Flashcards in Topic 1.1 - Cell Biology Deck (54)
The 3 ideas of the cell theory:
1. All living things are composed of cells (or cell products)
2. The cell is the smallest unit of life
3. Cells only arise from pre-existing cells
Examples of cells that don't fit the cell theory:
Aseptate fungal hyphae
...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.
...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?
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:
Cells need to produce chemical energy via _______ to survive and this requires the __________ with the environment.
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?
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
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?
What are the 2 key qualities that stem cells have?
1. 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?