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BLGY1115 > Cells > Flashcards

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
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2
Q

What does energy metabolism in all cells have in common?

A

-creation of a proton gradient across a membrane

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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

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4
Q

Basic Prokaryotic Cell

A
  • cytoplasm rich in ribosomes
  • single circular chromosome
  • plasmid(s)
  • cell membrane
  • cell wall
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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
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6
Q

Pillus

A
  • protein tube
  • can penetrate the surface of other bacteria
  • used to exchange DNA
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7
Q

Carboxysome

A
  • protein based organelle
  • self assembles
  • looks like virus
  • filled with proteins (2 enzymes) for highly efficient carbon fixation
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8
Q

Variety in Prokaryotes

A
  • lots of different cell shapes

- plenty of motility types

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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

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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
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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
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12
Q

Flagella

A
  • for motility
  • protein filaments with motors
  • require ATP
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13
Q

Dormancy

Definition

A

the ability to make spores

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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
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15
Q

Bacterial Parasite

Definition

A

Bacterium that lives at the expense of other bacteria

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16
Q

Gram Positive

A
  • plasma membrane

- very thick peptidoglycan cell wall

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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
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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
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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
Q

Eukaryotic Cells

Organelles

A
  • ER
  • golgi apparatus
  • lytic vacuole / lysosome
  • peroxisome
  • mitochondria
  • chloroplast
26
Q

What kind of proteins are synthesised in the ER?

A

-only proteins that will enter the secretory pathway are synthesised in the ER

27
Q

Where is DNA found in a eukaryotic cell?

A
  • nucleus
  • mitochondria
  • chloroplast
28
Q

Nuclear Envelope and ER

Function

A

protein synthesis, folding and export

29
Q

Golgi Body

Function

A

protein sorting (back to ER or secretion)

30
Q

Vesicles

Function

A
  • transport carriers
  • bud from donor membranes
  • fuse with acceptor membranes
31
Q

Plasma Membrane

Function

A
  • surrounds cell

- one end location of the secretory pathway (the other is the vacuolar membrane)

32
Q

Secretory Pathway

Anterograde Transport

A

ER to Golgi

COPII mediated

33
Q

Secretory Pathway

Retrograde Transport

A

Golgi to ER

COPI mediated

34
Q

Endosomes / Pre-vacuoles

Function

A
  • 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
Q 
Eukaryotic Secretory Pathway
Conserved Names (same in all eukaryotes)
A
  • nuclear envelope
  • ER
  • Golgi
  • vesicles
  • plasma membrane
36
Q

Eukaryotic Secretory Pathway

Names that aren’t conserved

A

Endosomes (mammals) / Prevacuolar Compartments (plants & yeast)
Lysosome OR Lytic Compartment (mammals) / Vacoles (plants & yeast)

37
Q

How did eukaryotic cells evolve?

A
  • eukaryotic cells probably evolved from symbiosis

- phagocytosis of a unicellular prokaryote

38
Q

How did mitochondria and chloroplasts evolve?

A
  • 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
Q

Possible Evolutionary Origin of the Nuclear Membrane

A

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
Q

Selection Pressure for Evolution of the Secretory Pathway

A
  • 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
Q

Cell Size and Fragility

A

the larger the cell the more fragile it is

this means that eukaryotic cells need a cytoskeleton to support them

42
Q

Cytoskeleton

Actin Filaments

A
  • 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
Q

Cytoskeleton

Microtubuli

A
  • 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
Q

Cytoskeleton

Intermediate Filaments

A
  • 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
Q

Increase in Cell Size

Advantages

A
  • ability to create storage compartments

- additional room for complexity

46
Q

Increase in Cell Size

Disadvantages

A
  • 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

BLGY1115 (10 decks)

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