Topic 1.1 - Cell Biology Flashcards
The 3 ideas of the 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
Examples of cells that don’t fit the cell theory:
Skeletal muscle
Aseptate fungal hyphae
Giant Algae
Skeletal muscle
…is made up of muscle fibers. Like cells, these fibers are enclosed inside a membrane, but they are much larger than most cells (300 or more mm long) and contain hundreds of nuclei.
Aseptate fungal hyphae
…consist of thread-like structures called hyphae. These hyphae are not divided up into sub-units containing a single nucleus. Instead, there are long undivided sections of hypha which contain many nuclei.
Giant Algae
…such as Acetabularia can grow to a length of as much as 100mm so we would expect them to consist of many small cells but they only contain a single nucleus so are not multicellular.
What are the 7 functions of life?
Metabolism Reproduction Sensitivity Homeostasis Growth Respiration Excretion Nutrition
Definition of a unicellular organism:
Unicellular organisms are composed of a single cell, but still, carry out all the life functions
Examples of unicellular organisms:
Paramecium (heterotroph)
Scenedesmus (autotroph)
Cells need to produce chemical energy via _______ to survive and this requires the __________ with the environment.
Metabolism
Exchange of materials
The rate of metabolism of a cell is a function of its?
Mass/volume (larger cells need more energy to sustain essential functions)
The rate of material exchange is a function of its?
Surface area (large membrane surface equates to more material movement)
As a cell grows, volume (units 3) increases faster than the surface area (units 2), leading to an increased or decreased SA: Volume ratio?
Decreased
What happens if the metabolic rate exceeds the rate of exchange of vital materials and wastes (low SA:Vol ratio)?
The cell will eventually die
Growing cells tend to divide and remain small in order to maintain a high SA: Volume ratio suitable for survival
How to calculate magnification?
Magnification = Image size (with ruler) ÷ Actual size (according to scale bar)
How to calculate actual size?
Actual Size = Image size (with ruler) ÷ Magnification
How do light microscopes work?
Use visible light and a combination of lenses to magnify images of mounted specimens
Emergent properties arise when?
….when the interaction of individual component produce new functions
Organization of a multicellular organism:
Cell –> tissue –> organ –> system –> organism
Why can multicellular organisms capable of completing functions that unicellular organisms could not undertake?
This is due to the collective actions of individual cells combining to create new synergistic effects
What is cell differentiation?
The process during development whereby newly formed cells become more specialized and distinct from one another as they mature
All cells of an organism share an identical genome. What does this mean?
Each cell contains the entire set of genetic instructions for that organism
What causes a cell to differentiate?
The activation of different instructions (genes) within a given cell by chemical signals
Gene packaging:
Within the nucleus of a eukaryotic cell, DNA is packaged with proteins to form chromatin
What are active genes?
Active genes are usually packaged in an expanded form called euchromatin that is accessible to transcriptional machinery
What are inactive genes?
Inactive genes are typically packaged in a more condensed form called heterochromatin (saves space, not transcribed)
What happens when a cell differentiates and becomes specialized?
It loses its capacity to form alternative cell types
Are stem cells specialized or unspecialized cells?
Unspecialized
What are the 2 key qualities that stem cells have?
- Self Renewal – They can continuously divide and replicate
2. Potency – They have the capacity to differentiate into specialized cell types
There are four main types of stem cells, what are they?
Totipotent
Pluripotent
Multipotent
Unipotent
What are totipotent stem cells?
Can form any cell type, as well as extra-embryonic (placental) tissue (e.g. zygote)
What are pluripotent stem cells?
Can form any cell type (e.g. embryonic stem cells)
What are multipotent stem cells?
Can differentiate into a number of closely related cell types (e.g. hematopoietic adult stem cells)
What are unipotent stem cells?
Can not differentiate, but are capable of self-renewal (e.g. progenitor cells, muscle stem cells)
Why are stem cells necessary for embryonic development?
Because they are an undifferentiated cell source from which all other cell types may be derived
Cell types that are not capable of self-renewal (e.g. amitotic nerve tissues) are considered to be? and why?
- Non-stem cells
- As these tissues cannot be regenerated or replaced, stem cells have become a viable therapeutic option when these tissues become damaged
What are stem cells used for?
Can be used to replace damaged or diseased cells with healthy, functioning ones
The process for stem cells to be used:
- The use of biochemical solutions to trigger the differentiation of stem cells into the desired cell type
- Surgical implantation of cells into the patient’s own tissue
- Suppression of host immune system to prevent rejection of cells (if stem cells are from a foreign source)
- Careful monitoring of new cells to ensure they do not become cancerous
Examples of stem cells therapy:
Leukemia
Stargardt’s Disease
Parkinson’s Disease
Stem cells can be derived from one of three sources:
- Embryos
- Umbilical cord blood or placenta of a new-born baby
- Certain adult tissues like the bone marrow
How are stem cells used to treat leukemia?
Bone marrow transplants for cancer patients who are immunocompromised as a result of chemotherapy
How are stem cells used to treat Stargardt’s disease?
Treated by replacing dead cells in the retina with functioning ones derived from stem cells
How is leukemia caused?
It is not clear what causes the mutations to occur.
How is Stargardt’s disease caused?
Caused by a gene mutation that impairs energy transport in retinal photoreceptor cells, causing them to degenerate
What is Stargardt’s disease?
An inherited form of juvenile macular degeneration that causes progressive vision loss to the point of blindness
What is leukemia?
Mutations in their DNA that cause them to grow abnormally and lose functions of typical white blood cells.
How are stem cells used to treat Parkinson’s Disease?
Treated by replacing dead nerve cells with living, dopamine-producing ones
What is Parkinson’s Disease?
A degenerative disorder of the central nervous system caused by the death of dopamine-secreting cells in the midbrain
Dopamine is a neurotransmitter responsible for transmitting signals involved in the production of smooth, purposeful movements
How is Parkinson’s Disease caused?
Consequently, individuals with Parkinson’s disease typically exhibit tremors, rigidity, slowness of movement and postural instability
What are the 2 Artificial Stem Cell Techniques?
Somatic cell nuclear transfer (SCNT) & Nuclear Programming
What is Somatic cell nuclear transfer (SCNT)?
- Involves the creation of embryonic clones by fusing a diploid nucleus with an enucleated egg cell (therapeutic cloning)
- More embryos are created by this process than needed, raising ethical concerns about the exigency of excess embryos
What is Nuclear Programming as an artificial stem cell technique?
- Induce a change in the gene expression profile of a cell in order to transform it into a different cell type (transdifferentiation)
- Involves the use of oncogenic retroviruses and transgenes, increasing the risk of health consequences (i.e. cancer)
How do electron microscopes work?
Use electromagnets to focus electrons resulting in significantly greater magnifications and resolutions
Difference between electron and light microscopes?
Light: Uses light, used to view living specimens in natural color
Electron: Uses electrons, used to view dead specimens in monochrome
What are the two key advantages that Electron microscopes have compared to light microscopes?
- They have a much higher range of magnification (can detect smaller structures)
- They have a much higher resolution (can provide clearer and more detailed images)
