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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
Q

highly hydrophilic molecules and ions

A

must go through transporters–> still diffusion and not driven by ATP e.g. facilitated glucose transport (allows glucose to flow in one direction)

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26
Q

energy consuming active transport uses

A

ATP to open channels to allow molecules to flow into the cell

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27
Q

membrane passage of polar proteins or ions requires

A

protein channels

–> atp driven transporters e.g. proton pumps- energy consuming active transport

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28
Q

how can sucrose diffuse into the the cell via

A

proton pumps can be linked to coo transporters, due to the proton gradient produced by the proton pump–> indirect ATP dependency

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29
Q

channels will close and open depending on

A

diff concentration in the inside outside of the cell

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30
Q

permeability of in channels is controlled by

A

gates in response to stimuli

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31
Q

types of channels

A

voltage gates, mechanically gated, temp gated, ligand gated

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32
Q

cells in the epithelium establish

A

tight and lateral and basal contact

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33
Q

gap junction

A

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
Q

tight junction

A

function as a diffusion barrier, holds cell together- BB, consists of plasma membrane proteins (claudin,occulidin) that interact

35
Q

which proteins are present in tight junctions

A

claudin and occuldin

36
Q

adherens jucntion

A

consists of cadherin and catenin, cadherin bridge between ells, catenins link to the cytoskeleton

37
Q

adhere junctions seem to be involved in

A

controlling actin organisation in epithelial cells

38
Q

desomosome

A

contains specialised catherin proteins that interact with each other and with intermediate filaments (cytoskeleton)
–> resists shear force in epithelial and in muscle

39
Q

extracellular matrix

A

fibres of secreted proteins (collagen, matrix proteins, glycoproteins). Holds tissues together and provides strength directing cell migration etc

40
Q

tight junction

A

diffusion barrier, tissue integrity

41
Q

adherens junction

A

organisation of actin

-cadherin and other proteins

42
Q

gap junction

A

exchange between adjacent cells- connexins

43
Q

desomosomes

A

resistance to shear forces

  • cadherin and the proteins and intermediate filaments
  • lateral
44
Q

hemi-desomsomes

A

-connection to extracellular matrix –>basal

45
Q

hemi-desomosomes more detail

A

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
Q

ribosomes

A

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
Q

the c70s ribsoomes

A

34 proteins in large subunit and 21 proteins in small subunit

48
Q

80s ribosomes

A

49proteins in large subunit and 33 proteins in small unit

49
Q

svedberg unit (S)

A

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
Q

the cytoplasm is

A

crowded and diffusion is restricted e.g. larger objects almost don’t diffuse int the cell

51
Q

the cytoplasm is made up of

A

300MG/ML PROTEINS AND RNA, MANY RIBOSOMES

52
Q

Particles and molecules undergo random

A

brownian motion temp dependent –> movement is random

53
Q

diffusion depends on

A

the size of the molecule –> the smaller the molecule the more it can move e.g. sugar molecule will more than a protein

54
Q

how are molecules moved

A

by water

55
Q

70s

A

50s and 30s

56
Q

80s

A

60s and 40s

57
Q

the nucleus

A

is the largest organelle in the cell, usually just 1, where mitosis occurs- known as the library of the cell

58
Q

size of nucleus

A

2-10um (10% of cell volume)

59
Q

what do nucleolus’ found in the nucleus form

A

ribosomes

  • -> granular component
  • -> ribosome assembly site
  • fibrillar centre- rRNA transcription.
60
Q

ribosomal proteins are imported into the

A

nucleolus

61
Q

assembled ribosomes produced in the nucleolus are

A

exported into the cytoplasm

62
Q

nucelar pores are found in the

A

nuclear envelope

63
Q

nuclear pores are

A

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
Q

how many diff nucleoprins in a pore

A

30

65
Q

nuclear transport depends on

A

small GTPas and soluble import//export receptors

66
Q

why are nuclear pores so evenly spaced

A

if a nuclear pores were clustered, this would not support an efficient transport method in or out of the nuclear

67
Q

what prevent nuclear pores from clustering

A

lamina

68
Q

lamina

A

found on the inside of the nuclear envelope made up of fibres keep the pores evenly space.

69
Q

how can lamina importance be established

A

by using dna technology genes can be turned off to show how important they are when it comes to dispersion of pores

70
Q

what forms intermediate filaments of the nuclear lamina

A

several lamins

71
Q

how is the nuclear membrane broken down

A

lamina are phosphorylated

72
Q

how is the nuclear envelope reformed at the end of mitosis

A

dephosphorylation of lamins. then the nuclear envelope fragments are fused

73
Q

lamina and phosphorylation

A

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
Q

what helps visualise the nucleus and its interaction with the ER

A

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
Q

during mitosis the ncleus

A

releases its content and has to re-import nuclear proteins

76
Q

when matching of tRNA and mRNA codons occur

A

elongation factor TU is released

77
Q

what triggers a forward movement of ribosomes

A

elongation factor G

78
Q

what may help with ‘walking along the mRNA in order to synthesise a protein ‘molecular ratchet’

A

a conformational change in the ribosome caused by translation-elongation factor

79
Q

how many ribosomes will work on a single mRNA molecule and what is this structure called

A

numerous and known as a Polysome

80
Q

definition of a protocell

A

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
Q

definition of lipid raft

A

are subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids.

Molecular cell (21 decks)

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