Chapter 2: The Cell Cycle and Cell Growth, Death and Differentiation Flashcards
How do prokaryotes reproduce?
Asexually
How do eukaryotes reproduce?
Asexually and sexually
Why do cells divide?
- reproduction
- growth
- repair
What is asexual reproduction?
Asexual reproduction is a form of reproduction which requires one parent cell to create offspring that are an exact copy of the parent cell.
List the types of asexual reproduction in prokaryotes
- binary fission
- budding
- parthenogenesis
- regeneration
Describe the stages involved in binary fission
- The circular DNA in prokaryotic cells are copied into two identical chromosomes
- The cell begins to elongate and the two chromosomes go to opposite ends of the cells
- A cell wall is created in between the two chromosomes (known as septum) which extends and breaks in half to create two cells
What is budding?
An offspring grows out the body of the parent cell
What is regeneration?
The body of the parent cell breaks into two distinct pieces of which can produce an offspring
What is parthenogenesis?
Females produce eggs which do not need fertilisation to develop
List the three stages of the cell cycle in eukaryotic cells.
- Interphase
- Mitosis
- Cytokinesis
What occurs during interphase?
Interphase is the period in which the cell’s DNA replicates.
Interphase is broken down into three stages: G1, S and G2.
G1 stage is also known gap 1 stage. This is where the cytosol increases and the cells starts to grow. The cell’s mitochondria and synthesis proteins to split in order for DNA replication
At the end of this stage, cells either continue to divide or does not which is known as g0.
The synthesis or the S stage of interphase is when the parent cell synthesises or replicates its DNA, the genetic material of the cell. At the end of the S stage, the parent cell contains two identical copies of its original DNA.
The g2 stage is where the cell continues to grow and also continues to synthesise proteins.
What occurs during mitosis?
The mitosis stage is also known as the M phase. The mitosis phase can be broken down into prophase, metaphase, anaphase and telophase.
Prophase: chromosomes contracts and become visible. Centrioles start to move to opposite poles and spindle fibres start to form.
Metaphase: mitotic spindle fibres are formed and centrioles are at the opposite ends of their poles. The nuclear membrane has disappeared and chromosomes align around the equator of the cell.
Anaphase: The chromosomes separate into chromatid (single stand of a chromosomes) and are pulled to opposite ends of the spindle by the contraction of spindle fibres
Telophase: A nuclear membrane forms around each separate group of single-stranded chromosomes and the chromosomes gradually decondense.
What occurs during cytokinesis?
At the end of mitosis, the division of the nucleus into two new identical nuclei is complete. However, the cell cycle is completed only after the cytosol, and the organelles in the cytosol, distribute around the new nuclei and become enclosed within an entire plasma membrane. This final process of the cell cycle is called cytokinesis
For the cell cycle for eukaryotic cells, what does the cell start and end with?
The cell starts with one cell containing 4 single stranded chromosomes.
The cell ends with two cells each containing 4 single stranded chromosomes.
How is the cell cycle regulated?
Cell cycle is regulated through checkpoints.
During g1, the DNA of the cell is checked and if it is found to be damaged or incomplete, the cell is stopped from
continuing through the cell cycle. This occurs because of p53 which is a tumour-suppressant protein. If the cell is damaged it goes to g0.
The S stage occurs as normal and during g2, the replicated DNA of the cell is checked for completeness and lack of damage. If the cell passes this checkpoint, it can then advance to the mitosis stage of the cell cycle.
During mitosis, if an error is detected, the cell cycle is delayed until the error is fixed.
Describe the different types of cell cycle in different organisms.
Cell cycle in humans: In mammals, such as a human adult, actively dividing cells are found in several tissues, such as the epidermis of the skin, the epithelial lining of the gut and the bone marrow. Cell division normally occurs at a tightly regulated rate, so that the production of new cells matches or balances the rate of cell loss.
Cell cycle in plants:
Cell cycle in animals:
Cell cycle in fungi: Mitosis occurs within the spore case and thousands of black spores are formed. On maturing, the spore case splits open and the tiny, light spores are scattered.
List the two types of cell death
- Apoptosis
- Necrosis
What is necrosis?
Necrosis is cell death where a cell has been badly damaged through external forces such as trauma or infection. This results in the cell to swell up and eventually burst
What is apoptosis?
the programmed death of cells that occurs as a normal and controlled part of an organism’s growth or development. This results in the cell to shrink and gets engulfed by phagocytes.
What causes signals to be sent for apoptosis?
- Cells at the end of their natural life
- Dysfunctional, damaged or diseased cells
- Excessive cells
What are the purposes of apoptosis?
- To eliminate cells that are infected or defective
- Apoptosis sculpts the body from tissues
List and describe the stages of apoptosis?
- Signal for apoptosis begins
- The cell separates from other cells and its cytoskeleton collapses.
- The cell shrinks
- Its organelles and nucleus breaks down.
- “Blebbing” of plasma membrane occurs.
- Budding of plasma-membrane-bound vesicles called apoptotic bodies which prevent toxic or immunogenic substances from leaking form.
- The apoptotic bodies are phagocytosed.
Describe the terms differentiation and specialisation in relation to cells and tissue
Differentiation is the process by which cells, tissues and organs acquire specialised features. Specialisation is the adaptation of something for a specific function
What is a stem cell?
Stem cells are undifferentiated or unspecialised cells that have the ability to differentiate into organ or tissue-specific cells with specialised functions, such as nerve cells, blood cells, bone cells, heart cells, skin cells and so on.
Why are stem cells important?
Stem cells are important as they divide and renew themselves, remain undifferentiated in form and can develop into a variety of specialised cell types
What are the two types of stem cells?
- Adult stem cells (somatic stem cells)
- Embryonic stem cells
Describe the two types of stem cells
Adult stem cells: undifferentiated cells obtained from various sources and capable of differentiating into related cell types; also known as somatic stem cells
Embryonic stem cells: an undifferentiated cell obtained
from early embryonic tissue that is capable of differentiating into many cell types
Define potency
In the context of stem cells, “potency” refers to a cell’s ability to differentiate into other cell types, with higher potency meaning a wider range of cell types a stem cell can become
List the different types of potency and define them
- Totipotent: a cell that is able to give rise to all different cell types
- Pluripotent:
- Multipotent: a cell that can
differentiate into a number of closely related cell types
What type of stems cells are pluripotent?
What type of stem cells are totipotent?
Embryonic stem cells
What type of stems cells are multipotent?
Adult stem cells
