Chapter 4 Flashcards
(23 cards)
What are the three purposes of cell replication
growth and development
maintenance and repair
reproduction
How does cell replication help growth and development
All humans begin as a single cell. From there, we replicate rapidly, becoming an embryo, foetus, and then a baby. As we grow larger, our cells don’t actually become larger. Instead, we are simply made of more cells. Therefore, for a multicellular organism to grow and develop, it is important that cells replicate
How does cell replication help maintenance and repair
Cells are constantly dying as they age or become damaged. Cell replication allows these cells to be replaced, ensuring the proper functioning of an organism
How does cell replication help reproduction
Prokaryotic and eukaryotic cells replicate to reproduce. When they replicate, they are enlarging their population
What is Exponential growth
Cells replicate exponentially- after each round of replication the number of cells present doubles
The rapid nature of binary fission allows a single bacterium to replicate into a few millions’ bacteria in a very short span of time
What is binary fission
A type of asexual reproduction seen in prokaryotic cells where the cells replicate themselves
What are the four stages of binary fission
D- DNA replication
E- Elongation
S- Septum formation
C- Cell division
What is the formula for growth rate of cells using binary fission
Growth rate of cells using binary fission is Cell # = 2^n where n is the number of generations
What are the three stages of the eukaryotic cell cycle
There are three stages of the eukaryotic cell cycle
1. Interphase-cellular growth & duplication of chromosomes
2. Mitosis- separation of sister chromatids and the formation of two new nuclei
3. Cytokinesis- division of the cytoplasm and th formation of 2 daughter cells
What is interphase
- First and longest stage of the cell cycle
- Cell synthesises necessary DNA, proteins, and organelles required for growth and replication
- The DNA in the nucleus exists as long chromatin threads instead of discrete chromosomes
There are 3 substages of interphase
What are the three substages of interphase
Gap 1 (G1) Phase:
Cell grows by increasing the volume of the cytosol
Synthesizing proteins for DNA replication
Replicating its organelles
Synthesis (S) phase:
Cell replicated its DNA turning one chromosome into 2 identical sister chromatids
Gap 2 (G2) phase
Final stage of interphase
cells grows and prepares for mitosis
Increasing the volume of cytosol
Synthesizing proteins in preparation for mitosis
How are sister chromatids are held together
Sister chromatids are held together by a centromere.
When the sister chromatids separate in mitosis, each chromatid is considered a sister chromosome.
what are human somatic cells?
In humans, our somatic cells are diploid, meaning they contain 2 sets of paired chromosomes.
As there are 23 chromosome pairs in humans, each somatic cell will contain 2 x 23 = 46 chromosomes
What is mitosis
Mitosis is the 2nd stage of the eukaryotic cell cycle and involves the separation of the newly replicated chromosomes into 2 new nuclei
What is cytokinesis
Cytokinesis is the 3rd and final stage of the eukaryotic cell cycle, where the cells divides into 2 daughter cells
* After mitosis the cytoplasm divides and the organelles evenly distribute themselves before dividing into 2 daughter cells
* In animals a cleavage furrow develops and pinches the plasma membrane into 2 cells
* In plants a cell plate first forms at the equator before separating into 2 cells
What are the 4 stages of Mitosis
Prophase (prepare)
Metaphase (meet in middle)
Anaphase (move apart)
Telophase (towards two)
Describe Prophase
Prophase begins with the condensation of chromatin around histones into distinct chromosomes, so that they become visible under a microscope. Simultaneously, the centrioles migrate towards opposite ends of the cell, and spindle fibers begin to form. The nuclear membrane breaks down and the nucleolus dissapears.
Describe Prophase
Prophase begins with the condensation of chromatin around histones into distinct chromosomes, so that they become visible under a microscope. Simultaneously, the centrioles migrate towards opposite ends of the cell, and spindle fibers begin to form. The nuclear membrane breaks down and the nucleolus dissapears.
Describe Metaphase
In metaphase, the spindle fibers fully form and attach to the centromere of each chromosome. This allows the spindle fibers to guide the chromosomes towards the equator of the cell where they line up
Describe Anaphase
The spindle fibers contract, splitting the centromere and pulling sister chromatids to opposite ends of the cell
Describe Telophase
The chromosomes densely pack together at either end of the cell, and new nuclear membranes form, producing two genetically identical nuclei. The spindle fibers disintegrate and the chromosomes decondense. Telophase is very similar to the reverse of prophase.
Describe the regulation of cell cycle
- The cell cycle has 3 checkpoints that inspect for errors before moving to the next stage
- If errors are detected the cell can pause for repairs
- If the damage is irreparable, then the cell undergoes programmed cell death
What are the 3 checkpoints of cell regulation
Metaphase checkpoint: cell checks formation of spindle fibers
If chromosomes are lined up in the correct location, the cell proceeds to anaphase
G1: verifies that cell has grown to the correct size, has enough protein for DNA replication checks if DNA damaged during mitosis and checks if there is enough nutrients and oxygen
G2: ensures that DNA has replicated properly in the S phase, and the cell has enough resources for mitosis
