Eukaryotic and prokaryotic cell structure and function Flashcards
What is the cell theory ?
cells are the fundamental unit of structure, function and organisation in all living organisms
what is differentiation ?
the development process by which the structure of the cells of a multicellular organism specialise for a specific function
what is a tissue ?
a group of cells that have a common origin and a similar structure that work together to form a single function
what is an organ ?
a structure that has a specific function
what is a system ?
a group of organs and tissues that perform a particular function
nucleoid
the circular DNA molecule found in prokaryotic cells
plasmid
circular DNA molecules in their cytoplasm
- usually contain a few genes including : genes conferring resistance to specific antibiotics
What are 70s Ribosomes ?
these ribosomes are involved in protein synthesis but they are smaller than 80s ribosomes found in eukaryotic cells
Cell wall
prevents cells bursting when in dilute solutions - made of peptidoglycan
Pili and flagella
pili - help prokaryotic cells to attach to surfaces or each other
flagella - help the cells to move about
what do bacterial cell walls contain ?
polymers of amino acids and sugars called peptidoglycan
Gram positive bacteria have ..
thick walls made almost entirely of peptidoglycan
what colour does the gram positive bacteria wall become ?
purple when stained by crystal violet
Gram negative bacteria have ..
thin walls of peptidoglycan with an additional outer membrane
why does the gram negative bacteria wall not become purple ?
the high lipid content of this outer membrane prevents the crystal violet stain getting to the cell wall
The effects of antibiotics on these two types of bacteria ?
Gram negative bacteria - the outer membrane is relatively impermeable to antibiotics SO is resistant to many types of antibiotic, including penicillin
Gram positive bacteria - susceptible to penicillin
Structure and function of nucleus
- surrounded by a double nuclear membrane that contains many pores
what is the function of nuclear pores ?
Function: allow movement of molecules between the cytoplasm and the nucleus
what is the function of the nuclear envelope ?
Function: controls what enters and exists nucleus
what is the function of the nucleolus ?
Function: site in the nucleus where the rRNA is created according to instructions in DNA
what is the structure and function of chromatin ?
Structure: Chromatin( between nucleolus and nuclear envelope )
Function: makes up eukaryotic chromosomes
Structure and function of 80s ribosomes
Structure: larger than 70s ribosomes
Function: synthesis protein
Structure and function of rough endoplasmic reticulum
Structure: ribosomes attached to its outer surface
Function:
- develops the tertiary and quaternary shapes of proteins
- packages to vesicles, transports to the Golgi apparatus
Structure and function of smooth endoplasmic reticulum
Structure: no ribosomes are attached to it
Function: synthesis lipids, phospholipids and steroids
what is the function of the smooth endoplasmic reticulum in the cytoplasm of voluntary muscle fibres ?
site of storage of calcium ions - contraction of muscle fibres
Structure and function of cell membrane
- double membrane surrounding organelle
- controls entry and exit of material
Structure: Cristae
Function: extensions of inner membrane - providing a large surface area for the attachment of enzymes and other proteins during respiration
Structure: Matrix
Function: interior of the mitochondria
- contains an aqueous solution of metabolites and enzymes
- site of aerobic respiration producing ATP for energy
Structure and function of centrioles
Structure: microtubules
Function: forms a network of unbranched, hollow cylinders
- involved in moving organelles around in the cytoplasm - form centrioles
Structure and function of lysosomes
Structure: small spherical vesicles bound by single membrane
- contain a concentrated mixture of hydrolytic enzymes
Function: breakdown of imported food vacuoles, old organelles and harmful bacteria
Structure and function of Golgi apparatus
Structure: consists of flattened membranous sacs
Function: modifying and packaging polymers for secretion or for use within the cell
Structure and function of Cell wall
Structure: made of polysaccharide - cellulose
Function: prevents the cell changing shape and bursting (lysis)
Structure and function of chloroplasts
-biconvex in shape
- double membrane
- site of photosynthesis
Structure: Thylakoids
Function: system of branching membranes
Structure: Grana
- thylakoids arranged in flattened circular piles
Function: where chlorophylls and other pigments involved light capture are located
Structure: Stroma
Function: containing enzymes and small starch grains
Structure and function of vacuole
Structure: contains cell sap - weak solution of sugars and salts
Function: maintains pressure in the cell - stop wilting
Structure and function of tonoplast
Structure: membrane of the vacuole
Function: barrier between the fluid contents of the vacuole
How do prokaryotic cells differ from eukaryotic cells ?
Prokaryotic cells:
- no membrane bound organelles
- no nucleus containing free-floating DNA
- DNA is circular and is not associated with proteins
- made of murein and peptidoglycan
Eukaryotic cells:
- membrane bound organelles
- nucleus
- DNA is linear and is associated with proteins
- made of cellulose and 70s ribosomes
what is magnification ?
the extent to which an object has been enlarged by a microscope
formula of magnification
size of image / size of specimen
what is resolution ?
the ability to distinguish between points that are very close together
what is the importance of staining specimens ?
provides contrast to distinguish between different structures in the sample
what is a light microscope ?
A light microscope is a type of microscope that uses light to magnify the image of a specimen. It works by passing light through a specimen and focusing the light on an eyepiece or camera, which magnifies the image.
advantages of light microscope
- Inexpensive to buy and operate.
- Relatively small
- Both living and dead specimens can be viewed
disadvantages of light microscope
- Maximum magnification of 1500x
- Specimen may be disfigured during preparation to be viewed under the microscope
- The resolving power is 1 nm for biological specimens
what is an electron microscope ?
The electron microscope uses a beam of electrons and their wave-like characteristics to magnify an object’s image, unlike the optical microscope that uses visible light to magnify images.
advantages of electron microscope
- has a large depth of field, which allows more of a specimen to be in focus at one time.
- much higher resolution, so closely spaced specimens can be magnified at much higher levels.
disadvantages of electron microscope
- expensive
- large
- must be housed in an area free of any possible electric, magnetic or vibration interference
what is the structure of gram positive bacteria ?
thick layer of peptidoglycan
no outer membrane
what is the structure of gram negative bacteria ?
thin layer of peptidoglycan
outer membrane contains lipopolysaccharides
what does the function of outer membrane in gram negative bacteria ?
provides additional protection and barrier against certain antibiotics
what happens to gram positive bacteria when stained ?
The thick peptidoglycan layer retains the crystal violet stain. The bacteria appear purple under the microscope.
what happens to gram negative bacteria when stained ?
The thin peptidoglycan layer does not retain the crystal violet stain after the decolorization step. The bacteria lose the crystal violet and instead take up the counterstain (safranin or fuchsine), appearing pink under the microscope.
how does gram positive bacteria react with antibiotics ?
effective because these antibiotics target the peptidoglycan layer, disrupting cell wall synthesis. Since Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, these antibiotics can easily reach their target.
how does gram negative bacteria react with antibiotics ?
more resistant
due to the presence of outer membrane, which acts as a barrier to antibiotic molecules
