Chapter 7 Flashcards
What is microscopy?
An instrument used to see objects that are too small to be seen by the naked eye
When were microscopes invented?
In 1590 and was further refined during the 1600s
When were cells first seen by Robert Hooke?
1665
What is a light microscope (LM)?
A light microscope uses focused light and lenses to magnify a specimen, usually a cell.
What is resolution?
A measure of the clarity of the image. The minimum distance between two points that can be separated and still be distinguished at different points.
What is magnification?
The ratio of an object’s image size to its actual size
What is contrast?
The difference in brightness between the light and dark areas of an image.
What is the electron microscope (EM)?
Electron microscopy (EM) is a technique for obtaining high resolution images of biological and non-biological specimens.
What is the scanning electron microscope (SEM)?
A scanning electron microscope (SEM) scans a focused electron beam over a surface to create an image. The electrons in the beam interact with the sample, producing various signals that can be used to obtain information about the surface topography and composition.
What is a brightfield (Unstained specimen) (LM)?
Where light passes straight through the specimen unless the cell is naturally pigmented or artificially stained.
What is a brightfield (stained specimen) (LM)?
Staining with various dyes which enhances contrast. This requires that cells be fixed thereby killing them
What is a phase-contrast (LM)?
Variations in density within the specimen are amplified to enhance contrast in unstained cells. This is useful for living cells.
What is the differential interference contrast (LM)?
Similar to phase-contrast where optical modifications are used to exaggerate differences in density. This image appears almost 3D
What is fluorescence (LM)?
Where the locations of specific molecules in the cell can be revealed by labelling the molecules with fluorescent dyes or antibodies.
What is confocal (LM)?
Using a lazer an optical sectioning technique eliminates out-of-focus light from a thick sample creating a single plane of fluorescence in the image. This allows for a 3D construction to be formed.
What is deconvolution (LM)?
Images through deconvolution software which digitally removes out-of-focus light and re-assigns it to its source creating a much sharper 3D image.
What is super resolution (LM)?
Where sophisticated equipment is used to light up individual florescent molecules and record their position. Combining information from many molecules in different places breaks the limit of resolution resulting in a super sharp image.
What does LM stand for?
Light micrograph
What does SEM stand for?
Scanning electron micrograph
What does TEM stand for?
Transmission electron micrograph.
What is the transmission electron micrograph?
Used to study the internal structure of the cells. It aims an electron beam through a very thin section of the specimen allowing scientists to observe features such as structure.
What is cytology?
The study of cell structure
What is cell fractionation?
Used to seperate cell components based on size and density. It takes cells apart and separates major organelles and other sub cellular structures from one another.
What is the centrifuge?
A machine with a rapidly rotating container that applies centrifugal force to its contents, typically to separate fluids of different densities (e.g. cream from milk) or liquids from solids.
What does cell fractionation allow for?
It enables researchers to prepare specific cell components in bulk and identify their functions.
What is a prokaryotic cell?
Cells that do not have a true nucleus or membrane-bound organelles
What is a eukaryotic cell?
Eukaryotic cells are cells that contain a nucleus and organelles, and are enclosed by a plasma membrane.
What are the types of prokaryotic cells?
Bacteria and Archea
What are the types of eukaryotic cells?
Protists, Fungi, animals and plants.
What is a cytosol?
the aqueous component of the cytoplasm of a cell, within which various organelles and particles are suspended.
What are chromosomes?
Chromosomes are thread-like structures in which DNA is tightly packaged within the nucleus.
What are ribosomes?
Ribosomes carry out protein synthesis. Ribosomes can be found floating within the cytoplasm or attached to the endoplasmic reticulum
Where does DNA sit in prokaryotic cells?
Concentrated in a region that is not membrane-enclosed called the nucleoid
Where does DNA sit in Eukaryotic cells?
In the nucleus which is bounded by a double membrane
What is the cytoplasm?
The interior of the cell
Which cells are bigger prokaryotic or eukaryotic cells?
Eukaryotic cells
What is a plasma membrane and its function?
A selective barrier that allows the passage of enough oxygen, nutrients, and wastes to service the cell.
Do larger organisms have larger cells or just more cells?
More cells as we want the surface area of cells as cell exchange a lot of material with their surroundings
What is the endoplasmic reticulum (ER)?
An organelle consisting of a network of membranes within the cytoplasm of eukaryotic cells that is important in protein synthesis and folding and is involved in the transport of cellular materials.
What is the smooth ER?
The smooth ER functions by the synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions. It is called smooth ER because it does not have ribosomes on its outer surface.
What is the rough ER?
Its main function is to produce proteins. It is made up of cisternae, tubules and vesicles. It is called the rough ER because its outer surface contains ribosomes.
What is the nuclear envelope?
The nuclear envelope surrounds the nucleus with a double membrane with multiple pores. The pores regulate the passage of macromolecules like proteins and RNA, but permit free passage of water, ions, ATP and other small molecules.
What is the nucleous?
It a collection of ribosomal RNA and proteins along with ribosomal genes and processing enzymes. The role of the nucleolus is to process RNA into ribosomes.
What is the chromotin?
The function of chromatin is to efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence.
What is the Golgi apparatus?
An organelle which has major functions of modifying, sorting and packaging of proteins for secretion. It is also involved in the transport of lipids around the cell, and the creation of lysosomes. The sacs or folds of the Golgi apparatus are called cisternae.
What is the lysosome in the cell?
Digestive organelles where macromolecules are hydrolysed.
What is the mitochondrion in the cell?
The organelle where cellular respiration occurs and most ATP is generated.
What is peroxisome in the cell?
An organelle with various specialised metabolic functions; produces hydrogen peroxide as a by-product and then converts it to water.
What is the microvilli?
Projections that increase the cell’s surface area
What is the cytoskelleton?
This reinforces the cells shape and functions in cell movement
What are microfilaments?
Microfilaments assist with cell movement and are made of a protein called actin. Actin works with another protein called myosin to produce muscle movements, cell division, and cytoplasmic streaming. Microfilaments keep organelles in place within the cell.
What are Intermediate filaments?
The most important function of intermediate filaments is to provide mechanical support for the plasma membrane where it comes into contact with other cells or with the extracellular matrix. Unlike microfilaments and microtubules, intermediate filaments do not participate in cell motility.
What are Microtubles?
Microtubules are hollow, fibrous shafts whose main function is to help support and give shape to the cell. They also serve a transportation function, as they are the routes upon which organelles move through the cell.
What is the centrosome?
The region where the cells microtubes are initiated. It contains a pair of centrioles.
What is the flagellum?
A motility structure present in some animal cells. A flagellum is a whip-like structure that allows a cell to move
What is the central vacuole?
A predominant organelle in older plant cells. Its functions include storage, the breakdown of waste products, and hydrolysis of macromolecules. Enlargement of the vacuole is a major mechanism of plant growth.
Is all the DNA in the cell located in the nucleus?
No it is also located in the mitochondria and chloroplasts.
What encloses the nucleus?
The nuclear envelope which separates its contents from the cytoplasm.
What is the nuclear envelope perforated by?
Pore structures
What is the pore complex?
An intricate protein structure that lines each pore of the nuclear envelope and plays an important role in the cell by regulating the entry and exit of proteins and RNAs as well as large macromolecules.
What is the nuclear lamina?
A netlike array of protein filaments that maintain the shape of the nucleus by mechanically supporting the nuclear envelope
What is the nuclear matrix?
A framework of protein fibres extending throughout the nuclear interior.
What do the nuclear lamina and matrix do?
They may help organise the genetic material so it functions efficiently.
What is the chromatin?
The complex of DNA and proteins making up chromosomes.
How many chromosomes does a typical human cell have in its nucleus?
46
What is the nucelolus?
A small body in the nucleus of a cell that contains protein and RNA and is the site for the synthesis of ribosomal RNA and for the formation of ribosomal subunits.
Where is rRNA synthesised?
in the nucelolus
Where are free ribosomes suspended in the cell?
In the cytosol
Where the the bound ribosomes in the cell?
attached to the outside of the endoplasmic reticulum or nuclear envelope.
True to False? free and bound ribosomes are structurally identical.
True
What do free ribosomes do?
The proteins from these ribosomes usually make enzymes that catalyse the first steps of sugar
What do bound ribosomes do?
Generally make proteins that are destined for insertion into membranes for packaging within certain organelles such as lysosomes or for export from the cell
What tasks does the endomembrane system carry out?
The synthesis of proteins, transport of proteins into membranes and organelles
or out of the cell, metabolism and movement of lipids, and detoxification of poisons.
What is the endoplasmic reticulum (ER)?
An organelle consisting of a network of membranes within the cytoplasm of eukaryotic cells that is important in protein synthesis and folding and is involved in the transport of cellular materials.
True or False the endoplasmic reticulum accounts for all of the total membrane in eukaryotic cells.
False it accounts for over half.