Cells Flashcards
1
Q
ATP Synthesis in Halobacterium
A
- protein called bacteriohodopsin in cell plasma membrane absorbs light
- this causes the protein to change shape allowing it to squeeze a protein through the membrane
- this pumping of protons creates a proton gradient across the membrane
- the cell wall restrict diffusion of protons to maintain the gradient
- protons pass back through the membrane via an ATP synthase enzyme
- the motion of several protons through the ATP synthase provides enough energy for one molecule of ATP to be produced frm ADP + Pi
2
Q
What does energy metabolism in all cells have in common?
A
-creation of a proton gradient across a membrane
3
Q
How does increasing the surface area of the membrane effect energy metabolism?
A
-allows more ATP to be produced as there is space for more membrane proteins
4
Q
Basic Prokaryotic Cell
A
- cytoplasm rich in ribosomes
- single circular chromosome
- plasmid(s)
- cell membrane
- cell wall
5
Q
Complex Prokaryotic Cell
A
- cytoplasm
- cytoplasmic inclusion
- ribosomes
- DNA coiled into nucleoid
- plasma membrane
- infoldings of plasma membrane
- cell wall
- capsule
- pili
- flagella
6
Q
Pillus
A
- protein tube
- can penetrate the surface of other bacteria
- used to exchange DNA
7
Q
Carboxysome
A
- protein based organelle
- self assembles
- looks like virus
- filled with proteins (2 enzymes) for highly efficient carbon fixation
8
Q
Variety in Prokaryotes
A
- lots of different cell shapes
- plenty of motility types
9
Q
Why do single celled prokaryotes need to be able to move around?
A
As they are small, they can’t store much food so have to travel wherever food is avaliable
10
Q
Apparent Viscosity of Fluids Relative to Object Size
A
- turbulence increases with object size and speed
- laminar flow is promoted by high viscosity of liquid medium
- for very small objects a liquid medium appears to have a much higher viscosity
11
Q
Laminar Flow and Prokaryotic Cells
A
- prokaryotic cells are very small and move slowly compared to other objects
- as a result it is easier for them to achieve a laminar flow as they move through a liquid medium
12
Q
Flagella
A
- for motility
- protein filaments with motors
- require ATP
13
Q
Dormancy
Definition
A
the ability to make spores
14
Q
Spore Formation
A
- asymmetric cell division
- valuable nutrients and a copy of the cells DNA are moved to one end of the cell
- the cell begins to divide
- a small section of the cytoplasm containing the nutrients and DNA copy is sectioned off
- the bigger part of the cytoplasm then stretches and reforms around the spore so that it is enclosed within the cell
15
Q
Bacterial Parasite
Definition
A
Bacterium that lives at the expense of other bacteria
16
Q
Gram Positive
A
- plasma membrane
- very thick peptidoglycan cell wall
17
Q
Gram Negative
A
- plasma membrane
- thin layer of peptidoglycan
- outer membrane
- space between the membranes is called the periplasm
- the outer membrane and periplasm combined are called the cell wall
18
Q
Peptidoglycan
A
- made of strands of two alternating sugar compounds, NAM and NAG
- there are cross links between the strands
- NAM = N-Acetylglucosamine
- NAG = N–Acetylmuramic Acid
19
Q
The Gram Stain
A
- crystal violet is applied, it stains both cell types by binding to the cell envelope
- iodine is added and forms large crystals with the crystal violet which combine with the peptidoglycan
- more crystals are deposited in a gram positive membrane as there is more peptidoglycan
- application of alcohol dissolves the outer membrane lipids of a gram negative cell leading to the release of the crystal violet-iodine crystals
- crystal violet - iodine crystals are able to remain in the thicker wall of the gram positive membrane despite the alcohol
- a counter stain is added so that the now colourless gram negative membrane appears red, the gram positive membrane will appear purple
20
Q
Basic Features of Prokaryotes
A
- reproduction
- maintenance of genetic traits
- evolution through variation and selection
21
Q
Advanced Features of Prokaryotes
A
- multicellularity
- cell differentiation and specialisation
22
Q
Eukaryote
Definition
A
organism made up of one or more cells having a distinct nucleus
23
Q
Relative Size of Prokaryotic and Eukaryotic Cells
A
A prokaryotic cell is smaller than a eukaryotic cell nucleus
24
Q
Eukaryotic Cell
Characteristics
A
- high degree of cell compartmentalisation
- true nucleus
- very large genome
- often depends on other life forms to acquire building blocks
25
Eukaryotic Cells
| Organelles
- ER
- golgi apparatus
- lytic vacuole / lysosome
- peroxisome
- mitochondria
- chloroplast
26
What kind of proteins are synthesised in the ER?
-only proteins that will enter the secretory pathway are synthesised in the ER
27
Where is DNA found in a eukaryotic cell?
- nucleus
- mitochondria
- chloroplast
28
Nuclear Envelope and ER
| Function
protein synthesis, folding and export
29
Golgi Body
| Function
protein sorting (back to ER or secretion)
30
Vesicles
| Function
- transport carriers
- bud from donor membranes
- fuse with acceptor membranes
31
Plasma Membrane
| Function
- surrounds cell
| - one end location of the secretory pathway (the other is the vacuolar membrane)
32
Secretory Pathway
| Anterograde Transport
ER to Golgi
| COPII mediated
33
Secretory Pathway
| Retrograde Transport
Golgi to ER
| COPI mediated
34
Endosomes / Pre-vacuoles
| Function
- number of organelles between Golgi and the end of the secretory pathway
- called endosomes in mammals
- called pre-vacuoles in plants and yeast
- sorting stations like Golgi
35
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Eukaryotic Secretory Pathway
Conserved Names (same in all eukaryotes)
```
- nuclear envelope
- ER
- Golgi
- vesicles
- plasma membrane
36
Eukaryotic Secretory Pathway
| Names that aren't conserved
Endosomes (mammals) / Prevacuolar Compartments (plants & yeast)
Lysosome OR Lytic Compartment (mammals) / Vacoles (plants & yeast)
37
How did eukaryotic cells evolve?
- eukaryotic cells probably evolved from symbiosis
| - phagocytosis of a unicellular prokaryote
38
How did mitochondria and chloroplasts evolve?
- by phagocytosis of unicellular prokaryotes
- there are some chloroplasts that still have their own peptidoglycan cell wall
- endocytic and phagocytic activity must have evolved early (before organelles)
39
Possible Evolutionary Origin of the Nuclear Membrane
HYPOTHETICAL
- evolution of membrane bound ribosomes in an ancient prokaryote
- invagination of membrane increasing surface area for secretion & absorption
- this also happens to create ER and nuclear membrane (which are continuous)
40
Selection Pressure for Evolution of the Secretory Pathway
- protein transport across the cell plasma membrane would be rate limiting as cell size increased
- invaginations of the plasma membrane could have helped to increase surface area
- photosynthesis and chemolithotrophic bacteria often have large internal membranes
41
Cell Size and Fragility
the larger the cell the more fragile it is
| this means that eukaryotic cells need a cytoskeleton to support them
42
Cytoskeleton
| Actin Filaments
- 2 stranded helical
- 5-9nm diameter
- flexible
- determine cell surface shape
- mediate whole cell motion
- organised in parallel bundles giving gel like properties
- form 2D network under plasma membrane
43
Cytoskeleton
| Microtubuli
- polymers of tubulin
- 25nm diameter
- very rigid
- provide 'highways' for membrane enclosed organelles
- help direct intracellular transport
- organised into long strands with minor bends
- usually attached to microtubule organising centre (MTOC) aka centrosome
44
Cytoskeleton
| Intermediate Filaments
- polymers of heterogeneous protein family
- cylinders of 10nm
- reasonably flexible
- organised into rope like fibres
- give cell mechanical strength
- resist shear stress
- some extend cross entire cytosol
- others form specialised cell structures
45
Increase in Cell Size
| Advantages
- ability to create storage compartments
| - additional room for complexity
46
Increase in Cell Size
| Disadvantages
- decrease in surface area to volume ratio
- nutrient uptake rate decreases
- protein secretion rate
- disposal of toxic waste is harder
- proton gradient across the membrane s insufficient for adequate ATP synthesis
- cell becomes more fragile
