1.2 (Ultrastructure of Cells) Flashcards
1
Q
What is ultrastructure?
A
Ultrastructure is all the structures of a biological specimen that are at least 0.1nm in their smallest dimension
2
Q
Electron vs light microscope resolution.
A
- Light microscopes allow us to see the structure of cells
- Electron microscopes allow us to see the ultrastructure of cells
- Electron microscopes can see viruses (0.1μm diameter) , but light microscopes cannot
3
Q
Prokaryotes (what are they and reproduction).
A
- Smaller than eukaryotes, came first in terms of evolution.
- Reproduce asexually using the process of binary fission
- Two DNA loops attach to the membrane
- Membrane elongates and pinches off (cytokinesis) forming two separate cells
- Two daughter cells are genetically identically
4
Q
Advantages of compartmentalisation.
A
- Efficiency of metabolism - enzymes and substrates can localized and much more concentrated
- Localised conditions - pH and other such factors can be kept at optimal levels
- Toxic / damaging substances can be isolated
- Numbers and locations of organelles can be changed dependent on the cell’s requirements
5
Q
Nucleus.
A
- Spherical with a double membrane
- Pores (holes) present in the membrane
- Contains genetic information in the form of chromosomes (DNA and associated histone proteins)
- Uncoiled chromosomes referred to as chromatin – they stain a dark colour and are concentrated at the edges of the nucleus
- mRNA is transcribed in the nucleus (prior to use in protein synthesis in the cytoplasm)
- mRNA leaves the nucleus via the pores (DNA is too large to move through the pores)
6
Q
Mitochondrion.
A
- Has a double membrane
- Smooth outer membrane and a folded inner membrane
- Folds are referred to as cristae
- Variable in shape
- Site of ATP production by aerobic respiration (if fat is used as a source of energy it is digested here)
7
Q
Free ribosomes.
A
- 80S Ribosomes (approx. 20nm diameter) - larger than the ribosomes found in prokaryotes
- No membrane
- Appear as dark granules in the cytoplasm
- Synthesises proteins to function in the cytoplasm, for use within the cell
8
Q
Rough endoplasmic reticulum.
A
- Consists of flattened membrane sacs, called cisternae
- Often located near to the nucleus
- 80S Ribosomes are attached to the outside of the cisternae are ribosomes
- rER synthesizes proteins which are transported, by vesicles, to the golgi apparatus for modification before secretion outside the cell
9
Q
Golgi apparatus.
A
- Consists of flattened membrane sacs called cisternae, like rER.
- Different to rER:
No attached ribosomes
Often sited close to the plasma membrane
Cisternae are shorter and more curved that those of the rER - Golgi apparatus processes (modifies) proteins from from the rER. Proteins are then repackaged in vesicles for secretion outside the cell.
10
Q
Vesicles.
A
- Single membrane with fluid inside
- Very small in size
- Used to transport materials inside of a cell
11
Q
Lysosomes.
A
- Spherical with a single membrane
- Formed from Golgi vesicles.
- Contain digestive enzymes for breakdown of:
- ingested food in vesicles *unwanted/damaged organelles
- the cell itself
- High concentration of enzymes cause this organelle to stain heavily and hence appear dark on micrographs
12
Q
Vacuoles.
A
- Single membrane with fluid inside
- In plant cells vacuoles are large and permanent, often occupying the majority of the cell volume
- In animals vacuoles are smaller and temporary and used for various reasons
13
Q
Flagellum (animals only).
A
- Thin projection (usually singular) from the cell surface.
- Contain microtubules
- Used to move the cell
14
Q
Cilia.
A
- Thin projections from the cell surface.
- Contain microtubules
- Used to either move the cell or to move the fluids next to the cell
15
Q
Microtubles and centrioles.
A
- Small cylindrical fibres called microtubules
- Have a variety of functions
- Consist of two groups of nine triple microtubules
- Mainly found in animal cells, not present in vascular plants or fungi.
