B1.1 Flashcards
Are cells the same?
Cells are different depending on the job they do and the organism they’re from
What do cells contain?
Subcellular structures
What are the two types of cells?
Eukaryotic & prokaryotic cells
What are eukaryotic cells?
Contain genetic material in a nucleus
Complex and large (10 - 100 micrometers)
Plant and animal cells
What are prokaryotic cells?
Don’t contain a nucleus
Genetic material floats in cytoplasm
Simple cells, smaller than eukaryotic (1 - 10 micrometers)
Bacteria cells
What are the subcellular structures in animal cells?
Nucleus - contains the genetic material arranged as chromosomes , controls the activity of the cell, determines cell appearance. Contains new instructions for new cells/organisms.
Mitochondria - site of respiration,
Cytoplasm - jelly - like substance where chemical reactions that keep the cell alive occur
Cell membrane - selective barrier that controls which substances pass into and out of the cell. Contains receptor cells.
Ribosomes
What are the subcellular structures in plant cells?
Nucleus
Mitochondria
Cell membrane
Cytoplasm
Chloroplast - site of photosynthesis, contain chlorophyll which transfers energy from the sun as light.
Cell wall -surrounds the cell, made of tough fibre called cellulose, supports the cell
Sap vacuole -full of cell sap, a watery solution of sugar and salts, helps keep the cell rigid and upright
What are bacteria?
Smallest living organisms
Unicellular organisms (consist of just one cell)
Every cell can carry out the seven life processes (MRS GREN)
What subcellular structures are in prokaryotic cells?
Cytoplasm
Cell wall - made of peptidoglycan
Genetic material - floats freely in cytoplasm
Cell membrane
What are some extra structures?
Slime capsule - layer outside the cell wall, protects bacterium from drying out and from poisonous substances , helps bacteria to stick to smooth surfaces
Plasmid - circular piece of DNA that stores extra genes
Flagella - tail like structure that allows the cell to move through liquids
Pili -tiny hairlike substances that enable the cell to attach to structures (digestive tract), used to transfer genetic material between bacteria
What is a light microscope? How does it work?
Used to observe small structures in detail
Microscope passes light through an object placed on a slide on the stage then through two glass lenses
The lenses magnify the object to see in more detail.
How do you use the light microscope?
- Move stage to the lowest position
- Select the objective lens with the lowest magnification
- Place the slide with the cells on the stage
- Raise the stage to the highest position
- Lower the stage with the coarse focus knob until you see your cell
- turn the fine focus knob until your object comes into clear focus
- To see the cell in better detail use a higher magnification
How do you calculate total magnification?
Eyepiece lens magnification x objective lens magnifation
Why do we stain cells?
- To make them easier to observe
- Some organisms are colourless
- increases contrast
What are the 3 common stains?
Methylene blue - makes the the nucleus of an animal cell easier to see
Iodine - makes it easier to see a plant cell nuclei
Crystal violet - stains the bacteria walls
How do you apply the stain?
- Place the cells on a glass slide
- Add one drop of stain
- Place a coverslip on top
- Tap the coverslip with a pencil to remove any air bubbles
What is the resolution?
The smallest distance between two points that can be seen as separate entities
What are electron microscopes?
Use electrons instead of light to produce an image
Developed in 1930’s, allowed scientists to see in greater detail
What are the two types of electron microscopes? How do they work?
TEM - produce the most magnified image. Beam of electrons pass through a thin slice of the sample. The beam is focused to produce an image
SEM - produces a 3D image of a surface. Beams of electrons are sent across the surface of a specimen. The reflected electrons are collected to produce an image
Advantages of light microscopes:
Cheap to buy and operate
Small and portable
Simple to lrepare a sample
Natural colour of sample is seen
Specimens can be living or dead
Disadvantages of electron microscopes:
Expensive to buy and operate
Large and difficult to move
Sample preparation is complex
B,ack and white images produced
Specimens are dead
