does the protein bind and where is it?

What precursors enter this way?

What is the pathway for a soluble protein?

What are the 2 requirements for the proteins to get through both complexes?

A

Proteins synthesised on free ribosomes in cytoplasm are translocated into mitochondria & peroxisomes with protein channels/transporters

Post-translational

Travels into ER lumen- co-translational translocation

TOM complex- outer membrane

Pre-sequence, hydrophobic or beta barrel

TIM23 complex in inner membrane & then matrix

Electrochemical gradient in inner membrane (+ intermembrane space - matrix from electron transfer chain), activity of TIM chaperones (help proteins fold & pull them into matrix)

35
Q

What is vesicular trafficking & what is it mediated by?

What 2 pathways does it occur in?

How does an mRNA signal sequence on a cystolic protein send it to the lumen of the ER?

What is the signal sequence recognised by?

If translocation of the protein is halted, what can this particle do?

What happens to the particle after?

When & where is the signal sequence cleaved off? How is this different from the mitochondria?

A

Membrane proteins & lipids transport from one cell/organelle to another, mediated by cytoskeleton elements & motor proteins

ER to golgi
Golgi to plasma membrane/lyosomes/endomes

mRNA encoding cytosilic protein is free in cytosol- ribosomal subunits assemble to synthesise the polyribosome from the protein’s sequence. If the terminus of mRNA has ER signal sequence (binds to ER membrane) & the ribosome & proteins are recruited to ER & protein is co-translated into the lumen

SRP (signal recognition particle) protein

SRP binds to ribosome to form complex- which then allows binding to the SRP receptor protein on the RER membrane so nasant protein is translocated with translocators on RER

SRP dissociates to be recycled

in the RER (its N terminus)- in translation. Mitochondria is during translocation

36
Q

What helps with folding of proteins in the ER lumen?

What is the process for misfolded proteins degradation?

What is a proteasome?

What is the protein tagged with before the process?

A

Chaperones

Enter cytosol from ER lumen via an ER protein translocation (sec61 complex).
Protein is tagged with ubiquitin (signal for degradation) & will then be degraded in proteasome

Multi enzyme complex with lots proteases & peptides

Blue sugar tag from ER

37
Q

What was the purpose of the Pulse-Chase experiments?

What cells are the most ideal for this experiment?

How do you prepare the cell of interest?

What was the path found?

What are the 2 methods of analysis?

A

Identify the paths that proteins take in the cell

Secretory cells e.g from pancreas

Label leucine 3H for 3 mins & wash with cold leucine

3 min in ER, 20 mins golgi, 87 mins plasma membrane & vesicles

  1. EM autoradiography: image of radioactively labelled proteins
  2. Cell fractionation: homogenisation & centrifugation & put supernatant on sucrose gradient allowing separation of organelles by density
38
Q

What are the 5 steps of forward anterograde transport of vesicular trafficking from the ER to golgi?

What about the backwards retrograde transport? What is it mediated by?

A
  1. Vesicles build from ER facing the golgi containing secretory proteins & KDEL receptor
  2. Vesicles gain COPII coat
  3. Vesicle pinches. off & transported to vesicular tubular cluster
  4. Coat removed & vesicle fuses with vesicular tubular structure to release secretory proteins its lumen & present receptor onto membrane
  5. both proteins transported to golgi & golgi stacks (orientation of receptor same)
  6. Vesicles builds from golgi containing the proteins & gain COPI coat
  7. Fuse with vesicular tubular cluster where coat is removed
  8. Then fuses with ER

KDEL receptor- can bring proteins back to ER

39
Q

How does a vesicle form from the ER?

What is a cargo receptor made of?

How does the vesicle dock with the target membranes?

What is fusion triggered by? What happens?

What happens to the snares after?

What are RAB proteins used for?

A

Subunits of COPII coat & their assembly mends the membrane outwards. Exit signals on cargo receptors are packaged into transport vesicles when coat assembles

Exit signal, receptor and soluble cargo protein

Coat disassembles.
V snares (in transmembrane vesicle) and t snares (on target) need to be correctly matched

GTP-ase (GAP) of Rab-GTP into Rab-GDP causing change of snare proteins & brings vesicle close to target membrane = fusion

disassembled & recycled- v snares need return to ER to be packaged back into vesicles

fusion, coat assembly, vesicle budding, transport & cytoskeleton elements

40
Q

What happens in the ER & Golgi as well as transport & distribution?

From where does secretion/exocytosis take place?

What are the 2 secretory pathways?

What does exocytosis of secretory vesicles depend on?

A

Protein & lipid modifications with glycosylation (covalent addition of sugar group)

Golgi apparatus to plasma membrane

  1. Constitutive (in all cells & causes secretion proteins destined for extracellular matrix)
  2. Regulated (specific cells, not all time & secretion neurotransmitters from synapse to respond to action potential)

GTPase (GAP) & snare proteins docking & fusion

41
Q

What is endocytosis?

What is it triggered by?

What happens after?

what is wrong with LDL?

what do statins do?

what is a clathrin coat? What does it require?

How is it different to COPII or COPI?

A

Transporting material from outside cell to endosomes & lysosomes

binding of LDL to LDL receptors on plasma membrane

  1. forms a pit & coat is assembled to form vesicle containing receptor & LDL
  2. vesicle then uncoats & fuses with endosome
  3. receptor is packed into vesicles & transported back to the membrane
  4. LDL is transported from endosome to lysosome containing lots hydrolytic enzymes at low pH
  5. LDL is degraded by enzymes into free cholesterol- released into cytosol & recycled

causes heart disease- mutations in the gene required in endocytosis can cause conditions

increase uptake of LDL to reduce the amt of LDL circulating

coat that covers endocytotic vesicles- requires dynamin (type of GTPase) to pinch vesicle off

requires an enzyme

z. CELL0007 (4 decks)

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