cell theory and functions of life Flashcards
What is the hierarchy of life?
- atom
- molecule
- organelles
- cell
- tissue
- organ
- organ system
- multicellular organism
- population
- community
- ecosystem
- biosphere
What is the first structure of life that can function on its own?
It is a cell.
What are the emergent properties?
They are properties of a system as a whole rather than the properties that can be derived from any of the components of a system.
State the cell theory?
All living things are composed of cells. Cells are the smallest living structures and buildings of life. All cells come from the division of pre-existing cells
What do all cells have in common?
- genetic information
- a plasma membrane
- own energy release system
What are the exceptions to cell theory?
- red blood cells
- muscle cells
- aseptate fungal hyphae
- giant algae (acetabularia)
Why are muscle cells exception to cell theory?
- they fuse to form fibres that may be very long (>300)
- have multiple nuclei despite being surrounded by a single, continuous plasma membrane
- challenges the idea that cells always function as autonomous units
Why are aseptate fungal hyphae exception to cell theory?
- are formed of filamentous structures called hyphae, which are separated by internal walls called septa
- some fungi are not divided by septa hence have a single, continuous plasma membrane along the length of the hyphae
- challenges the idea that living structures are composed of discrete cells
Why are giant algae an exception to cell theory?
- certain species of unicellular algae may grow to very large sizes (acetabularia may exceed up to 7 cm)
- challenges the idea that larger organisms are always made of many microscopic cells
Who was the first man to ever use the word cell?
Robert Hooke in the 1660s.
What are the two main types of cells?
eukaryotic (that have a nucleus) and prokaryotic (that lack nucleus)
What is the rate of metabolism?
It’s a function of its mass/volume (larger cells need more energy to sustain essential functions)
What is the rate of material exchange?
It’s the function of its surface area (large membrane surface equates to more material movement)
What happens when the cell grows?
Volume increases faster than the surface area, leading to decreased SA: Vol ratio
Why do cells divide?
If the metabolic rate exceeds the rate of exchange of vital materials and wastes (there is a low SA: Vol ratio); the cell may overheat, because the metabolism produces heat faster than it is lost (the cell will eventually die.) Hence cells divide and tend to remain small to maintain a high Sa: Vol ratio suitable for the cell’s survival.
