Chapter 4 Flashcards
Why do cells replicate?
- Growth and development
- Maintenance and repair
- Reproduction
Why do prokaryotes replicate?
To reproduce
What is binary fission?
the method of cell replication used by prokaryotes
What is exponential growth?
The rapid nature of binary fission, to replicate the number of cells into double
What is asexual reproduction?
A method of reproduction that produces genetically identical cells without the fusion of gametes
What is a plasmid?
A small, circular loop of DNA that is separate from the chromosome. The genes carried in plasmids provide bacteria with genetic advantages, such as antibiotic resistance.
What is the process of binary fission?
- Circular chromosome is uncoiled and the DNA and Plasmids are replicated
- Cell elongates to prepare for division and duplicated circular chromosomes migrate to opposite ends
- cell begins to undergo cytokinesis by pinching inwards and creating a septum
- Results in two genetically identical cells
Why do eukaryotes replicate?
- maintenance (cells constantly die and are replaced)
- growth (as a zygote)
What does the cell cycle consist of?
G1
Synthesis
G2
Mitosis
Cytokinesis
What is G1?
Gap 1 - cell prepares for mitosis by growing the cell (replicating organelles)
What is S?
Synthesis - single chromosome is replicated to make a sister chromatid
What is G2?
Gap 2 - cell further prepares to enter mitosis by growing, producing proteins and enzymes
What is the process of mitosis?
PMAT
Prophase - chromosomes condense with the nuclear membrane breaking down, centrioles and spindle fibres begin to form
Metaphase - chromosomes line up in the middle of the cell with the centromeres in a single line & attach to spindle fibres at the centromere
Anaphase - sister chromatids are pulled apart to either side of the cell via centrioles
Telophase - new nucleus forms around separate chromatids and begin to cleave
What is cytokinesis?
The cytoplasm splits and a new cell membrane forms around the two cells
How does cytokinesis split in animal cells?
A cleavage furrow forms (an indentation of the cell membrane) and meets in the centre to eventually divide in two
Why does cytokinesis occur in plant cells?
A cell plate forms in the middle of the cell, which is a extension of the cell wall
Where are the checkpoints?
G1 Checkpoint (nutrients, growth factors, DNA damage)
G2 Checkpoint (Cell size, DNA replication)
Metaphase Checkpoint (spindle attachment)
G0
What is apoptosis?
The controlled death of cells in the body, AKA programmed cell death
- remove cells that are no longer required and to remove cells that may be detrimental
What is apoptosis triggered by?
Aging, the cells not being required any more or damaged DNA
What is necrosis?
Occurs when cells are damaged to the extent they can no longer function, and it involves cell swelling, bursting and losing its contents
What are caspases?
Enzymes responsible for apoptosis, and when signaled, will stimulate other caspases to be activated
What is the process of apoptosis?
- Cell separates from others
the cell begins to shrink, with the cytoskeleton breaking down and cytoplasm and organelles beginning to condense
- the nucleus begins to disintegrate along with other organelles
- Blebbing occurs (the cell forms blebs on its plasma membrane)
- Blebs then break off as apoptotic bodies which are then engulfed by phagocytes
What occurs with inhibited apoptosis?
webbing between fingers
tail
What occurs with excessive apoptosis?
- Alzheimer’s disease
- Parkinson’s disease
What is cancer?
A group of diseases involving unregulated cell division and growth, with a tumour being a collection of abnormal tissues
Why is cell division essential for both single-celled and multi-cellular organisms?
Cell division is important to both single-celled organisms and multicellular organisms, as single-celled organisms need to divide to reproduce, while multicellular organisms need cell division to grow and replace dead or damaged cells.
What is differentiation?
Differentiation is when cells stop dividing to specialize in their structure and function.
What are checkpoint proteins?
Cell cycle regulators are specialized proteins also known as “checkpoint proteins” that regulate the progression from one phase of the cell cycle to the next.
What is the G0 phase?
Some cells can receive a signal to differentiate to exit the cell cycle
What factors determine whether a cell enters G0?
The factors that determine whether a cell enters G0 are whether the cell receives a signal to differentiate, or whether the cell has enough resources to grow and divide. If there is not enough resources then it will enter the G0 phase.
What are cell cycle regulators?
Cell cycle regulators are proteins that control the progression of a cell through the cell cycle and either simulate or inhibit the cell cycle progression (checkpoints)
What are the two ways cells can form tumours?
A way that cells can form tumours is when proteins that normally stimulate the cell cycle are accelerated it can produce an uncontrolled cell cycle.
Another way that cells can form tumours is when the proteins needed to inhibit the cell cycle is affected by a mutation, causing a loss of inhibition.
What are stimulating proteins encoded by?
Proto-oncogenes
What are inhibitory proteins encoded by?
Tumor supressor genes
What are oncogenes and how do they affect the cell cycle?
Oncogenes increase stimulation in the cell cycle, making the cell divide and replicate an excessive amount.
How do mutated tumour supressor genes affect the cell cycle?
Mutated tumor suppressor genes affect the cell cycle by not having enough restraint on the cell cycle, allowing there to be a faster cell cycle and replication.
