1.1 Cell Introduction Flashcards
What are the 3 main principles of cell theory?
- All living things are composed of cells (or cell products)
- The cell is the smallest unit of life
- Cells only arise from pre-existing cells
What are 3 examples of cells/tissues that do not conform to cell theory?
- striated muscle fibres
- aseptate fungal hyphae
- giant algae
What component of cell theory do striated muscle fibres not conform to ?
Challenges the idea that cells always function as autonomous units
How doe s a striated muscle fibre challenge cell theory?
Muscle cells fuse to form fibres that may be very long (>300mm)
Consequently, they have multiple nuclei despite being surrounded by a single, continuous plasma membrane
How does aseptate fungal hyphae challenge cell theory?
Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls called septa
Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae
What component of cell theory does aseptate fungal hyphae challenge?
Challenges the idea that living structures are composed of discrete cells
How does giant algae challenge cell theory?
Certain species of unicellular algae may grow to very large sizes (e.g. Acetabularia may exceed 7 cm in length)
What component of cell theory does giant algae challenge?
Challenges the idea that larger organisms are always made of many microscopic cells
What 7 characteristics are all living organisms capable of carrying out?
- metabolism
- reproduction
- sensitivity
- homeostasis
- excretion
- nutrition
- growth
Define metabolism
Living things undertake essential chemical reactions - a total of all the chemical reactions that take place within an organism
Define reproduction
Living things produce offspring, either sexually or asexually
Define sensitivity
Living things are responsive to internal and external stimuli
Define homeostasis
Living things maintain a stable internal environment
Define excretion
Living things exhibit the removal of waste products
define nutrition
iving things exchange materials and gases with the environment
define growth
Living things can move and change shape or size
Give an example of a unicellular heterotroph
paramecium
Explain how paramecium show sensitivity
Paramecia are surrounded by small hairs called cilia which allow it to move
Explain how paramecium show nutrition
Paramecia engulf food via a specialised membranous feeding groove called a cytostome
Explain how paramecium show metabolism
Food particles are enclosed within small vacuoles that contain enzymes for digestion
Explain how paramecium show excretion
Solid wastes are removed via an anal pore, while liquid wastes are pumped out via contractile vacoules
Explain how paramecium shows homeostasis
Essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion
Explain how paramecium reproduce
Paramecia divide asexually (fission) although horizontal gene transfer can occur via conjugation
Give an example of a unicellular autotroph
scenedesmus