Cell Structure Flashcards
Function of cell surface membrane?
- Controls exchange of materials between internal cell environment and external environ
-Partially permeable and formed from phospholipid
bilayer
Function of cell wall?
- in plant cells
- offer support and structure by the polysaccharide cellulose in plants
Function of a nucleus?
Control cell activity
- Nucleus separated from cytoplasm by nuclear envelope - has pores
- pores important for allowing mRNA and ribosomes to travel out nucleus
- nucleus contains chromatin - material that makes up chromosomes
Function of mitochondria and structure?
- Aerobic respiration in eukaryotes
- surrounded by double membrane with inner membrane folded - cristae
- matrix contains enzymes for respiration,to produce ATP
Chloroplasts function and structure?
- Site of photosynthesis
- Surrounded by double membrane
Compartments called thylakoids stack to form grana -these are joined together by lamellae (thin thylakoid membranes )
Function of ribosomes?
- Composed of 2 subunits and where proteins are produced
- each ribosome consists of rRNA and proteins
Structure and function of endoplasmic reticulum?
RER - series of flattened sacs in a membrane with ribosomes on the surface
- formed from continuous folds of membrane continuous with the nuclear envelope
- folds and processes proteins made on ribosomes
SER- membrane bound sacs
- produces and processes lipids
Structure and function of Golgi apparatus?
- Fluid filled flattened and curved sacs with vesicles on the edges
- packages and modifies proteins and lipids
- produces lysosomes
Function of large permanent vacuoles?
-a sac in plant cells surrounded by tonoplast
Function of vesicles?
- In plant and animal cells
- membrane bound sac for transport and storage
Function of lysosomes?
- Specialist form of vesicles - contain hydrolytic enzymes
- break down worn out organelles
Function of centrioles ?
- Hollow fibres made of microtubules arranged at right angles to each other
- involved is cell division
What is the cytoskeleton made up of?
2 types of protein fibres: microfilaments and microtubules
→ microfilaments - solid strands made from actin
- cause cell movement/ organelles
→ microtubules - tubular hollow strands made from tubulin
- organelles / other cell contents move along these fibres
Importance of cytoskeleton?
Strength and support - maintains shape of cell/ keeps organelles in place
Intracellular movement - form tracks along which organelles can move/ movement of chromosomes when they separate in cell division due to contraction of microtubules in spindle
Cellular movement - enables cell movement e.g movement of cilia and flagella a used by cytoskeletal protein filaments that run through them
How are prokaryotic cells different from eukaryote cells?
Prokaryotes have:
- cytoplasm that lacks membrane bound organelles
- smaller ribosomes (70S instead of 80S)
- no nucleus
- cell wall that contains MUREIN/peptidoglycan instead of cellulose and lignin
- SOMETIMES have PLASMIDS, CAPSULES and FLAGELLUM
- 0.5 - 5 um instead of 100um diameter
- cell division occurs by BINARY FISSION instead of mitosis and meiosis
Purpose of plasmids?
→ small loops of DNA
→ contain genes that can be passer between prokaryotes
Purpose of capsules?
→ final outer layer
→ protects bacteria from drying out / attack from immune system cells
Purpose of flagellum?
→ long hair like structure that rotates, enabling prokaryote to move
Difference between magnification and resolution?
Magnification - how many times bigger image produced is than the real life object
Resolution - ability to distinguish between objects
How are light microscopes useful?
- max resolution of 200nm - used to observe eukaryotic cells/nuclei (maybe mitochondria and chloroplasts)
- max magnification is 1500x
Ad and dis of transmission electron microscopes?
- beam of electrons are transmitted through the specimen - CAN SEE ULTRASTRUCTURE
AD: high resolution images - Can see smaller structures
DIS: can only be used with very thin specimens
- can’t use live specimens
- lengthy preparation of specimens
- not colour image
Ad and dis of scanning electron microscopes?
- scan a beam of electrons across the specimen
- beam bounces off surface of specimen/electrons are detected - forms image
AD: can be used on thick/3D specimens
- allow external 3D structure o be seen
DIS : lower resolution than TEMS
- cannot be used to see live specimens
- not a colour image
Ad and dis of laser scanning confocal microscopes?
Type of light microscope:
Use laser beams to scan a specimen that is tagged with fluorescent dye - laser causes dye to give off light
Detectors connected to computer - generates IMAGE
AD: used on thick/3D specimens
- allows external 3D structure to be seen
- clear images - high resolution
DIS : - slow
- laser can cause photo damage to cells
PAG 1 : microscopy
- Prepare slide :
Using liquid specimen: ADD SPECIMEN TO SLIDE
- cover liquid with coverslip/press to remove air bubbles
- add stain on edge of coverslip dab with paper towel drawing it under coverslip
Using solid specimen : cut small sample from tissue /peel away thin layer of cells from tissue sample
- apply stain /apply coverslip
- add drop of water to specimen can prevent dehydration of tissue
- Calibrate Graticule
- start with lower power objective lens
- by using the scale on the graticule lens/ stage micrometer , can work out the size of 1 division on eyepiece graticule
Take repeat measurement/calculate mean if taking measurements
