cell structure: CONDENSED! Flashcards
Light microscopes
- beam of electrons have short wavelength = a high resolution small organelles and internal structures can be visualised
-image is created using an electromagnet to focus bream fo negatively charged electrons - electrons absorbed by air, so electromagnet must be in a vacuum
- only non living specimens can be examined
- images black and white as samples must be stained.
transmission electron microscope (TEM)
- extremely thin specimen stained + placed in vacuum
- electron gun produces a beam of electrons that passes through a specimen.
-some parts of specimen absorb the electrons and this makes them appear darker - image 2D, detailed internal structure
SEM
specimen does not need to be thin as electrons aren’t transmitting through
- electrons beamed onto surface + electrons are scattered in different ways depending on the contours
- produced 3D images.
laser scanning
- fluorescent microscope -> image created using high light intensity to illuminate specimen stained with fluorescent dye.
- combine the benefits of high resolution optical imaging with depth selectivity
- view sections of tiny structures + 3D image
-> created point by point using a focused laser beam to create 2D images, or 3D image in different focal planes used. As light emitted from specimen if cause florescence.
what does the nucleus consist of and its function
- nuclear envelope
- nuclear pore
- nucleoplasm
- chromosomes (linear)
- nucleolus (RNA production)
function = site of DNA replication and transcription
= contains genetic code for each cell
= site of ribosome synthesis
flagella + function
whip-like tail
- used for mobility
structure of cilia + function
- hair like projections
function: can be mobile/stationary, beat-like motions move substances
centrioles + function
- made of microtubules
- occurs in pairs to form a centrosome
function - involved in production of spindle fibres and organisation of chromosome in cell division
cytoskeleton + function
- network of fibres found in cytoplasm
- microfilament/tubules intermediate fibres
function: mechanical strength
- maintain shape/stability
- microfilaments -> cell movements
- microtubules -> responsible for scaffold-like structure
- intermediate fibres -> mechanical strength
endoplasmic reticulum + function
- RER and SER both have folded membranes = cisternae
- RER have ribosomes on their cisternae
function-
RER = protein synthesis
SER = synthesis and store lipids and carbohydrates
Golgi apparatus + function
-folded membranes making cisternae
-secretary vesicles pinch off from cisternae
function:
-add carbs to proteins (glycoproteins)
-produce secretory enzymes
-secrete carbs
-transport, modify, store lipids
- form lysosomes
- transported to cell surface via vesicles where they fuse with membrane then are released.
lysosomes + function
- bags of digestive enzymes
function;
- autolysis = break down dead cells
- exocytosis - release enzymes outside of cell to destroy material
mitochondria + function
- double membrane
- inner membrane cristae
- fluid centre called mitochondrial
matrix loop of mitochondria DNA
function
- site of aerobic respiration
- atp production
- dna to code for enzymes needed for resp
ribosomes + function
- 80s = large in eukaryotic cells
- 70s = found in prokaryotic cells, mitochondria, chloroplasts
functions: protein synthesis
chloroplasts + functions
- surrounded by double membrane
- contain thylakoids (folded membranes)
function: site of photosynthesis
cell wall + function
plants = made of microfibrils of cellulose polymer
fungi = made of chitin, nitrogen containing polysaccharides
plasma membrane + function
- found in all cells
- phospholipid bilayer + (proteins, carbohydrates, cholesterol)
functions: controls what goes in and out of cells
production and secretion of proteins
- polypeptide chains are synthesised on the RER
- these polypeptide chains move to the cisternae in the RER and are packaged into vesicles to be sent to the golgi apparatus via the cytoskeleton
- In the Golgi apparatus, the proteins are modified and packaged into vesicles
- the secretory vesicles carry the proteins to the cell surface membrane where it fuses and released the protein by exocytosis.
key differences between prokaryotic and eukaryotic cells:
- cells are much smaller
- no membrane bound organelles
- smaller ribosomes
- dna is not contained within a nucleus
- a cell wall made of meurin
they may contain:
- plasmids
- a capsule around the cell
- flagella
