Cells Flashcards
what feature do only plant cells have
- plastids
- vacuole
- cell wall
what are plastids
the remains of a cyanobacterium engulfed through endosymbiosis
how are plastids inherited in cells
from a single parent
what is special about plastids
they have their own dna
it is circular
they are semi-autonomous so they can synthesize some proteins
what are the types of plastids
plastids containing chloroplasts
chromoplasts
leucoplasts
what is the chloroplast
the site of photosynthesis
what are the pigments in the chloroplasts
chlorophyll
carotenoids
what are thylakoids
membrane bound compartment inside the chloroplast
pigments are embedded in its membrane
what are grana
stacks of thylakoids
the site of light reactions of photosynthesis
what is the stroma
the aqueous liquid inside the chloroplast
what is cytoplasmic streaming
chloroplasts move through the cytoplasm and orient themselves to maximize or minimize light exposure
what are actin filaments
filaments that connect chloroplasts and other organelles
what is the role of myosin molecules
to pull the chloroplasts along the actin filaments
what induces cytoplasmic streaming
temperature
light
pH
what are chromoplasts
pigmented plastids that dont contain chlorophyll
what pigment is found in chromoplasts
carotenoid
what is the role of chromoplasts
attract pollinators or animals that help seed dispersal
absorb excess energy from chloroplasts during photosynthesis
what are leucoplasts
plastids with no pigments or internal membranes
what is the role of leucoplasts
storage
What are all plastids derived from
proplastids
what is special about plastid differentiation
it is not permanent
plastids can change between types
what is a vacuole
fluid filled organelle surrounded by a single membrane
what is the name of the vacuoles membrane
tonoplast
what is the largest component in the plant cell
the vacuole
what is special about the vacuole
it presses the rest of the cytoplasm into a layer along the cell wall
what is the role of the vacuole in the plant
store a wide range of compounds and functions
what are the general functions of the vacuole
- ion, sugar or water storage
- increase cell size/structure
- sequestration of toxins
- recycling organelles
- pigments
how does the vacuole increase the cell size/structure
through turgor and hydrostatic pressure
what are the types of ions stored in the vacuole
Ca2+
Na+
Cl-
K+
can vacuoles synthesize compounds
no
how do vacuoles acquire compounds
they are moved across the tonoplast membrane to the cell sap by a variety of pumps, transporters and channels
what is turgor pressure
the force of the vacuole on the inside of the cell
what is the role of turgor pressure
to maintain cell rigidity along the cell wall
what is hypertonic
when water leaves the cell
what is isotonic
a cell with normal amount of water
what is hypertonic
when there is too much water in the cell
what causes water to flow in and out of the cell
osmosis
why are toxic compounds stored in the vacuole
to separate them from parts of the plant it would harm
how are toxins absorbed in the plant
through the roots
how are most heavy metals and salts stored in the plant
in the roots
how can toxin storage be a plant defence
when vacuole is broken by being eaten, it releases its toxins
what is autophagy
the disposal and recycling of worn out organelles
what are the functions of the cell wall
- cell shape
- constrains expansion of protoplasts
- permits creation of turgor pressure
- defends against fungus and bacteria
what is the cell wall composed of
- primary wall
- secondary wall
- middle lamella
what is the primary wall composed of
cellulose
hemicellulose
pectins
what does the primary wall sometimes contain
lignin
suberin
cutin
what is cellulose
a linear chain of hundreds/thousands of linked glucose units
what is the most abundant macromolecule on earth
cellulose
does cellulose have very high energy
yes
what is hemicellulose
a random amorphous structure
hydrogen bonded to cellulose microfibrils
what is the role of hemicellulose
limit extensibility of the cell wall tethering adjacent microfibrils to each other
regulate cell expansion
what are pectins
highly hydrophilic polysaccharides
where are pectins found
in primary cell wall and in the middle lamella
what is the role of pectins
pliability of the cell
what is the role of the middle lamella
joins adjacent cells
what is the middle lamella mainly composed of
pectins
what bisects the middle lamella
plasmodesmata
what is plasmodesmata
passages across the cell wall that lets cytoplasm from adjacent cells connect
what is the role of plasmodesmata
to allow material to pass from cell to cell
when do we find a secondary cell wall
in cells with strengthening function or role in water support
what is in the secondary cell wall
cellulose
what are the layers of the secondary cell wall
S1 : outer
S2: middle
S3: inner
