Growth
Growth is anisotropic as it occurs at different rates in different directions
creating diverse shapes and structures. This is due to variations in cell division
rates, mechanical constrains of organs, and different gene expression. Plant
stems exist anisotropic growth when they bend towards the light through
phototropism.
Proportionality refers to the maintenance of specific ratios or relationships
between parts of an organism. It ensures growth is balanced.
Adaptability is the ability of an organism to adjust its growth patterns in
response to environmental conditions. This ensures survival.
Discontinuous Scaling refers to the growth that occurs in abrupt stages (not a
smooth manner). As organisms grow they do not scale up continuously
instead going through distinct phases.
Limitation of Cellular Growth is mostly due to mRNA synthesis:
Cellular growth seems to be limited mostly by mRNA synthesis being a rate-limited
step. Some cells that do get very large have special adaptations such as multiple
copies of their genome (polyploidy) or increased numbers of ribosomes. This
maintains a favourable gene-to-cytoplasm volume ratio preventing mRNA from
limiting cell growth. Cellular growth is also limited by communication and
coordination.
Growth 1
, Growth beyond the Cellular Level:
Growth of things larger than cells usually involves multiplication of constituent
cells. The multiplication of cells allows the development and expansion of tissues
and organs. Growth occurs because there are more cells (proliferation) not the
size of the cells increasing.
Making Bigger Cells:
Vacuoles are membrane-bound organelles containing water, enzymes, and
nutrients. When vacuoles fill with water they expand pushing against the cell
wall causing the cell to expand.
Syncytia is a single cell containing several nuclei, formed by fusion of cells or
by division of nuclei. This is caused by viral infection but makes the cell larger.
Polytene Chromosomes are large chromosomes produced by DNA replication
(without cell division) which increase the volume of a cells nucleus causing
cell expansion.
Helper Cells can provide growth factors and signals promoting growth and cell
fusion.
Paracrine Control: Cellular communication where cells secrete signalling
molecules into the extracellular space where they diffuse short distances to reach
nearby target cells.
Autocrine Control forming cancer: Neoplasia is a consequence of cells acquiring
autocrine control of their own proliferation. Neoplasia refers to the abnormal and
uncontrolled growth of cells, leading to the formation of tumours. One significant
mechanism underlying neoplasia is the acquisition of autocrine control, where
cells produce and respond to their own growth factors. This self-stimulating
growth mechanism can drive cellular proliferation and contribute to tumorigenesis.
Cleavage Division
Cleavage division is a rapid process during early embryonic development, where
the cell divides multiple times without the typical growth phases (like G1 and G2).
The main goal is to produce a large number of cells quickly, all of which are
Growth 2
Growth is anisotropic as it occurs at different rates in different directions
creating diverse shapes and structures. This is due to variations in cell division
rates, mechanical constrains of organs, and different gene expression. Plant
stems exist anisotropic growth when they bend towards the light through
phototropism.
Proportionality refers to the maintenance of specific ratios or relationships
between parts of an organism. It ensures growth is balanced.
Adaptability is the ability of an organism to adjust its growth patterns in
response to environmental conditions. This ensures survival.
Discontinuous Scaling refers to the growth that occurs in abrupt stages (not a
smooth manner). As organisms grow they do not scale up continuously
instead going through distinct phases.
Limitation of Cellular Growth is mostly due to mRNA synthesis:
Cellular growth seems to be limited mostly by mRNA synthesis being a rate-limited
step. Some cells that do get very large have special adaptations such as multiple
copies of their genome (polyploidy) or increased numbers of ribosomes. This
maintains a favourable gene-to-cytoplasm volume ratio preventing mRNA from
limiting cell growth. Cellular growth is also limited by communication and
coordination.
Growth 1
, Growth beyond the Cellular Level:
Growth of things larger than cells usually involves multiplication of constituent
cells. The multiplication of cells allows the development and expansion of tissues
and organs. Growth occurs because there are more cells (proliferation) not the
size of the cells increasing.
Making Bigger Cells:
Vacuoles are membrane-bound organelles containing water, enzymes, and
nutrients. When vacuoles fill with water they expand pushing against the cell
wall causing the cell to expand.
Syncytia is a single cell containing several nuclei, formed by fusion of cells or
by division of nuclei. This is caused by viral infection but makes the cell larger.
Polytene Chromosomes are large chromosomes produced by DNA replication
(without cell division) which increase the volume of a cells nucleus causing
cell expansion.
Helper Cells can provide growth factors and signals promoting growth and cell
fusion.
Paracrine Control: Cellular communication where cells secrete signalling
molecules into the extracellular space where they diffuse short distances to reach
nearby target cells.
Autocrine Control forming cancer: Neoplasia is a consequence of cells acquiring
autocrine control of their own proliferation. Neoplasia refers to the abnormal and
uncontrolled growth of cells, leading to the formation of tumours. One significant
mechanism underlying neoplasia is the acquisition of autocrine control, where
cells produce and respond to their own growth factors. This self-stimulating
growth mechanism can drive cellular proliferation and contribute to tumorigenesis.
Cleavage Division
Cleavage division is a rapid process during early embryonic development, where
the cell divides multiple times without the typical growth phases (like G1 and G2).
The main goal is to produce a large number of cells quickly, all of which are
Growth 2
