L3 - cells in their environment

Question 1

why is it believed that all cell types evolved from a common ancestor

Answer 1

cell types all share many features eg
cell membranes
utilise same classes of macromolecules
similarities in genetic code

Question 2

what is the one common ancestor believed to be

Answer 2

ancestral prokaryote

Question 3

what is LUCA

Answer 3

Last Universal Common Ancestor

Question 4

explain the evolution of LUCA

Answer 4

1. simple chemicals in prehistoric warm oceans reacted via catalysis to form simple RNA’s (could store info)
2. these folded and formed ribozymes which had enzymatic activity (more complex RNA’s which could carry genetic info and catalyse their own reproduction)
3. DNA was formed, more stable
4. bilayers were formed (amphipathic lipids spontaneously form vesicles)
5. a DNA molecule could have been trapped in one of these vesicles
6. first cell

Question 5

what simple molecules were thought to exist first

Answer 5

minerals , catalysts , phosphates, HCN etc

Question 6

specialisation of a prokaryote

Answer 6

flagella
acidophiles / thermophiles etc
can use different energy sources (H, methane etc)

Question 7

what is the endosymbiotic theory

Answer 7

1. eukaryotes were originally anaerobic however were invaded by mitochondria via a symbiotic relationship between archaea and bacteria
2. also the crossing of photosystem 1 and 2 to form photosynthetic bacteria, and then this crossing into plants

Question 8

examples of single celled eukaryotes

Answer 8

1. protozoans eg gregarina (slime mould)

2. yeast

Question 9

examples of multicellular eukaryotes

Answer 9

plants

animals

Question 10

explain concept of cellular specialisation

Answer 10

in multicellular organisms cells can be specialised to perform a particular function