UNIT 1 - AOS 2 Flashcards
What is a eukaryotic cell?
Any cell or organism that possesses a clearly defined nucleus (they have membrane-bound organelles).
What is a prokaryotic cell?
Any cell or organism that lacks a distinct nucleus (they do not have membrane-bound organelles).
What is a nucleotide?
It contains phosphate, sugar, and a nitrogen-containing base.
What does it mean by complementary?
Having opposite shapes and changes, so that they pair together.
What does it mean by antiparallel?
Running side by side in the opposite direction.
What is binary fission?
One parent cell produces 2 identical daughter cells.
What are the steps of binary fission?
- A prokaryotic cell before cell replication.
- The circular chromosome is uncoiled and the DNA is replicated. Plasmids also replicate.
- The cell elongates as it prepares to separate into two new cells and the duplicated circular chromosomes migrate to opposite ends.
- The cell undergoes cytokinesis, this is the process of separating into two new cells – by pinching inwards and creating a septum.
- A new cell wall and membrane are formed down the centre of the cell.
- Finally, two new genetically identical cells are formed.
What are the stages of interphase?
G1, Synthesis, G2, Cytokinesis
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What is interphase - G1?
This is the phase when the contractile ring has constricted to its fullest extent, membrane vesicles move to the constriction and fuse with the membrane, creating 2 separate cells. Cytokinesis is complete.
What is interphase - Synthesis?
Is the phase when DNA is packaged into chromosomes, DNA is replicated.
What is interphase - G2?
The cell grows more, makes proteins and organelles and begins to reorganise its contents in its preparation for mitosis.
What is interphase - Cytokinesis?
The nuclear membrane is fully formed, the chromosomes have decondensed and the nucleolus has reappeared. The contractile ring contracts, deepening the cleavage furrow.
What is prophase?
The nucleolus disappears and the chromatin starts to condense and become visible.
The chromatin starts to condense and the nuclear membrane starts to break down.
What is metaphase?
The nuclear membrane is gone. The chromosomes assemble along the equator and the kinetochore at each chromosome centromere extends kinetochore fibres attach spindle fibres.
What is anaphase?
The spindle fibres shorten and the chromatids of. each chromosome is dragged to opposite poles of the cell by its kinetochores.
What is telophase?
The chromosomes begin to decondensed back into expanded chromatin. The nuclear membrane starts to reform around each nucleus. A contractile ring of the fibres and motor proteins start forming, creating a cleavage furrow in the cell membrane
How many bonds are required to bond guanine and cytosine?
3 hydrogen bonds
How many bonds are required to bond adenine and thymine?
2 hydrogen bonds
What are the stages of DNA replication?
- DNA helix unwinds and unzips by the helicase and the DNA strands are separated.
- DNA polymerase binds to each DNA strand and adds primer.
- DNA polymerase adds new nucleotides (bases) to the new DNA strands. Nucleotides add the 3’ end.
What are the key enzymes in DNA replication?
Helicase
DNA polymerase
Primase
Ligase
What is Helicase?
The unzipping enzyme
What is DNA polymerase?
The builder
What is Primase?
The initializer
What is ligase?
Facilitates the joining of DNA strands together
What is the purpose of apoptosis?
Cells may be damaged or defective and must be eliminated
What are the 2 types of cell death?
Apoptosis
Necrosis
What is necrosis?
Is cell death when a cell has been badly damaged through external forces (trauma or infection). Necrosis is uncontrollable.
What is apoptosis?
It is programmed cell death, it is a tightly controlled cell death carried out by an orderly sequence of cellular events.
What are the 2 types of apoptotic pathways?
The intrinsic (mitochondria) pathway The extrinsic (death ligand) pathway
What is the intrinsic (mitochondria) pathway?
When internal components of the cell (such as DNA) are damaged mitochondria detect this damage and release cytochrome c into the cytosol. Cytochrome c binds with cytosolic proteins to form an apoptosome, which activates caspase enzymes, initiating apoptosis.
What is the extrinsic (death ligand) pathway?
Death signalling molecules can be recognised by death receptor proteins on the surface of cells, and are often released by immune cells. When these molecules bind to a death receptor surface protein, caspase enzymes are activated, initiating apoptosis.
What are the major steps in apoptosis?
- Cell begins apoptosis once being separated from other cells.
- Collapse of the cytoskeleton
- Cell shrinkage
- Breakdown of organelles
- Blebbing of the plasma membrane
- Budding of the plasma membrane-bound organelle/vesicles called apoptotic bodies
- Phagocytosis
What is potency?
Refers to their abilities to produce different cell types.
What is Totipotent?
They give rise to all cell types
What is Pluripotent?
They give rise to many cell types
What is Multipotent?
They give rise to related families of cells
What is Oligopotent?
They differentiate into a few cells
What is Unipotent?
They only produce cells of their own type
What is Differentiation?
The specialisation of a cell for a particular function in the body, by regulation of the expression of its genes.
What are stem cells?
They are undifferentiated cells with the capability of differentiating into specialised cells.
What is Self-renewal?
Stem cells have the capacity to replicate without disrupting their ability to differentiate by producing both a differentiated cell and a copy of themselves when they replicate.
What is the checkpoint of apoptosis?
G1 checkpoint – inspects for DNA damage
G2 checkpoint – confirms that DNA has correctly replicated in the S phase
Metaphase checkpoint – confirms that spindle fibres have correctly attached to the centromeres of chromosomes.
Apoptosis and cancer:
For example, cells may no longer express functional death receptor proteins, leading to an inability for death signalling molecules to initiate apoptosis By failing to initiate, cells have a reduced rate of apoptosis.
