Beginnings of Life Flashcards
What do purines and pyrimadines polymerise into?
Polynucleotides.
Describe the plasma membrane.
- Every cell is surrounded by a plasma membrane.
- Maintains homeostasis.
- Selectively permeable.
- Important sin communicating with outside environment.
- Aids in binding and adhering.
State the ‘Cell Theory’.
- Cells are the fundamental units of life.
- All organisms are composed of cells.
- All cells come from pre-existing cells.
How is cell size limited and why?
Surface area: volume ratio.
The volume determines how much chemical activity it can carry out per unit of time. Surface area determines the amount of a substance it can take in and waste it can expel.
Define prokaryotic cells.
Cells which have no nucleus or other membrane bound compartments - lack distinct organelles.
Define eukaryotic cells.
Have a membrane enclosed nucleus and other membrane enclosed compartments and organelles.
Describe the cell walls of prokaryotes.
- Some prokaryotes have them.
- Maintains cell shape.
- Most bacteria have peptidoglycan in their cell walls.
What are mycoplasma?
Bacteria which lack a cell wall.
- Makes them unaffected by some antibiotics.
- Some are pathogenic to humans.
Describe the slime layer.
- Present in some bacteria.
* Outer layer of polysaccharides enclosing the cell wall.
Describe flagella.
- Present in some prokaryotes.
* Locomotory structures shaped like corkscrews.
Describe pili.
- Present in some prokaryotes.
- Thread-like structures which help bacteria to adhere to each other during exchange of genetic material and to animal cells for protection or food.
Describe inclusions.
- Present in some prokaryotes.
* Deposits found within cytoplasm for reserves of lipids, starch or glycogen.
Describe endospores.
- Present in some bacteria.
* Dormant endospores which are highly resistant to environmental stresses.
Describe reproduction in prokaryotes.
They divide by binary fission after replicating their DNA by asexual replication.
Prokaryotes do not undergo mitosis.
What do amino acids polymerise into?
Proteins.
