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cell biology y1 > cell and membranes > Flashcards

cell and membranes Flashcards

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1
Q

how do dyes help biologists

A

give a better picture of cells and their insides

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2
Q

how were dyes used in the brain

A

black dye showed separate neurones in the brain, showing the brain was made of different cells

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3
Q

what is the zymogen granule

A

specialised organelle in pancreatic acinar cells for digestive enzyme storage and secretion.

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4
Q

what is a tight junction

A

a junction between animal cells which ensure a watertight seal between two adjacent animal cells. Made of transmembrane proteins which interlink both plasma membranes.

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5
Q

what are desmosomes

A

Junctions which resist tearing by a protein called cadherins which connect the cytoskeleton filaments in each cell.

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6
Q

what is a gap junction

A

channel connecting cells made of tubes called connexins

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7
Q

what do gap junctions do

A

allow passage of electrical and chemical stimuli. this synchronises contractions of smooth muscle responsible for peristaltic movements. and cardiac

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8
Q

what is the extracellular matrix

A

composed of proteins and polysaccharides which are secreted locally and form a meshwork with the cells.

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9
Q

how do plant cells communicate

A

through plasmodesmata

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10
Q

what is a protein channel

A

membrane proteins with a hydrophilic opening which allows hydrophilic molecules to pass through, most are gated

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11
Q

what is a carrier protein

A

membrane protein which changes shape when a molecule binds to it, letting the molecule inside.

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12
Q

what carrier protein allows glucose to diffuse

A

Glut1

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13
Q

how is the glucose gradient maintained

A

glucose is phosphorylated which means that glucose cannot travel back through Glut1

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14
Q

what are the three main ways that active transport takes place

A

coupled transporter
ATP driven pumps
Light-driven pumps

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15
Q

what are coupled tranporters

A

when the transport of one solute is coupled with another to allow movement against gradient. (secondary)

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16
Q

what are ATP driven pumps

A

when energy from hydrolysis of ATP is used

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17
Q

why must the electrochemical pump be maintained

A

if ions flowed down their gradients, this would affect osmotic balance
movement of ions like Na drives movement of other substances

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18
Q

how does the Sodium potassium pump work

A

pumps 3 Na out and 2 K in against conc gradients. Does this by phosphorylation

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19
Q

what is an example of secondary active transport (symport)

A

sodium glucose symporter where glucose is coupled with sodium to allow glucose to flow against conc gradient

20
Q

example of antiport

A

diffusion of na into cardiac muscle allows ca to leave, this is important in regulating contraction

21
Q

how does digoxin work

A

this inhibits the sodium potassium pump, increasing the levels of sodium in cells and therefore the sodium calcium antiport is less effective so more calcium inside the cardiac muscle for a contraction

22
Q

how do tight junctions play a role in membrane proteins

A

prevent movement of proteins such as symporters away from where they are needed.

23
Q

why are cells typically small

A

to maintain a high surface area to volume ratio

24
Q

what methods can be used to see cells

A

staining, immunostaining and fluorescence microscopy and fluorescent protein tagging

25
Q

what gives cells their shape

A

cell wall and cytoskeleton

26
Q

where are the ribosomes made

A

in the nucleolus

27
Q

outline lysosomes

A

example of compartmentalization which contain lots of catabolic enzymes in an acidic environment
they also have a role in autophagy
digestion of both external and internal bodies

28
Q

What is Lysosome storage disease

A

where a key enzyme is not working and so material accumulates in the lysosome.

29
Q

how do we know all eukaryotic cells are related

A

genes that are conserved across eukaryotes leave no doubt we come from a last eukaryote common ancestor

30
Q

how is gene expression different in prokaryotes to eukaryotes

A

translation and transcription are coupled in prokaryotes but in eukaryotes they are separate

31
Q

what is different in eukaryotes with gene expression

A

RNA can be modified by splicing

32
Q

what is the transmembrane domain

A

the part of an integral protein which goes through the membrane

33
Q

integral vs peripheral proteins

A

integral have a part of the protein which passes through membrane but the peripheral proteins arent inserted in membrane
may be attached by a lipid or by protein interactions

34
Q

why is a fluid membrane important

A

allows fusing with other membranes such as vesicles
ensured membrane is equally shared in cell division
cell migration requires fluid membrane

35
Q

how is the membrane fluidity demonstrated experimentally

A

using laser beam and bleaching

dye the lipids then bleach a part of the membrane using a laser
this will prevent the fluorescence
but when left for some time, it returns, showing lipids have moved around

36
Q

how do lipids move in the membrane

A

by rotation, flexion and flip flop

37
Q

what enzymes does flip flop require to work

A

flipases and flopases

37
Q

what enzymes does flip flop require to work

A

flipases and flopases

38
Q

what is the problem for pure phospholipid bilayers

A

they experience rapid phase change over a narrow range of temp

39
Q

how do prokaryotes control membrane fluidity

A

they synthesise more lipids with smaller chain length and unsaturation in order to decrease van da walls when it is cold. this increases spacing between molecules
reverse when temp increases

40
Q

how do eukaryotes regulate the membrane fluidity

A

using cholesterol
at 37 degrees the membrane would be too fluid so it stabilises interactions between phospholipids
at lower temperatures, it prevents the molecules from getting too close and becoming hard and immobile

41
Q

what prevents proteins from moving too far along the membrane

A

tight junctions

42
Q

how does number of tails influence membrane shape

A

two tails forms a cylinder structure and will form a bilayer
1 tail forms a cone and will interact into a micelle

43
Q

how is membrane asymmetry maintained

A

scramblases (passive) and flipases and flopases
flipases bring PS and PE onto cytosolic side
flopases bring SM and PC onto the exoplasmic side

44
Q

outline scramblases

A

new lipids are only added on the cytosolic side so this must be scrambled
scramblases arent specific and transfer phospholipids from one side to the other

cell biology y1 (4 decks)

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