2.1 eukaryotic cells Flashcards
(36 cards)
what is the difference between magnification and resolution
magnification is a measure of how much bigger the image is in comparison to the real object, whilst resolution is a measure of how close two objects can be together before we can see them as one
what is the magnification and resolution of:
- a light microscope
- an electron microscope
light
-mag: 1500X, res: 200 nano meters
electron
-mag: 500 000, res: 0.1-1 nano meter
why do people stain things before viewing them under the microscope
-it is used particular types, or different parts of the cell under the microscope, the cell absorbs this stain and enhances the visualisation
name 3 advantages and two disadvantages of using a light microscope
ADVANTAGES
-can see living plants and animals and their parts directly, so you can compare slides with living tissue
-relatively cheap, which makes them more available for schools and universities ect.
-they’re light and portable so can be used anywhere
DISADVANTAGES
-limited resolution and magnification
-preservation and staining tissue can produce artefacts in the tissue being observed which will affect the image
how does an electron microscope work
the electrons form an image by being scattered by the specimen. The electromagnetic or electrostatic lenses focus the electron beam to form an image.
what are the conditions needed for an electron microscope to work
- the specimen must be in a vacuum
- could involve chemical preservation, freeze drying, dehydration etc.
- stained using heavy metal ions
why are specimens going under an electron microscope stained with heavy metal ions
to improve the scattering of the electrons to make greater contrast in the image, ultimately making it easier to interpret
name and explain the two types of electron micrographs
transmission electron micrographs, 2D images
scanning electron micrographs, lower magnification but 3D
give an advantage and four disadvantages of using an electron microscope
ADVANTAGE
-huge powers of magnification and resolution, can see cell structure and tissues in much more detail
DISADVANTAGE
-all specimens are examined in a vacuum
-specimens undergo severe preparation treatment which is likely to result in artefacts
-extremely expensive
-large, and must be kept at constant temperature and pressure
what is the job if the cell surface membrane
to control what goes in and out of the cell
describe the structure of the phospholipid bilayer
the phospholipids in the membrane form a bilayer or a unit membrane. The lipids are polar lipids and phospholipids
with water on each side
hydrophilic heads pointing towards the water, shielding their hydrophobic tails
what are the two main function of the membrane proteins
- they move channels across the membrane, form pores that allow specific molecules to move through that open and shut based on the conditions of the cell (gated channels)
- they can act as receptor molecules, making cells sensitive to a particular hormone e.g enzymes
what is the function of membranes of the cell and membranes in the cell
They control the movement of substances
localise enzyme reaction pathways
whats the name of cytoplasm + nucleus
protoplasm
describe the nucleus and its function
surrounded by a nuclear membrane and contains nuclear pores, the nuclear envelope. so chemicals can pass in and out which allows the nucleus to control the events in the cytoplasm
what is the nucleolus and its function
extra dense area of almost just pure DNA and protein, it is involved with the production of ribosomes and plays a part in cell growth and division
describe the structure and function of the mitochondria
1 micro meter wide and up to 10 micro meters long
it produces ATP through the oxidation of simple molecules through cellular respiration
it has an outer and inner membrane, and the inner one is folded to form cristae which gives it a very large surface area
how do mitochondria contribute to the endosymbiotic theory
Mitochondria have their own DNA, and since scientists believe that mitochondria and chloroplasts originated as a single eubacteria, it is proof of evolution
describe the structure and function of the centrioles
usually a pair near the nucleus , made up of a bundle of tubules
when a cell divides, centrioles pull apart the spindle of micro tubules that are involved in the movement of chromosomes
describe the structure and function of the cytoskeleton
3D web like structure that fills the cytoplasm, made up of microfilaments and microtubules
It gives the cytoplasm structure and keeps the organelles in place
describe the structure and function of vacuoles in animal cells
they are membrane lined enclosures that are formed and lost as needed
why are contractile vacuoles important to animals that live in bodies of water
the allow the water content of the cytoplasm to be controlled
name the types of ribosomes, where their found, and their structure and function
-70S, found in prokaryotic cells and chloroplast
-80S cytoplasm of eukaryotic cells
- consist of a large sub unit and a small sub unit and are the organelles on which protein synthesis takes place
describe the structure and function of the rough endoplasmic reticulum
it is covered in ribosomes, that make proteins
RER isolates and transports them
has a large surface area for the synthesis of all the proteins
stores and transports them
