Chapter 2 - Basic components of living systems Flashcards
What are the two lenses of a compound light microscope?
The objective and eyepiece lens
Where is the objective lens positioned?
Near the specimen
Where is the eyepiece lens positioned?
Near your eye
How do the objective and eyepiece lens work together and what does this allow for?
The objective lens produces a magnified image, which is magnified again by the eyepiece lens. This allows for much higher magnification and reduced chromatic aberration
What are transmission electron microscopes (TEMs)?
Where a beam of electrons is transmitted through a specimen
What are scanning electron microscopes (SEMs)?
Where a beam of electrons Is sent across the surface of a specimen and the reflected electrons are collected to produce the image
What type of image will SEMs give?
3D
3 pros of light microscopes
Inexpensive
Small and portable
Simple sample preparation
In electron microscopes, what do the specimens have to be?
Dead
3 difference between light and electron microscopes
In electron a vacuum is required, black and white images are produced and specimens must be dead, whereas in light a vacuum is not required, the natural colour or staining of specimen is seen and specimens can be living or dead
What is an artefact?
A visible structure detail caused by the processing of the specimen, not a feature of a specimen
What often causes artefacts in light microscopes?
Bubbles trapped under the cover slip
What often causes artefacts in electron microscopes?
Changes in the structure of the cell are inevitable, due to the processing that samples must undergo
Which has the best resolution, SEMs or TEMs?
TEMs, with a resolving power of 0.5nm compared to 3-10nm
How do laser scanning confocal microscopes work?
It moves a single spot of focused light across a specimen (point illumination). This causes fluorescence, which is sent back up through a pinhole opening and detected by the detector
What is fluorescence?
The absorption and re-radiation of light
What happens to the out of focus light and what does this mean for the resolution in confocal microscopy?
The out of focus light is blocked and does not pass through the pinhole, and so is not detected. This light from other parts of the specimen would reduce resolution and cause blurring, however this is prevented
2 uses of confocal microscopes
- Diagnosis of diseases of the eye
- Development of new drugs, as it can see the distribution of molecules
What does the use of a laser in confocal microscopes mean?
A higher light intensity, which improves illumination
What is the definition of resolution?
The shortest distance between two points that can be distinguished
Where is the nucleolus?
An area within the nucleus
What is the nucleolus composed of?
A higher density of proteins and RNA
What is the nucleolus responsible for?
Producing ribosomes
How are ribosomes formed?
RNA is used to produce ribosomal RNA, which is then combined with proteins
What are mitochondria the site of?
The final stages of cellular respiration
Where is ATP stored?
Mitochondria
What are vesicles?
A single membrane with fluid inside
What are the roles of vesicles?
Storage and to transport materials around the cell
What are lysosomes?
Specialised forms of vesicles that contain hydrolytic enzymes, which can be used to break down cells
What are the roles of lysosomes?
Breakdown of waste material in cells:
- Programmed cell death
- Breakdown of pathogens ingested by phagocytes
What is apoptosis?
Programmed cell death
What are the 3 components of the cytoskeleton?
Microfilaments
Microtubules
Intermediate fibres
What are microfilaments?
Contractile fibres formed from the protein actin
What are microfilaments responsible for?
Cell movement
Cell contraction during cytokinesis
What are microtubules formed from?
Globular tubulin
What are microtubules responsible for?
Determine the shape of the cell
Act as tracks for the movement of organelles around the cell
What do intermediate fibres do?
Give mechanical strength to cells
Help maintain cell integrity
What are centrioles composed of?
Microtubules
What are centrioles responsible for?
They form centrosome, which is responsible for the assembly and organisation of the spindle fibres during cell division
What is the smooth endoplasmic reticulum responsible for?
Lipid and carbohydrate synthesis
Storage
What is the rough endoplasmic reticulum responsible for?
The synthesis and transport of proteins
What is Golgi apparatus formed from?
Cisternae
What cell type is procaryotic?
Unicellular
What cell type is eukaryotic?
Unicellular but mostly multicellular
How do prokaryotic cells reproduce?
Binary fission
How do eukaryotic cells reproduce?
Asexual or sexual
What is the difference between binary fission and mitosis?
Mitosis is nuclear fission therefore only in eukaryotic cells. Binary fission is very similar to mitosis, however binary fission is for prokaryotic cells
What surrounds the nucleus?
The nuclear envelope
What is the cell wall primarily made out of in plants?
Cellulose
What is the cell wall made out of in fungi?
Chitin
What is the cell wall primarily made out of in animal cells?
There is no cell wall in animals
What is the general structure of a plant cell?
- A large vacuole in the centre of the cell
- Cytoplasm surrounding the vacuole contains chloroplasts and a nucleus
- Cell surface membrane and cell wall
What are vacuoles?
Membrane lined sacs in the cytoplasm containing cell sap
What do plant vacuoles contain?
Cell sap
What is the membrane of a vacuole in a plant cell called?
The tonoplast
What is the permeability of plant cell membranes?
It is selectively permeable, which means that some molecules can pass through but others cannot
What is found on rough endoplasmic reticulum?
Ribosomes
What do secretory vesicles do?
Carry proteins that are to be released from the cell
What happens on the ribosomes of endoplasmic reticulum?
Proteins are synthesised
What happens during protein production after the protein is synthesised?
They pass into the cisternae of the rough endoplasmic reticulum and are packed into transport vesicles
What happens during protein production after the newly synthesised proteins are packed into transport vesicles?
The vesicles move towards the Golgi apparatus via the transport function of the cytoskeleton
What happens during protein production as the proteins reaches the Golgi apparatus?
The proteins fuse with the cis-face of the Golgi apparatus before leaving the trans face in secretory vesicles
During protein production, what do the secretory vesicles do?
They carry proteins that are to be released from the cell. They fuse with the cell-surface membrane and release their contents by exocytosis
What two locations do you find ribosomes?
On rough endoplasmic reticulum and floating in the cytoplasm
What are ribosomes the site of?
Protein synthesis
Are ribosomes surrounded by a membrane and if so what are its properties?
No it is not
What is secretion?
Transport of out the cell
What are flagella and cilia?
Extensions that protrude from some cell types
What do flagella look like?
One long whip-like tail
What do cilia look like?
Many short hair-like extensions
What two forms can cilia be?
Stationary and mobile
What are the main roles of stationary cilia?
On the surface of many cells and have important functions in sensory organs (e.g. nose)
What are the main roles of mobile cilia?
Beat in a rhythmic manner, creating a current which causes fluids or objects to move
What is the permeability of plant cell walls?
Freely permeable
What is the 2 key purposes of plant cell walls?
- Give structure and shape to the cell
- Defence mechanism, protecting the contents of the cell from pathogens
What two structures are unique to plant cells?
- Vacuoles (if they appear in animal cells they are small and transient)
- Chloroplasts
Where are chloroplasts found?
In the green parts of the cell (e.g. leaves and stem, but not in roots)
What membrane structure do chloroplasts have?
Double membrane
What membrane structure do mitochondria have?
Double membrane
What is the structure of the inner membrane of mitochondria and what does this form?
It is highly folded to form structures called cristae
What is the fluid interior of mitochondria called?
The matrix
What does mitochondria contain that is special, and what does this allow them to produce?
They contain a small amount of DNA, which allow them to produce their own enzymes and reproduce themselves
What is the stroma?
The fluid enclosed in the chloroplast
What are thylakoids?
Flattened sacs, which are formed by the internal network of membranes in chloroplasts
What do several thylakoids stacked together form?
Grana (singular Granum)
What are lamellae?
The membranes that grana are joined by
What do grana contain?
Chlorophyll pigments
What do chloroplasts contain that allow them to make their own proteins?
DNA and ribosomes
What is the purpose of the internal membranes?
To provide a large surface area that is required in photosynthesis
What is stroma similar to?
Cytoplasm in non-plant cells
Where are starch grains located in chloroplasts?
In the stroma
What is the singular of flagella?
Flagellum
What are extremophiles?
Organisms that were able to live in early Earth, which was very hostile
How is DNA in prokaryotes packaged?
- Only one molecule of DNA (a chromosome)
- This chromosome is supercoiled to make it more compact
What are the genes on the chromosome in prokaryotes grouped into, and what does this mean?
The genes are grouped into operons, which mean some genes are turned on and some off at times
What size are eukaryotic and prokaryotic ribosomes comparatively?
Eukaryotic ribosomes are larger than prokaryotic ribosomes
Which ribosomes are bigger, in eu or pro?
In eu the ribosomes are bigger
What is murein?
Another name for peptidoglycan, which is what pro cell walls are made from
How is eu cells DNA packaged?
- Multiple chromosomes that are supercoiled
- Each wraps around a number of proteins called histones
- This forms a complex for efficient packaging
What are histones?
What chromosomes in eu wrap around
What is chromatin?
The complex in which DNA forms in eu cells
Are eu organelles membrane bound?
Some are, some aren’t
Are pro organelles membrane bound?
No
Why are cells stained?
To increase contrast
Cell components can more easily be distinguished
2 other roles of mitosis outside of the growth and repair of tissues
- Asexual reproduction
- Production of new stem cells
What is empty magnification?
Where increasing the magnification past a certain point results in no higher increase in resolution. So although the image will be more magnified, the resolution will remain low
