B3a-molecules Of Life Flashcards
Why do liver and muscle cells have large numbers of mitochondria?
They need lots of energy
Liver cells-carry out metabolic reactions
Muscle cells- contract
What do chromosomes do?
Carry coded information in the form of genes
Made of a molecule called DNA
What are proteins needed for?
Growth and repair of cells
What is the structure of DNA?
- Two strands coiled to form double helix
- Each strand contains chemical bases
- four bases: A T C G
- crosslinks between strands formed by pairs of bases
What are the complementary base pairings?
A T
G C
What is the genetic code?
Information in genes in the form of coded instructions
What are chromosomes?
Long coiled molecules of DNA divided up into regions called genes
What does the genetic code control?
Controls cell activity
Characteristics of the organism
What does each gene do?
Contains a different sequence of bases
Codes for a particular protein
How is protein structure determined by DNA base code?
Base sequence determines amino acid sequence
Each amino acid is coded for by a sequence of 3 bases
What happens in the mitochondria?
Respiration takes place
Respiration provides energy for cell processes
Where are proteins made?
In the cytoplasm
Why is a copy of the gene needed?
Gene itself cannot leave the nucleus
Its really big
How is the code needed to produce a protein carried from DNA to ribosomes?
- proteins made in cytoplasm by ribosomes
- ribosomes use code in DNA
- mRNA made by copying code from DNA
- mRNA carries code between two
What are ribosomes?
- tiny structures
- in the cytoplasm and are the site of protein synthesis
- too small to be seen with light microscope
How did Watson and crick discover structure of DNA?
- x ray data showing that there were two chains wound in a helix
- data indicating that bases occurred in pairs
Why was Watson and cricks work not accepted immediately?
Other scientists need to repeat work first and make sure results are reliable
How does DNA control cell function?
-cells have different functions because they make different proteins
-switched on genes determine the function of the cell
Eg genes for muscle cell proteins switched on = muscle cell
What are switched off genes?
The proteins they code for aren’t produced
What are switched on genes?
The proteins they code for are produced
