2.1 cell structure and microscopes Flashcards
name the four types of microscopes
light microscope
transmission electron microscope
scanning electron microscope
laser scanning microscope
what is the difference between magnification and resolution?
magnification is the process of enlarging the apparent size
resolution is the ability to distinguish 2 objects as separate
what is the maximum magnification and resolution of a light microscope
magnification 1500x
resolution 200nm
what is the maximum magnification and resolution of an SEM
magnification 200.000x
resolution 0.1nm
what is the maximum magnification and resolution of a TEM
magnification 2millionx
resolution 0.1nm
what is the maximum magnification and resolution of a laser scanning microscope
magnification 1000x
resolution 180nm-500nm
how is the beam focused in a light microscope
light beam is focused through glass lenses
how is the beam focused in an SEM
an electron beam is focused with electromagnetic coils
how is the beam focused in a TEM
an electron beam is focused with electromagnetic lenses
how is the beam focused in a laser scanning microscope
a laser beam through a light source is focused with objective glass lenses
which microscopes have a sectional or external view of the specimen
light - both
TEM - sectional
SEM - external
Laser - both
what is an application of a light microscope
can be used to provide information about the activity of cells
what is an application of a TEM
internal view of organelles and cells
what is an application of an SEM
external 3D viewing of cells
what is an application of a laser scanning microscope
medical progression
why is the maximum magnification of a light microscope limited to 1500x
the wavelength of visible light ranges from 400-700nnm so structures closer than 200nm will appear as one object.
state advantages of light microscopes
cheap
easy to use
able to study live specimens
state disadvantages of light microscopes
limited resolution due to wavelength of light
state advantages of SEM
high resolution
high magnification
produces 3D images
state disadvantages of SEM
inability to analyze live specimens
costly
training is required
black and white images only
state advantages of TEM
high magnification
high resolution
provides information on the internal structures of cells
state disadvantages of TEM
inability to analyze live specimens
costly
training required
black and white images only
explain why a vacuum is needed for electron microscopes
they prevent the electrons from being scattered by air particles
explain in terms of staining how electron microscopes differ
in an SEM the metal salt stain sits on top of the specimen whereas on a TEM the metal salt stain passes through the specimen
use a named example to explain why staining is needed for light microscopes.
the main reason for staining is to highlight cells and parts of cells for a better visual, for example, acetic orcein stains DNA and chromosomes in cells dark red
briefly describe how to use a light microscope
put the slide on the STAGE and clip it in place
turn on the power supply and light source
look through the EYEPIECE and make sure the OBJECTIVE LENS is on the lowest magnification
adjust your FINE and COARSE focus as well as IRIS DIAPHRAGM
describe how to change between units
mm -> microm =1000 micromm-> mm=/1000
microm -> nm=1000 nm ->microm /1000
what is the formula for magnification
magnification = image size/actual size
what is the difference between prokaryotic and eukaryotic cells
prokaryotic cells contain a cell wall and plasmids in the cytoplasm. However, it doesn’t have a nucleus and membrane-bound organelles
describe the 10 structures of a prokaryotic cell
they contain:
a waxy protective capsule
peptidoglycan cell wall
plasma membrane
mesosome
plasmid
pili
ribosomes
cytoplasm
DNA loop
flagella
describe the endosymbiotic theory
the idea that eukaryotes arose from prokaryotes- that organelles were once prokaryotes ingested by a larger bacteria
what is the difference between the nucleus and the nucleolus
the nucleolus is inside the nucleus
describe the structure of the nucleus
the nucleus is surrounded by a double membrane called the nuclear envelope that contains pores
the outer membrane joins up to the endoplasmic reticulum
it is the largest organelle 10-20micro metres in diameter
the nucleoplasm contains chromatin
describe the function of the nucleus
contains nearly of all a cells genetic material; instructions for making proteins and makes mRNA for protein synthesis
describe the structure of the nucleolus
not surrounded by a membrane
the dense spherical structure inside the nucleus
describe the function of the nucleolus
makes RNA and ribosomes that pass into the cytoplasm through the nuclear pores
describe the structure of the ribosomes
non-membrane bound
small spherical organelle that is about 20nm in diameter
made of ribosomal RNA
made in the nucleolus as two separate sub-units which pass through the nuclear envelope into the cytoplasm and then combine (40s and 60s sizes )
describe the function of ribosomes
ribosomes that bind to the exterior of the endoplasmic reticulum are mainly used for synthesising proteins that will be exported outside the cell
ribosomes that are free in the cytoplasm, either singly or in clusters are primarily the site of assembly of proteins that will be used inside the cell
describe the structure of rough ER
system of membranes containing fluid-filled cavities (cisternae) that are continuous with the nuclear membranes
coated in ribosomes
describe the function of rough ER
it is the intracellular transport system: the cisternae form channels for transporting systems from one area of a cell to another
provides a large surface area for ribosomes which assemble amino acids into proteins - these proteins then actively pass through the membrane into the cisternae and are transported to the Golgi body for modification and packaging
describe the structure of smooth ER
system of membranes with fluid-filled cavities (cisternae)that are continuous with the nuclear membrane
no ribosomes
describe the function of smooth ER
contains enzymes that catalyse reactions involved with lipid metabolism such as:
-synthesis of cholesterol
- synthesis of steroid hormones
it is involved with absorption synthesis and transportation of lipids (from the gut)
describe the structure of the Golgi apparatus
consists of stacks of membrane-bound flattened sacs
secretary vesicles bring materials to and from the Golgi body
describe the function of the Golgi apparatus
proteins are modified for example:
-adding sugar molecules to make glycoproteins
-adding lipid proteins to make lipoproteins
-being folded into their 3D shape
then proteins are packaged into vesicles that are then pinched off and :
-stored in the cell or
-moved into the plasma membrane, either to be incorporated into the plasma membrane or exported outside the cell
describe the structure of the mitochondria
they may be spherical or rod-shaped or branched and are 2-5 micrometers long
they are surrounded by two membranes with a fluid-filled space between them. The inner membrane is highly folded into cristae
the inner part of the mitochondrion is a fluid-filled matrix
describe the function of the mitochondria
site of ATP during aerobic respiration
self-replicating so mare can be made if the cell needs more energy
they are abundant in cells where much metabolic activity occurs
describe the structure of chloroplasts
these are large organelles that are 4-10 micrometers long
they are surrounded by a double membrane or envelope
the inner membrane is continuous with stacks of flattened membrane sacks called thylakoids which contain chloroplasts. Each stack of thylakoids is called a granum
the fluid-filled matrix is called stroma
describe the function of chloroplasts
chloroplasts are the site of photosynthesis
during the first stage of photosynthesis, when light energy is trapped by chlorophyll and used to make ATP occurs in the grana, water is also split to supply hydrogen ions
describe the structure of lysosomes
these are small bags formed from the Golgi apparatus and each is surrounded by a single membrane
they contain powerful hydrolitic (digestive) enzymes
describe the function of lysosomes
they keep powerful hydrolitic enzymes separate from the rest of the cells
they engulf old organelles or foreign matter, digest them and return the digested components to the cell for reuse
they are abundant in phagocytic cells such as white blood cells and neutrophills
describe the function of the plasma membrane
separate contents of the cell from the outside
permeable so it allows solutions to pass-through
describe the structure of the plasma membrane
a thin flexible layer of phospholipids
describe the structure of the cellulose cell wall
on the outside of the plasma membrane
made from bundles of cellulose fibers
describe the function of the cellulose cell wall
strong and prevents plant cell from bursting when turgid
provides strength and support
maintains the cells shape
permeable and allows solutions to pass through
describe the structure of the vacuole
surrounded by a membrane called the tonoplast and contains fluid
describe the function of the vacuole
filled with water and solutes and maintains cell stability because when full it pushes against the cell wall and makes the cell turgid
describe the structure of the vesicle
made from phospholipids
describe the function of the vesicle
used for transportation
how does the function of ribosomes that are free and those on the RER differ
Free ribosomes are mainly concerned with assembling proteins to be used within the cell. Ribosomes on RER
mainly assemble proteins that are exported out of the cell.
how are chloroplasts moved nearer the surface on a dull day
Motor proteins drag chloroplasts along cytoskeleton threads or ‘tracks’.
name one substance that passes into the nucleus
mRNA
suggest why hydrolytic enzymes need to be inside a vesicle
To prevent them from digesting/breaking down the cell components.
describe the structure of centrioles
consists of two bundles of microtubules at right angles to each other
the microtubules are made of tubulin protein subunits arranged to form a cylinder
describe the function of centrioles
before the cell divides the spindle, made of threads of tubulin, forms from the centrioles. Then chromosomes attach to the middle part of the spindle and motor proteins walk along the tubulin threads and pull the chromosomes apart
involved in the formation of cilia and undulipodia
describe the structure of microfilaments
they are 7nm in diameter and made of subunits of the protein actin
describe the function of microfilaments
they are within the cytoplasm and give support and mechanical strength to keep the cell’s shape stable and allow cell movement
describe the structure of intermediate filaments
10nm in diameter
made of a variety of proteins
describe the function of intermediate filaments
they anchor the nucleus within the cytoplasm
extend between cells in some tissues between special junctions enabling cell-cell communication and allowing cells to adhere to a basement membrane stabilising the tissue
describe the structure of microtubules
18-30nm in diameter
made of protein subunits called tubulin
describe the function of microtubules
also, provide shape and support to cells and help organelles/substances move through the cytoplasm
they form the track along which motor proteins (kinesin) walk and drag organelles from one part of the cell to another
they form the spindle before a cell divides and these spindle threads enable a chromosome to be moved within the cell
why are some human cells ciliated
to waft mucus
name a type of human cell that can move and explain why that is important for its function
phagocytes
the can move so that they can engulf pathogens
How do you use a graticule
lace a stage micrometer on the stage of the microscope.
Line up one of the divisions on the eyepiece graticule with a fixed point on the stage micrometer.
Count the number of divisions on the eyepiece graticule that correspond with a set measurement on the stage micrometer.
Calculate the distance in micrometres of one division on the eyepiece graticule.
