B1.1 - Cell Structures Flashcards
What is a Eukaryotic Cell?
Cells where the genetic material is contained within a nucleus.
What is a Prokaryotic Cell?
Cell where the genetic material floats in the cytoplasm.
Around 10 μm - 100 μm in size.
Eukaryotic Cells.
Around 1 μm - 10 μm in size.
Prokaryotic Cells.
What subcellular structures do you find in all basic Eukaryotic cell?
- Nucleus
- Mitochondria
- Cell Membrane
- Cytoplasm
What extra subcellular structures can be found in plat cells?
- Chloroplast
- Cell Wall
- Vacuole
What is the function of the Nucleus?
- Controls the activities of the cell
- Contains genetic material (arranged as chromosomes)
- Determines the cells appearance and function
What are mitochondria?
Mitochondria are membrane bound organelles that are the site of aerobic respiration.
What is the cell membrane?
- Selective semi-permeable ‘barrier’
- made of two layers of phospholipid molecules
- Holds the cell together
- Contains receptor molecules for cell communication
What is the cytoplasm?
- ‘jelly-like’ substance
- site of all chemical reactions which make up metabolism
Which English inventor and scientist where discovered cells using his self-designed microscope in 1665?
Robert Hooke
MRS GREN
M = ovement
R = espiration
S = ensitivity
G = rowth
R = eproduction
E = xcretion
N = utrition
What are ribosomes?
- Small organelles present in all cells
- site of protein synthesis
What are chloroplasts?
- The organelle that is responsible for photosynthesis
- Contains ‘chlorophyll’ - green pigment which absorbs light energy.
What is a a vacuole and what is its function?
- A large cavity filled with a watery solution of salts and sugars (cell sap).
- It keeps the cell rigid, pushing outwards.
What is the cell wall?
- Surrounds the cell
- Thick wall made of cellulose ( tough rubbery fibre)
- Gives the cell rigidity and support.
Explain why leaf cells contain chloroplasts but roots do not.
Leaf cells are able to photosynthesise because they have access to sunlight. Root cells do not so cannot photosynthesise, so do not need chloroplasts.
Name a few examples of Bacteria and what they do.
- Escherichia Coli (E.coli) – food poisoning
- Streptococcus bacteria – sore throats
- Streptomyces bacteria – found in soil & Antibiotic streptomycin comes from it.
Name extra subcellular structures bacteria can have.
- Plasmids
- Slime Capsule
- Pilli
- Flagella
What is a plasmid and how can it be advantageous?
- A circular piece of DNA found in bacteria cells
- Not needed for day-to-day survival but can give the bacterium advantages such as antibiotic resistance
What are pilli?
- Tiny ‘hair-like’ structures that allow the cell to attach to structures (e.g. cells in your digestive tract).
- They are also used to transfer genetic material between bacteria cells.
What is the function of a slime capsule?
- Protects bacteria from drying out and from poisonous substances.
- Helps bacteria to stick to smooth surfaces.
What are flagella?
Tail-like structures that allow bacteria cells to move through liquids.
What is the equation for magnification?
Image size = Actual size x Total Magnification
I = A x M
Define Resolution.
The degree to which it is possible to distinguish between two objects that are very close together, rather than them look merged into one object.
Name the two types of electron microscopes.
- Transmission electron microscope (TEM)
- Scanning electron microscope (SEM)
Describe the key features and how TEM microscopes work.
- Used to examine an extremely thin slice or section of cells or tissues.
- A beam of electrons passes through a thin slice of the sample; the beam is focused to produce an image.
- Has revealed subcellular structures in cells not visible with a light microscope such as mitochondria and chloroplasts.
Describe the key features and how SEM microscopes work.
- SEM has a large depth of field so can be used to examine the surface structure of specimens.
- A beam of electrons is sent across the surface of a specimen; the reflected electrons are collected and produce a 3D image.
What are the advantages and disadvantages of light microscope and electron microscopes?
Light microscope
- Cheap to buy and operate
- Small and portable
- Simple to prepare sample
- Natural colour of sample is seen unless staining is used.
- Specimens living or dead
- Resolution up to 0.2 µm (2 x 10-7 m)
Electron Microscope
- Expensive to buy and operate
- Large and difficult to move
- Sample preparation is complex
- Black and white images produced; false colour can be added to images
- Specimens are dead
- Resolution up to 0.1 nm (1 x 10-10 m)
Name three common stains used.
methylene blue - makes it easier to see the nucleus of an animal cell
iodine - makes it easier to see plant cell nuclei
crystal violet - stains bacterial cell walls
How do you use a microscope?
To observe cells under the microscope, follow the steps below:
1) Move the stage to its lowest position
2) Select the objective lens with the lowest magnification.
3) Place the slide, which has cells on it, on the stage.
4) Raise the stage to its highest position, taking care that the slide does not touch the lens.
5) Lower the stage slowly using the coarse focus knob until you see your object (it will normally be blurred).
6) Turn the fine focus knob slowly until your object comes into clear focus.
7) To see the cells in greater detail, switch to a higher magnification objective lens without moving the stage, Use the fine focus knob to bring the object into clear focus again.
How do you apply a stain?./
This is how to apply a stain:
1) Place the cells on a glass slide.
2) Add one drop of stain.
3) Place a coverslip on top.
4) Tap the coverslip gently with a pencil to remove air bubbles.
