cell structure Flashcards
what are all cells surrounded by?
A cell surface membrane which controls which controls the exchange of materials between the internal cell environment and the external environment
- partially permeable
formed from a phospholipid bilayer (diameter of around 10nm)
where are cell walls formed?
outside of the cell membrane and offer structural support to the cell
structural supporter is provided by the polysaccharide cellulose in plant
peptidoglycan in most bacterial cells
what are narrow thread (surrounded by a cell membrane) which connect the cytoplasm of neighbouring plant cells?
plasmodesmata
what does the nucleus cell contain?
chromatin
a complex of DNA and histone proteins
which is the genetic material of the cell
what is the nucleus separated from the cytoplasm by ?
a double membrane ( the nuclear envelope) which has many pores
why are nuclear pores important?
They are important channels for allowing mRNA and ribosomes to travel out of the nucleus, as well as allowing enzymes
(e.g. DNA polymerases) and signalling molecules to revel in
what is chromatin?
the material from which chromosomes are made
chromosomes are made of sections of linear DNA tightly wound around proteins called histones
what is the nucleolus?
the site of ribosome production
what are mitochondria the site of?
the site of aerobic respiration
what is mitochondria’s structure?
surrounded by double-membrane with the inner membrane folded to form cristae
the matrix formed by the cristae contains enzymes needed for aerobic respiration, producing ATP
what is found in the matrix of the mitochondria?
small circular pieces of DNA (mitochondrial DNA)
ribosomes (needed for replication)
what’s a structure that is larger than mitochondria and also surrounded by a double membrane?
chloroplast
what structures are found in chloroplasts ?
membrane bound compartments called thylakoids contains chlorophyll stack to form structures called grana
where is chlorophyll stored?
in thylakoids
what are grana joined together by?
lamellae - thin and flat thylakoid membranes
what are chloroplast the site of?
photosynthesis
- the light dependent stage takes place in thylakoids
- the light independent stage (calvin cycle) takes place in the stroma
what are chloroplast the site of?
photosynthesis
- the light dependent stage takes place in thylakoids
- the light independent stage (calvin cycle) takes place in the stroma
chloroplast components:
granum
lamella
thylakoid
ribosome
stroma
drop of lipids
chloroplast DNA
starch granule
where are ribosomes found?
freely in the cytoplasm of all cells
or
as part of the rough endoplasmic reticulum
where are ribosomes formed?
in the nucleolus
composed of equal amounts of ribosomal RNA (rRNA) and proteins
where are 80S ribosomes found?
in eukaryotic cells
(composed of 60S and 40S subunits)
where are 70S ribosomes found?
prokaryotes
mitochondria
chloroplasts
(composed of 50S and 30S subunits)
what are ribosomes the site of?
site of translation
protein synthesis
What is on the surface of the Rough Endoplasmic Reticulum ?
surface is covered in ribosomes
what is the Rough Endoplasmic Reticulum formed from?
formed from continuous folds of membrane continuous with the nuclear envelope
what does the rough endoplasmic reticulum do?
processes proteins made by the ribosomes
what is the smooth endoplasmic reticulum involved in?
involved in production, processing and storage of lipids, carbohydrate and steroids
what is the structure of the golgi apparatus?
flattened sacs of membrane
what does the golgi apparatus do?
modified proteins and lipids before packaging them into golgi vesicles
the vesicles then transport the proteins and lipids to their required destination
proteins that go through the golgi apparatus are usually exported, put into lysosomes or delivered to membrane bound organelles
what is the large permanent vacuole?
it is a sac in plant cells surrounded by the tonoplast, selectively permeable
allows the cell to remain rigid
what are vesicles?
membrane bound sac for transport and storage
what are lysosomes?
specialist forms of vesicles which contain hydrolysis enzymes
what are centrioles?
hollow fibres made of microtubules,
two centrioles at right angles to each other form a centrosome ,
which organises the spindle fibres during cellular division
what are microtubules?
make up cytoskeleton of the cell about 25nm in diameter
made of alpha and beta tubulin combined to form dimers
the diners are then joined by protofilaments
the cytoskeleton is used to provide support and movement of the cell
how many protofilaments in a cylinder make up a microtubule?
13
what is cytoplasm made up of?
made up of organelles suspended in the gel like cytosol
70% of the cytoplasm is made up of water
contains proteins, sugars, ions and fatty acids
