Cells Flashcards
Define prokaryotic cell
What is the origin of the name “prokaryote”?
“pro” meaning before and “kary” means nut or shell. The term prokaryote, therefore, refers toa cell without a nucleus.
A prokaryote is a unicellular organism that lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle.
What are the 3 principals of cell theory?
- All living things are made up of 1 or more cells
- Cells are the basic units of organisation in all organisms
- All cells are made from other cells - that is a cell is created by dividing and replicating it’s self.
What is the benefit of having a third lens in a compound microscope?
Ina compound microscope with 2 lenses, due to the way the lenses bend light, the image you are viewing will be flipped/ inverted. By adding a third lens, the image will be flipped back the right way.
What is one major advantage and one major disadvantage of a light microscope?
Major advantage: they use the natural light in the room so can view living cells, behaving as they would in a living system
Major disadvantage: only able to resolve structures that are at least 200nm apart, which doesn’t allow for much detail in the intricacies of some tiny cells.
How is an electron microscope different from a light microscope and what are it’s advantages/ disadvantages?
Instead of using a beam of light to produce the image, an electron microscope will use a beam of electrons. Electrons have a much shorter wavelength than visible light so they are able to produce much higher resolution images of even smaller structures. Can resolve images 0.2nm / 0.0002um apart - 1000 X the resolving power of a light microscope)
It’s biggest limitation is that the sample needs to be placed under a vacuum in the electron microscopy (and typically prepared via an extensive fixation process), meaning living cells can not be imaged.
What is the difference between a scanning electron microscope (SEM) and a transmission electron microscope (TEM)?
A scanning electron microscope passes a beam of electrons back and forward over the surface of a sample to create a detailed 3D image of the surface
A transmission electron microscope requires that the sample be sliced into tiny slices (i.e. using a diamond cutting edge) prior to imaging. Then the beam of electrons will pass through the slices, rather than skimming over the surface. This is usually what is used to image the internal structure of cells.
What does a cell’s surface area have to do with its likelihood of survival?
The larger the cells surface area to volume (SA:V) ratio is, the more efficiently it is in diffusion an removal of waste products.
As a cell gets larger, it’s volume will increase faster than it’s surface area and therefore eventually will not be able to diffuse/ remove wast products quick enough to survive.
What 4 key features do all cells share, regardless of whether they are prokaryotes or eukaryotes?
- A plasma membrane that separates the cell’s interior from its surrounding environment
- Cytoplasm - which is the jelly like cytosol and the cellular structures suspended in it.
In eukaryotes, cytoplasm specifically means the region outside the nucleus but inside the plasma membrane. - DNA - the genetic information of a cell
Ribosomes molecular machines that synthesize proteins.
- Cytoplasm - which is the jelly like cytosol and the cellular structures suspended in it.
What it the main way prokaryotes differ from eukaryotes?
Prokaryotes are not divided up on the inside by membrane bound organelles like eukaryotes are; instead they have one single open space known as the nucleoid
Where is peptidoglycan usually found in a prokaryotic cell and what is it’s function?
Peptidoglycan is a polymer of carbohydrates and proteins and forms the cell walls of most prokaryotic cells.
How do prokaryotic and eukaryotic cells differ in terms of size?
Prokaryotes are much smaller - usually 0.1 to 5.0 micrometers (μm) in diameter, while eukaryotes are usually 10 - 100μm
Where is a flagellum found on a prokaryote and what is it’s functions?
They are found on the capsule of the cell. The flagellum is a whip like tail found at the tip of the cell and is used to propel it forward.
What are Fimbriae and pilus/ pili ? How are they different from each other?
Fimbriae are hair-like structures found on the capsule of bacteria which can help it stick to a host or other surfaces.
- Most commonly Fimbriae is used to describe a class of numerous cell protrusions that are relatively short and involved in the attachment to surfaces
The pili are rod-like structures that can also help the cell to move, but may have other roles like transferring DNA molecules to other bacteria
- Most commonly describes cell protrusions which are less numerous, longer than fimbriae and more specialised.Where is DNA found in prokaryotes? How is this different to eukaryotes?
In prokaryotes a single circular molecule of DNA is found in the centre of the cell in the nucleoid. In DNA it is found in the membrane bond nucleus.
Which part of the endoplasmic reticulum (network of tubes and membranes that carry material through the cell) contains ribosomes?
Rough ER contains ribosomes, smooth ER does not
What is the function and location of the chloroplast? Which type of cell is it found in?
Chloroplasts are found in in the cytoplasm of plant cells and are used in photosynthesis to convert energy from the sun into energy for the plant.
