Unit 1 Microscopes and cells Flashcards
What is the structure and function of the nucleus?
Structure - has double membrane - nuclear envelope - contains pores
- contains chromatin ( DNA wrapped around histones)
- at centre - nucleolus
Function - nucleolus makes ribosomes
- pores allow substances (mRNA) to move between nucleus and cytoplasm
- DNA (in chromatin) controls cell’s activities
What is the structure and function of the mitochondria?
Structure - usually oval shaped, have double membrane; inner membrane folded forming cristae. Inside is matrix which contains enzymes involved in respiration.
Function - site if aerobic respiration - which produces ATP (energy source in cell).
What is the structure and function of the endoplasmic reticulum (rough and smooth)?
Structure - smooth-system of membranes enclosing a fluid-filled space
- rough - same however covered in ribosomes
Function - smooth - synthesises and produces proteins
- rough - folds and processes proteins that have been made at ribosomes
What is the structure and function of the Golgi apparatus?
Structure - group of fluid filled flattened sacs
Function - processes and packages new lipids and proteins that are further transported by vesicles
- also makes lysosomes
What is the structure and function of lysosomes?
Structure - round organelle surrounded by membrane with no clear internal structure
Function - contains digestive enzymes that are kept separate from cytoplasm so they can be used to digest invading cells or break down worn out components of cell.
What is the structure and function of microvilli?
Structure - folds in plasma membrane
Function - found on cells involved in processes such as absorption (epithelial cells in small intestine) as they increase the surface area of the plasma membrane
How are epithelial cells in the small intestine adapted to absorb food efficiently?
Walls of small intestine have lots of villi ( finger like projections) to increase surface area
Have microvilli on surface of villi to increase surface area further
Lots of mitochondria - provide lots of energy for transport of digested food molecules into cell
What is magnification and resolution?
Magnification - how much bigger an image is than the specimen
Resolution - how detailed the image is, how well microscope distinguishes between two points which are close together.m
What is cell fractionation?
Done to separate organelles from cell to look at them under a microscope. Three steps:
- Homogenisation - breaking up the cells - can be done by grinding cells up in a blender - it breaks up cells plasma membranes releasing organelles into solution - kept ice cold and isotonic
- Filtration - getting rid of big bits - cell solution filtered through gauze separation cell debris/tissue debris from organelles
- Ultracentrifugation - separating organelles
How does ultracentrifugation work?
Cell fragments poured into tube which is placed into centrifuge and span at low speed.
The heaviest organelles (nuclei) get flung to the bottom of the tube forming a thick sediment (pellet).
Rest of organelles stay suspended in the fluid above the sediment - supernatent.
This supernatent is drained off and span again at a higher speed.
The same happens again, this time the heaviest organelle is the mitochondria which forms a pellet at bottom.
Process is repeated at higher and higher speeds until all organelles are separated.
Separate in order of mass, usually - nuclei, mitochondria, lysosomes, endoplasmic reticulum, ribosomes. ( naughty monkeys like eating red raspberries)
How do electron microscopes work?
Use electrons to form image. Give more detailed images compared to light microscopes, as have a higher resolution. They produce black and white images (can be coloured using computer). Can only be used on non- living specimens.m
What are the differences between a transmission electron microscope and a scanning microscope?
Transmission - beam of electrons transmitted through specimen - denser parts absorb electrons so look darker.
They give high resolution images showing small objects.
However can only be used on thin specimens.
Scanning - scan beam of electrons across specimen which knocks off electrons from specimen and they are gathered on cathode ray tube which forms image.
Can form 3D image, can be used on thick specimens.
Give lower resolution images than TEMs.
What is the difference between prokaryotic organisms and eukaryotic organisms?
Prokaryotic - they are single celled organisms (prokaryotic cells) they are small and simple, e.g. Bacteria.
Eukaryotic - made from eukaryotic cells which are complex, they include all animal and plant cells.m
