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Molecular cell > cells key organelles and features > Flashcards

cells key organelles and features Flashcards

1
Q

why do we need a lipid bi layer

A

to make a cell

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2
Q

some minerals

A

catalyse the formation of fatty acids from hydrogen and carbon monoxide

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3
Q

what are fatty acids made from

A

hydrogen and carbon monoxide

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4
Q

micelles

A

where polar fatty acids have self organise into circular formations where fatty acid tails point inward

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5
Q

why do micelles look the way they do

A

in water hydrophobic chains of fatty acid molecule turn towards each other –> thereby exposing the hydrophilic head

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6
Q

vesicles are spontaneously formed from

A

micelles

  • requires acidic pH
  • vesicles grow by fusion with micelles
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7
Q

what can trigger vesicle formation

A

clay surfaces

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8
Q

lipids in vesicle membranes are

A

dynamic –>flipping of lips can transport molecules over the membrane –> in this molecules can accumulate within the vesicle e.g. ribozymes

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9
Q

protocell

A

combining RNA replicase and vesicles

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10
Q

formation a protocell

A
  • -> the RNA replicase used ribonucleotides to make a copy of another RNA replicase
  • -> micelles fuse with he vesicle and enlarge it until it becomes unstable and divided
  • -> random mistake could form better replicase and uptake of new RNA could incorporate new ribosomes, which could make the protocol grow and divide faster
  • -> protocols compete for resources (fatty acids, ribonucleotides) and faster growing protocols are more competitive
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11
Q

faster growing protocols are more competitive

A

evolution

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12
Q

what are present in plasma membrane

A

specific proteins, lipids and sugars

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13
Q

plasma membrane

A

surround the cell and keeps contents inside whilst allowing transfer or info

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14
Q

the plasma membrane is made up of

A

two layers of fatty acid and head, tails on the inside and in the presence of water will assemble into a lipid bilayer

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15
Q

amphiphatic

A

have both hydrophilic and hydrophobic parts e.g. lipid bilayer

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16
Q

the plasma membraneeis

A

fluid

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17
Q

what can be used to demonstrate the fluidity of the plasma membrane

A

laser tweezers to pull the plasma membrane of a neuronal cell

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18
Q

what can effect membrane fluidity

A

steroids

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19
Q

cholesterol and the plasma membrane

A

reduces membrane fluidity at moderate temperatures and avoids solidification at low temperatures (temp buffer)

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20
Q

what is cholesterol involved in

A

the formation of vic D and estradiol and testosterone

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21
Q

how may an organelles be identified

A

by their lipid composition

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22
Q

lipid rafts

A

specialised lipid-protein regions found in membranes. Regions which assemble specialised lipids and proteins to perform a certain task e.g. sites of uptake in the plasma membrane are rich in cholesterol and sphingolipids and receptors

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23
Q

bio membranes are..

A

SEMI-PERMEABLE if molecules are uncharged and hydrophobic

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24
Q

charged molecules cannot

A

pass the bio-membrane e.g. sugars, ATP, proteins

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25
highly hydrophilic molecules and ions
must go through transporters--> still diffusion and not driven by ATP e.g. facilitated glucose transport (allows glucose to flow in one direction)
26
energy consuming active transport uses
ATP to open channels to allow molecules to flow into the cell
27
membrane passage of polar proteins or ions requires
protein channels | --> atp driven transporters e.g. proton pumps- energy consuming active transport
28
how can sucrose diffuse into the the cell via
proton pumps can be linked to coo transporters, due to the proton gradient produced by the proton pump--> indirect ATP dependency
29
channels will close and open depending on
diff concentration in the inside outside of the cell
30
permeability of in channels is controlled by
gates in response to stimuli
31
types of channels
voltage gates, mechanically gated, temp gated, ligand gated
32
cells in the epithelium establish
tight and lateral and basal contact
33
gap junction
a field connecting channels each made of connexions, channels allow passage of ion and small molecules (1-2nm); supports exchange between the cytoplasm of adjacent cells
34
tight junction
function as a diffusion barrier, holds cell together- BB, consists of plasma membrane proteins (claudin,occulidin) that interact
35
which proteins are present in tight junctions
claudin and occuldin
36
adherens jucntion
consists of cadherin and catenin, cadherin bridge between ells, catenins link to the cytoskeleton
37
adhere junctions seem to be involved in
controlling actin organisation in epithelial cells
38
desomosome
contains specialised catherin proteins that interact with each other and with intermediate filaments (cytoskeleton) --> resists shear force in epithelial and in muscle
39
extracellular matrix
fibres of secreted proteins (collagen, matrix proteins, glycoproteins). Holds tissues together and provides strength directing cell migration etc
40
tight junction
diffusion barrier, tissue integrity
41
adherens junction
organisation of actin | -cadherin and other proteins
42
gap junction
exchange between adjacent cells- connexins
43
desomosomes
resistance to shear forces - cadherin and the proteins and intermediate filaments - lateral
44
hemi-desomsomes
-connection to extracellular matrix -->basal
45
hemi-desomosomes more detail
contain many proteins, including integrins (protein) that interact with the extraceullar matrix - found in epithelial cells - anchor the epithelial cells to basal lamina -_> involved in signalling. - only one-link intermediate filaments to extracellular matrix
46
ribosomes
consists of 2 subunits can be 70s and 80s and proteins . ribosomes in the cytoplasm are attached to membranes and translate info from mRNA into proteins --> translation
47
the c70s ribsoomes
34 proteins in large subunit and 21 proteins in small subunit
48
80s ribosomes
49proteins in large subunit and 33 proteins in small unit
49
svedberg unit (S)
described sedimentation behaviour of particles (ribose) - he developed a technique of analytical ultracentrifugation and seperated pure proteins from each other.. - particle mass, density and shape will determine s value
50
the cytoplasm is
crowded and diffusion is restricted e.g. larger objects almost don't diffuse int the cell
51
the cytoplasm is made up of
300MG/ML PROTEINS AND RNA, MANY RIBOSOMES
52
Particles and molecules undergo random
brownian motion temp dependent --> movement is random
53
diffusion depends on
the size of the molecule --> the smaller the molecule the more it can move e.g. sugar molecule will more than a protein
54
how are molecules moved
by water
55
70s
50s and 30s
56
80s
60s and 40s
57
the nucleus
is the largest organelle in the cell, usually just 1, where mitosis occurs- known as the library of the cell
58
size of nucleus
2-10um (10% of cell volume)
59
what do nucleolus' found in the nucleus form
ribosomes - -> granular component - -> ribosome assembly site - fibrillar centre- rRNA transcription.
60
ribosomal proteins are imported into the
nucleolus
61
assembled ribosomes produced in the nucleolus are
exported into the cytoplasm
62
nucelar pores are found in the
nuclear envelope
63
nuclear pores are
Gates for transport in and out of the nucleus: highly ordered multi-protein complexes, which have eight fold symmetry. Numerous proteins build the pore and control nuclear export
64
how many diff nucleoprins in a pore
30
65
nuclear transport depends on
small GTPas and soluble import//export receptors
66
why are nuclear pores so evenly spaced
if a nuclear pores were clustered, this would not support an efficient transport method in or out of the nuclear
67
what prevent nuclear pores from clustering
lamina
68
lamina
found on the inside of the nuclear envelope made up of fibres keep the pores evenly space.
69
how can lamina importance be established
by using dna technology genes can be turned off to show how important they are when it comes to dispersion of pores
70
what forms intermediate filaments of the nuclear lamina
several lamins
71
how is the nuclear membrane broken down
lamina are phosphorylated
72
how is the nuclear envelope reformed at the end of mitosis
dephosphorylation of lamins. then the nuclear envelope fragments are fused
73
lamina and phosphorylation
When the Lamins are phosphorylated it causes the nuclear envelope to disassemble and for chromosome to condense. The dephosphorisation of the Lamins occurs and the nuclear envelope starts to reform. Then nuclear envelope fragments will fuse.
74
what helps visualise the nucleus and its interaction with the ER
GFP is joined to the nucleus and the GFP is attached to the endoplasmic reticulum helps visualise the interaction between the ER and the nucleus within a living cell.
75
during mitosis the ncleus
releases its content and has to re-import nuclear proteins
76
when matching of tRNA and mRNA codons occur
elongation factor TU is released
77
what triggers a forward movement of ribosomes
elongation factor G
78
what may help with 'walking along the mRNA in order to synthesise a protein 'molecular ratchet'
a conformational change in the ribosome caused by translation-elongation factor
79
how many ribosomes will work on a single mRNA molecule and what is this structure called
numerous and known as a Polysome
80
definition of a protocell
A protocell (or protobiont) is a self-organized, endogenously ordered, spherical collection of lipids proposed as a stepping-stone to the origin of life.
81
definition of lipid raft
are subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids.

Molecular cell (21 decks)

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