a2.2- cell structure Flashcards
disadvantages of electron microscopy
- specimen needs to die
advantages of electron microscopy [2]
- higher range of magnification (can detect smaller structures)
- higher resolution
why electron microscopy have higher resolution
shorter wavelength
freeze fracture
cut in half → spray metal
- see inside of membrane
cryogenic electron microscopy
see proteins with atomic precision- can design drugs that fit into them
florescent stains
bright colours- see it clearer
immunofluorescence
tag antibodies
structures common to calls in all living organisms [2]
- dna as genetic material
- cytoplasm enclosed by plasma membrane composed of lipids
use of plasma membrane
separating interior form its surrounding
functions of cytoskeleton [3]
- maintain cell shape
- organises cell parts
- enables cells to move and divide
components of cytoskeleton
- microtubules (movement)
- actin filaments (movement)
- intermediate filaments (structural)
process of life in unicellular organisms
metabolism
reproduction
homeostasis
growth
response to stimuli
excretion
nutrition
difference between eukaryotes (animals, plant and fungi)
see table
endosymbiotic theory
- explains the existence of several organelles of eukaryotes
- originated as symbioses between separate single-celled organisms
- eukaryotic organisms engulfed by a prokaryotic cell, was not digested
- remained inside host cell, carrying out aerobic respiration and providing energy to their host cells, evolving into mitochondria.
what does evidence suggest about eukaryotes
- all eukaryotes evolved form common ancestor that had a nucleus and reproduced sexually
evidence of endosymbiotic theory [4]
MAD DRS
Membranes
- double membrane
- inner membrane has proteins similar to prokaryotes
Antibiotics
- susceptible to antibiotics (chloramphenicol)
- organelles may have bacterial origins
Division
- reproduction occurs via a fission-like process
- only through division of pre-existing mitochondria and chloroplasts
DNA
- own DNA: naked and circular
- like prokaryotic DNA structure
- transcribe their DNA
- use the mRNA to synthesise some of their own proteins
Ribosomes
- 70S
- similar to prokaryotes
Size
- similar size to bacteria
cell differentiation
- development of a cell to carry out specific function
- different patterns of gene expression: often triggered by changes in the environment
advantages to multicellularity
- larger body size
- cell specialisation
polymer that forms part of cytoskeleton
tubulin
doesnt conform to the idea of standard notions of a cell [5]
- striated muscle fibres
- aseptate fungal hyphae
- red blood cell
- phloem sieve tube
- giant algae
striated muscle fibres
multiple nuclei surrounded by a single, continuous plasma membrane
challenges: cells always function as autonomous units
asephate fungal hyphae
each aseptate hyphae is an uninterrupted tube-like structure with many nuclei spread along it
red blood cell
no nucleus
phloem sieve tube element
- considered living cels without a nucleus
nucleus of companion cells - controls their functional activities
giant algae
may grow to very large sizes
challenges- larger organisms are always made of many microscopic cells
why growing cells tend to divide and remain small
maintain high sa : vol ratio
- fast exchange of nutrients
emergent properties
- a property in which a collection or complex system had but the individual members do not have
- interaction between parts produce more complex function than individually work together
eg. grped cells → tissues, grped tissues → organs
protista
- eukaryote
- uni/multi cellular
- no specialised tissue
fungi
- cell wall made of chitin
- obtain nutrition via heterotrophic absorption
plantae
- call wall made of cellulose
- obtain nutrients autotrophically
animalia
- no cell wall
- nutrition via heterotrophic ingestion
factors that determine how a cell develops [4]
- position
- hormones
- cell to cell signals
- chemicals
why is cell division necessary [5]
- more cells needed for growth
- replacement
- cells specialise
- cells have to divide when 5. they reach a certain size
SA:vol ratio + nutrients cant be absorbed quickly enough
nucleosome
DNA molecule wrapped around a core of eight histone proteins held together by an additional histone protein attached to linker DNA
evidence that living organisms are composed of cells
- living organisms are multicellular
- organelles are specialised and contribute to the functions for the whole cell
- cells multiply through cellular division
resolution definition
ability to differentiate two objects in a microscope, distinguishing the details of the specimen
ultrastructure definition
structure of the cell as observed under the electron microscope
formation of the nucleus
nucleoid region enclosed in the internal membrane- becomes the nucleus
development of mitochondria
- aerobic proteobacterium enters a larger anaerobic prokaryote (as prey or parasite)
- survives digestion- becomes valuable endosymbiont
- aerobic proteobacterium provides rich source of ATP to its host- enables it to out-compete the other anaerobic prokaryotes
- host cell grows and divides so does the aerobic proteobacterium
- subsequent generations- contain aerobic proteobacterium
- aerobic proteobacterium
evolves and is assimilated to become a mitochondrion
advantages of cell differentiation [2]
- helps the body to carry out very specific functions efficiently
- helps the organisms acquire specialisation for survival
in which type of cells is the entire genome active
embryotic cell
how newly formed cells become specialised
transcription regulators
- some genes turned on or off
- depends on the specialisation and location of cell during embryotic stage
organelles both prokaryotes and eukaryotes have [4]
- cell membrane
- cytoplasm
- ribosomes
- genetic material
