2.1.1 cell structure Flashcards
what is the function of the plasma membrane
controls what enters and leaves the cells and has receptors for cell signalling and responding to chemicals.
what is the cell wall
a rigid structure which surrounds plant cells. plant cell walls are made of cellulose.
what is the function of a cell wall
supports the cell
what is the nucleus
a large organelle surrounded by a nuclear envelope which has pores. it contains all the DNA . it contains a nucleolus.
what is the function of a lysosome
it contains digestive enzymes to digest invading cells and break down worn-out components. these enzymes are separated from cytoplasm via a membrane
what is a ribosome
a small organelle that floats freely or is attached to rough endoplasmic reticulum. made of proteins and RNA.
what is the function of a ribosome
the site where proteins are made
what is the rough endoplasmic reticulum
a system of membranes enclosing a fluid filled space. it is covered in ribosomes
what is the function of the rough endoplasmic reticulum
it folds and processes proteins made at the ribosomes
what is the smooth endoplasmic reticulum
a system of membranes enclosing a fluid filled space.
what is the function of the smooth endoplasmic reticulum
synthesises and processes lipids
what is a vesicle
a fluid filled sac in the cytoplasm that is surrounded by a membrane
what is the function of a vesicle
transports substances in and out of the cell via the plasma membrane or between organelles.
what is the Golgi apparatus
a group of fluid filled flattened sacs, vesicles are often found at the edges
what is the function of the Golgi apparatus
packages and processes new lipids and proteins and makes lysosomes
what is the function of mitochondria
the site of aerobic respiration where ATP is produced
what is mitochondria
they are oval shaped and have a double membrane. the inner membrane is folded to create cristae. the inside is called the matrix which contains enzymes used in respiration
what is a chloroplast
a small flattened structure found in plants. it is surrounded by a double membrane and has thylakoid membranes inside which are stacked up to form grana which are linked together by lamellae.
what is the function of a chloroplast
the site where photosynthesis takes place.
what is a centriole
small hollow cylinders made of microtubules found in animal cells
what is the function of a centriole
involved in the separation of chromosomes in cell division
what is cilia
small hair like structures found on the cell membrane of some animal cells. they have an outer membrane and a ring of 9 pairs of microtubules with 2 microtubules in the middle.
what is the function of cilia
the microtubules allow them to move so they can move substances along the cell surface.
what is the function of flagella
microtubules contract to move the flagellum. this propels the cell forward
what is flagella
have 9 pairs of microtubules around the edge and 2 in the middle. are longer than cilia
how are organelles involved in protein production
- ribosomes synthesise proteins
- proteins produces at ribosomes on the RER are processed and folded by the RER
- they are transported to the Golgi apparatus
- the Golgi apparatus processes and packages the proteins into vesicles to be transported round the cell.
what is the cytoskeleton
a network of protein threads in the cytoplasm. in eukaryotic cells they are microfilaments and microtubules
what are the functions of the cytoskeleton.
- support organelles and keep them in place
- strengthen cell to maintain shape
- movement of materials inside cells
- movement of cell itself
why is the cytoskeleton said to be dynamic
it changes in response to the environment to carry out its functions
what is the difference in size between Eukaryotic and prokaryotic cells
eukaryotic cells are larger (10-100 micrometres). prokaryotic cells are less the 2 micrometres
how is DNA different in eukaryotic and prokaryotic cells.
eukaryotic cells have linear DNA enclosed in a nucleus and prokaryotic cells have circular DNA called plasmids which are free in the cytoplasm
how is the cell wall different in eukaryotic and prokaryotic cells
it is made of chitin (fungi) or cellulose (plants) in eukaryotic cells. in prokaryotic cells it is a different polysaccharide.
which type of cell does not contain membrane bound organelles
prokaryotic cells
how is the arrangement of the flagella different in eukaryotic and prokaryotic cells
in eukaryotic cells it is in the 9+2 arrangement of microtubules and in prokaryotic cells it is arranged as a helix
which type of cell has larger ribosomes
eukaryotic cells (80s rather than 70s)
define magnification
how much bigger the image is than the actual specimen
define resolution
how well it can distinguish between two objects close together
what is the equation for magnification
magnification = image size/object size
what is the resolution and magnification of a light microscope
resolution: 0.2 micrometres
magnification: x1500
how does a laser scanning confocal microscope work
- laser beams scan the specimen which is tagged by a fluorescent dye. the laser causes the dye to give off light.
- the light is focused through a pinhole to a detector hooked up to a computer that generates an image (3D)
- they produce a clearer image than a normal light microscope as out of focus light is blocked
why do we use a laser scanning confocal microscope
it can be used to look at objects at different depths in thick specimens
what are the two types of electron microscope
scanning and transmission
how does a scanning electron microscope work
a beam of electrons is scanned across the surface of the specimen. this knocks electrons off the specimen which are collected in a cathode ray tube to form an image, the images produced are 3D
what is the resolution and magnification of a scanning electron microscope
resolution: 0.002 micrometres
magnification: less than x 500 000
how does a transmission electron microscope work
a focused beam of electrons is passed through the specimen. denser parts of the specimen absorb more electrons making them look darker in the image. specimen must me thin and image is 2D
what is the resolution and magnification of a transmission electron microscope
resolution: 0.0002 micrometres
magnification: can be more than x1 000 000
why do we stain specimen
increases the contrast and allows transparent components to be picked up in the image
how do we stain for light microscopes
we use a dye. different parts of the specimen absorb different amounts of dye so it increases contrast. we can use different dyes at the same time.
how do we stain for electron microscopes
specimen dipped in heavy metal like lead, metal ions spread the electrons increasing contrast.
how do we prepare a microscope slide
- take thin slice of specimen
- use tweezers to place on the slide
- on a wet mount we add a drop of water on the slide before placing specimen.
- gently add the cover slip at a tilt to prevent air bubbles.
how do we use a microscope
- clip slide in place
- select lowest powered objective lens
- use coarse adjustment knob to bring the stage up until image is roughly in focus
- use fine adjustment knob to get a clear image
- increase magnification by moving up an objective lens and refocusing.
how do we calibrate an eyepiece graticule
Line up the zero of the eyepiece graticule and the zero of the stage micrometer.
Make sure the scales are parallel.
Look at the scales and see where they are in line again.
see how many micrometres each division of the eyepiece graticule is. we use magnification x number of divisions of stage micrometer.
