B1: Cell-level systems Flashcards
eukaryotic cell
-membrane bound organelles
-complex and relatively large from 10-100 micrometres.
-plant and animal cells are examples of this
prokaryotic cells
-do not contain membrane bound organelles;instead their genetic material floats in the cytoplasm.
-simple cells with sizes of 1-100 micrometres
-bacterial cells are example of this
nucleus
-contains genetic information needed to make proteins
-controls activities of the cell
mitochondria
site of aerobic respiration
cytoplasm
-jelly-like substance
-site of chemical reactions in the cell
cell membrane
selective barrier which controls what goes in and out of the cell
what does a plant cell have that an animal cell doesnt
chloroplast- contains chlorophyll which is needed for photosynthesis
vacuole-contains cell sap and also keeps the cell rigid,keeping the cell upright
cell wall-cellulose structure and makes the cell rigid and supports the cell.
what are bacteria
-smallest living bacteria
-unicellular organisms
-can carry out 7 life processes
-1 micrometre in size
examples of prokaryotes
E.COLI-causes food poisioning
STREPTOCOCCUS-causes sore throats
STREPTOMYCES-used to make an antibiotic for the soil.
what structures do all prok cells have
-cell membrane
-cell wall
-genetic material
extra prok structures
-flagella-tail like structures all cells to move through liquids
-pili-tiny hairlike structures that enable cells to attatch to structures and are also used to transfer genetic material between bacteria
-slime capsule-layer outside the cell wall that protects a bacterium from drying out and from poisonous substances.Also helps bacteria to stick to smooth substances.
plasmid-circular ring of DNA used to store extra genes.Where anti biotic resistance genes are normally found.
what is a light microscope
-used to observe small structures in detail
-passes light through an object placed on a stage ],then through two glass lenses-the objective and eyepiece .These magnify the object, so when you view it through the eyepiece you can see it in more detail
to observe cells under a microscope
1) move stage to its lowest position
2)select the objective lens with lowest magnification
3)place slide with cells on stage
4)raise stage to highest position making sure it does not touch the lens
5)lower stage slowly using coarse focus knob until you see the object
6)turn the fine focus knob slowly until your object comes into clear focus
7) to see cells in greater detail, switch to a higher magnification objective lens without moving stage. Use FINE FOCUS KNOB to bring the object into clear focus again
total magnification formula
total magnification=eyepiece lens maginfication X Objective lens magnification
t,l,o
why are cells stained
makes them easier to observe
common stains
methylene blue-nucleus of an animal cell
iodine-plan cell nuclei
crystal violet-stains bacterial cell walls
how to apply a stain
1)place the cells on a glass slide
2) add drop of stain
3)place coverslip on top
4)tap the coverslip with a pencil to remove air bubbles
what is resolution
the smallest distance between two points that can be seen as separate entities
electron microscope
-uses electrons instead of light to prodcue an image.
-The greater resolution is achieved by using high-energy electrons as the light source
-
two types of electron microscope
TEM(transmission electron microscope)-produce the most magnified image by sending a beam of electrons pass a thin sample of the surface of the specimem.Beam focuses to produce an image
SEM(scanning electron microscope)-produces a 3D image of a surface.Sends a beam of electrons accross the surface of a specimen.These collect to produce an image
comparisons of the two types of microscopes
-light is cheap to buy and operate,electron is expensive
-light is small and portbale,electron is large and difficult to move
-light is simple prepare,electron is not
-in light natural colour can been seen unless stains used,in electron it is black and white until false colour added
-in light,speciemns can be living or dead,in electron specimen must be dead
-electron has higher resolution
-
development of electron microscopy
-has allowed scientists to see the detail within subcellular structures.
-for e.g.TEM showed chloropyll is stored in flattened membranes within a choroplast.
chromosome
long strand of DNA-most people have 46 in each cell. 23 pairs-one from mother,one from father
genes
short sections of DNA that code for a characteristic.contains code for specific proteins to be made.
structure of DNA
-polymer
-made of nucleotides(sugar phosphate base)
-made up of two strands joined by bases and twisted together to form a double helix shape.
The four bases
A-T
C-G
what is a base pair
when a base from on strand bonds with another to hold the strands of DNA together
what is mRNA
-messenger RNA
-A copy of DNA made as DNA is too bif to leave the nucleus
transciption
-DNA around a gene unzips so both strands are separated.One strand acts as a template
-complemenatry bases attacth to the strand being copied-this forms a strand of mRNA.no thymine,so bases called uracil(u)binds with adenine.
-when complete the strand will detatch itself and the DNA will zip up.
-mRNA is small enough to move out the nucleus to ribosmomes in the cytoplasm,where proteins will be made
what are proteins made from
amino acids
what determines the proteins that are produced
The order of nucleotides in your DNA determines the type and the order of amino acids,and this determines which proteins are produced.
translation
-mRNA attaches to a ribosome
-the ribosome reads the nucleotides in 3’s(codons)-each codon codes for a specififc amino acid
-ribosome continues to read the triplet code,adding more and more amino acids
-these join togeteher forming a protein
what does the sequence of amino acid determine
-How the protein will unfold.
-each type of protein has a specific shape.this is important for protein function
what are enzymes
biological catalysts-speed up reactions without being used up themselves
