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Building blocks of life > transport into and around the cell > Flashcards

transport into and around the cell Flashcards

1
Q

what is the function of a membrane?

A

separates cells from their external environment

also defines spaces

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2
Q

functions of membranes

A 
transport
enzyme activity
signal transduction
intercellular joining
cel recognition
attachment to ECM
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3
Q

what is the membrane structure?

A 
very thin 
2 molecules thick 
forms a closed boundary
made of lipids
proteins embedded in the layer
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4
Q

why are proteins found in membranes

A

give the membrane function and ability to do certain tasks

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5
Q

what is a bacteria membrane like?

A

can have multiple ones and cell walls

different composition but same lipids

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6
Q

what are virus membranes like?

A

enveloped viruses with lipid layer from the cell in infected

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7
Q

how does the fluid mosiac model describe membranes?

A

a mix of lipids in layer that move around in flux
proteins are embedded within too
membrane is flexible

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8
Q

what is the evidence for the fluid mosaic model?

A

surface tension of the membrane did not match that of lipid only models but did match when proteins added

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9
Q

how did evidence for the fluid modaic model come about?

A

fused mouse and human cellls together in a hybrid

proteins mixed and moved therefore they are fluid and can move proving the fluid mosaic modeel

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10
Q

examples of lipids

A

cholesterol
phospholipids
glycolipids

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11
Q

what is special aboout lipids?

A

each organ and organelles has a differnt composition of them and the types

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12
Q

why is pH key for membranes?

A

ensures head groups are in their ionised charged form and thus suitably hydrohobic

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13
Q

what is self assembely?

A

if phospholipids are added to a tube of water a neural pH they will spontaneously form a closed bilayer in structures called liposomes

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14
Q

what is a phospholipid?

A

phosphate containing two lipids

two fatty acid chains with a glycerol backbone

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15
Q

what is the difference between a phosphoglyceride and a sphingolipid?

A

phosphoglyceride is glycerol base lipid

sphingolipid is sphingosine bases lipid

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16
Q

if the membrane is too cold and rigid what changes does it make?

A

more unsaturated lipids, adds kinks to the tail to space out molecules
proteins can move around and membranes become more fluid

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17
Q

if the membrane is too hot and fluid what changes does it make?

A

lipids become more saturates and packed more tightly making the membrane more fluid

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18
Q

what does adding cholesterol to a membrane do?

A

controls the fluidity of the membrane

but too much makes it rigid and viscous

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19
Q

how is the membrane asymmetrical

A

outer layer is different to inner

eg receptors

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20
Q

what are found on the outside of the membrane?

A

glycolipids

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21
Q

what is a glycolipid?

A

sugar group headed lipid

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22
Q

what is the function of a glyocolipid

A

provides protection for the cell sugar coating.

helps with ice crystals and stresses

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23
Q

what is found on the inside of the membrane?

A

phosphatidylserine

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24
Q

what is the function of phosphatidylserine

A

signal molecules
flips over during death signals to act as the signalling molecules for death and that the cell needs to be engulfed and disposed of
process called flip-flop

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25
what causes flip-flop movement?
very rare | enzymes called flippases can sometimes do this but its never spontaneous
26
how does the membrane have an electrical charge?
inside the cell are proteins and ions that at a neural pH have a new negative charge the ions move in and out of the cell to balance this charge out causes and electrochemical gradient
27
what is the gradient in a cell
positive outside | negative inside
28
why is the electrical gradient in cells so important?
nerve signal transmission requies it
29
what does the membrane favour in terms of ions?
transport of cations into the cell | anions out
30
how do things move across the membrane?
it is selectively permeable | highly controlled what goes in and out
31
what can and cant go across membranes
hydrophobic moecules cant disolve | sugars are repelled
32
what facilitates movement of thing across the membrane
transport proteins | channel proteins
33
why are transport protens used?
a hydrophillic substance that cant go through on their own
34
what transport water?
aquaporins
35
how do carrier proteins work?
bind to molecules and change shape to shuttle things across the membrane not open all the time, specific works down a concentration gradient, passive
36
what is passive transport?
diffusion | carrier proteins
37
how does active transport work>
against a concentration gradient | requires energy in form of ATP
38
what do cells contain that remain largely trapped within the cell?
``` sugar protein amino acids nucleotides ions ```
39
because there are lots of things within the cell it creates a what gradient?
strong osmotic gradient | meanign water will move into the cell
40
how is the osmotic gradient controlled?
Na/K pump
41
how does the Na/K pump work?
pumps out some ions open on the outside and removes sodium through ATP open on the inside too allowing K to bind 3Na out for every 2K in net loss from cell and equalibrium made
42
why is endocytosis used in cells?
cant have large channels for large molecules because then everything smaller would also flow through so endocytosis is used
43
describe the process of receptor-mediated endocytosis
1. ligand binds to membrane receptor 2. receptor-ligand migrates into clathrin-coated pill, membrane pulls molecule into cell 3. endocytosis 4. endosome/vehicle made with molecule inside losing clathrin coat 5. enzymes degrade lipids
44
how does the process of coated vesicles in endocytosis work?
ligand binds to receptor | membrane curves a proteins bind to inside of receptor fitting together to form a circle endosome
45
in a coated vesicle endosymbiosis what is the endosome coated in?
clathrin molecule forms a cage/coat
46
what is pinocytosis?
takes in little bits of the environment
47
how are proteis secreted?
transported to the plasma membrane in vesicles which then fuse with the membrane releasing their contents
48
what balance keep cells shrinking?
endocytosis and exocytosis
49
where are proteins synthesised?
rough ER
50
where are proteins packaged?
golgi body
51
what are the two pathways for a substance to be secreted?
constitutive secretory pathway | regulated secretory pathway
52
how does the constitutive secretory pathway work?
used immediately and constantly made used for molecules to be secreted as soon as they are made the molecule is packaged and sent to surface quickly to be secreted the membrane fusion is unregulated
53
how does the regulated secretory pathway work?
the packaged molecule stays around for a while it is stored and only released when it recieves the correct signal such as a hormone or neurotransmitter made in advance to save time
54
how do viruses exploit membrane transport
use the host membrane to get in and out of the cell ligands on virus cell iminates the cells ones fools the cells and allows it to undergo endocytosis enzymes on the virus protect it from being degrades budd out taking some membrane with it
55
what helps viruses fool cells?
ligands on surfaces and lipids
56
what are cellular membranes and why are they imporant
golgi and ER key to move things around the cell once inside compartmentalisation of cells
57
how do proteins end up where they need to be?
labels on they act as tags to signal where they need to be sent
58
what signal sends a protein to the nucleus?
lys-lys-lys-arg-lys
59
how can proteins be modified after being made
glycosylated phosphylation ubiqunation
60
a glycosylated protein goes where?
plasma membrane
61
a phosphylated protein can do what?
change what it can bind to
62
what does unbinquination do to a molecule?
sends the protein for break down in the proteosome
63
how can you move things between compartments
gated transport transmembrane transport vesicles
64
how does gated transport work?
eg nuclear pore acts like a channel proteins allowing large things through needs sequence tagging to work
65
how does transmembrane transport work
cant have a large pore to move proteins so this allows single amino acids through at a time acts as a proteins translocator an the peptide chain is fed through
66
example of transmembrane transport
mitochondria | moving cytochrome C around
67
exmple of vesicular transport
motor proteins
68
why is vesicular transport needed?
vesicles need to be moved around the cell to they are waked down microtubues
69
three types of motor proteins used to transport vesicles?
1. myosin 2. kinesin 3. dynein
70
which motor protein used actin filaments?
myosin
71
which motor proteins use microtbules
kinesin and dynein
72
which motor protein moves things towards the edge of the cell
kinesin
73
which motor protein moves things towards the middle of the cell?
dynein
74
what do motor proteins move?
vesicles and whole organelles | drag chromosomes durig mitosis
75
what do endosomes use to move?
dynein
76
what do secretory vesicles use to move?
kinesin
77
how do nerve cells use motor proteins?
transmitting nerve signals they need they neurotransmitter down the other end to where its mad use mtoro proteins to move it where its needed
78
what do motor proteins require to work?
ATP
79
structure of a motor protein
head/feet stalk tail attaches to the molecules to be moved add ATP to head/ foot to move in a step like way

Building blocks of life (17 decks)

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