Cell Introduction (1.1) Flashcards
Spontaneous Generation
The idea that certain animals, like fleas could arise (spontaneously generate) from dust or that maggots could arise from dead flesh. This theory was proposed by Aristotle and held true for 2000 years until the invention of microscopes and the work of Louis Pasteur.
Basic Cell Theory
The initial theory of cells;
- All organisms are made up of one or more cells.
- The cell is the most basic unit of life.
- All cells arise only from pre-existing cells by division.
Modern Cell Theory
The updated theory of cells;
- The activity of an organism depends on the total activity of its independent cells.
- Energy flow (metabolism and biochemistry) occurs within cells.
- Cells contain DNA in the chromosomes and RNA in the cell nucleus and cytoplasm.
- All cells have basically the same chemical composition in organisms of the same species.
Exceptions to the Cell Theory:
- Striated muscle which challenges the idea that a cell has one nucleus that controls its function.
- Aseptate fungal hyphae which challenges the idea that a cell is a single unit.
- Acetabularia, giant algae, which challenges the ideas that a cell must be simple in structure and small in size.
MR H GREN
Metabolism:
A web of all enzyme-catalysed reactions in a cell or organism eg. respiration.
Response:
Living things can respond to and interact with the environment.
Homeostatis:
The maintenance and regulation of internal cell conditions eg. water and pH
Growth:
Living things can grow and change in size/shape.
Reproduction:
Organisms can produce offspring, either sexually or asexually.
Excretion:
The removal of metabolic waste.
Nutrition:
Feeding by either the synthesis of organic molecules eg. photosynthesis, or the absorption of organic matter.
Under what microscope can a typical protist cell be observed?
A light microscope (magnification 400x).
Paramecium
Unicellular, heterotrophic organisms. Live in marine and freshwater habitats, especially stagnant ponds/basins.
100μm in size (1mm)
Paramecium (MR H GREN functions)
Metabolism: Cytoplasm
Most metabolic activities occur in the cytoplasm eg. respiration.
Response: Cilia
The wave action of the cilia moves the paramecium in response to changes in the environment eg. towards food.
Homeostasis: Contractile Vacuoles
Fill up with water and expel this water through the plasma membrane to regulate/maintain water content in the cell.
Growth
After consuming and assimilating biomass from food the paramecium will grow larger in size until it divides.
Reproduction: Cell Nucleus
The nucleus can divide. Reproduction is often asexual.
Excretion: Plasma Membrane
Controls the entry/exit of substances, including the expulsion of metabolic waste.
Nutrition: Food Vacuole
Stores the organisms the paramecium has consumed.
Chlorella
Unicellular, autotrophic organisms.
Diameter of 2-10μm in size.
Chlorella (MR H GREN functions)
Metabolism: Cytoplasm
Most metabolic activities occur in the cytoplasm eg. respiration.
Response: Cilia
The wave action of the cilia moves the paramecium in response to changes in the environment eg. towards light.
Homeostasis: Contractile Vacuoles
Fill up with water and expel this through the plasma membrane to regulate water content in the cell.
Growth
After consuming and assimilating biomass from food the algae will grow larger in size until it divides.
Reproduction: Cell Nucleus
The nucleus can divide to support cell division (by mitosis).
Excretion: Plasma Membrane
Controls the entry/exit of substances, including the expulsion of waste oxygen.
Nutrition: Chloroplast
Photosynthesis occurs in the chloroplasts to provide Chlorella with nutrients/food.
Mass/Volume (SA:Vol ratio)
The rate of metabolism in a cell is a function of its mass/volume. Larger cells need more energy to sustain essential functions.
Surface Area (SA:Vol ratio)
The rate of material exchange in/out of a cell is a function of its surface area. A large membrane surface equates to more material movement.
What happens when a cell grows? (SA:Vol ratio)
When a cell grows, its volume increases faster than its surface area, leading to a decreased SA:Vol ratio.
If metabolic rate exceeds the rate of exchange of vital materials and waste (low SA:Vol ratio) the cell will eventually die. So, the cell must divide in order to maintain a viable SA:Vol ratio for survival.
However, cells and tissues specialised for gas or material exchange will increase their surface area to optimise the transfer of materials. Eg. microvilli on alveoli, bioncave disc shape of red blood cells.
Emergent Property
Emergent properties arise when the interaction of individual components produces new functions.
Emergent Properties in multicellular organisms
- Groups of cells form tissues
- Organs can then be formed from a group of multiple tissues
- Organs can interact to form an organ system which carries out a specific function
- Organ systems collectively carry out life functions for the entire organism
Eg. Muscle cells -> Cardiac tissue -> Heart -> Vascular system -> A Human
