B1.1 Cells Flashcards
What are eukaryotic cells?
They are complex cells containing genetic material in the nucleus. Plants and animals are eukaryotes.
What is the size of a eukaryotic cell?
10 - 100 micrometers
What is a prokaryotic cell?
A simple cell where genetic material floats in the cytoplasm. Bacteria and proticists are prokaryotes .
What is the size of a prokaryotic cell?
1 - 10 micrometers
What extra sub cellular structures do plant cells have?
Cell wall - made from cellulose to support the cell and keep it rigid
Vacuole - full of cell sap to help with stability
Chloroplast - contain chlorophyll(green pigment) which is needed for photosynthesis
List the main organelles of an animal cell and their functions
Nucleus - contains genetic material(chromosomes) and controls cell activity. Also contains instructions for cell replication
Cytoplasm - a substance where chemical reactions occur
Mitochondria - the powerhouse of the cell where respiration occurs. They contain enzymes
Cell membrane - controls what enters and passes out of the cell. Also have receptor molecules
Why do plant cells need extra structures?
They are producers which photosynthesis to make their food
What are bacteria?
They are small unicellular organisms which can carry out the 7 life processes(mrs gern)
Size of a bacterial cell?
1 micrometer
Name some examples of prokaryotes
E.coli- food poisoning
Streptococcus- sore throats
List the sub cellular structures that prokaryotic cells have and their function
Cell wall - holds cell together and protects it
cytoplasm - where the chemical reactions occur
Genetic material- floats in circular stands in the cytoplasm
Cell membrane - selects what enters and exits
What extra subcellular structures does a bacterial cell have?
Flagella
Pili(hairs)
Slime capsule
Plasmids
What are the functions of flagella and pili?
Flagella is a tail like structure which is used for movement
Pili are hairs which enable the cell to stick to cells and transfer genetic material
What is the function of the slime capsule and plasmids?
Slime capsule protects the cell from dying out and helps it stick to surfaces
Plasmids are extra loops of dna which store extra genes for helping in times of stress
What are microscopes and what do they do?
Microscopes are a piece of equipment which is used to magnify images and increase resolution of an image
How does a light microscope work?
Light passes through a specimen on a slide and then through the objective lens and the eyepiece lens. The lenses magnify the image
How do you prepare a sample?
1) take a clean slide and carefully place the sample onto it. Use a thin slice if you are using a thick sample
2) apply a drop of stain if needed or add a drop of water
3) place a coverslip on and gently tap into place to get rid of air bubbles
Why do we use stains?
Many cells are colourless so we stain cells to differentiate different structures or highlight the whole cell. There are different stains used for different structures.
List some common stains and their uses
Methylene Blue - animal cell nuclei
Iodine - plant cells nuclei
Crystal violet - bacteria cell walls
Eosin - cytoplasm
Steps for using a microscope
1) move the stage to the lowest position
2) select the objective lens to the lowest magnification
3) place the slide on the stage and use clips
4) turn the coarse focus knob and then the fine focus until you see a clear image
5) change the objective lens for more detail
What is resolution?
The smallest distance between 2 points which can be seen as separate entities
What size of structures can the light microscope not see
Less than 0.2. Micrometers
What is an electron microscope?
A microscope that uses electrons to view an image in the best detail possible yet. They allow use to study tiny things like viruses and mitochondrion
How does a transmission electron microscope work?
They produce the most magnified image
A beam of electrons passes through the sample which is focused to form an image. Similar to light microscopy
How does a scanning electron microscope work?
It produces a 3D image
Electrons are sent across the surface and are collected to form an image
Which electron microscope produces the highest magnification
SEM
Which electron microscope produces a 3D image?
TEM
What are the advantages and disadvantages of using a light microscope? (5v1)
It is cheap to buy, easy to maintain, easy to prepare a sample, portable, specimens can be living or dead
Resolution is only up to 0.2 micrometers
What are the advantages and disadvantages of using an electron microscope?
Resolution up to 0.1 nm
Expensive to buy and operate, large and difficult to move, hard to prepare a sample, specimens must be dead, colouring must be added
Explain how electron microscopy has increased our understanding of subcellular structures
Electron microscopes have allowed scientists to view inside subcellular structures and observe very small structures to improve our understanding
Calculation to find total magnification
Total magnification = eyepiece lens magnification x objective lens magnification
Calculation to find real size, image size
Real size x magnification = image size
Magnification = image size/ real size
