Flashcards in Goldberg Deck (29):
What is the consequence of deficiencies in lysosomal enzyme lipid degradation?
- accumulation of harmful quantities of gangliosides
- nerve cell death.
What is the function of actin in the cytoskeleton?
- cell shape and organisation
- cell movement
- mutations in actin = cardiomyopathy
What are microtubules important for in the cytoskeleton?
- Mitotic spindle
- target for anti-cancer drugs
- intra-cellular movements: vesicles, organells
- driven by motor proteins
What is the function of intermediate filaments in the cytoskeleton?
- Strucutral proteins
Defects > skin blistering
What does a convex Lens do?
- converges parallel beams to the focal point
What does a concave lens do?
- diverges parallel light.
- focal pint is the point they would have converged to.
What is the effect is decreasing the focal length?
- increases the magnification.
What is the magnification strength of long focal length compared to short?
- long = less magnifying
If the object is closer to the focal point what happens?
- single lens produces an enlarged virtual image
What are the 2 components of a microscope?
1. An objective lends to produce a magnified real image
2. An eyepiece to produce a magnified virtual image of the real image (that you see with your eye).
What are phase contrast microscopes useful for?
- can amplify refractive index differences in cell components- excellent for live cells.
What is fluorescence microscopy used for?
- diff parts in cell can be specifically stained
- or using antibodies, usually to individual proteins attached to fluorescent molecules.
How do fluorescence microscopes work?
- specimen is illuminated with light of a specific wavelength (e.g. Green) whcih excites flurophore.
- this then emits light of another wave elgnth (e.g. Red)
- image is magnesia iced and focused on retina or detector.
- the chromatic beam splitter reflects and transmits light of different wavelengths differently.
What is the purpose on confocal microscopy?
Pinhole prevents out-of-focus light reaching the detector.
What is the difference in information given by TEM and SEM microscopes?
- TEM = 2D projection of image of a thin specimen
- SEM = unlimited thickness of specimen
What are the 4 stages of SEM?
1. Primary beam is focused to a fine point
2. Beam scanned across sample surface
3. Secondary electrons emitted from specimen as the beam passes over it.
4. Secondary e- are collected by detector and picture is build up.
Explain the permeability of membranes.
Dynamic lipid and protein content of membrane.
gases = permeable
Small uncharged polar molecules = permeable/slightly permeable.
What is the importance of membrane compartments?
1. For cell function
2. In disease and disorders
> contains and organise genome- nuclear membranes
> localise and facilitate ATP synthesis
> general degradation of unwanted components.
What is a phosphoglyceride?
- the most common phospholipids.
Head = alcohol; phosphate; glycerol
Tail = hydrocarbon chains
Where do phospholipid orientate to hide tails from water?
- at the interface between oil and water.
- if forced into an aq enviroments it is energertaiclly favourable to form spherical vesicles
What happens to hydrophobic molecules in water?
- they do not interact with water they therefore prevent water-water interactions. And this imposes order on the water molecules.
What is the effect of place a hydrophobic molecules in water?
- decreases entropy. As it is theromodynamically unfavourable to increase order.
What is the effect of aggregation?
- decreases order and increases entropy - favourable
> water forms 'ice like' cages around hydrophobic molecules
> aggregation reduces hydrophobic molecules
> therefore reduces order in the water > less water in cage
> therefore increases entropy.
Why do water molecules form cages around hydrophobic molecules?
- reduced H-bonding increases bond strength
- there are less H-bonds available to each water molecule
- the fore they are stronger and hence more stable
- surface area of 2 separate hydrophobic molecules is greater than two aggregated ones.
>> aggregation releases water molecules and increases entropy.
How can lateral diffusion be demonstrated and measured?
- By fluorescence recover after photobleaching (FRAP)
What are sphingolipids?
- bases on sphingosine
- long chain amino alcohol
- equivalent to glycerol and one fatty acid tail of phospholipid
- second hydrocarbon tail added by amide bond.
- Phosphate + alcohol head group added to C1.
- they have a similar sharpe to glycerophospholipid
- usually saturated
- usually have one unsaturated fatty did chain
- therefore sphingolipids pack closer together and have stronger van dear walls
What is the structure of cholesterol?
- Small head group (OH)
- does not form bilateral on its own (too hydrophobic)
- but can insert into membrane
- riding 4 ring structure
- cholesterol interacts mainly with fatty acid tail of phospholipids.
- they stiffen the fatty acid tails and thicken membrane
- introduces order in tail region
But maintains fluidity
Why does cholesterol prefer to interact with sphingolipids?
- more stable interaction between stiff flat steroid of cholesterol and long unsaturated fatty acid tail of sphingolipids
- therefore cholesterol and sphingolipids partition from phospholipids.