2-1 Cell structure Flashcards
1
Q
What is the formula for magnification?
A
- Magnification = Size of image/size of real object.
2
Q
What is resolution?
A
- Minimum distance apart that two objects can be distinguished as separate objects in an image.
3
Q
What are light microscopes?
A
- Resolution of 0.2um because this is the wavelength of light
- Shine a light through a specimen through a lens.
4
Q
What are electron microscopes?
A
- Resolution of 0.1nm
- Two types, transmission, and scanning.
- Transmission electron microscope, a beam of electrons passes through a thin section of a specimen. Areas that absorb the electrons appear darker on the electron micrograph that is produced.
- Scanning electron microscope, beam of electrons passes across the surface and scatter. The pattern of scattering builds up a 3D image depending on the contours of the specimen.
5
Q
What are the limitations of electron microscopes?
A
- The whole system must be in a vacuum so live specimens cannot be observed.
- A complex staining process is required which may introduce artefacts into the image.
- Specimens have to be very thing, particularly for TEM so that the electrons can pass through.
- SEM has a lower resolving power than TEM.
6
Q
What is cell fractionation?
A
- The process in which different parts and organelles of a cell are separated so that they can be studied in detail. The most common method of cell fractionation is differential centrifugation.
7
Q
Describe the process of homogenation?
A
- The cells are first blended in a homogeniser forming the resultant fluid called the homogenate. This tube of homogenate is then placed in a centrifuge and spun at a slow speed.
- The heaviest organelles, the nuclei, are forced to the bottom of the tube where a thin sediment or pellet forms.
- The fluid at the top, called the supernatant, is removed which leaves just the sediment of the nuclei. The supernatant is then transferred to another tube and spun at a slightly faster speed. This time the pellet that forms contains the next heaviest organelle, the mitochondria.
- This process continues so that each time the speed is increased the next heaviest organelle is sedimented and separated out.
8
Q
Why is the homogenate placed in a cold, buffered solution of the same water potential as the cells.?
A
- Prevent organelles from bursting under osmotic pressure.
- To inactivate any enzymes from breaking down organelles.
- So that the pH does not fluctuate.
9
Q
Describe the structure and function of the nucleus?
A
- Nucleus has a double membrane called the envelope with nuclear pores than enables molecules to enter and leave.
- Also contains chromatin and a nucleolus which is the site of ribosome production.
- A granular jelly like material called nucleoplasm makes up the bulk of the nucleus.
10
Q
Describe the structure and function of the rough endoplasmic reticulum?
A
- Series of flattened sacs enclosed by a membrane with ribosomes on the surface.
- RER folds and processes proteins made on the ribosomes.
11
Q
Describe the structure and function of the smooth endoplasmic reticulum?
A
- System of membrane bound sacs.
- SER produces and processes lipids.
12
Q
Describe the structure and function of the golgi apparatus?
A
- Series of fluid filled, flattened and curved sacs with vesicles surrounding the edges. Golgi apparatus processes and packages proteins and lipids. It also produces lysosomes.
13
Q
Describe the structure and function of the mitochondria?
A
- Oval shaped, bound by a double membrane called the envelope.
- The inner membrane is folded to form projections called cristae with a matrix on the inside containing all the enzymes needed for respiration.
14
Q
Describe the structure and function of the centrioles?
A
- Hollow cylinders containing a ring of microtubules arranged at right angles to each other.
- Centrioles are involved in producing spindle fibres for cell division.
15
Q
Describe the structure and function of the ribosomes?
A
- Composed of two sub-units and are the site of protein production.
