A2 unity and diversity of cells Flashcards
protocell
definition
any unit contained by a membrane that is comleting cellular reactions
what does the central dogma describe?
that the process goes DNA then RNA then Proteins
RNA world hypothesis
explain
a series of nucleic acids were in water, they easily self assemble so formed a polymer, can then act as a catalyst for protein synthesis and for DNA replication
LUCA
define
the last universal common ancestor before living organisms split into bacteria, archae and eukaryotes
evidence of shared ancestory (LUCA)
- universal genetic code
- same biomolecules and metabolic processes
- traked ~300 shared genes for anaerobic processes
where is LUCA thought to be?
- in a low O2 environment
- where there are other favorable conditions
Hydrothermal Vents (fossils have been found here)
index fossil
definition
a fossil that we know an approximate timing of and is widespread
relative dating
definition
the use of an index fossil to declare whether a found fossil is younger/older than it and thus its approximate age
absolute dating
definition
using carbon-14 (a radioactive isotope) with a known half life to measure it’s age
atypical cell
definition
a cell that lacks certain crutial organelles
fungal hyphae
example of atypical cell
loss of cell membrane between cells
results in long cells with many nuclei
phloem seive tube element
example of atypical cell
have lost all of their organelles and nucleus
transport sugar and sap in plants
rely on a companion cell with a nucleus and mitochondria to function
skeletal muscle cells
example of atypical cells
fibres are long and thin for muscle contraction
manyu nuclei per cell
internal and external mitochondria
red blood cells
example of atypical cells
no nucleus
biconcave shape to increase SA:V and have more surface haemaglobin to carry O2
Endosymbiotic theory
- early eukaryote engulfs a prokaryote
- the prokaryote functions inside the eukaryote
- more energy for the cell so better evolutionarily
- cell survives more over time
- these become mitochonria (same thing happens for chloroplasts)
evidence of endosymbiotic theory
mitochondria and chloroplasts have
- 70s ribosomes
- double membrane (one form host)
- own circular loop of DNA
- about the same size as a prokaryote
- self replicate seperate to cell
process of evolution of specialised cells
different genes are expressed from the genome
this effects the proteins made
cells have different structure
cells have different function
features common to all viruses
- envelope (host cell membrane)
- protein caspid
- protein spikes
- nucleic acid
what types of genetic material can viruses have?
double and single stranded DNA
double and single stranded RNA
Stages of the lytic cell cycle of viruses
- attachment
- DNA penetration
- DNA replication
- Transcription
- translation of viral parts
- assembly and lysis
lysogenic life cycle of viruses
- attachment
- DNA penetration
- integration to form a prophage
- mitosis/binary fission
- cell division
- trigger of entrance into lytic cycle (viral DNA leaves prophage)
- DNA replication
- transcription
- translation of viral parts
- assembly and lysis
virus first hypothesis
origin of viruses
- viruses existed before cells
- cells evolved form them
contry evidence - cells originated from primordial soup
regressive hypothesis
origin of viruses
viruses are cells that lost structures and functions and became parasidic
progressive hypothesis
origin of viruses
strand of nucleic acid escaped a cell, gained function and evolved into a virus
