2.1 eukarotes and prokaryotes Flashcards
2.1 v
state the principle of the cell theory
cella are fundamental structural units in all living organisms. they determine the function and organisation of biological systems.
describe difference between organ and tissue
A tissue is a group of similar cells
am organ is tissues working together to perform a specific function
what is the nucleoid
irregularly-shaped region of cytoplasm where loop of bacterial DNA is located
what is a plasmid
1 or more rings of DNA found in some bacterial cells
contains non-essential genes(not needed for the survival of bacteria)
can be exchanged between bacterial cells via conjugation
describe the structure of a bacterial cell wall and slime capsule
peptidoglycan(murein) cell wall provides mechanical strength
may be coated by slime layer to prevent desiccation(drying) ,adhere cells and provide nutrients
outline process of gram staining
- fixation-imobalises bacteria and makes it more permeable to dyes
- crystal violet dye-absorbed by peptidoglycan
- iodine solution forms crystals in violet dye
- decorization- alcohol gram positive will be clear as dyes will be washed out. gram negative will stay purple as peptidoglycan has more layers
- add red safranin to make negative appear red and examine under microscope
describe gram positive cell walls
have thicker layer of pepidoglycan (insoluble in alcohol)
purple under microscope when stained
describe gram negative cell walls
thinner layer of petidoglycan with outer lipopolysaccharide membrane(surface membrane) (alcohol-soluble)
appear red under microscope when stained
why do Gram positive and Gram negative bacteria respond differently to certain antibiotics
Gram negative bacteria have an outer membrane and a much thinner peptidoglycan layer, they are not affected.
compare ribosomes in eukaryotic and prokaryotic cells
formed of protein and rRNA
made up of a large and a small subunit. During translation, the two subunits come together around a mRNA molecule, forming a complete ribosome.
contrast ribosomes in eukaryotic and prokaryotic cells
larger subunit eukaryotic: 80S (bigger)
smaller subunit prokaryotic 70S (smaller)
describe the structure of the nucleus
surrounded by nuclear envelope, a semi permeable double membrane
nuclear pores allow substances to enter and exit
dense nucleolus made of RNA and proteins assembles ribosomes
describe the function of the nucleus
contains DNA in chromosomes coiled around chromatin
controls cellular processes: gene expression determines specialisation and site of mRNA transcription, mitosis
describe the structure and function of the endoplasmic reticulum(ER)
Cisternae- network of tubules and flattened sacs extends from cell membrane and connects to nuclear envelope
rough ER(has ribosomes on outside)- many ribososmes attached from protein synthesis and transport
smooth ER-lipid synthesis
Describe the structure of a mitochondrion
surrounded by double membrane
folded inner membrane forms cristae: site of electron transport chain
fluid matrix-contains mitochondrial DNA,respiratory enzymes,lipids,proteins
describe structure of chloroplast
vesicular plastid with double membrane
thylakoids-flattened discs stack to form grana- photosystems with chlorophyll
intergranam lamellae-tubes attach thylakoids in adjacent grana
stroma-fluid filled matrix
state the function of mitochondria and chloroplasts
mitochondria- site of aerobic respiration to produce ATP
chlotoplats-site of photosynthesis to convert solar energy into chemical energy
describe the structure and function of the Golgi apparatus
planar stack of membrane-bound, flattened sacs
molecules are processed in cisternae vesicles
Proteins and lipids from the ER enter the Golgi apparatus at its cis face and exit at its trans face.
Exit via exocytosis(large number of molecules transferred out of the cell)
modifies and packages proteins for export
synthesises glycoproteins
describe the structure and function of a lysosome
structure
bag of digestive enzymes
function
phagaocytosis in white blood cells
first the white blood cell forms a vacuole around the bacteria this is called a phagasome; the lysosome fuses with the phagasome and lysosomal enzymes digests the bacteria the soluble digestion products now pass into the cytoplasm
exocytosis-release enzymes outside of the cell to destroy material
digest worn-out organelles for the reuse of materials
structure and function plant cell wall
made of cellulose microfibrils for mechanical strength
plasmodesmata connect the two cytoplasms together- these connections form the symplast and the symplastic pathway pathway- to allow molecules to pass between cells through cytoplasm
cell walls join for the appoplast and the appoplastic pathway- material are able to move through the cell wall
middle lamella separates adjacent cell walls (like the glue)
hemicelluloses harden the walls further.
Pectin-(polysaccharide) found in fruits, helps bind cells together
describe the structure of the cell vacuole in plants
filled with fluid surrounded by a single membrane called tonoplast
stores cell sap, which contains mineral ions,water, enzymes, soluble pigments
describe the function of the cell vacuole in plants
controls turgor pressure
absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm
describe the structure and function of animal vacuoles
numerous and much smaller than in plants
temporary membrane bound sacs containing water and chemicals
more commonly referred to as vesicles
describe the structure and function of centrioles
spherical group of 9 microtubules arranged in triplets
located in centrosomes
migrate to opposite poles of cell during prophase and spindle fibres form between them
What is Cell fractionation
A process which allows scientists to extract pure samples of a particular organelles eg mitochondria
Steps of cell fractionation
1) The tissue for example liver is chopped up. When cells are broken apart substances mix together and begin to react
2) to prevent this a fluid is added that is
Ice cold- minimise enzyme reaction
Isotonic- same water concentration so cells don’t burst
Contains a buffer- to resist any changes in pH
3) the mixture is put in a homogeniser(blender) to break up the cells
4) the resulting mixture is centrifuged at high speeds(mixed) this separates the organelles depending on their density and shape. The densest organelles to sediment out are the nuclei. The remaining fluid is supernatant which poured off and centrifuged again to collect other organelles
The order of sedimentation and density is:
1) nuclei
2) mitochondria
3) rough ER
4) smooth ER
5) ribosomes
