1.1 Introduction to cells Flashcards
The Cell theory
- All living things are composed of cells (cell products)
- Cells are the smallest unit of life
- Cells only arise from pre-existing cells
Exceptions to the Cell theory
- Striated muscle cells
- Giant Algae
- Aseptate fungal hyphea
Striated Muscle cells
- It is a result of the fusion of cells creating a cell with many nuclei and one cell membrane.
It challenges the idea that cells always function as independent units
Aseptate fungal Hyphae
- Fungi might be filamentous structures called hyphae and it would separated into cells by walls called Septa.
- Some might not be separated.
It challenges the idea that living structures are composed of separated cells
Giant Algae
- It is unicellular organisms that can grow very long, even more than 7cm in hight.
It challenges the idea that living organisms are composed of various microscopic cells.
The functions of life
MR H GREN:
Metabolism: Living things can undertake chemical reactions
Reproduction: Living things can produce offspring (Sexually or asexually)
Homeostasis: Living things maintain a balanced internal environment
Growth: Living things can move and increase there size
Response: Living things are responsive to external and internal stimuli
Excretion: Living things can undertake the process of removal of waste products
Nutrition: Living things exchange gas and materials with the surrounding environment.
Paramecium vs Chlorella
M: Heterotrophic vs Autotrophic
R: Asexual for both
H: Maintain equilibrium in the cytoplasm for both.
G: Moves via cilia vs non-motile but increases in size when undergoing mitosis.
R: Chemotaxis (towards food) vs Phototaxis (Towards light)
E: Excrete waste products via anal pore vs via diffusion.
N: Food vacuoles vs photosynthesis.
SA:Vol Ratio, rate of metabolism and rate of exchange.
how fast does the SA and VOL increase.
What happens if Sa:Vol was low? What happens if it was high?
Finally, what are reasons for the increasing of SA:Vol?
It is the ratio of the Surface area divided by the volume of the cell. The rate of metabolism is dependent on the mass and volume, the rate of exchange is dependent on the surface area of the cell.
The Surface area grows in a lower speed than the volume, as cell grows Volume (units^3) and Surface area (Unites^2).
Too low then the cell dies as the rate of metabolism would be higher than the rate of exchange.
there is nothing called too high as the higher the better (depending on the function of the cell) it wold maintain a high stable ratio for survival.
For cells specialised in exchange like Alveoli and villi, it would naturally be having membrane extensions to increase the surface area and hence increase the ratio.
Magnification
M= I/A A= I/M I = MxA
Emergent properties (multicellular organisms)
Cells to Tissues to Organs to Systems to Organisms
Cells group to form tissues
Tissues group to form organs
Organs work together producing functioning systems
Systems collaborate to fulfil the functions of life for an organism.
Differentiation
The process during development whereby newly formed cells become more specialised and distinct as they mature.
It happens as a result of the activation of certain instructions (genes) within a given cell by chemical signals that cause it to differentiate.
Single cells can be unspecialised stem cells that undergo expression of a specific gene causing it to differentiate into it.
Gene Packaging
Euchromatin: Active genes, fulling most of the space in the cell to make it accessible for transcription machinery.
Heterochromatin: Inactive genes, packaged in a more condensed form to save space.
Stem cells special properties.
Self Renewal
Potency: capacity to differentiate into a number of cells.
Types of Stem cells
Totipotent: Can form any cell type including extra embryonic tissues (Placental) like Zygote
Pluripotent: Can form any cell type.
Multipotent: can differentiate into a number of related cells.
Unipotent: Can not differentiate, however, capable of self renewal.
Use of Stem cells, And steps of the usage of Stem Cells
Stem cells can be used to replace non-Stem cells as they cannot differentiate.
The process steps:
1. The use of biochemical solutions to trigger the differentiation of the stem cells into the wanted cell.
2. Surgical implantation of cells into the patient’s tissue.
3. Suppression of the patients immune system to ensure that the body wont reject the newly implemented cells.
4. Carefully monitoring the new cells to ensure that they don’t become cancerous.
