CELL STRUCTURE Flashcards
Definition of a stain
Coloured chemicals that bind to molecules in a specimen
What are the uses of stains?
- makes cells visible
- increases contrast as different components of a cell take up different amounts of stains
- details inside cell can be seen (organelles can be ice identified)
What are examples of stains?
METHYLENE BLUE -all purpose stain, stains living cells blue IODINE SOLUTION -staining living plant cells ACETIC ORCEIN -staining nuclei and chromosomes LIGHT GREEN -stains plant cell walls green
Differential staining definition
More than one stain, stains that bind to specific structures
Resolution definition
Ability to distinguish between two separate points
-two objects closer together than 200nm is seen as one image under light microscope
Magnification definition
Number of times larger the image size is compared to the real size of the object
Mag=image/acual
What image is produced and what does a scanning electron microscope scan?
3D image
Surface of cell
CONFOCAL LASER SCANNING MICROSCOPE
- function
- disadvantages
- useful for looking at
-can look at thin samples and intact samples
- low resolution
- only fluorescent objects cause artefacts
- living cells
- cell relationships
SCANNING ELECTRON MICROSCOPE
- function
- disadvantages
- useful for looking at
-surface in high resolution
- resolution is lower
- must be dead
- expensive
- object surface
- 3D image
TRANSMISSION ELECTRON MICROSCOPE
- function
- disadvantages
- useful for looking at
-thin cross section of objects
- cant be used on living thing
- expensive
- internal structure of objects
- high resolution
COMPOUND MICROSCOPE
- function
- disadvantage
- useful for looking at
- use visible light on a thin section of sample
- low resolution
- living things
- cells an tissues
What are the uses of laser scanning microscopes?
- developing drugs as not invasive
- see specific parts of cells
- can look at whole cell
What does an electron microscope need to work?
How do you prepare the specimen?
Vacuum
Dehydrate using different solutions, coat in gold so it can attract electrons
TRANSMISSION ELECTRON MICROSPCOPE
- what image does it produce?
- what does it look at?
- what passes through the specimen?
2D image
Inside of cell
Electron beam
What is the structure and function of the nucleus?
Double membrane (nuclear envelope)- encloses DNA
Nucleus pores- allows molecules in to make DNA and RNa exit
Nucleoplasm (contains chromatin)- cell division
Nucleolus- manufactures ribosomes
Outer membrane continuous with room ER
What is the structure and function of the ER?
A system of hollow tubes and sacs
Rough ER- covered in ribosomes
-transport in cells, ribosomes synthesise proteins
What are the structure and function of ribosomes?
What are the different types?
Two sub-units made of RNa and protein
- protein synthesis
- ribsosomes can move along mRNa
18nm=prokaryotic
22nm=eukaryotic
What is the structure and function of the Golgi apparatus?
Flatterned membrane bound cavities called cisternae (stacked on top of eachother)
- modifies (eg: carbohydrates)
- package protein into vesicles
What is the structure and function of the lysosomes?
Vesicles containing hydrolytic enzymes
- isolate potentially harmful enzymes
- break down old organelles
- break down cell once dead
What is the structure and function of mitochondrion?
Double membrane- inner membrane folds to make cristae
- isolates reactions in aerobic respiration for production of ATP
- increase SA for enzymes to attach
What is the structure and function of chloroplasts?
Examples of cells containing them
Double membrane
Membrane bound sacks (thykaloids) stacked into grana and connected by lamellae
-isolate photosynthesis reactions
> palisade cell
spongy mesophyll
What does the stroma contain?
- enzymes
- starch grains
- 18nm ribosomes
What is the structure and function of centrioles?
2 centrioles in all animal cells- at right angles to each other, adjacent to the nucleus
Composed of 3 set of microtubules
-form spindle fibres during nuclear division to control separation of chromatids and chromosomes
What is the structure and function of the vacuole?
Absent in animal cells, common in plant cells
Membrane called a TONOPLAST
>contain cell sap (water, sugar, fat etc)
-maintain turgor for support and storage
What is the structure and function of the flagella and cilia?
Examples
2 central microtubules surrounded by 9 pairs of microtubules
-sliding of microtubules brings about movement (energy required)
>trachea- waft mucus
>oviduct- egg to uterus
>udulippodia- sperm cell
What is the structure and function of the cytoskeleton?
Microtubules (fine, hollow tubes)
Microfilaments (small, solid protein strand)
- enable movement
- support cell organelles
- strengthen cell and maintain shape
What is the structure and function of the plant cell walls?
Rigid and permeable (strengthened by LIGNIN)
- support
- protection
Division of labour process
- Proteins synthesised on rough ER
- Proteins travel to cisternae (apart of rough ER)
- Packaged proteins from the cisternae travels to the Golgi apparatus as a vesicle
- In the Golgi, proteins are modified and packaged
- From the Golgi the vesicle is released and exits through the cell SURFACE membrane
What are always present in prokaryotic cells?
- cell surface membrane
- nucleoid (contains circular DNA)
- cytoplasm (contains cytoskeleton)
- ribosomes (18nm)
- cell wall (made of cross linked PEPTIDOGLYCON
What is sometimes present in a prokaryotic cell?
- plasmids (small circular DNA (helps become resistant to antibiotics))
- pili- cell to cell attachment (or surfaces)
- slime capsule (additional protection)
- flagellum=movement
