Topic 1:Cell Biology Flashcards
Caveats to the cell theory: Striated Muscle Fibres
-Muscle cells fuse to form fibres that may be very long (>300mm)
-They have multiple nuclei despite being surrounded by a single, continuous plasma membrane
-Challenges the idea that cells always function as autonomous units
Caveats to the cell theory: Asceptate Fungal hyphae
-Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae
-Challenges the idea that living structures are composed of discrete cells
Caveats to the cell theory: Giant Algae
-Certain species of unicellular algae may grow to very large sizes
-Challenges the idea that larger organisms are always made of many microscopic cells
Metabolism, give example of how paramecium does this
Living things undertake essential chemical reactions
Food particles are enclosed within small vacuoles that contain enzymes for digestion
Reproduction (with paramecium example)
Living things produce offspring, either sexually or asexually
Paramecia divide asexually (fission) although horizontal gene transfer can occur via conjugation
Sensitivity (with paramecium example)
Living things are responsive to internal and external stimuli
Paramecia are surrounded by small hairs called cilia which allow it to move
Homeostasis (with paramecium example)
Living things maintain a stable internal environment
Essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion
Excretion (with paramecium example)
Living things exhibit the removal of waste products
Solid wastes are removed via an anal pore, while liquid wastes are pumped out via contractile vacuoles
Nutrition (with paramecium example)
Living things exchange materials and gases with the environment
Paramecia engulf food via a specialised membranous feeding groove called a cytostome
Growth (with paramecium example)
Living things can move and change shape or size
How do cells and tissues that are specialised for gas or material exchanges increase their surface area to optimise material transfer
intestinal tissue of the digestive tract may form a ruffled structure (villi) to increase the surface area of the inner lining
Alveoli within the lungs have membranous extensions called microvilli, which function to increase the total membrane surface
Magnification of an image =
Image size (with ruler) ÷ Actual size (according to scale bar
Actual Size of an organism =
Image size (with ruler) ÷ Magnification
Differentiation
Process during development where newly formed cells become more specialised and distinct from one
Each cell contains the entire set of genetic instructions for that organism. The activation of different instructions (genes) within a given cell by chemical signals will cause it to differentiate
What are the two key qualities of stem cells?
- Self Renewal – They can continuously divide and replicate
- Potency – They have the capacity to differentiate into specialised cell types
Totipotent
Can form any cell type, as well as extra-embryonic (placental) tissue (e.g. zygote)
Pluripotent
Can form any cell type (e.g. embryonic stem cells)
Multipotent
Can differentiate into a number of closely related cell types (e.g. haematopoeitic adult stem cells)
Unipotent
Can not differentiate, but are capable of self renewal (e.g. progenitor cells, muscle stem cells)
Outline Stargardt’s Disease, how it can be treated via the use of stem cells.
An inherited form of juvenile macular degeneration that causes progressive vision loss to the point of blindness, Caused by a gene mutation that impairs energy transport in retinal photoreceptor cells
-Treated by replacing dead cells in the retina with functioning ones derived from stem cells
What are the three ways stem cells can be derived?
- Embryos (may be specially created by therapeutic cloning)
- Umbilical cord blood or placenta of a new-born baby
- Certain adult tissues like the bone marrow (cells are not pluripotent)
Discuss the disadvantages/ethical concerns of stem cell therapy
- Using multipotent adult tissue may be effective for certain conditions, but is limited in its scope of application
- Stem cells derived from umbilical cord blood need to be stored and preserved at cost, raising issues of availability and access
- The greatest yield of pluripotent stem cells comes from embryos, but requires the destruction of a potential living organism
- Sometimes involves the use of oncogenic retroviruses and transgenes, increasing the risk of health consequences (i.e. cancer)
