B2.2 Organelles and Compartmentalisation Flashcards
Compartmentalisation
One of the carbon compound thought to have been present on early Earth was fatty acids.
When place in water they form vesicles, and the boundary is used in compartmentalisation in the first cell.
RNA as the First Genetic Material
Hypothesis: Ribonucleic acid (RNA) acted initially as both the genetic material and the enzymes of the earliest cells
Evidence of RNA as the first genetic material
RNA can assemble spontaneously from simpler organic molecules (nucleotides)
RNA can form copies of itself (self-replicate)
RNA can control chemical reactions (catalytic role), e.g. ribozymes are still used in modern cells to remove introns and allow faster development of peptide bond
LUCA
Last universal common ancestor
The genetic code is universal, and all life shares a common mechanism of transcription and translation
Certain genes are broadly distributed across all cellular organisms
Similar transport mechanisms for cellular materials in and out of cells, as well as within cells
LUCA does not represent the first cellular organism and it is probable that the other lifeforms coexisted at the time of the LUCA.
It is hypothesized that the other forms of life would demonstrate distinctive characteristics other than what the LUCA had.
The other life forms are not present today might be the result of unsuccessful competition with the LUCA and its descendants.
Estimating the Dates of the First Living Cells and LUCA
Estimating dates using microbes in fossils
Biochemical evidence in sediment (Biosignatures)
Phylogenetic comparisons
Molecular clock
The Location of the Origin of Life
LUCA is hypothesized to exist in the vicinity of hydrothermal vents.
hydrothermal vents
a heat source some into close contact with fluid system within the Earth’s crust, resulting in the convective flow of fluid to the seafloor
evidence of LUCA
Some of the oldest fossilised traces or precipitates have originated at these vents
LUCA is also thought to have possessed a gene that is currently found in extremophiles living near the vents
Presence of mineral-rich environment with both acidic and basic fluids that are necessary for chemical reactions
Presence of both hydrogen and carbon dioxide at these locations, resulting in the reducing environment for carbon compound formation
cell compartmentalisation
Organelles are discrete subunits of cells that are adapted to perform specific functions
Cell wall, cytoskeleton and cytoplasm are not considered as organelles.
All eukaryotic cells possess compartments that are involved with:
Energy production
Metabolism
Biosynthesis
Degradation
structures of mitochondrion
outer mitochondrial membrane
matrix
cristae
inner mitochondrial membrane
space between inner and outer membrane
outer mitochondrial membrane
a membrane that separates the contents of the mitochondrion from the rest of the cell
matrix
an internal cytoplasm-like substance that contains the enzymes for the first stages of respiration that take place in the mitochondria (the link reaction and the Kreb cycle)
Cristae
Tubular regions surrounded by membranes that increase the surface area for reactions that take place towards the end of respiration (oxidative phosphorylation)
inner mitochondrial membrane
a membrane that contains the carriers and enzymes for the final stages of respiration (electron transport chain and chemiosmosis )
space between inner and outer membranes
a reservoir for hydrogen ions (protons, allowing a high concentration of protons
structures of chloroplasts
extensive membrane surface area of the thylakoids
small space (lumen) and low volumes of fluid within the thylakoids
stroma region similar to the cytoplasm of the cell and the matrix of the mitochondrion
double membrane on the outside
extensive membrane surface area of the thylakoids
Greater absorption of light by photosynthesis
small space (lumen) and low volumes of fluid within the thylakoids
faster accumulation of protons to create a concentration gradient
stroma region similar to the cytoplasm of the cell and the matrix of the mitochondrion
provides a region where the enzymes necessary for the Calvin cycle can work
double membrane on the outside
isolates the working parts and enzymes of the chloroplast from the surrounding cytoplasm
nucleus structure
nuclear envelope
nuclear pore
nucleolus
chromatin
nuclear envelope
Provides an area where DNA can carry out its functions without being affected by the processes in other parts of the cell.
nuclear pore
Allow ions and small molecules to diffuse through and control the passage of mRNA
nucleolus
Contains RNA-Protein complex, where ribosomes are made
chromatin
Contains inactive DNA
ribosome
Site for protein synthesis (translation)
Ribosomes are made of proteins and ribosomal RNA (rRNA)
The small subunit
- mRNA binding site
The large subunit
- Three tRNA binding sites
(aminoacyl (A) site, peptidyl (P) site, exit (E) site)
Ribosomes can be found either freely floating in the cytoplasm or bound to the rough ER (in eukaryotes)
Ribosomes differ in sizes in prokaryotes and eukaryotes (70S for prokaryotes, 80S for eukaryotes)
4 types of vesicles
Peroxisome
Lysosome
Transport vesicle
Secretory vesicle
transport vesicle
moves molecules within the cell
secretory vesicle
contains materials that are to be excreted from the cell, such as neurotransmitters (involved with the nerve and muscle action) and hormones (control many general functions in plants and animals)
what are clathrins
Clathrins are proteins in the cell membrane that anchor certain proteins to specific sites.
Lined up at coated pits and allow the molecules to bind to specific receptors.
Pit then deepens and seals off
