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
How is the structure of mitochondrial membranes related to function of mitochondria?
- site of ATP synthesis
- outer membrane is highly permeable to allow movement of molecules
How to improve cell drawings?
- label
- add scale
- add title
Role of RER membrane?
- Maintains different conditions between cytoplasm and RER (compartmentalisation)
- separates proteins from cytoplasm
How are organelles involved in protein synthesis?
- Nucleolus manufactures ribosomes for proteins synthesis in RER
2) nucleus manufactures mRNA /attached to ribosome on RER
3) proteins in RER are sent in VESICLES to Golgi body
4) Golgi body processes proteins/sends them in vesicles to the PLASMA MEMBRANE
5) vesicles fuse with plasma membrane to secrete finished protein product
Types of dyes used in microscopy and what are they used for?
Acetic orcein —> bind to DNA/stain chromosomes dark red
Eosin- stains CYTOPLASM dark red/pink
Iodine - stain starch blue-black
Iodine in potassium iodide solution - stains CELLULOSE yellow
Haematoxylin - stains RNA/DNA purple/blue
Methylene blue - all purpose stain - blue
Magnification formula?
Image size /actual size
How is colorimeter calibrated? Why is it important to calibrate ?
Set to zero absorbance
- using distilled water
- values all measured to same standard
Micrometers to cm?
10,000 micrometer = 1 cm
Compare magnification and resolution of Light microscope, TEM and SEM?
Microscope type LIGHT. TEM. SEM
Resolution 0.2 micrometers 0.0002 micrometers 0.002 micrometers
Magnification X1500. >X1,000,000. < 500,000
Stains used for electron microscopes?
Heavy metal compounds - absorb electrons well
So no colour
