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Flashcards in Goldberg Deck (29):
1

What is the consequence of deficiencies in lysosomal enzyme lipid degradation?

- accumulation of harmful quantities of gangliosides
- nerve cell death.

2

What is the function of actin in the cytoskeleton?

- cell shape and organisation
- cell movement
- mutations in actin = cardiomyopathy

3

What are microtubules important for in the cytoskeleton?

- Mitotic spindle
- target for anti-cancer drugs
- intra-cellular movements: vesicles, organells
- driven by motor proteins

4

What is the function of intermediate filaments in the cytoskeleton?

- Strucutral proteins
Defects > skin blistering

5

What does a convex Lens do?

- converges parallel beams to the focal point

6

What does a concave lens do?

- diverges parallel light.
- focal pint is the point they would have converged to.

7

What is the effect is decreasing the focal length?

- increases the magnification.

8

What is the magnification strength of long focal length compared to short?

- long = less magnifying

9

If the object is closer to the focal point what happens?

- single lens produces an enlarged virtual image

10

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).

11

What are phase contrast microscopes useful for?

- can amplify refractive index differences in cell components- excellent for live cells.

12

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.

13

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.

14

What is the purpose on confocal microscopy?

Pinhole prevents out-of-focus light reaching the detector.

15

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

16

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.

17

Explain the permeability of membranes.

Dynamic lipid and protein content of membrane.
gases = permeable
Small uncharged polar molecules = permeable/slightly permeable.

18

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.

19

What is a phosphoglyceride?

- the most common phospholipids.
Head = alcohol; phosphate; glycerol
Tail = hydrocarbon chains

20

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

21

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.

22

What is the effect of place a hydrophobic molecules in water?

- decreases entropy. As it is theromodynamically unfavourable to increase order.

23

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.

24

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.

25

How can lateral diffusion be demonstrated and measured?

- By fluorescence recover after photobleaching (FRAP)

26

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

27

What is the structure of cholesterol?

- Amphipathic
- 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

28

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.

29

What are microdomains?

- known as lipid rafts- concentrated thicker domains rich sphingomyelin and cholesterol
> rafts are thicker than the rest of membrane
-proteins with long transmembrane domains partition to rafts.
. short domains partition to phospholipid containing domains
- recruit proteins with lipid anchors