Basic Components of Living Systems

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  • Created by: LBCW0502
  • Created on: 11-05-16 17:10
What are the two types of lenses in a compound light microscope?
Objective lens (placed near specimen) and eyepiece lens (specimen is viewed)
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What is the significance of the objective/eyepiece lens configuration?
Allows for much higher magnification and reduced chromatic abberation
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What is sectioning?
Cutting a specimen into very thin slices
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What is a dry mount?
Solid specimens are sectioned and placed on a slide with a cover slip placed on top e.g. hair, pollen, dust, insect parts, plant and muscle tissue
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What is a wet mount?
Specimens suspended in liquid (water/immersion oil) and a cover slip is placed on from an angle e.g. aquatic samples
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What is a squash slide?
Wet mount is prepared then a lens tissue is placed on the cover slip. Squash the sample between two microscope slides e.g. root tip squashes (soft samples)
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What is a smear slide?
Edge of a slide is used to smear the sample, creating a thin, even coating on another slide. Cover slip is placed over the sample e.g. blood samples
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What is differential staining?
A type of staining used to distinguish between two types of organisms (which would be hard to identify) e.g. differentiate between different organelles of a single organism within a tissue sample
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What is gram stain technique?
Used to separate bacteria into two groups: Gram-positive bacteria (blue/purple/violet) and Gram-negative bacteria (red). This type of staining causes different reactions in the cells walls of bacteria
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What is acid-fast technique?
Used to differentiate species of Mycobacterium from other bacteria (which appear red)
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What are the stages involved in the production of slides?
Fixing (chemical used to preserve specimen in its near-natural state), sectioning (specimens dehydrated with alcohol then placed in wax to form a block which is cut), staining (show structures) and mounting (specimen placed on slide with cover slip)
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What is magnification?
How many times bigger an image is compared to the size of the actual object
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What is resolution?
The ability to see individual objects as separate entities (detail). This is limited by diffraction
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How do you calculate magnification?
Magnification = Size of image / size of object
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What are the three types of microscopes?
Light microscope, transmission electron microscope and scanning electron microscope
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What is the magnification and resolution on a light microscope?
Magnification: x1500. Resolution: 200nm
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What is the magnification and resolution of an SEM?
Magnification: x100,000. Resolution: 3-10nm
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What is the magnification and resolution of an TEM?
Magnification: x500,000. Resolution: 0.5nm
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How are specimens prepared for electron microscopes?
Fixation, dehydration, embedded in resin or wax and stained with heavy metals (to allow electrons to bounce off the specimen)
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What are the advantages of using a light microscope?
Small and portable, simple sample preparation (does not lead to distortion), vacuum is not required, natural colour of sample is seen and specimens can be living or dead
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What are the disadvantages of using a light microscope?
Resolving power is 200nm and the magnification is up to x2000
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What are the advantages of using an electron microscope?
Over x500,000 magnification, resolving power of TEM is 0.5nm and SEM is 3-10nm
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What are the disadvantages of using an electron microscope?
Expensive to buy and operate, large and needs to be installed, complex sample preparation (can distort material), vacuum is required, black/white images produced (but can be coloured digitally) and specimens are dead
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What are artefacts?
Visible structural detail caused by processing the specimen and not a feature of the specimen (changes in ultrastructure of cells when processing samples e.g. distortion of organelles)
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How can artefacts be identified?
Mesosomes are seen (inward foldings of cell membranes)
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What is laser scanning confocal microscopy?
Involves a single point of focused light (point illumination) across a specimen. Fluorescent dye is seen clearly. Emitted light from the specimen is filtered through a pinhole aperture. Light radiated from very close to the focal plane is detected
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What is the function of the nucleus?
Contains coded genetic information in the form of DNA (protein synthesis)
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What is the name of the double membrane around the nucleus?
Nuclear envelope
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What is the name of the complex when DNA associates with proteins (histones)
Chromatin
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What is the function of the nucleolus?
Area within the nucleus responsible for producing ribosomes. It is composed of proteins and RNA. RNA is used to produce rRNA
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What is the function of mitochondria?
Produces energy in the form of ATP (in aerobic respiration)
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What are lysosomes?
Specialised forms of vesicles that contain hydrolytic enzymes. They are responsible for breaking down waste material in cells (including old organelles)
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What are the three components of the cytoskeleton?
Microfilaments (cell movement/contraction during cytokinesis), microtubules (scaffold-like structure, tracks movement of organelles) and intermediate fibres (mechanical strength/maintain integrity)
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What are centrioles?
Component of cytoskeleton which is present in eukaryotic cells (animal cells). They are composed of microtubules. Two associated centrioles form centrosome
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What is the function of flagella?
Flagella are whip-like extensions (longer and fewer in number). They are used for cell motility and as a sensory organelle detecting chemical changes in the cell's environment
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What is the function of cilia?
Cilia are hair-like extensions (shorter and greater in number). They can be mobile or stationary and present on the surface of many cells. Mobile cilia beat in a rhythmic manner (e.g. trachea)
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What is the 9+2 arrangement in cilia?
Two central microtubules (black circles) are surrounded by nine pairs of microtubules (arranged like a wheel)
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What is the function of the smooth ER?
Responsible for lipid and carbohydrate synthesis and storage
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What is the function of the RER?
Has ribosomes bound to the surface and is responsible for the synthesis and transport of proteins
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What are ribosomes?
They are constructed of RNA molecules made in the nucleolus of the cell (they are the site of protein synthesis)
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Which organelles also contain ribosomes in eukaryotic cells?
Mitochondria and chloroplasts
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What is the function of the Golgi Apparatus?
Modifies proteins and packages them into vesicles. These may be secretory vesicles if the proteins need to leave the cell or lysosomes, which stay in the cell
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What are the stages of protein production in a cell?
Proteins synthesised on ribosomes bound to ER, they pass into cisternae and are packaged into transport vesicles, they move to the Golgi Apparatus, fuse to cis face and proteins enter, proteins are modified, secretory vesicles release proteins
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What is the cell wall of a plant cell composed of?
Cellulose
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What is the function of the plant cell wall?
Freely permeable so substances can pass into and out of the cell. It gives the plant cell its shape and contents of the cell press against the cell wall making it rigid. Cell wall is also a defence mechanism (protection against pathogens)
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What is a vacuole?
Membrane-lined sacs in the cytoplasm containing cell sap. Plant cells have a large permanent vacuole the maintain turgid pressure. It is also selectively permeable (animal cell has a small non-permanent vacuole)
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What is the membrane of a vacuole called?
Tonoplast
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What is the function of chloroplasts?
Contains chlorophyll which absorbs sunlight for photosynthesis
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Describe the structure of chloroplasts
Double membrane, fluid enclosed in the chloroplast (stroma), contains thylakoids (internal network of membranes which form flattened sacs). Several thylakoids stacked together form a granum. Grana are joined by lamellae, DNA, ribosomes
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Describe the general structure of prokaryotic cells
DNA, 70S ribosomes, peptidoglycan cell wall, flagella
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State the features of a prokaryotic cell
No nucleus, circular DNA, proteins fold/condense DNA, plasmids, non-membrane bound organelles, peptidoglycan cell wall, 70S ribosomes, cytoskeleton, binary fission, unicellular, cell surface membrane
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State the features of a eukaryotic cell
Nucleus, linear DNA, DNA associated with proteins (histones), DNA in mitochondria/chloroplasts, cellulose/chitin cell wall, 80S ribosomes, complex cytoskeleton, asexual/sexual, unicellular/multicellular, cell surface membrane
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Card 2

Front

What is the significance of the objective/eyepiece lens configuration?

Back

Allows for much higher magnification and reduced chromatic abberation

Card 3

Front

What is sectioning?

Back

Preview of the front of card 3

Card 4

Front

What is a dry mount?

Back

Preview of the front of card 4

Card 5

Front

What is a wet mount?

Back

Preview of the front of card 5
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