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Phase 1 > Cell Biology > Flashcards

Cell Biology Flashcards

1
Q

how does cholesterol control membrane fluidity?

A

packs phospholipids

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2
Q

what are 3 functions of proteins in the phospholipid bilayer?

A
  • transport of hydrophilic molecules
  • cell-cell communication
  • communication via endocrine / cytokine etc. systems
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3
Q

what are 3 categories of protein transporters?

A
  • passive
  • active
  • secondary active pumps
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4
Q

what is the difference between endocytosis, phagocytosis and pinocytosis?

A
  • endocytosis - general intake
  • phagocytosis - done by phagocytes
  • pinocytosis - bulk intake of fluids
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5
Q

what allows the surface membrane to form internal vesicles?

A

clathrin molecules allow bilayer to bend inwards, forming a clathrin-coated vesicle

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6
Q

what is cytosol?

A

intracellular fluid

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7
Q

what allows the cytoplasm to maintain its structure?

A

cytoskeleton network

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8
Q

what structure makes up the ER?

A

external nuclear membrane

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9
Q

how do ribosomes get to the RER? (3)

A

1 - signal peptide on N-terminal of protein
2 - SRP (signal recognition particle) attaches to signal peptide
3 - SRP receptor binds to RER

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10
Q

what are 3 functions of the SER?

A
  • lipid synthesis
  • steroid / drug metabolism
  • calcium store
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11
Q

what is the cis-maturation model? (4)

A

1 - vesicles fuse to cis cisterna
2 - cis cisterna becomes part of medial cisternae
3 - eventually become part of trans cisternae
4 - joins the trans Golgi network (TGN) from which vesicles leave to particular destinations

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12
Q

how are proteins directed to 1. lysosomes, 2. plasma membrane, 3. outside cell (via secretion)?

A

1 - addition of mannose-6-phosphate (glycosylation)
2 - ‘stop translocation’ peptide
3 - no modification

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13
Q

what are glycosylated proteins called?

A

glycoproteins

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14
Q

what are heavily glycosylated proteins called?

A

proteoglycans

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15
Q

what is the effect of phosphorylation?

A

alters the activity of a protein

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16
Q

give an pathological example of phosphorylation as a post-translation modification, and its significance

A

hyperphosphorylation of Tau protein - present in many neurological disorders

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17
Q

what is the effect of acetylation?

A

on histones - regulate gene expression

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18
Q

what are 2 common effects of farnesylation?

A
  • mediates protein interactions

* targets proteins to plasma membrane

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19
Q

what is the effect of ubiquitination?

A

tags a protein for degradation

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20
Q

what are endosomes? (3)

A
  • immature lysosomes
  • contain proteins from Golgi
  • fuse with phagocytotic vesicles
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21
Q

why does the lysosome require an acidic environment? how is this maintained?

A
  • digestive enzymes work in acidic environments (think stomach)
  • proton ATP-ase pumps
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22
Q

what 3 types of proteins need to de degraded?

A
  • old proteins
  • faulty proteins
  • foreign proteins
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23
Q

when is lysosomal degradation used? (4)

A
  • autophagy of proteins with long half-lives (20 hrs)
  • membrane proteins (endocytosis)
  • extracellular proteins (receptor mediated endocytosis)
  • pathogenic proteins (phagocytosis)
24
Q

what is the simple structure of a proteasome? (4)

A
  • cylinder
  • protease enzyme in walls
  • internal active site
  • open tube to allow protein to enter
25
Q

when is proteasomal degradation used? give 2 examples

A

• dangerous proteins with short half-lives (seconds or minutes) -> tagged with ubiquitin

  • metabolic enzymes
  • defective proteins
26
Q

what is the sequence of proteasomal degradation? (5)

A

1 - protein tagged with Ub
2 - shuttled to proteasome
3 - recognised, unfolded and translocated
4 - degraded in proteasome into a peptide
5 - extruded and digested by cytosolic peptidases

27
Q

why is the mitochondria membrane-bound?

A

separate powerful enzymes from other organelles

28
Q

what are 4 common functions of the mitochondria?

A
  • ATP production
  • Kreb’s cycle
  • electron transport chain
  • oxidative phosphorylation
29
Q

how does the mitochondria contribute to apoptosis? (4)

A

1 - increase membrane permeability
2 - release cytochrome c
3 - forms apoptosome
4 - apoptosome activates caspase cascade

30
Q

what is the effect of apoptosis on the cell? (3)

A
  • destroy nuclear lamins
  • activate DNases (degrades DNA phosphate backbone)
  • destroy cell adhesion proteins
31
Q

how do materials enter the nucleus?

A

via nuclear pores

32
Q

what is the nuclear lamina?

A
  • supports the inner membrane

* composed of lamins (intermediate filaments)

33
Q

how is genetic material stored?

A

chromatin

34
Q

what are the 3 functions of the cytoskeleton?

A

shape, strength and movement

35
Q

what is the structure of microtubules, and why is this useful?

A

tubular - resists bending and stretching

36
Q

what is the main function of microtubules?

A

act as the ‘highway’ of the cell - transport organelles and vesicles

37
Q

what is the MTOC and what are its 2 functions?

A

• microtubule organising centre

  • microtubules attach to this
  • forms mitosis spindle
38
Q

where are intermediate filaments centred?

A

around nucleus - extend to periphery

39
Q

what important structures use intermediate filaments?

A

desmosomes and hemidesmosomes

40
Q

what quality of intermediate filaments helps its function?

A

maintains structural integrity - hence presence in epithelial cells

41
Q

what material makes up microfilaments?

A

actin formed into a polymer

42
Q

what are the 2 functions of microfilaments?

A
  • controls cell shape

* involved in cell movement

43
Q

what cell structures are made of microfilaments?

A
  • microvilli
  • lamellipodia (motor pulling cell forward)
  • filopodia (extend beyond lamellipodia)
44
Q

what is the structure of a tight junction? (4)

A
  • fusion of integral proteins
  • between lateral membranes
  • in epithelial cells
  • held in place by actin fibres
45
Q

what are 2 functions of tight junctions?

A
  • do not allow diffusion between cells

* forms a barrier between polar apical and basolateral membranes (maintains polarity)

46
Q

what are gap junctions made of?

A

connexins

47
Q

what is the purpose of gap junctions?

A

permit passage of small molecules between adjacent cells

48
Q

what is meant by the gate-fence model for gap junctions?

A

gate - regulates permeability

fence: prevents mixing between apical and basolateral surfaces

49
Q

where are desmosomes found in the skin?

A

between keratinocytes in the epidermis

50
Q

where are hemidesmosomes found in the skin?

A

between stratum basale cells and basement membrane in epidermis: dermoepidermal junctions

51
Q

what condition is caused by a mutation which alters the function of respiratory chain proteins in the mitochondria?

A

Leigh syndrome (CNS)

52
Q

what type of conditions are caused by defects in oxidative phosphorylation?

A

mitochondrial cytopathies

53
Q

why do mitochondrial diseases particularly effect the brain and CNS?

A

high energy systems

54
Q

what is Tay-Sach’s disease? what does this result in?

A
  • failure to degrade lipids in lysosome

* lipids accumulate in neurones and progressively damage the nervous system

55
Q

what is Kartangener’s disease? what does this result in?

A
  • mutations to dynein (responsible for movement) in cilia and flagella
  • frequent lung infections and male infertility
56
Q

what do defects in hemidesmosomes or intermediate filaments result in? (2)

A
  • disruption of dermo-epidermal junction

* leads to blistering: epidermolysis bullosa simplex (butterfly skin)

57
Q

what can mutations in connexins result in? (2)

A
  • defective GAP junctions

* associated with inherited deafness

Phase 1 (14 decks)

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