revision 1 Flashcards
how many cell types are there?
3 types
bacteria
archaea
eukarya
what does cell theory state?
-cells are there fundamental units of life
-all organisms are composed of cells
- all cells come from pre-existing cells
what are endospores?
-some bacteria produce dormant, resistant endospores within vegative cells
- endospores are highly resistant to environmental stresses like high or low temperature and drought.
endospores enable the cell to survive in periods of environmental stress
what are lysosomes?
-vesicles containing digestive enzymes that come in part from the Golgi
- sites for the breakdown of food and foreign material brought into the cell by phagocytes.
-the site where autophagy occurs - digestion of spent celllular components
organelle that contain many digestive enzymes
what is the smooth endoplasmic reticulum (SER)?
- more tubular than RER
- lacks ribosome on the outside
- responsible for chemical modification of small molecules taken into the cell - e.g. drugs.
-site of hydrolysis of glycogen in animal cells.
-site for synthesis of lipids and steroids
in dna the sugar is…
deoxyribose
in rna the sugar is…
ribose
what rna what is replaced?
thymine with uracil
can rna form secondary structures?
yes
what rna sequence initiates translation?
shine-dalgarno sequence
what is the ribosomes 3 sites?
A aminoacyl-tRNA
P peptidyl-tRNA
E exit
what’s the ribosome?
-where mRNA meets charged tRNA
- has 2 subunits: small and large
-has 3 sites (A,P,E)
what are polysomes/polyribosomes?
-several ribosomes can work together to translate the same mRNA producing multiple copies of the polypeptide
-a strand of mRNA with associated ribosomes is called a polyribosome or polysome
-multiple copies of the same protein are made from a single mRNA (12 per second)
what does a uniport transport?
1 solute in the same direction
what does a symport transport?
2 solutes in the same direction
what does a antiport transport?
2 solutes in opposite directions
what transporters have coupled transport?
symport and antiport
what are nuclear pores?
- transport of molecules across the nuclear envelope
-8 large protein granules surround each pore
FROM nucleus: RNA, ribosomal proteins
TO nucleus: proteins (DNA polymerase and lamins), carbohydrates, signalling molecules and lipids
-nuclear pores do NOT transport DNA
what can cross the lipid bilayer through simple diffusion?
gases
hydrophobic molecules
small polar molecules
what cannot cross the lipid bilayer through simple diffusion?
large polar molecules
charged molecules
e.g. amino acids, sugars, and ions
what is the exception to simple diffusion across the lipid bilayer?
water
the more lipid soluble the molecule, the more rapidly it diffuses
water is the exception to this which can pass through the lipid bilayer more readily than it’s lipid solubility would predict
what does RNA polymerase bind to during transcription initiation?
promoter region
what is transcription?
how RNA is synthesised
what’s the flow of information?
<- DNA replication
)
DNA. ->. RNA. ->. protein
transcription translation
termination of transcription
-special DNA sequences and protein helpers terminate transcription
-the transcript is released from the DNA
-the primary transcript is called the “pre-mRNA”
-the pre-mRNA is processed to generate the mature mRNA
what is the genetic code?
-the genetic code consists of triplets of nucleotides- codons
-4 bases mean 64 possible codons since 4^3 (if there were 3 bases it would be 27 3^3)
-1 start codon (encodes methionine)
-3 termination codons (stop translation)
-60 codons for 20 amino acids
-the genetic code is redundant because there is more than 1 codon for certain amino acids however a single codon does not specify more than one amino acid
-the genetic code is almost universal
what does amino acyl-tRNA synthetases do?
attach specific amino acids to the appropriate tRNAs
