M2: ch 2 - basic components of living systems Flashcards
what are the types of sample preparation
- dry mount
- wet mount
- squash slides
- smear slides
how is a dry mount sample prepared + examples
- solid specimens viewed whole or cut into very thin slices with a sharp blade –> sectioning
- specimen placed on centre of slide + cover slip placed over sample
- hair, pollen, dust, muscle tissue, plants, insect parts
how is a wet mount sample prepared + examples
- specimens are suspended in a liquid, such as water or an immersion oil
- cover slip is placed at an angle
- aquatic samples, other living organisms
how is a squash slide sample prepared + examples
- wet mount first prepared
- lens tissue used to gently press down the cover slip
- potential damage to cover slip can be avoided by squashing the sample between two microscopic slides
- squash slides is a good technique for soft samples
- care needs to be taken that the cover slip isn’t broken when being pressed
- root tip squashes - to look at cell division
how are smear slides prepared + examples
- edge of a slide used to smear the sample –> creating a thin, even coating, on another slide
- cover slip then placed over sample
- blood - to view blood cells
why is staining used
- to make components of sample more visible + easier to distinguish the different components, as many specimens such as cells + tissue sections are relatively colourless
what is magnification
how many times larger the image is than the actual size of the specimen (object)
what is resolution
the ability to distinguish between two objects closely together
- the minimum distance at which 2 points can be distinguished, from the other
what is the calculation for magnification
magnification = image size/actual size
what is the calculation for actual size
actual size = image size/magnification
what is the calculation for image size
image size = magnification x actual size
what are the two types of electron microscope
- transmission electron microscope (TEM)
- scanning electron microscope (SEM)
what are features of a TEM
- electron passes through + around the specimen, giving some contrast
- image is 2D
- magnification of x500,000
- looks within the cell
what are features of a SEM
- electron doesn’t go through or pass around the sample but reflects off
- image is 3D
- magnification of x100,000
- looks on surface of cell
compare a light microscope + an electron microscope
- L = inexpensive to buy + operate
E = expensive to buy + operate - L = small + portable
E = large + needs to be installed - L = simple sample preparation
E = complex sample preparation - L = sample preparation doesn’t usually lead to distortion
E = sample preparation often distorts material + produces artefacts - L = vacuum isn’t required
E = vacuum is required - L = natural colour of sample seen (or stains used)
E = black + white images produced (can be coloured digitally) - L = up to x1,500 - x2,000 magnification
E = up to x500,000 magnification - L = specimens can be living or dead
E = specimens are dead - L = resolution is very poor
E = resolution is 1,000 times more
what are the advantages of electron microscopes
- resolution is 0.2nm, 1,000 times more than light microscope
- we can see structured detailed images of organelles inside the cells
- SEM produces 3D images, that can uncover details of contorts + cellular tissue arrangement, can’t do with light microscope
what are the disadvantages of electron microscopes
- sample has to be dead
- very expensive
- preparing slides + samples requires high levels of training + skill
what is a eukaryote cell + examples
- DNA in a membrane bound nucleus, separate from the cytoplasm
- contain a large number of specialized, membrane-bound organelles
- animals, plants, fungi, protists
what is the structure of a nucleus
- nucleus
- chromatin
- nucleolus
- nuclear envelope
what is the function of the nucleus
- contains cells DNA
- site of DNA replication/transciption
what is the function of chromatin
- consists of DNA + proteins, some of the proteins regulate the cell’s activity
what is the function of the nucleolus
- site of ribosome synthesis (RNA synthesis)
- makes RNA which is made into ribosomes
what is the function of the nuclear envelope
- double membrane bound organelle
- compartmentalizes DNA from the rest of the cells
- has nuclear pores which allow the exchange of substances in + out of the nucleus, + lets relatively large molecules pass through
what is the function of mitochondria
site of aerobic respiration, to produce ATP
what are the features of mitochondria
- double membrane bound
- inner layer folds inwards to form the cristae, which project into a liquid called the matrix
- larger SA of matrix means more reactions, so more ATP can be produced
- inner membrane coated in enzymes, which catalyses aerobic respiration - to produce ATP
- contains DNA + ribosomes
- may have started from the endosymbiotic theory
