A2.2 Cell Structure Flashcards
What are cells
the basic structural units of all living organisms
what are unicellular organisms, and examples
Organisms that are made of a single cell such as prokaryotes, protists and fungi
What are multicellular organisms
organisms that are made of many cells such as mammals and plants
what are the components of cell theory
all living things are composed of cells
cell is the basic unit of life
cells come from pre existing cells
can there be exceptions to cell theory
yes
What is 1 meter in terms of millimeters
1000 mm
what is a thousand micrometers
1 mm
what is a thousand nanometres
1 micrometer
what is the turret in microscopes
where the different lenses are rotated under the lenses
what is the stage in microscopes
where the slide is placed
what is the condenser in microscopes
focuses light on the object with an iris diaphragm
what is the fine focus in microscopes
used to focus high power lenses
what is the coarse focus in microscopes
used to focus low/medium power lenses
what is the eyepiece graticule
the scale that has arbitrary units ( alighned with stage micrometer to find true dimensions)
a material that is being magnified should be ____?
sufficiently transparent for light to pass through
what is magnification and its formula
the number of times large an object appears
size of image / size of specimen
what is resolution
the amount of detail that can be seen
how can resolution be improved
shorter wavelengths give better resolution
how do electron microscopes work
they replaced light with beams of electrons so that magnification and resolution are much better
Biological material must be dead
what is ultrastructure
the fine structure of cells
what is cryogenic electronic microscopy
a technique that involves flash freezing solutions and then exposing them to electrons
what is freeze fracturing
when biological material is instantly frozen solid in liquid nitrogen and the tissue is broken up in a vacuum
A replica then made of the exposed surface( freeze etching)
what is fluorescence microscopy
when dyes are used to bind specifically to target molecules, allowing their location to be revealed.
A fluorescence microscope is used to detect the stained cells.
what is the role of the cytoplasm
provides the medium in which many metabolic reactions of the cell occur ( need to be dissolved to perform their function)
what is the role of the nucleus
control and direct the activities of the cell, along with containing DNA
what is the role of the cell membrane
the barrier controlling entry and exit from the cytoplasm
what are the 4 structures common to all living cells
plasma membrane
cytoplasm
DNA
ribosomes
what are organelles
unit of the cells substructure that have a special function
what are features of prokaryotes
very small
have a single loop of DNA(nucleoid)
no membrane bound organelles inside
what structures are always found in prokaryotes
cell wall
cell membrane
cytoplasm
chromosome
food store
70s ribosomes
what structure are sometimes found in prokaryotes
pili
capsule
plasmid
flagellum
what is the role of pili
enables the cell to attach to surfaces
what is the role of flagellum
used for movement of the bacterium
what is the role of the capsule
helps the cell from dehydrating and adheres to other surfaces
difference between 70s ribosomes and 80s ribosomes
70s are smaller and found in bacteria
80s are larger and found in eukaryotic cells
where is DNA found in prokaryotes
found in nucleoids which is a loop of DNA
Can also be found in plasmids which is smaller and replicate independently
what organelles are present in eukaryotes
nucleus
mitochondria
ribsomes
ER
golgi apparatus
lysosomes
what features are present in eukaryotic cells but not considered as organelles
cytoskeleton
plasma membrane
what are features of the nucleus
largest organelle
surrounded by double layered membrane known as nuclear envelope which contains nuclear pores
contains chromosomes which may appear as chromatins
contains nucleoli which is the site where sub units of the ribosomes are formed
what are features of mitochondria
relatively large and present in large numbers
has a double membrane, inner membrane folds to form cristae
the matrix is the fluid inside that contains enzymes, ribosomes and DNA
what is the role of mitochondria
adapted for production of ATP by aerobic cellular respiration
what are ribosomes and their features
tiny structures with no membrane
can be free or bound to the ER
they are the site where proteins are made
difference between free and bound ribosomes
free synthesises proteins within the cell
bound synthesizes proteins that are secreted from the cell or become integral proteins
What is the Endoplasmic Reticulum
network of folded(flattened) membranous sacs that are interconnected
connected to the membrane of the nuclear envelope
What is the difference between bound SER and RER
RER has bound ribosomes and continuous with the nuclear envelope
SER is continuous with the RER and lacks ribosomes. Main function is synthesis of phospholipids and cholesterol
what is the golgi apparatus
modifies polypeptides into their functional state
sorts concentrates and packs proteins into vesicles
what is the structure of the golgi apparatus
stack like collection of flattened membranous sacs
one side is formed by fusion of membranes of vesicles, other side is formed by vesicles swellings which get pinched off
what is the role of lysosomes
contains enzymes which digest large molecules when they are old or damaged
can be used for immunity by digested pathogens
breakdown of foreign matter
involved in ‘programmed cell death’ and self digestion
what are features of the lysosomes
tiny spherical vesicles bound by a single membrane
contains concentrated mixture of digestive enzymes
what is the cytoskeleton
a network of fibers extending throughout the cytoplasm
organizes the structures and activities of the cell
what are the three main types of fiber in the cytoskeleton
microtubules
microfilaments
intermediate filaments
what are microtubules
the thickest class of fibres
straight,unbranched,hollow,cylindrical
made of the protein tubulin
used to move chromosomes during cell division
organelles moved with motor proteins along microtubules
support and maintain shape of the cell
what are microfilaments (actin filaments)
thinnest fiber
made of solid rods of actin
each filament is a twisted double chain of actin molecules, designed to resist tension
used to divide the cell during cell division, and maintain and change cell shape
what are the different function of life
homeostasis
metabolism
nutrition
movement
excretion
growth
sensitivity
reproduction
what is homeostasis
maintenance of a constant, stable environment
what is metabolism
the network of interdependent and interacting chemical reactions occurring in living organisms
what is nutrition
process by which organisms take in, and make use of food
what is movement
moving from one place to another
what is excretion
metabolic waste is eliminated from an organism
what is growth
increase in size,mass or number of cells
what is sensitivity
recognise an respond to changes in environmental conditions
what is reproduction
formation of new individuals by sexual or asexual means
what feature do plant cells have that other eukaryotic cells do not
plastids such as chloroplasts and amyloplasts
what features do plant and fungi have that animal cells dont
cell wall
made of cellulose in plants
made of chitin in fungi
what features do animal cells have that plant and fungi dont
animal cells have centrioles
two centrioles create a centrosome which grow spindle fibers before an animal cell replicates
They also have cilia and flagella for movement
difference between cilia and flagella
cilia made of microtubules, shorter and more numerous
flagella less numerous and long
what are hyphae
fungi form threadlike structures with no walls between the cells, resulting in multiple nuclei not divided into separate cells
what are a collection of hyphae known as
mycelium
How are skeletal muscle fibers an example of atypical cell structure
fusion of multiple cells which results in a single large cell that has multiple nuclei
How are RBC’s atypical
they discard their nucleus and mitochondria, increasing surface area and making them smaller
How are sieve tubes an example of atypical cell structure
sieve plates are connected to companion cells known as plasmodesmata which help service and maintain them, meaning sieve plates have no nucleus or organelles
what is a micrograph
a photograph taken through a microscope to show a magnified image of an item
What is endosymbiotic theory
suggests some organelles in eukaryotic cells were once free living prokaryotes which became incorporated into a host cell
both parts would have then become integrated through natural selection leading to an endosymbiotic relationship
what organelles are believed to have originated from endosymbiotic theory
mitochondria and chloroplasts
what is the evidence for the endosymbiotic theory
chloroplast and mitochondria reproduce like prokaryotes
they contain circular DNA, like prokaryotes
contain 70s ribosomes
transcribe mRNA from their DNA, like prokaryotes
similar in size to prokaryotes
they have double membrane, which suggests they were engulfed by endocytosis
what is a tissue
a group of similar cells that are specialised to perform a particular function
what is an organ
a collection of different tissues which perform a specialised and coordinated function
how do cells differentiate when they all have the same genes
different sets of genes are expressed according to history and signals received from the environment
what controls how cells specialize
controlled by the immediate environment of the differentiating cell and the cells position in the developing organism
what is a proteome
the totality of proteins expressed within a cell, tissue or organism at a certain time.
Means its unique to each individual
what does the genome do
instructs the expression of proteins
what is the result of specialisation of cells
due to division of labour, increased efficiency is acheived
However, specialised cells are now completely dependent on the acitvities of other cells
due to the amount of species that are multicellular, what does it suggest
it is relatively easy to evolve with few barriers
what are the advantages of multicellularity
larger body sizes and cell specialisation
what could have led to multicellularity
strong selective pressures favoring it ( clusters of cells were less likely to be predated) , few genetic changes necessary or a combination of the two
