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Cell and Developmental Biology > Eukaryotic Cells > Flashcards

Eukaryotic Cells Flashcards

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1
Q

What are Eukaryotic cells?

A

Bigger and more complex than prokaryotes. Very diverse

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2
Q

What are the relative sizes of Eukaryotic and Prokaryotic cells?

A 
E = 10 -100 micrometres
P= 1 - 5 micorometres
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3
Q

What are some features of eukaryotes?

A
  • Intracellular compartmentalization (organelles)

- Nucleus

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4
Q

What makes Red Blood Cells different from other eukaryotes?

A
  • No nucleus
  • Must have had one to begin with in order to differentiate and replicate
  • Lost in when they became specialised
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5
Q

Describe the structure of the nucleus.

A
  • Largest organelle
  • Contains most of the genetic material
  • Nucleolus
  • Nuclear Envelope
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6
Q

Describe the function of the nucleus.

A
  • Store genetic material
  • DNA strands packaged with histones - condensed
  • Transcription
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7
Q

How does dividing trnascription and translation allow for regulation?

A

Transcription - nucleus. Translation - cytoplasm. mRNA needs to be moved. Process regulated.

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8
Q

Describe the nuclear envelope

A
  • Selective openings to allow mRNA out

- Some proteins may need to be moved back into the nucleus

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9
Q

Describe the structure of ribosomes

A
  • Ribonucleoprotein complexes

- Large and small subunits

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10
Q

Describe ribosome assembly

A
  • Transcription → nucleus
  • Translation → cytoplasm
  • Polypeptide assembled onto nascent rRNA → nucleolus
  • Subunits transported to cytoplasm for function
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11
Q

Describe the function of the ribosome

A
  • Translate mRNA into proteins
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12
Q

What happens in if the protein is destined to remain in the cytosol?

A

Translated by ribosomes free in the cytosol

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13
Q

What happens if the protein is destined to be secreted?

A
  • Translated by proteins on the RER

- Enter the secretory pathway

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14
Q

Describe the process of translation for proteins destined to remain in the cytosol

A
  • Polypeptide emerges
  • Folds as its emerging from the ribosomal tunnel
  • Chain grows more ribosomes attach to create a polysome
  • Once a stop codon is reach the polypeptide is released
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15
Q

Describe the process of translation for proteins destined to be secreted.

A
  • Short hydrophpbic section emerges first
  • Known as a signal peptide
  • Recognised by the signal recognition peptide
  • Halts translation
  • Carries the ribosome to the RER
  • Ribosome attaches to the RER
  • Polypeptide grows again
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16
Q

Outline the secretory pathway

A

Recognition of signal pathway - Golgi - Secretory Vesicles - Fused with the membrane - Released

17
Q

What is glycosylation?

A

Form of post translational modification. Addition of carbohydrates. Diverse

18
Q

Describe how post translational modification works

A
  • Different enzymes are housed in different membrane bound compartments (cisternae)
  • Proteins travel through in a different and specialised order
  • Golgi is like an assembly line
  • Cell ensures they move through in a defined order
  • Receiving sequential modifications
19
Q

What is the trans golgi network?

A
  • Sorting station
  • Part of the endocytic pathway
  • Interconnected tubules and vesicles
  • Proteins trafficked through the ER are packaged into secretory vesicles that fuse with the plasma membrane to leave the cell
20
Q

What is endocytosis?

A

Taking in

21
Q

Describe endocytosis

A

Portion of plasma membranes invaginates and pinches off to form a vesicle called an endosome

22
Q

What does the lysosome do?

A

Degradative enzyme. Proteases and lipases

23
Q

What does compartmentalisation allow for?

A
  • Coordination/regulation of complex of biochemical reactions
  • Sequestrations of components
  • Energy generation
24
Q

How do you move molecules between organelles?

A
  • Vesicular transport

- Need a high level of communication

25
Q

What is autoradiography?

A
  • Bio-analytical technique - helps visualise the distribution of molecules labelled with radioisotope
  • Can localise molecules within tissues etc
  • Sensitive and quantitative
  • Works by incorporating radioisotopes into molecuels, energy emitted can be deteced
26
Q

What is Pulse chase labelling?

A
  • Incorporate radioactive isotopes into molecules synthesized during a defined time period
  • Radio-labelled compound added to system of choice for a brief period of time (the ‘pulse’)
  • (the ‘chase’) is initiated by either washing the sample to remove the isotope and/or adding excess non-labelled compound
  • Used to follow the dynamic of cellular processes and pathways
27
Q

Describe an a specific pulse chase labeling experiment

A
  • Slices of pancreas in culture synthesisze and secrete enzyme
  • Add 3Hleucine become incorporated into newly synthesized proteins
  • After 10’ wash the slices and initate ‘chase’
  • Perform audioradiography after 0, 10 and 60 minutes
28
Q

Where do proteins enter the secretory pathway?

A

RER

29
Q

What was the SNARE hypothesis proposed to explain?

A

Specificity of vesicular transport

30
Q

What do free cell assays allow scientists to do?

A

Identify new physiological processes

31
Q

what are the 2 types of SNARe PROTEINS?

A
  1. v-Snare on vesicles

1. t-SNARE on target membranes

32
Q

describe the process of SNARE proteins.

A
  • on trnasport vesicles
  • v SNARE recognises its partner t SNARE on appropriate target membrane
  • binding docks the vesicle onto target membrane and recruit machinery that meidates mebrane fusion
33
Q

what does SNARE stand for>

A

Soluble NSF attachment receptors

34
Q

outline the SNARE hypothesis

A
  • a family of proteins that localize to different intracellular
    organelles
  • Transport vesicles carry specific v-SNAREs (1 mark)
    that recognize and bind to t-SNAREs
  • Membrane fusion can only proceed following formation of a functional
    SNARE complex
35
Q

how is molecular machinery required for membrane traffic evolutionary conserved?

A
  • Sequence analysis of mammalian NSF and yeast Sec18 revealed homology
  • cDNA encoding NSF
  • complements the growth phenotype
    of sec18 mutant yeast
36
Q

evidence that indicates cell to cell signalling

A

single celled eukaryotes like yeast use secreted cell signals to signal
mating-type during sexual reproduction

Cell and Developmental Biology (4 decks)

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