revision 1

Question 1

how many cell types are there?

Answer 1

3 types
bacteria
archaea
eukarya

Question 2

what does cell theory state?

Answer 2

-cells are there fundamental units of life
-all organisms are composed of cells
- all cells come from pre-existing cells

Question 3

what are endospores?

Answer 3

-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

Question 4

what are lysosomes?

Answer 4

-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

Question 5

what is the smooth endoplasmic reticulum (SER)?

Answer 5

• 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

Question 6

in dna the sugar is…

Answer 6

deoxyribose

Question 7

in rna the sugar is…

Answer 7

ribose

Question 8

what rna what is replaced?

Answer 8

thymine with uracil

Question 9

can rna form secondary structures?

Answer 9

yes

Question 10

what rna sequence initiates translation?

Answer 10

shine-dalgarno sequence

Question 11

what is the ribosomes 3 sites?

Answer 11

A aminoacyl-tRNA
P peptidyl-tRNA
E exit

Question 12

what’s the ribosome?

Answer 12

-where mRNA meets charged tRNA
- has 2 subunits: small and large
-has 3 sites (A,P,E)

Question 13

what are polysomes/polyribosomes?

Answer 13

-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)

Question 14

what does a uniport transport?

Answer 14

1 solute in the same direction

Question 15

what does a symport transport?

Answer 15

2 solutes in the same direction

Question 16

what does a antiport transport?

Answer 16

2 solutes in opposite directions

Question 17

what transporters have coupled transport?

Answer 17

symport and antiport

Question 18

what are nuclear pores?

Answer 18

• 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

Question 19

what can cross the lipid bilayer through simple diffusion?

Answer 19

gases
hydrophobic molecules
small polar molecules

Question 20

what cannot cross the lipid bilayer through simple diffusion?

Answer 20

large polar molecules
charged molecules
e.g. amino acids, sugars, and ions

Question 21

what is the exception to simple diffusion across the lipid bilayer?

Answer 21

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

Question 22

what does RNA polymerase bind to during transcription initiation?

Answer 22

promoter region

Question 23

what is transcription?

Answer 23

how RNA is synthesised

Question 24

what’s the flow of information?

Answer 24

<- DNA replication
)
DNA. ->. RNA. ->. protein
transcription translation

Question 25

termination of transcription

Answer 25

-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

Question 26

what is the genetic code?

Answer 26

-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

Question 27

what does amino acyl-tRNA synthetases do?

Answer 27

attach specific amino acids to the appropriate tRNAs