1.2 Ultrastructure Of Cells Flashcards
Scanning vs transmission electron microscope
Scanning (SEM) - electrons focused on the surface of a specimen to provide an image that appears 3D
Transmission (TEM) - electrons focused thru a sample, used to study internal structure of cells
three domains of biological classification
- archaea – “primitive”, mainly microorganisms
- bacteria
- eukaryota
organisms under both archaea and bacteria are prokaryotes
describe the cell structure of prokaryotes
- genetic mat NOT encased in membrane, coiled into nucleoid
- do not contain membrane-bound organelles
- cytoplasm within plasma membrane
- one chromosome – circular DNA
- may cont plasmids, extra-chromosomal dna
how do mesosomes form in prokayotes
from infolding of cell surface membrane, incr surface for activities eg cellular respiration
how do bacteria feed
extracellular digestion
- enzymes secreted out the cell, nutrients absorbed, all transport reg by cell surface mem
how do prokaryotes divide?
binary fission
- DNA replicated in semi-conservative manner
- 2 DNA loops attach to cell surface membrane – CSM elongates and divides into 2 (cytokinesis)
- genetically identical daughter cells
describe eukaryotes cell structure
- DNA encased in nuclear envelope (double membrane)
- cytoplasm found between nuclear membrane and CSM
- membrane-bound organelles aid compartmentalisation
how do membrane bound organelles in eukaryotes aid in compartmentalisation?
- incr efficiency of metabolism – molecules close tgt, incr speed of reactions
- diff organelles kept at diff conditions, efficient reactions within a cell (compartmentalised)
- isolation of compounds – some organelles may contain enzymes/ harmful toxins
- numbers – there can be a diff no. of organelles (depending on the needs of the cell)
isolation of compounds – lysosomes
what are lysozomes? why do they need to be isolated?
vesicles that contain enzymes that need to be isolated to prevent autodigestion – destruction of cell thru action of its own enzymes
describe nucleus 7
- largest organelle
- location of genetic material in form of chromosomes
- nucleoplasm within nucleus
- double membrane – nuclear envelope
- pores in nuclear envelope to regulate entry and exit of subtances like mRNA
- connected to endoplasmic recticulum
- nucleolus – dense region responsible for ribosomal RNA production
decribe ribosomes
- primarily protein production
- made of ribosomal RNA prod in nucleolus
- quantity depends on amt of proteins cell needs to produce
- ribosomes either membrane bound or free floating
free ribosomes vs membrane bound ribosomes
free
- floating in cytoplasm
- prod proteins needed within cytoplasm
bound
- mainly on RER
- proteins are packaged in other organelles and exported out the cell
6 parts of endomembrane system
- nuclear envelope
- endoplasmic recticulum
- golgi apparatus
- lysosomes
- vacuoles
- plasma membrane
function of RER
(has ribosomes)
RER involved in prod of polypeptides transported via vesicles to golgi apparatus for packaging and exported
function of SER
SER involved other metabolic processes – production of enzymes needed to prod lipids and steroids, enzymes that process drugs & alcohol
function of golgi apparatus
involved in further processing and packaging of molecular products of the cell
- folds and packages polypeptides tgt into functional proteins
- prodcts travel via vesicles to one side on GA
- products are processed and modified as they travel to other side
- vesicles containing final products pinch off and travel to other organelles/ cell surface for exocytosis
function of lysosomes 5
membrane bound sacs containing digestive enzymes
- from golgi apparatus, w og polypeptides forming enzymes prod in RER
- presence of membrane – isolate digestive enzymes, prevent auto-digestion
- needed for digestion of food molecules taken in via phagocytosis
- used to digest worn out organelles in the cell (nutrient recycling)
- some fuse will CSM for exocytosis of enzymes
function of contractile vacuoles
found in many protists (type of single celled organism)
- able to mehcanically pump water for osmoregulation
function of large central vacuole
found in plant cells
- help osmoreg by buffering changes in water potential of cytoplasm
(plant cells also may contain some that store toxins or pigments)
function of food vacuoles
found in many cells
- envelope food particles taken in via phagocytosis
function of mitochondria
found in almost all eukaryotic cells
- responsible for cellular respiration, prod energy in form of Adenosine Tri-Phosphate (ATP)
function of chloroplasts
responsible for photosyntehsis
similarities between mitochondria and chloroplasts (3)
- double membrane
- not part of cellular endomembrane system
- have their own chromosomes (circular DNA)
structure of mitochondria
- double membrane: smooth outer, folded inner to form cristae – incr surfac area for reactions that syn. ATP
- 2 compartments: mitochondrial matrix, intermembrane space
mitochondrial matrix contains: 3
- enzymes that catalyse cellular resp processes
- ribosomes
- mitochondrial DNA
what in the mitochondria makes ATP synthesising reactions more efficient?
folding of cristae (folded inner membrane) – incr surface area
compartments in chloroplasts 2
- intermembrane space
- stroma
structure and constituents of stroma 3
- cont enzymes, chloroplast DNA and ribosomes
- cont internal network of membranes arranged to form interconnected sacs – THYLAKOIDS
- stacks of THYLAKOIDS form a GRANUM, rich in chlorophyll
prokaryote and eukaryote difference – ribosomes
pro – 70s
euk – 80s, 70s in organelles
80s larger than 70s
