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.
Why would some cells increase their surface area?
Cells and tissues that are specialized for gas or material exchanges will do it to try and optimize material transfer. (The surface must allow sufficient exchange to support the contents of the cell)
What are two examples of the increased surface area?
- Intestinal tissue of the digestive tract may form a ruffled structure (villi)
- Alveoli within the lungs that have membraneous extensions (microvilli)
What is the first basic function of survival? (acronym to 7 functions: MR SHENG)
It’s metabolism- living things undertake chemical reactions.
What is the second basic function of survival?
It’s reproduction- producing offspring, either sexually or asexually.
What is the third one?
Response- living organisms are responsive to internal and external stimuli.
What is the fourth one?
Homeostasis- they maintain a stable internal environment.
The fifth one?
Excretion- they exhibit the removal of waste products.
What is the sixth function of life?
It’s nutrition- living things exchange materials and gases with the environment.
What is the final function of life?
Growth- living organisms can move and change shape or size.
How does the paramecium (heterotroph) fulfill the functions of responsiveness, nutrition, and metabolism?
- responsiveness- they have small hairs called cilia which allow them to move
- nutrition- they engulf food via a specialized membranous feeding groove called a cytostome
- metabolism- food particles are enclosed within small vacuoles that contain enzymes for digestion
How does the paramecium carry out excretion, homeostasis, and reproduction?
- excretion- solid wastes are removed via an anal pore, while liquid wastes are pumped out via contractile vacuoles
- homeostasis- essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion
- reproduction- paramecia divide asexually (fission)
How do paramecia allow gene differentiation?
They use the process called conjugation.
How does the scenedesmus (autotroph) metabolize, excrete, and provide nutrients?
- nutrition and excretion-occurs by an exchange of gases and other essential materials via diffusion
- metabolism- chlorophyll pigments allow organic molecules to be produced via photosynthesis
How does the scenedesmus reproduce?
Daughter cells form as non-motile autosphores via the internal asexual division of the parent cell.
How does the scenedesmus respond?
They may exist as unicells or form colonies for protection.
What is a hermaphrodite?
It’s an organism that has both male and female reproductive organs.
