B1 A - microscopes and cell structure Flashcards
Function of a microscope
Uses lens to magnify an object
Magnifcation
How much times bigger the specimen is seen
Why should you always use the lowest power objective lens first?
to get a wider field of view
resolution
how well you can distinguishe between objects close together
light microscope
Light microscopes have a lower resolution and magnification. The specimen can be living, and can be seen in colour.
Electron microscope
Have a higher resolution and magnification so can magnify smaller organelles e.g Ribosomes.
The specimen is dead, and cannot be seen in colour.
Method for the Microscopy practical?
- Place a tissue sample / specimen on the slide.
- Add a few drops of a suitable stain.
- Lower coverslip onto the tissue.
- Place the slide on the microscope stage and focus on the cells using the low power objective lens.
- Change to higher powered objective lens and refocus.
- Draw any types of cells that can be seen.
- Add a magnification scale to the diagram.
Why do you need a stain?
To make certain structures visible
Why lower the coverslip and press carefully?
to remove any bubbles
Why can you see the nucleus and cell wall but not the mitochondria?
They’re too small.
What is the function of the coarse adjustment knob?
Bring the specimen into focus
How could we see the smaller structures (e.g. ribosomes)?
You would need to use an electron microscope which has a higher magnification and higher resolution.
Actual size =
Image size / magnification
How can we now have a greater understanding of subcellular structures?
Smaller subceller structures e.g ribosomes can be seen under an electron microscope
1 mm to um?
multiply by 1000
1 um to nm?
multiply by 1000
What type of cells are plant and animal cells?
Eukaryotic (U)
Features of animal cells:
- nucleus (contains the genetic materials, controls the cell’s activities)
- cytoplasm - where the chemical reactions occur
- cell membrane - controls what leaves and enters the cell
- mitochondria - where aerobic respiration occurs
- ribosomes - where protein synthesis occurs
Additional features of plant cells:
- have lots of chloroplasts - containing chloropyll, absorbing light for photosynthesis
- Have cell wall - provides strength and structure (containg celll sap)
- permanent vacule - keeps cells turgid
What type of cells are bacterial cells?
Prokaryotic cells
Differences between prokaryotic and eukaryotic cells?
- Prokaryotic cells do not have a nucleus - they have a single DNA loop, and plasmids.
- They have no membrane-bound organelles.
- Eukaryotic cells are much bigger than Prokaryotics.
How the sperm cell adapted to its funtion?
Its function is to swim to the egg and fertilise it.
- It is streamlined so can swim faster
- It is tail which allows movement
- Has lots of mitochondria
- Contains enzymes which help it to digest into an egg cell
How is the nerve cell adapted to its funtion?
It passes electrical impulses around the body.
- Lots of denrites to make connections to other nerve cells
- Long axon which carries the electrical impulses
- Contains lots of mitochondria to make the transmitter chemicals that allow the impulses to be transferred to another cell.
How are muscle cells adapted for their funtion?
Function - is to contract to allow movement
- there are protein fibres that contract
- lots of mitochondria so more energy is released for the fibres to contract
- store glycogen which is a chemical that is broken down and used by the mitochondria to release energy needed.
How are root hair cells adapted for their funtion?
Function - to absorb water and minerals from the soil
- have surface area
- lots of mitochondra to release energy for active transport of mineral ions.
- large permanent vacuole which speeds up omosis of water from the soil
How are xylem cells adapted for their function?
function - carry water and mineral ion from the roots to the highest parts of the plant
- has a chemical called lignin which allows a hollow tube to be formed which allows a continuous flow of water and minerals
- spirals of lignin makes the tube strong
How are phloem adapted for their function?
function - carries the food made by photosynthesis around the plant
- cell walls between the cells break down and form sieve plates, which allow dissolved food to move from cell to cell.
- companion cells keep them alive. Its mitochondria transfers energy needed to move the dissolved food up and down.
Why does a red blood cell burst, but a plant cell does not burst?
Water enters the cell by osmosis.
A plant cell has a cell wall which prevents it from bursting, but a red blood cell doesn’t.
