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Cell Biology and Signalling > Cells and Organelles > Flashcards

Cells and Organelles Flashcards

1
Q

What is a Cell?

A
  • semi-independent, living unit within the body (in unicellular organisms, completely independent)
  • sited the mechanisms for metabolism, growth and replication (by division).
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2
Q

What is an organelle?

A
  • subunit (functional unit) within a cell
  • defined structure
  • performing specific, integrated activities.
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3
Q

What is a Tissue (and 2 e.g.s)?

A
  • organised assembly of cells and their extracellular products (what those cells secrete)
  • carry out similar and coordinated activities within the body
  • (connective, lymphoid)
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4
Q

What is a Organ (and e.g.s)?

A
  • assembly of tissues

- coordinated to perform specific functions within the body (eye, ear, heart, lungs, liver)

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5
Q

What is a System (and 2 e.g.s)?

A
  • assembly of organs
  • specific, related activities
  • sharing regulatory influences (e.g. respiratory).
  • OR it may be a diffuse functional network of cells situated in many parts of the body
  • sharing specific activities (e.g. immune)
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6
Q

What is a Prokaryote?

A
  • single-celled organism

- chromosome is a circular strand lying free in the cell - - (i.e. no nucleus)

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7
Q

What is a Eukaryote?

A
  • one or more cells

- chromosomes are enclosed in a nucleus

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8
Q

What is a Virus?

A
  • an assemblage of nucleic acid (DNA or RNA)
  • and proteins (and often other molecules)
  • parasitic on prokaryotes/eukaryotes.
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9
Q

What is Cell Theory?

A
  • “All living things are made of cells and these arise through the division of pre-existing cells”
  • all present day cells evolved from same ancestral cell.
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10
Q

How do cells vary and how are they the same?

A
  • Cells vary in shape, chem requirements and function

- all cells are rel the same size explained by fick’s law.

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11
Q

At what distance is diffusion efficient in a cell?

A
  • Less than 50micrometers

- its red above 50

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12
Q

How do cells reproduce?

A
  • replicating its DNA
  • div in 2
  • passing a copy of its gen instructions encoded in its DNA to each of its daughter cells
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13
Q

Why do distances within the cell have to be the same?

A
  • Distance from nucleus to cell edge influences movement of intermediates, waste products and nutrients.
  • as lots of diffusion in cell - this allows diffusion to occur efficiently or part of cell won’t get O2
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14
Q

How do specialised cells overcome this problem of diffusion? (Thin processes)

A
  • cells are long and thin so distance of things diffusing in and out and in any part of the cell with the outside remains the same
    – Directed transport of substances around cell via cytoskeleton e.g. neurones and oligodendrocytes
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15
Q

How do specialised cells overcome this problem of diffusion? (“Giant” multinucleate cells)

A
  • If u need to proteins to be made and there’s only one nucleus, there’s a limit to how far the messages are carried around the cell
    – Gene expression can occur in more than one place in the cell e.g. skeletal muscle cells
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16
Q

How do specialised cells overcome this problem of diffusion? (Gap juctions)

A
  • Channels between cells e.g. Epithelial to allow movement of substances
  • e.g. In an env where O2 can’t get access to a cell - Oxygen from one cell to the next can go through
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17
Q

Why is division of labour good?

A
  • Multicellular org - allows some cells to become spec to extreme degree for certain tasks
  • these cells dependent on other cells for basic requirements
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18
Q

Which type of microscope best reveals subcellular details and why?

A

EM - highest mag + best resolution

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19
Q

What is a Transmission EM used for and how?

A

to look inside a cell (electrons go through the specimen)

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20
Q

What is a Scanning EM used for and how?

A

to see the cell surface (electrons scattered off cell surface by heavy metal coating e.g. Au)

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21
Q

What prep is needed for EM?

A
  • Cut v. thin sections,
  • aq env removed,
  • samples fixed (preserved by pickling in reactive chem sol)
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22
Q

What must the sample be like for EM?

A

Dead cells not living, wet cells

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23
Q

What is a difference between some organelles?

A

some mem-bound, others not e.g. ribosomes

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24
Q

What does the mem around some organelles allow? (4)

A
  • Spec env to exist within it
  • Diff spec functions in cell can op under diff cond e.g. pH
  • Single cell can have numerous diff functional compartments
  • Acts as phys barrier + can reg what crosses it + diff process + differentiate between them in cell
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25
Q

What are some features of eukaryotic cells in terms of:

  • organelles
  • chromosomes
  • cells within same org
  • types of organisms cells are found in
  • size compared to pro
A
  • typically have cytoplasmic, membrane-bound organelles
  • DNA divided into a series of linear chromosomes
  • considerable differences occur between cells within the same organism.
  • All complex organisms (plants, fungi, animals, protozoa, algae) are eukaryotes but some single-celled e.g. amoebae + yeasts
  • bigger than pro
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26
Q

What are some features of prokaryotes in terms of: (5)

  • organelles
  • example
  • shape
  • size
  • extra feature it has eu doesn’t
A
  • Has no membranous organelles
  • e.g. Bacteria - Many diseases caused by them
  • spherical, rod-like/corkscrew-shaped
  • small - 1 micrometer
  • cell wall surrounding plasma mem enclosing cytoplasm + DNA
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27
Q

Compare form and location of genetic material in both pro + eu

A 
Pro:
 - form: in single circ chromosomes 
- location: in nucleiod
Eu:
 - form: in paired chromosomes 
- location: in nucleus
28
Q

Compare location of extrachromosomal DNA in pro + eu

A 
Pro: 
- in plasmids
Eu:
- in mit
- plasmids
29
Q

Compare plasma + internal mem in pro + eu

A 
Pro:
- plasma mem: lacks sterols,
- internal mem: only in photosyn org
Eu:
- plasma mem: contains sterols
- internal mem: many mem-bound org
30
Q

Compare location of resp in pro + eu

A

Pro:
- at cell mem
Eu:
- in mit

31
Q

Compare cell wall + external layer in pro + eu

A

Pro:
- cell wall: peptidoglycan, LDS + teichoic acid
- external layer: capsule/slime layer
Eu:
- cell wall: none in most but chitin in fungal cells
- external layer: none in most but pellicle/shell in some parasites

32
Q

Compare presence of cilia, pili + flagella in pro + eu

A 
Pro: 
- cilia absent, 
- pili present, 
- flagella present
Eu: 
- cilia present in some
- pili absent, 
- flagella present in some
33
Q

Compare cell division + reproduction mode in pro + eu

A 
Pro: 
- cell div: binary fission 
- rep mode: asexual
Eu: 
- cell div: mitosis/meiosis 
- rep mode: sexual/asexual
34
Q

Compare size of ribosomes in pro + eu

A 
Pro: 
- 70s
Eu: 
- 80s in cytoplasm + RER, 
- 70s in mit
35
Q

How do viruses operate?

A
  • invade cells,
  • subvert their protein synthesis machinery to make more viruses instead of normal cell proteins,
  • then escape to infect other cells.
36
Q

Why are viruses not cells/org/pro?

A
  • not cells/organisms - lack a plasma membrane and only operate chemically within host cells.
  • Not prokaryote - can’t function without host - not free living. No ability to reproduce themselves
37
Q

Put in order of decreasing size: animal cell, virus, bacterial cell

A

Animal cell (10-100micrometres), bacterial cell (1 micrometre), virus (50nm)

38
Q

What is cytoplasm?

A

cytosol + organelles

39
Q

What is cytosol?

A
  • aqueous environment within the plasma membrane
  • part of cytoplasm not contained in within intracellular mem
  • water-based gel, protein rich fluid
  • site of many chem reactions fundamental to cell’s existence
40
Q

What is the nucleus structure in terms of:

  • size
  • vis by LM
  • DNA
A
  • Largest organelle in the cell (diam. 3-10μm, 80-800 nm)
  • Only organelle clearly visible by light microscopy
  • DNA winds round histones into nucleosomes
    – “naked” human DNA : 1.8m
    – DNA packaged in nucleosomes: 95mm
    – further condensed in mitosis as chromosomes: 120μm
    – Unless cell is dividing chromatin is decondensed
41
Q

What is chromatin?

A

complex of DNA/histone and non-histone proteins

42
Q

What is nucleolus?

A
  • Site of rRNA genes transcription

- where rDNA is transcribed and ribosome subunits assembled

43
Q

What is nuclear envelope structure and function?

A
  • two layers of membrane enclosing nucleus

- allows protection of nuclear DNA, control of pH in that region

44
Q

What is a nuclear pore?

A
  • hole in nuclear envelope

- allows transport in and out nucleolus - e.g. mRNA can enter into cytoplasm

45
Q

What is the Plasma mem?

A
  • phospholipid bilayer where hydrophil heads face out + hydrophob fatty acid tails face in aq env
  • mem is fluid - lateral diffusion (phos diffuse freely within each layer) + cholesterol
  • cell surface proteins - glycosylated = sugars added - signalling, transport/structural functions
46
Q

What is a lysosome structure and function?

A
  • Electron-dense spheres (vesicles)
  • diameter: 80-800nm
  • contain acid hydrolase enz - catabolise macromol
    – Lysosomal proteins are tagged with mannose -6- phosphate (sugar) - receptors recognise it and allow vesicles to be taken up by the lysosome - useful way of targeting proteins/vesicles within the cell
47
Q

What is a peroxisome structure?

A
  • small mem bound vesicles

– Large (0.5-1.5μm), not very electron-dense

48
Q

What is SER?

A
  • site of Biosynthesis of lipids, steroids;
  • metabolise carbohydrates/steroid
  • store intracellular Ca2+
49
Q

What is RER structure and function?

A
  • Irregular maze of interconnected spaces enclosed by mem
  • Coated with ribosomes
    – Proteins + mem are folded - max SA
50
Q

What is Golgi body structure?

A
  • 4-8 closely-stacked, membrane-bound channels

- (many stacks/mammalian cell)

51
Q

What are secretory vesicles?

A
  • small mem surrounded pockets
  • bud off from the Golgi
  • fuse with the inner surface of the plasma membrane and release their contents (exocytosis) e.g. hormones and neurotransmitters
52
Q

What is endocytosis?

A

Portions of plasma mem tuck inward + pinch off to form vesicles that carry material into cell

53
Q

What is nucleus function?

A

Contains genetic material that is packaged – DNA organised as chromosomes;

54
Q

What is lysosome function?

A
  • digest unwanted + defective proteins – (Protein, RNA and DNA degradation)
  • recycle raw materials within cell from breakdown of unwanted mol/excrete from cell - prevent acc of waste
  • release nutrients from ingested food particles
  • work optimally at pH5 – Powerful enzymes that require low pH
55
Q

What is peroxisome function?

A
  • enz that gen + degrade H2O2
  • provides safe env for Detoxification of proteins/chem - compartmentalised
    – Phospholipid synthesis
  • mem form many diff types of small transport vesicles - carry materials between 1 mem-bound org + another
56
Q

What is function of RER?

A
  • translation of proteins mainly for secretion or insertion into cell membrane
    – Vesicles = are budded from RER and transported to the Golgi body
57
Q

What is Golgi body function?

A

• Modifies proteins delivered from RER e.g. by adding sugar (carbohydrate) or lipid (fat) side-chains (All proteins on cell surface covered with carbs and fats)
- Synthesise/package materials to be secreted out/transported within cell
• Direct new proteins to their correct compartments in vesicles - e.g. to mem, lysosomes etc
• Transport lipids around cell
• Create lysosomes
- trim aa side chains to right length, protein folding,
- identify improperly folded proteins tagged for destruction by lysosomes

58
Q

What is a normal size for a virus?

A

50nm

59
Q

What is smallest size resolvable by electron microscope?

A

0.2nm

60
Q

What is the smallest size resolvable by light microscope?

A

200nm

61
Q

What is a normal size for a bacterium?

A

1µm

62
Q

Where are cells with dimensions larger than 50µm found?

A

nervous system

63
Q

What is Myoclonic Epilepsy with Ragged Red Fibres (MERRF) syndrome cause and symptoms?

A
  • Mutation of mit gene for tRNA-lys
  • Disrupts syn of ox phos enz
    Symptoms:
  • lactic acid acidosis,
  • myoclonic seizures,
  • weakness,
  • un-coord etc
64
Q

What is Hutchinson-Gilford Progeria (Human premature ageing syndrome) cause and symptoms?

A
  • Mutation in lamin = part of nuclear envelope
  • Distorted shape of nucleus (blebbed)
  • production of unique progerin protein
    Symptoms:
  • Extreme growth delay,
  • skeletal dysplasia,
  • thin skin etc
65
Q

What is Tay Sachs disease cause and symptoms?

A
  • Disease of lysosome
  • mutation of lysosomal hexosaminidase
  • Acc of gangliosidase - neurotoxic
    Symptoms:
  • progressive paralysis,
  • inc loss of vision,
  • hearing loss,
  • seizures etc
66
Q

What is Zellweger Syndrome and cause?

A
  • Inherited absence of peroxisomes

- Mutations in specific proteins in peroxisome

Cell Biology and Signalling (7 decks)

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