cellssss Flashcards
Outline the importance of morphogens in the development of organisms
During early-stage embryo development, complex mechanisms of gene expression determine the
ways cells differentiate and take on specific roles. A small number of genes determine body patterns
during the embryo’s development. The specific signalling molecules that are involved in gene
expression are called morphogens.
Morphogens are extracellular (i.e. they exist outside the cells of a tissue) and occur across a
gradient of concentrations.
The gradient of the morphogen drives the process of differentiation of unspecialized stem cells into
different cell types.
Where there is a high concentration of morphogens, these cells will change differently to cells where there is a lower
concentration of morphogens.
The initiation or inhibition of gene expression is a result of different concentrations of morphogens,
which control the way cells differentiate and develop into specific tissues.
properties of stem cells (origin)
In the development of a new organism, the first step after the formation of the zygote is one of continual cell division to produce a tiny ball of cells, called the blastocyst. All these cells are capable of further divisions.
The cells of the inner cell mass are known as embryonic stem cells.
A stem cell is a cell that has the ability for endless repeated cell division.
Stem cells maintain an undifferentiated state (this is called ‘self-renewal’), while also having the capacity to differentiate into mature cell types (potency) along different pathways.
Stem cells are found in all multicellular organisms.
At the next stage of embryological development, very few cells within these tissues keep many of the properties of embryonic stem cells. These are called adult stem cells.
embryonic vs. adult stem cell
embryonic cells CONTINUALLY divide and can develop into any cell type with the adult organism/make up the bulk of the embryo as it begins development
adult stem cells can only develop into a limited range of cells within a tissue; e.g., blood stem cells can only develop into red and white blood cells, and platelets/found in most organs throughout the body
both could be used to repair dead or damaged cells (BONE MARROW to get healthy bone marrow cells)
stem cell niches
A stem cell niche is an area of a tissue that provides a specific environment where stem cells exist in an undifferentiated and self-renewable state, and where they receive stimuli to determine their behaviour.
Types: bone marrow and hair follicles (pigment-producing)
Differences between totipotent, pluripotent and multipotent stem cells
totipotent = first formed stem cells of a zygote; can develop into ANY type of cell, including totipotent cells & placental cells
pluripotent = stem cells in the blastocyst phase of the division of the embryo; can divide into any cell, except totipotent cells and placental cells
multipotent = can develop into more than one type of cell, but has a limited capacity for self-renewal; can create, maintain, and repair cells from only ONE TYPE OF ORGAN OR TISSUE.
Outline why the female gamete in humans is much larger than the male gamete.
Explain why red blood cells are smaller than white blood cells.
- The larger cell body of the egg allows it to store nutrients for the early development of the fertilized egg, whereas the cell body of the sperm only needs to hold the nucleus, for delivery to the egg, and so can be much smaller.
- Red blood cells need to be small so that they can fit through the small lumen of capillaries.
The larger size of white blood cells allows them either to engulf and digest pathogens or to produce antibodies that bind to the body’s foreign invaders and destroy them.
Explain why neurons and striated muscle cells are the size that they are.
The long length enables the electrical impulse to be sent without interruption over a long distance. Response to stimuli, especially those concerned with pain, need to happen quickly, and so fast transmission of the impulse is necessary – something achieved by the long length of the myelinated neuron.
This extended length allows them to coordinate contraction and has a significant effect on muscle force generation.
prophase
- Replicated DNA in the form of chromatin condenses into chromosomes
- Kineticores attach to the centromeres of the chromsomes
- Microtubles are formed to created mitotic spindles
- the nuclear membrane begins to dissolve
metaphase
- microtubules attach to kineticores on each chromatid
- chromosomes line up along the metaphase plate
anaphase
- the centromere divides, and so the sister chromatids are pulled apart.
- the motor proteins of the kineticore drive movement along the microtubles to the poles of the cell
telophase
- chromosomes are tightly grouped and pulled to each end of the cell
- nuclear membrane reforms around each set of daughter chromosomes
- chromosomes decondense into chromatin
- microtuble spindle fibers disappear
cytokinesis animals
A ring of contractile protein (microfilaments) immediately inside the plasma membrane at the equator pulls the plasma membrane inward.
The inward pull on the plasma membrane produces the characteristic cleavage furrow.
When the cleavage furrow reaches the centre of the cells it is pinched apart to form two daughter cells.
cytokinesis plants
during telophase, vacuoles form tubular structures. All form these tubular structures merge together to form a cell plate. The cell plate continues to develop until reaching the existing plasma membrane, and at that point, two new daughter cells have been created
NOTE: by exocytosis, vesicles distribute substances into the lumen between the 2 new cells which creates the middle lumella
G1
cell growth, gene expression, organelles produced, cellular respiration
S
DNA replicated
