Cell Structures Flashcards
2.1.1
Why do biologists use microscopes?
To magnify cells and investigate their structures
What was the first type of microscope developed?
The light (or optical) microscope
How do microscopes work?
They create an image that is much larger than the real object
What is the resolution and magnification of a light microscope?
Resolution - Maximum of about 0.2 µm.
Magnification - Maximum of about x 1,500.
What do light microscopes have lower of compared to other microscopes?
Light microscopes have a lower resolution and magnification compared to other microscopes
What are the steps for a wet (temporary) mount sample preparation?
(4 steps)
- Use a pipette to place a small drop of water onto the centre of the glass slide.
- Use a pair of forceps to place a thin section of the specimen onto the drop of water. The specimen should be thin enough to allow light to pass through.
- Add a few drops of stain (e.g. iodine in potassium iodide) to the specimen. This increases contrast and allows cell components to become visible.
- Slowly add a cover slip (a clear glass square) onto the specimen.
What is the first step a wet mount sample preparation?
- Use a pipette to place a small drop of water onto the centre of the glass slide.
What is the second step of a wet mount sample preparation?
- Use a pair of forceps to place a thin section of the specimen onto the drop of water. The specimen should be thin enough to allow light to pass through.
What is the third step of a wet mount sample preparation?
- Add a few drops of stain (e.g. iodine in potassium iodide) to the specimen. This increases contrast and allows cell components to become visible.
What is the fourth step of a wet mount sample preparation?
- Slowly add a cover slip (a clear glass square) onto the specimen.
What is differential staining?
Using more than one chemical stain
What is differential staining used for?
Used to distinguish between cells or organelles
What are the four types of sample preparation?
- wet mount
- dry mount
- squash slides
- smear slides
What is dry mount sample preparation?
The specimen is placed directly onto the slide and covered with a cover slip
What is squash slide sample preparation?
A wet mount is prepared and the cover slip is pressed to squash the cells
What is smear slides sample preparation?
The edge of a slide is used to smear the sample to create a thin, even coating on a separate slide
What are the steps for viewing a light microscope?
(6 steps)
- Clip the prepared microscope slide onto the stage.
- Select the objective lens with the lowest power.
- Use the coarse focus to bring the stage just below the objective lens.
- Look down the eyepiece and use the coarse focus to move the stage downwards until the image is roughly in focus.
- Use the fine focus to make the image clearer.
- If a higher magnification is needed, swap to a more powerful objective lens and refocus.
What are biological drawings?
Biological drawings are used to record observations when looking at specimens
What should biological drawing contain?
- Include a title
2.State the magnification or scale - Be drawn with a sharp pencil
- Include smooth, continuous lines
- Include labels
- Include accurate sizes of observable structures
What should biological drawings not contain?
1.Include shading or colouring
2.Include arrow heads for labels
3. Involve lines overlapping each other
What is magnification?
Magnification is how many times larger an image is than the object.
What is resolution?
Resolution is the ability to distinguish between two separate points (or how detailed the image is).
How to calculate magnification?
M = I/A
cm to mm
x10
mm to μm
x1000
μm to nm
x1000
nm to μm
÷1000
μm to mm
÷1000
mm to cm
÷10
When viewing a specimen, what can you measure?
length or width using an eyepiece graticule
What is an eyepiece graticule?
small scale (usually 1- 100) placed within the eyepiece
What is used to calibrate an eyepiece graticule?
stage micrometer
What is a stage micrometer?
glass slide with a scale
What is a stage micrometer measured in?
μm
How is the graticule calibrated?
(4 steps)
- Fix the stage micrometer into place on the stage.
- Look through the eyepiece to line up the micrometer and the graticule.
- Count the number of graticule divisions that fit into one micrometer division.
- Use the formula below to calculate the size of each graticule division at that magnification:
graticule division= size of one micrometer division/number of graticule divisions
What is the first stage of graticule calibration?
Fix the stage micrometer into place on the stage.
What is the second stage of graticule calibration?
Look through the eyepiece to line up the micrometer and the graticule.
What is the third stage of graticule calibration?
Count the number of graticule divisions that fit into one micrometer division
What is the fourth stage of graticule calibration?
Use the formula below to calculate the size of each graticule division at that magnification:
graticule division = size of one micrometer division/number of graticule divisions
Example:
If each division on the micrometer represents 10μm and the eyepiece graticule is 40 divisions, calculate the size of each graticule division.
What would you do?
Step 1: Count the number of graticule divisions in one micrometer division
40 graticule divisions = 1 micrometer division
Step 2: Equation
graticule division =
size of one micrometer division/number of graticule divisions
Step 3: Substitution and correct evaluation
graticule division = 40/10
graticule división =
0.25 graticule division =0.25µm
What are the steps and calculate the magnification of a specimen that is 40mm width in a micrograph and has real width 20µm
Step 1: Equation
Step 2: Conversion- convert from mm into μm, multiply by 1,000
image size= 40x1000=40000μm
object size=20μm
Step 3: Substitution and correct evaluation
mag= 40000/20
mag= x20000
What do electron microscopes use to form an image?
beam of electrons
Why do electron microscopes have better resolution than light microscopes?
they have a shorter wavelength
Why does having a shorter wavelength for electron microscopes help?
gives a better resolution
What is a disadvantage of electron microscopes?
- expensive
- only produces black and white images
- can only observe dead specimens
What are the advantages of using an electron microscope?
- better resolution
- better magnification
What are the two types of electron microscope?
- Transmission electron microscope (TEM)
- Scanning electron microscope (SEM)
What is an artefact?
Give two examples
Artefacts are visible details that aren’t part of the specimen being observed, such as air bubbles or fingerprints
What is a TEM?
Transmission Electron Microscope
How does a TEM magnify an image?
uses electromagnets to transmit a beam of electrons through a specimen
The darker the microscopic image the more…
electrons are absorbed in a particular area
Why can TEMs produce high-resolution images?
they can be used to observe the internal structures of organelles
When using a TEM, the specimen must be viewed under what conditions?
- in a vacuum
- only non-living or dead organisms can be observed
- the specimen must be thin
What is the resolution and magnification of a TEM?
Resolution= Maximum of around 0.5 nm
Magnification= Maximum of around x 1,500,000
What is an SEM?
Scanning Electron Microscope
How does a SEM magnify an image?
they scan a beam of electrons across the surface of a specimen and then reflected electrons are then used to form an image
Which Electron microscope forms a 3D image?
SEM
Which Electron microscope forms a 2D image?
TEM
When using a SEM specimens have to be ….1… and can also be a ……2…… specimen.
- dead
- thicker
What is the resolution and magnification of a SEM?
Resolution= Maximum of around 5 nm
Magnification= Maximum of around x 1,500,000
Laser scanning confocal microscopy is a type of what microscopy?
a type of fluorescence microscopy
what does laser scanning microscopy use to scan a specimen?
use a laser beam (a single spot of focused light)
What will the specimen be tagged with when using laser scanning microscopy?
a fluorescent dye
How does laser scanning microscopy create an image?
The dyed components give off light which is focused through a pinhole and onto a detector. This detector is connected to a computer which generates an image. This image can then be converted into a 3D image.
Laser scanning confocal microscopes can be used to….
- Look at different depths within a specimen.
- Observe living specimens.
What two groups are living organisms divided into?
- Eukaryotes
- Prokaryotes
What are Eukaryotes?
These are (mostly) multicellular organisms made up of eukaryotic cells like animals, plants, fungi, and protists
What are Prokaryotes?
These are single-celled organisms made up of prokaryotic cells like bacteria
Why are Eukaryotes more complex?
they contain membrane-bound organelles, and have their DNA in the form of chromosomes within a nucleus.
Name the 8 organelles in an animal cell
- RER
- SER
- plasma membrane
- mitochondria
- lysosome
- golgi apparatus
- ribosomes
- nucleus (nucleolus)
what are the parts of the nucleus?
- nucleolus
- nuclear pores
- nuclear envelope
- chromatin
what is the structure of the nucleolus?
- Contains genetic information in the form of chromosomes.
- Contains a structure known as a nucleolus.
- Surrounded by a nuclear envelope (double membrane) containing pores.
What are the functions of the nucleolus?
- Controlling the cell’s activities - It contains DNA with instructions to produce proteins.
- Synthesis of ribosomes - The nucleolus makes ribosomal RNA.
- Exchange between nucleus and cytoplasm - Substances can enter or leave the nucleus via the nuclear pores.
What are the parts of the plasma membrane?
- glycoprotein
- glycolipid
- phospholipid bilayer
- extrinsic proteins
- intrinsic proteins
- cholesterol
What is the structure of the plasma membrane?
- Found on the surface of animal cells.
- Mainly made up of lipids and protein.
What is the function of the plasma membrane?
- Controls movement of substances into and out of the cell - The membrane is partially permeable.
- Cell signalling - Receptors can detect signals from other cells.
True or False
Mitochondria are found in large numbers in cells that requires lots of energy.
true
What are the parts of the mitochondria?
- outer membrane
- intermembrane space
- inner membrane
- matrix
- ribosomes
- DNA
What is the structure of the mitochondria?
- Contain an enzyme-rich liquid known as the matrix.
- Surrounded by a double membrane in which the inner membrane is folded to form structures known as cristae.
- Contain their own DNA (mtDNA) and ribosomes.
What is the function of mitochondria?
Site of aerobic respiration - Produces ATP.
What is the organelle?
very small organelles found in the cytoplasm or attached to rough endoplasmic reticulum
ribosomes
The size of ribosomes are measured in what unit
S units
Eukaryotic cells contain what size ribosomes.
80S ribosomes
What is the structure of ribosomes?
- Made up of proteins and rRNA (ribosomal RNA).
- Consist of a large and a small subunit.
3.Not surrounded by a membrane.
What is the function of the ribosomes?
Site of protein synthesis - Involved in the process of translation.
What organelle contains vesicles and cisternae?
Golgi Apparatus
What is the structure of the golgi body?
Contain fluid-filled, membrane-bound sacs known as cisternae.
Contain smaller vesicles.
What is the function of the golgi body?
Process and package lipids and proteins - Carried out by the cisternae.
Store and transport lipids and proteins - Carried out by the vesicles.
Synthesise lysosomes - Specialised vesicles.
What is the structure of RER?
- Contains a network of membranes enclosing a fluid-filled space, known as cisternae.
- The surface of the cisternae is covered with ribosomes.
What is the function of the RER?
Synthesis and transport of proteins - The proteins are made using the ribosomes.
What is the structure of the SER?
Same as the rough endoplasmic reticulum without the ribosomes.
What is the function of the SER?
Synthesis, storage, and transport of lipids and carbohydrates - For example, cholesterol and steroid hormones.
True or False
Lysosomes are round organelles with no clear internal structure.
true
What is the structure of the lysosome?
Contain hydrolytic enzymes.
Surrounded by a membrane to keep enzymes separate from the cytoplasm of the cell.
What is the function of the lysosome?
Digest pathogens - This process uses enzymes.
Break down waste material - This material includes old organelles and cells.
Where is the cytoskeleton?
present throughout the cytoplasm
What does the cytoskeleton provides to the cell
provides structure and support to the cell
What are the 3 main components of the cytoskeleton?
1.microfilaments
2. microtubules
3. intermediate filaments.
What are microfilaments?
Made of the protein actin.
Involved in cell movement and
locomotion, such as crawling and muscle contraction.
What are microtubules?
Made of the protein tubulin.
Form a scaffold-like structure throughout the cell.
Form the main component of the mitotic spindle, used for cell division.
Act as tracks for intracellular transport of vesicles and organelles.
What are intermediate filaments?
Maintain the position of organelles within the cell.
Responsible for the mechanical strength of certain tissues, such as the skin and hair.
What organelles are in plant cells?
- mitochondrion
- RER
- SER
- nucleus
- golgi body
- nucleolus
- plasma membrane
- ribosomes
- permanent vacuole
- cell wall
- chloroplast
What components are in a cell wall?
- plasmodesmata
- cell wall
What is the structure of the cell wall?
Made up of cellulose.
Contains channels (gaps) known as plasmodesmata (or plasmodesma if just one).
What is the function of the cell wall?
Supports the cell - Contents of the cell press against the cell wall to make it rigid.
Prevents the cell from bursting - The cell wall can withstand high osmotic pressure.
Allows exchange of substances between cells - Plasmodesmata connects neighbouring cells.
Where are chloroplasts found?
Found in the green parts of plants such as the leaves and stems.
What components are in the chloroplast?
- outer membrane
- inner membrane
- granum
- lamella
- DNA
- starch grain
- stroma
- thylakoids
- ribosomes
What is the structure of the chloroplasts?
Contain fluid-filled sacs known as thylakoids which are stacked up to form grana.
Surrounded by a double membrane, enclosing a fluid known as stroma.
Contain their own DNA and ribosomes.
What is the function of the chloroplasts?
Site of photosynthesis - These reactions take place in the grana and stroma.
What are the components of the permanent vacuole?
- tonoplast
- cell sap
What is the structure of the permanent vacuole?
Contains cell sap (solution of salts and sugars, among other substances).
Surrounded by a selectively permeable membrane known as a tonoplast.
What is the function of the permanent vacuole?
Helps to maintain pressure within the cell, which keeps the cell rigid and stops the plant from wilting.
Are Algal and fungal cells unicellular, multicellular or both.
both
What is a similarity between plant cells and algal cell?
Contain the same organelles as plant cells.
What is a difference between plant cells and algal cell?
Contain chloroplasts with different shapes to those found in plant cells.
What are the structures and functions of fungal cells?
Contain most of the organelles found in plant cells.
Do not contain chloroplasts.
Contain cell walls made up of chitin rather than cellulose.
What are prokaryotic cells?
single-celled organisms, so consist of a single prokaryotic cell
Which is smaller: prokaryotic cells or eukaryotic cells?
prokaryotic
What does a prokaryotic cells not contain?
membrane bound organelles and a nucleus
What are the main components of prokaryotic cells?
- plasma membrane
- cell wall
- ribosomes
- DNA
- plasmids
How does the cell wall differ in prokaryotic cell compared to eukaryotic cells?
Cell wall - In prokaryotic cells, this is made of murein (peptidoglycan).
How do ribosomes differ in prokaryotic cell compared to eukaryotic cells?
Ribosomes - Prokaryotic cells have 70S ribosomes, which are smaller than the 80S ribosomes found in eukaryotic cells.
How does genetic material differ in prokaryotic cell compared to eukaryotic cells?
Genetic material - In prokaryotic cells, this is mostly found in a large circular strand of DNA (sometimes called a circular chromosome or nucleoid), and some extra genes (like those for antibiotics resistance) are found in smaller loops called plasmids.
Prokaryotic cells may also contain additional organelles such as…..
- slime capsule
- flagella
- pili
What is a slime capsule made of?
made up of polysaccharides
What is a slime capsules function?
protects the cells from attack by antibiotics or white blood cells.
Some prokaryotes contain a long, hair-like structure known as a…
flagellum
Where is the flagella attached and why?
cell membrane and rotates to push the cell through its environment.
Some prokaryotes contain short, hair-like structures on the cell surface known as….
pili
Pili are used for…
attaching prokaryotic cells to other cells or surfaces.
