2.1.1 cell structure Flashcards
prokaryotic cells
- no true nucleus (free loop of DNA)
- very few organelles
- exist as single cells.
- bacteria
eukaryotic cells
- true nucleus
- lots of organelles
- exist as single cells but usually form multi-cellular organisms
examples of eukaryotes
animal, plant, fungi
describe organelles
- membrane bound compartments
- provide the conditions for different cellular reactions to
take place
what do all the organelles together make up?
the ultrastructure (part which can only be seen by an electron microscope)
cilia on surface of cell
- “beat” in a co-ordinated way to move substances over the surface of the cell
example of a cell with cilia on its surface
ciliated epithelium -
found on the cells lining the airways - sweep mucus up and away from the
lungs to the back of the throat
microvilli on surface of cell
- folds in the cell surface membranes of cells which carry out a lot of secretion or absorption
- increase the surface area of the cell
examples of microvilli
the cells lining the intestines increase the SA for the absorption of digested food into the bloodstream
flagellum on surface of cell
- these stick out as long projections from the cell, and have membrane around them
- allow the whole cell to move
all organelles in a eukaryotic cells
- nucleus
- nuclelous
- chromatin
- Golgi apparatus
- Golgi vesicle
- RER
- SER
- ribosomes
- centrosome
- vacuole
- secretory vesicle
- mitochondria
- cytoskeleton
- intermediate filament
all structures in a plant cell
- cell wall
- nucleus
- nucleolus
- RER
- SER
- mitochondria
- ribosomes
- chloroplasts
- Golgi apparatus
- LARGE & PERMANENT vacuole
-plasmodesmata
-nuclear envelope
-nuclear pores
similarities and differences in eukaryotic and prokaryotic cells
prokaryotes
- no nucleus
- circular DNA
- proteins fold and condense DNA
- extra plasmids
- no membrane bounds organelles
- peptidoglycan cell walls
- smaller 70s ribosomes
- cytoskeleton
- binary fission
- unicellular
- cell surface membrane
eukaryotes
- nucleus
- linear DNA
- DNA wrapped around histones
- extra DNA present in chloroplasts and mitochondria
- membrane bound organelles
- chitin in fungi, cellulose in plants
- larger 80s ribosomes
- more complex cytoskeleton
- asexual or sexual reproduction
- uni or multi cellular
- cell surface membrane
what is the membrane around the LARGE and PERMANENT vacuole called?
tonoplast
structures in plant cell that aren’t in animal
- chloroplasts- site of photosynthesis
- large permanent vacuole
- plasmodesmata
- cellulose cell wall
describe large and permanent vacuole
- contains sap (various storage molecules + water).
- a membrane around it called the tonoplast
-involved in maintaining turgor in plant cells
describe the plasmodesmata
cytoplasmic connections between neighbouring plant cells,
allowing substances to move from cell to cell
describe cellulose cell wall
gives “tensile strength”
- supports the plant cell & prevents bursting when water enters the cell.
describe plasma membrane
- found around animal cell surface
- found inside plant cell
- made of lipids + proteins
function of plasma membrane
- regulates movement of substances into and out of cell
- receptor molecules on it, which allow it to respond to chemicals
describe the nucleus
- surrounded by nuclear envelope (double membrane)
- contains nuclear pores
- contains chromatin
- contains nucleolus
function of the nucleus
- contains the genetic material
- contains instructions on how to make proteins
- pores allow RNA to leave nucleus
- nucleolus makes ribosomes
describe ribosomes
- free floating in cytoplasm or attached to rough endoplasmic reticulum
- made of proteins and RNA
- no membrane
function of ribosomes
site of protein synthesis
describe RER
- system of membranes enclosing a fluid filled space
- surfaced covered with ribosomes
function of RER
- folds and processes proteins that have been made at the ribosomes
- involved in transport of proteins
describe SER
- system of membranes enclosing a fluid filled space
- no ribosomes
function of SER
synthesises and processes lipids and carbohydrates
describe vesicle
small fluid filled sac in cytoplasm, membrane bound
function of vesicle
- transports substances in and out of cell via plasma membrane and between cells
- some formed by Golgi apparatus
- some formed by endoplasmic reticulum
- some formed at cell surface
describe lysosome
- membrane bound
- no clear internal structure
- contains digestive enzymes
function of lysosome
- contains digestive enzymes
- can be used to digest invading cells
- breaks down worn down components
describe Golgi apparatus
- fluid filled flattened sacs
- formed of cisternae
function of Golgi apparatus
it produces and packages lipids and proteins into vesicles and modifies them. can be secretory vesicles or lysosomes.
describe mitochondria
- double membrane
- inner membrane is folded to form cristae
- inside is the fluid matrix
- contain (mt)DNA
- produce their own enzymes
- reproduce themselves
function of mitochondria
- site of aerobic respiration , where ATP is produced
- found in large number in active cells that need the energy
describe chloroplast
- small flattened structure
- double membrane
- contains grana which are attached by membranes called thylakoids
- grana are linked together by llamelae
- fluid is called stroma
function of chloroplasts
- site of photosynthesis
- some parts take place in grana
- other parts in stroma
describe centriole
small, hollow cylinders made of microtubules
function of centrioles
separates chromosomes in cell divison by producing spindle fibres
describe cilia
- small hair like structures
- outer membrane and ring of 9 pairs of microtubules inside
- with a single pair of microtubules in the middle
describe flagellum
- longer than cilia
- 2 microtubules in the centre, with 9 pairs of microtubules surrounding them inside.
describe cytoskeleton
network of protein fibres/ threads
describe microfilaments
-made from protein ACTIN
- each filament is about 7nm diameter
- gives support & mechanical strength to cell to help it keep its shape
- allows whole cells to move
- allows a cell to split into 2 daughter cells at the end of mitosis
describe microtubules
- made of protein sub-units called TUBULIN
- each microtubule is about 18-30nm
diameter - provide shape and support
- move organelles through cytoplasm from one part of the cell to another-
form a “track” for organelles and vesicles to move along - make up the spindle needed for chromosome movement during
mitosis/meiosis - make up cilia, flagella & centrioles
describe intermediate fibres
- made up of lots of proteins
- 10nm in diameter
- anchor the nucleus within the cytoplasm
- extend in between cells, helping to anchor cells in place together on a
“basement membrane” – stabilising the structure of tissues
