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MD2001 Week 1 > Cells and Organelles > Flashcards

Cells and Organelles Flashcards

1
Q

Cell theory?

A

> all organisms consist of one or more cells

> the cell is the basic unit of structure for all organisms

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2
Q

Why are cells so small?

A

to allow diffusion of waste products and nutrients

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3
Q

What size are cells in relation to a human hair?

A

1/10th of the size

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4
Q

Smaller cell and larger cell?

A

smaller - bacterial

larger - human egg

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5
Q

What are the properties of a cell?

A

> microscopic packages that act as independent units
originate from preexisting cells - grow and divide
have a finite lifetime - they die
their internal processes allow them to change/adapt/respond - different jobs for different cells/part of body

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6
Q

What is the plasma membrane?

A

enclose the cell space as an independent reaction container - contains a salty - protein rich solution

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7
Q

What is the structure of the membrane?

A

bilayer of lipid molecules with added protein - phospholipid bilayer

  • semipermeable
  • flexible
  • continuous bag - barrier to water
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8
Q

What function can proteins play in the membrane?

A
  • receptors
  • transporters
  • signalling
  • adhesion
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9
Q

Features of prokaryotes?

A
  • no nucleus - nucleoid instead
  • simple without internal membranes - no organelles - all processes in cytosol
  • few microns in size
  • simplest and smallest are bacteria
  • few microns in size -small and simple
  • circular DNA - not enclosed by membrane
  • simple cell division
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10
Q

Micron?

A

1x10 -6 of a meter - u

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11
Q

Features of eukaryotes?

A
  • internal compartments and membranes
  • 10+ microns in size
  • linear DNA arranged in chromosomes - enclosed by membrane
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12
Q

What are the three main systems of eukaryotes?

A
  • protein expression
  • secretion pathway
  • uptake and degradation
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13
Q

What are the stages of protein synthesis?

A

Transcription - DNA copied as mRNA

Translation - mRNA decoded to make protein

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14
Q

What is the purpose of protein synthesis?

A

allows growth and differentiation

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15
Q

How is DNA arranged in eukaryotes?

A
  • packaged and enclosed by a double membrane in the nucleus - the “nuclear envelope” is the membrane
  • nuclear envelope has nuclear pores - mRNA passes from nucleoplasm to cytoplasm via
  • packaged with histones - forming the complex chromatin
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16
Q

Where does translation occur?

A

ribosomes

- mRNA is decoded and proteins are made

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17
Q

What are chromatins?

A

DNA is packaged with proteins called histones forming the complex chromatin
two types - euchromatin, heterochromatin

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18
Q

What are the ways in which chromatin is packaged?

A

> euchromatin - more active genes

> heterochromatin - more dense

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19
Q

Where are ribosomes found?

A
  • free in the cytoplasm

- bound to the ER to make the rough ER

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20
Q

What is the nucleolus?

A

location of production of ribosome - at amplified ribosomal genes

  • found in the nucleus
  • involved in rRNA synthesis
  • composed of RNA and protein
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21
Q

What are the two options for proteins after translation starts?

A

> remain in cytosol for remainder of translation
fed into ER during translation
(all protein synthesis starts in cytosol)

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22
Q

When do proteins remain in the cytosol for the rest of translation?

A

proteins do not have a signal peptide
- proteins can then be sent to other organelles - mitochondria, chloroplasts, nucleus - organelles not part of the endomembrane system

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23
Q

When do proteins get sent to the ER during translation?

A

have a signal peptide
- proteins bound for organelles part of endomembrane system - ER, Golgi apparatus, lysosome
- or proteins bound for exterior of cell
(makes rough ER)

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24
Q

What is the endomembrane system?

A

modify, packages and transports proteins and lipids

- includes ER, Golgi apparatus, lysosome

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25
What is the ER?
interconnected network of flattened, membrane bound sacs known as cisternae - membranes continuous with the outer nuclear membrane - makes and packages proteins - lumen is the cisternal space - rough ER has ribosomes attached - when protein is created it is packaged and pinched off in a vesicle
26
What are the steps of the secretion pathway?
synthesis of proteins in the RER - (transition) vesicles carry proteins to Golgi apparatus Modification of proteins at golgi - vesicles carry modified protein to the plasma membrane for secretion into extracellular environment
27
Function of the Golgi?
packaging organelle - packages proteins into secretory vesicles for secretion - modifies lipids and proteins - grows sugar chains and adds phosphates
28
How do secretory vesicles release content at the plasma membrane?
exocytosis - membrane bound secretory vesicles release contents into the extracellular environment - active transport - vesicles temporarily bind to membrane
29
How do vesicles move towards and away from the Golgi?
- transport along microtubules in one direction - they contain instructions telling them where to go - use motor proteins attached to vesicle
30
What are the function of microtubules?
- track for vesicles and organelles
31
What is the centrosome?
where microtubules emulate from - microtubule organising centre
32
What is uptake process known as?
endocytosis
33
What carries out endocytosis of large particles?
phagocytosis
34
What carries out endocytosis of small particles?
pinocytosis - "cell drinking" of extracellular fluid - non specific
35
What happens to molecules that have been endocytose?
delivered to endosomes then passed on to lysosomes for degradation - some membrane is recycled back to the cell surface
36
What are endosomes?
membrane bound vesicles | - deliver cargo from plasma membrane to lysosome
37
What are lysosomes?
organelles in cytoplasm containing degradative enzymes enclosed in a membrane - low pH
38
What is autophagy?
parts of the cell itself are walled off and digested in lysosomes
39
What is receptor mediator endocytosis?
?
40
What are proteasome?
protein complexes which degrade unneeded or damaged proteins (proteins for degradation are tagged by a small protein called ubiquitin)
41
What is ubiquitin?
a small protein that tags damaged proteins for degradation - signal to other ligases to attach additional ubiquitin - resulting in a polyubiquitin chain that is bound by the proteasome - allowing it to degrade the protein
42
What is the advantage of internal compartments ?
specialised reactions can be separated, concentrated and optimised
43
What aids vesicle budding?
molecular scaffold supports - eg. clathrin
44
What is the function of mitochondria?
produce most of ATP supply | - enables cells to grow bigger
45
What is the structure of mitochondria?
> two membranes - inner folded into interior > contain own DNA > reproduce by dividing in two (> all mitochondria come from your mothers egg)
46
What are the functions of the cytoskeleton?
> moving > positioning > supporting > protecting
47
What protein filaments does the cytoskeleton consist of?
> microtubules > microfilaments > intermediate filaments
48
Microtubules?
- tiny (25nm) - thickness of ribosome - vesicle tracks - position/move organelles (mitosis) - dynamic made of subunits of the protein tubulins
49
Microfilaments?
- thiner than microtubules (7nm) tiny - generates contractile forces - enables cell and parts of cell to move, cells to contract - dynamic made of subunits of actin
50
Intermediate filaments?
- middle thickness (10nm) - strength and support - found in cytoplasm and nuclear envelope - not dynamic proteins - keratins, laminins
51
Function of smooth ER?
(no ribosomes) - involved in lipid, steroid production and detoxification - smooth ER expands
52
What are peroxides?
- do oxidative reactions using molecular oxygen - break down and oxidise some fatty acids - synthesis some specialised lipids - generate hydrogen peroxide which is broken down by catalase
53
What determines the type of cell?
protein expression
54
What are all cells types derived from?
totipotent stem cells
55
totipotent?
can become any cell type
56
pluripotent?
can become several different cell types
57
Least specialised to most specialised stem cell types?
totipotent, pluripotent, tissue specific
58
What are the ways in which cells communicate?
> endrocine > paracrine > neuronal > contact dependent
59
Paracrine?
relating to a hormone which only has effect in vicinity of gland secreting it
60
How do static cells live together?
adhere to each other
61
How do static cells adhere to each other?
``` > tight junctions > adherent junctions > desmosome > gap junction > hemidesmosome ```
62
Tight junctions?
seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them
63
Adherens junctions?
joins an actin bundle in one cell to a similar bindle in a neighbouring cell
64
Desmosome?
joins intermediate filaments in one cell to those in a neighbour
65
Gap junction?
forms channels that allow small water-soluble molecules including soluble molecules to pass from cell to cell
66
Hemidesmosome?
anchors intermediate filaments in cell to the basal lamina
67
What is hypercholesterolemia?
defective uptake of lipoproteins > LDL receptors bind LDL (bad cholesterol) for uptake - 3 causes of this: - LDLR not properly transported from RER to Golgi for expression on cell surface - LDLR bound to LDL does not cluster in endocytic vesicles on plasma membrane - LDLR not recycled back to cell surface
68
Cystic fibrosis cause?
misfolding of key protein
69
Hypertension cause?
defective cell-cell adhesion in kidney
70
Congenital heart defects cause?
errors in cell migration during development
71
Muscular dystrophy cause?
defective attachment of plasma membrane to cytoskeleton
72
Lysosomal storage disease cause?
defective intracellular transport of enzymes
73
Food-bourne illness cause?
salmonella, E.coli
74
Cancer cause?
errors in cell division, migration, cell polarity, growth etc

MD2001 Week 1 (4 decks)

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