ICT flashcards
Main components of eukaryotic cells and nucleus
surrounding outer membrane- double layer membrane that separates the cell from the env and communicates inside with outside
cytoplasm- cell contents in thick fluid
cytoskeleton- inside structure to keep shape
organelles- structures for specific cell functions
nucleus bound by membrane- control centre in DNA
nucleus structure
bordered by a porous double membrane - nuclear envelope
thin fibres of dna
protein - CHROMATIN
small round nucleolus - produces rRNA to make ribosomes
rRNA meaning
ribosomal RNA
Describe the structure of DNA double helix
DNA- nucleic acid
macromolecule
made up of two polynucleotide chains
each poly is many up of nucleotides
5 carbon sugar- deoxyribose
nitrogen containing bases - A+T, C+G
phosphate
2 strands joined by H bonds
nucleotides- cov linked via sugars
two strands wound into double helix
each strand= template for the other
genetic info function
directs the daily life of a cell
directs the development of the organism
accurately and continuously copies itself during cell division
how are the two strands held together
h bonds
what does each strand serve as for the other
a template
what enzyme is used in the process of dna replication
dna polymerase
during dna synthesis new nucleotides can only be added in which direction
3’ end
dna replication process
strands separate
new strand is made using each old strand as a template according to the rules of base pairing
two complete and identical double helices are produced
one old and one new strand
what are all living things made of
cells
main components of a eukaryotic cells and a nucleus
- A surrounding outer membrane - double layer membrane that separates the cell from the environment and communicates the interior of the cell with the outside
- Cytoplasm – cell contents in thick fluid
- Cytoskeleton structure inside to keep its shape
- Organelles – structures for specific cell functions
- Nucleus bound by membrane - control centre with DNA
the nucleus- brain of the cell - structure
- Bordered by a porous double membrane – nuclear envelope
- Contains thin fibres of DNA and protein called chromatin
- Contains a small round nucleolus which produces rRNA to make
ribosomes (appears more dense), most cells have 2 or more
dna function
- Genetic information:
- Directs the daily life of a cell
- Directs the development of an organism
- Accurately and continuously copies itself during cell division
describe the structure of DNA
-double helix
-DNA is a nucleic acid.
-macromolecule + made up of two polynucleotide chains.
-each polynucleotide made up of nucleotides
-nucleotide- deoxyribose, nitrogen, base, phosphate group
-strands held together by H bonds
-nucleotides- covalently bonded
-wound into a double helix
-bases on the inside
-complimentary strands + bases
-strands serve as a template
dna replication process
- The strands separate. Hydrogen bonds are broken by
enzyme helicase + uses ATP. - A new strand is made using each old strand as a template - via base pairing rule. Using
DNA polymerase. - Two complete & identical double helices are produced.
- One old & one new strand in each.
how does the structure of DNA enable genome duplication and cell division
Each strand contains sequence of nucleotides exactly complimentary to the sequence of the other strand. Each strand = template for the other strand. A-T, C-G. – comp base pairing = symmetrical structure
polarity of DNA synthesis
linkage of nucleotides- chemical polarity
2 strands- antiparallel
dna synthesis- new nucleotide can only be added at 3’ prime
synthesis always from 5’ to 3’’ end
uses dna polymerase
relevance of dna repair
dna- damaged by
-replication
-products of chemical reactions taking place in cells : env insults, radiation, UV
dna repair- if one strand needs repairing
lots of mechanisms developed
lots of enzymes/proteins used
relevance of dna repair in general
PROCESS
- Recognise unusual DNA structures
- The unusual structure is removed
- Damage to one strand can be repaired using the complimentary strand as a template
DNA double strand breaks (breaks in sugar-phosphate backbone) also occur and can lead to chromosomes
breaking into smaller parts. They are more difficult to repair; two mechanisms: - The broken ends are quickly put together (comes with errors!) – non-homologous end joining
- The other chromosome can be used as a template to mend the broken one (error-free) – homologous
recombination.
When the DNA is not repaired – cell cycle and/or cell death is activated. Can lead to mutations which cause
genetic diseases/cancer
describe how dna is packaged in the nucleus
understand the difference between euchromatin and heterochromatin
chromatin structure- regulates access to dna
changes arrangement of nucleosomes of dna
more or less accessible sequences
EUCHROMATIN- less condensed, both active/inactive genes
HETEROCHROMATIN- v condensed, often no genes
if genes- INACTIVE
the role of epigenetic modification in establishing cell fate and phenotype
Chromatin structure regulation = epigenetic regulation. Epigenetic modifications control nucleosome
arrangements, the chromatin state and therefore, gene activity.
- DNA methylation - Methyl marks added to certain DNA bases repress gene activity
- Histone modification - A combination of different molecules (methyl, acetyl) can attach to sticking out
histone tails. alter the affinity of histones to DNA and activity of the DNA wrapped around
them. form docking sites for other regulatory proteins.
what are proteins
molecules that perform all functions required for life
two major categories - fibrous and globular
~10,000 types in the human body
