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 cells in all living organisms [2]
- dna as genetic material
- cytoplasm enclosed by plasma membrane composed of lipids
use of plasma membrane
separating interior from 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 [6]
- cell wall
animals- none
plants- cellulose
fungi- chitin - vacuole
animals- many small
plant and fungi- large (central in plant) - chloroplasts only present in plants
- centrioles only present in animals
- cilia only present in animals and plants
- flagella only present in animals and plants
endosymbiotic theory
- Eukaryotic cells are believed to have evolved from early prokaryotes that were engulfed by phagocytosis
- originated as symbioses between separate single-celled organisms
- eukaryotic organisms engulfed by a prokaryotic cell, was not digested because of symbiotic relationship
- 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 from common ancestor that had a nucleus and reproduced sexually
evidence of endosymbiotic theory [5]
- double membrane
- inner membrane has proteins similar to prokaryotes
- organelles may have bacterial origins - able to replicate
- reproduction occurs via a fission-like process
- only through division of pre-existing mitochondria and chloroplasts - naked and circular DNA
- Ribosomes
- 70S
- similar to prokaryotes - Size
- similar size to prokaryotes
cell differentiation + caused by
- 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
aseptate 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 and how it obtains nutrients
- cell wall made of chitin
- obtain nutrition via heterotrophic absorption
plantae: cell wall and how it obtains nutrients
- call wall made of cellulose
- obtain nutrients autotrophically
animalia: cell wall and how they obtain nutrients
- 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 [4]
- more cells needed for growth
- replacement
- cells specialise
- cells have to divide when 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
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
