2.1.1 - Cell structure Flashcards
Name the different types of microscopes ?
- Light microscope
- Transmission electron microscope
- Scanning electron microscope
- Laser scanning confocal microscope
What are the features of a light microscope ?
- Uses visible light to view specimen
- Uses glass lenses to focus light/ magnify the specimen
- Specimen mounted on a glass slide and held in water/wax/oil
- Light is able to pass through specimen
Explain how a light microscope produces an image ?
- The specimen is placed on a glass slide on the stage
- Visible light ( from light bulb/ mirror ) passes through the specimen
- The objective lens produces a magnified image which is magnified again by the eye piece lens
What are the features of an electron microscope ?
- Uses a beam of electrons to view specimen
- Electrons are focused using electromagnets
- Specimen has to be inside a vacuum ( to allow electrons to pass through without deflection/ absorption )
Explain how a transmission electron microscope produces an image ?
A beam of electrons is focused using electromagnets and passed through a very thin specimen producing a high resolution image
Explain how a scanning electron microscope produces an image ?
- A beam of electrons is bounced/ reflected off the surface of a specimen
- The scattered/ reflected electrons are collected by a detector and a 3D image of the surface of the specimen is formed
What are the features of a laser scanning conical microscope ?
- A higher light intensity is used to view specimen
- Uses a laser to focus light/ magnify the specimen
- The specimen is treated with a fluorescent chemical/ dye
- Light is absorbed and re-emitted by the specimen
Explain how a laser scanning cofocal microscope produces a magnified image ?
- The microscope moves a spot of focused light across the specimen
- This causes fluorescence from the components labelled with a ‘dye’
- The emitted light from the specimen is filtered through a pinhole aperture producing a magnified image
Why is light filtered through a pinhole aperture during laser scanning cofocal microscopy ?
- This allows only light radiated from very close to the focal plane to be detected
- Light emitted from other parts of the specimen would reduce resolution and cause blurring
Do you know how to prepare microscope slides using an eyepiece graticule and micrometer ?
Yes
What is staining ?
The process of dyeing specimen to increase contrast or identify specific components
Why is staining used during light microscopy ?
- The interior of cells and cell structures are often transparent
- Staining is used to increase contrast and allow components to be visible so they can be identified
What is differential staining ?
The process of distinguishing between two types of organism or organelles of an organism ( that would otherwise be hard to identify ) by using more than one dye
How do you represent cell structures seen under a light microscope ?
- Draw solid confident lines
- Do not use any form of shading
- Label or identifiable organelles visible
- Draw all detail visible
What is the equation for magnification ?
magnification = ( image size ) / ( object size )
Do you know how to do magnification calculations ?
Yes
Define the term ‘magnification’ ?
Magnification - How many times larger the image in comparison to the size of the object
Define the term ‘resolution’ ?
Resolution - The ability to see individual objects as separate entities instead of as one
What are the differences in magnification and resolution between a light microscope, TEM and SEM ?
- Light microscope has up to 2000x magnification with a resolution of 200nm
- Electron microscope has a magnification of over 500,000x and very high resoltion
- TEM have a better resolution 0.5nm ( more detailed images produced ) in comparison to SEM
What are the differences in images produced between the TEM and SEM ?
- TEM produces very high resolution 2D images ( very detailed ) of thin specimen
- SEM produces slightly lower resolution 3D images of the surface of the specimen
List the differences between a light and electron microscope ?
Label the cell ?
What is the function of the nucleus ?
It contains coded genetic information in the form of DNA molecules that are associated with proteins called histones forming chromatin which forms chromosomes
What is the nucleolus ?
An area within the nucleus that is responsible for the production of ribosomes
What is the function of the nucleolus ?
It responsible for producing ribosomes
What is the nuclear envelope ?
A double membrane that surrounds the nucleus
What is the function of the nuclear envelope ?
It protects the nucleus from damage in the cytoplasm
What are nuclear pores ?
They are gaps/ holes in the nuclear envelope
What is the function of nuclear pores ?
It allows molecules to move in and out of the nucleus
What is the rough and smooth endoplasmic reticulum ?
- A network of membranes enclosing flattened sacs called cisternae
- The SER has no ribosomes attached to its surface
- The RER has ribosomes bound to its surface
What is the function of the rough endoplasmic reticulum ?
It is responsible for the synthesis and transport of proteins
What is the function of the smooth endoplasmic reticulum ?
It is responsible for lipid and carbohydrate synthesis and storage
What is the Golgi apparatus ?
A compact structure formed of cisternae which does not contain ribosomes
What is the function of the Golgi apparatus ?
It is responsible for modifying proteins and ‘packaging’ them into vesicles ( eg. secretary vesicles or lysosomes )
What are ribosomes ?
They are small granules made up of proteins and ribosomal RNA
Where are ribosomes found in a cell ?
- Free-floating in the cytoplasm
- Bound to the surface of the rough endoplasmic reticulum
What is the function of ribosomes ?
They are the site of protein synthesis
Label the mitochondrion ?
What is the function of the mitochondria ?
The site of aerobic cellular respiration
Explain the structure of the mitochondria ?
- Mitochondria have a double membrane, an inner and outer membrane
- The foldings of the inner membrane are called cristae and the fluid interior the mitochondrial matrix
- The inner membrane contains enzymes needed for aerobic respiration
- Mitochondria contain small amounts of DNA called mitochondrial DNA and ribosomes
- This allows mitochondria to produce they own enzymes and proteins
What are vesicles ?
They are membranous sacs that have transport and storage roles
What is the function of vesicles ?
They transport and store materials inside of the cell
What are lysosomes ?
They are specialised vesicles that contain hydrolytic enzymes called lysozymes
What is the function of lysosomes ?
- They are responsible for breaking down waste material in cells and old organelles
- They are responsible for breaking down pathogens ingested by phagocytic cells
What is the cytoskeleton ?
A network of fibres necessary for the shape and stability of the cell
What is the function of the cytoskeleton ?
- It provides mechanical strength to cells
- It aids transports within cells
- It holds organelles in place and allows cell/ organelles to move within the cell
What are the three components of the cytoskeleton ?
- Microfilaments
- Microtubules
- Intermediate fibres
What are microfilaments and what is their function ?
- They are contractile fibres formed by the protein actin
- They are responsible for cell movement and contraction during cytokinesis
What are microtubules and what are their function ?
- They are a scaffold-like structures
- They are responsible for determining the cell shape and tracking the movement of organelles around the cell
What are intermediate fibres and what are their function ?
- They are fibres
- They are responsible for providing mechanical; strength to cells and helping maintain their integrity
What are centrioles ?
A component of the cytoskeleton present in most eukaryotic cells ( except flowering plants / fungi )
What is the function of centrioles ?
- Two associated centrioles forma centrosome
- This is responsible for the assembly and organisation of the spindle fibres during cell division
Explain how the various organelles work together to produce and secrete proteins ?
1 ) Proteins are synthesised by ribosomes bound to RER
2 ) They pass into RER’s cisternae and are packaged into transport vesicles
3 ) Vesicles move towards the Golgi apparatus vi the transport function of the cytoskeleton
4 ) The vesicles fuse with the Golgi apparatus and the proteins enter. The protein are structurally modified before leaving the Golgi apparatus is vesicles
5 ) Secretory vesicles move towards and fuse with the cell surface membrane before releasing proteins by exocytosis
5 ) Some vesicles form lysosomes contain enzymes used by the cell
Label the cell ?
What is the cell wall made up of ?
- Cellulose in plants
- Chitin in fungi
What is the function of the cell wall ?
- It is freely permeable so allows for the passing of substances in and out of the cell
- It provides mechanical strength to cell and helps maintain its shape
- It acts as a defence mechanism and protects the cell against invading pathogens
What is the vacuole ?
They are membrane-lined sacs in the cytoplasm contains cell sap
What is the function of the vacuole ?
- It is responsible for maintaining turgor pressure within the cell and keeping it rigid
- It is selectively permeable and allows for the passage of small molecules in and out of the vacuole
What is the membrane of the vacuole made of ?
Tonoplast
Label the chloroplast ?
What is the function of chloroplasts ?
It is the site of photosynthesis
Explain the structure of chloroplasts ?
- Chlorplasts have a double membrane, an inner and outer membrane
- The guild enclosed within is called the storma
- Geranium are stack of disc-shaped sacs called thylakoids
- Grana are joined by lamellae
- Grana contain chlorophyll-pigments where light-dependant reactions occur during photosnyethsis
- Chlroplasts contain small amounts of DNA and ribosomes so can make their own enzymes and proteins required for photosynthesis
What is a flagella ?
They are tail-like structures
What is the function of the flagella ?
They enable cell mobility/ locomotion
What is the function of cilia ?
- Stationary cilia play an important role in sensory organs
- Mobile cilia beat in a rhythmic pattern and cause fluids/ objects adjacent cell to move
Lis the similarities and differences between prokaryotic and eukaryotic cells ?
