2.1.1 cell structure Flashcards
What is magnification?
How much bigger an image appears compared to the original object.
What is resolution?
The ability of a microscope to distinguish between two points that are close together.
What is the equation for magnification?
Image size= Actual size x Magnification
What are the advantages of TEM?
High resolution and magnification.
Observe internal structures.
What are the disadvantages of TEM?
Requires complex sample preparation.
Sample preparation often distorts material.
Vacuum is required.
Produces a black and white image only.
Expensive to buy and operate.
Large and needs installing.
Training typically required.
No live specimen.
What is the maximum resolution of a Light microscope?
200 nm
What is the maximum resolution of a TEM?
0.5 nm
What is the maximum resolution of a SEM?
3-10 nm
What is the maximum magnification of a Light microscope?
x2000
What is the maximum magnification of an Electron microscope?
over x500,000
What are the advantages of Laser scanning confocal microscopes?
It is non-invasive and thick specimens can be observed.
What are the disadvantages of Laser scanning confocal microscopes?
Slow process and requires training.
What do TEM, SEM, and LSC microscopes observe?
TEM-organelles
SEM-an object a certain distance in a cell
LSC-cell surfaces
What is an artefact?
An issue created in specimen preparation e.g. a bubble.
What is a stage micrometre?
A microscope with a very accurate scale in micrometres engraved on it.
What is an eyepiece graticule?
A glass disc marked with a fine scale of 1 to 100.
The scale has no unit, the relative size of dimensions increases with each increase in magnification.
The scale is calibrated using a stage micrometre.
What is differential staining?
Staining which helps distinguish between two types of organisms.
What is Methylene blue?
A positively charged dye which is attracted to negatively charged materials in cytoplasm.
It stains RNA/DNA.
What is Congo red?
A negatively charged dye which repels negatively charged cytosol.
It stains the outside of a cell, leaving the inside unstrained.
What is Eosin?
Common dye that stains pink/orange.
It is a negatively charged acidic dye that binds to basic components of a cell, mainly proteins in the cytoplasm.
What is Iodine used for?
A common stain used to observe plant cells.
What is the Gram stain technique?
A technique used to separate bacteria into two groups, Gram-positive bacteria(e.g. Streptococcus pneumonae) and Gram-negative bacteria(e.g. Yersinia pestis).
What is a method to permanently prepare a microscope slide?
Fixed with formaldehyde and dehydrated with ethanol, then impregnated with paraffin wax and thinly sliced.
What is the cryostat method to prepare a microscope slide?
Frozen in N2(l) or CO2(l) and cut.
What is acid-fast staining?
Staining used to differentiate species of Mycobacterium from other bacteria.
(A lipid solvent is used to carry carbolfuchsin dye into the cells, then washed with dilute acid-alcohol solution. Mycobacterium are not affected by the solution and retain the stain)
What organelles do eukaryotes contain?
-nucleus
-nucleolus
-nuclear envelope
-rough endoplasmic reticulum
-smooth endoplasmic reticulum
-Golgi apparatus
-ribosomes
-mitochondria
-lysosomes
-chloroplasts
-plasma membrane
-centrioles
-cell wall
-flagella
-cilia
What is the role of the nucleus?
Houses DNA and directs the synthesis of all protein required by the cell.
What is the role of the nuclear envelope?
The nuclear envelope has a double membrane which contains DNA with a fluid separating the inner and outer membrane.
It has nuclear pores which allow larger molecules to move into and out the nucleus.
What is the role of the smooth endoplasmic reticulum?
It makes lipids and carbohydrates needed by the cell.
What is the role of the rough endoplasmic reticulum?
Flattened membrane-bound sacs studded with ribosomes.
What is role of the Golgi apparatus?
Receives proteins from the rough endoplasmic reticulum and modifies them. Then packages them into vesicles to be transported.
What is the role of mitochondria?
They are the site of cellular respiration where energy is stored in bonds of organic molecules.
Produces ATP.
What is the role of lysosomes?
Lysosomes are specialised vesicles that contain hydrolytic enzymes.
Acts as a waste disposal system-involved in phagocytosis and apoptosis.
What is the role of Chloroplasts?
The site of photosynthesis.
What is the role of the plasma membrane?
It is selectively permeable and controls movement in and out of the cells-acts as a barrier.
What is the role of centrioles?
Self-replicating organelles made of nine bundles of microtubules that help organise cell division.
What is the role of the cell wall?
Cell wall made of polysaccharide cellulose that can function as a carbohydrate store.
It has pores called plasmodesmata for communication.
What is the role of flagella?
Primarily used for mobility but also for sensing chemical changes.
What is the role of cilia?
Stationary cilia-important for sensory organs.
Mobile cilia-beat in rhythmic pattern.
What is the role of cytoskeleton?
Microfilaments-contractive fibres for cell movement.
Microtubules-build a scaffold-like shape for structure.
Intermediate fibres-mechanical strength/integrity.
What is the role of permanent vacuoles?
Tonoplast membrane filled with cell sap and keeps plant cell firm.
How are proteins produced and packages?
Proteins synthesised on the ribosomes bound to the rough endoplasmic reticulum.
Packaged into transport vesicles and then transported to cis-face of Golgi apparatus with help of cytoskeleton(microfilaments).
Protein travels through cisternae and is packaged in the trans-face.
Packaged in a secretory vesicle-vesicle reaches cell-surface membrane.
Vesicle fuses with membrane and exocytosis occurs.
What path of organelles are used in protein production and packaging?
-Nucleus
-Rough endoplasmic reticulum
-Transport vesicle
-Golgi apparatus
-Secretory vesicle
-Cell-surface membrane
What organelles do prokaryotes contain?
-nucleoid
-plasma membrane
-ribosomes
-flagella
-capsule
-cell wall
-pilus
What are the differences between eukaryotic and prokaryotic cells?
Eukaryotic- meiosis and mitosis.
multi-cellular.
linear DNA
10-100 micrometres.
Prokaryotic- binary fission.
uni-cellular.
circular DNA.
0.1-10 micrometres.
How does DNA differ in prokaryotic cells compared eukaryotic cells?
Prokaryotes have one molecule of DNA which is supercoiled to be more compact.
They are grouped into operons and genes can be switched on and off.
How do ribosomes differ between prokaryotic and eukaryotic cells?
Eukaryotes have 80s ribosomes while prokaryotes have 70s ribosomes.
