Mitochondrion - Revision history

Vipul: /* Summary */

2024-04-19T09:07:53Z

Summary

← Older revision		Revision as of 09:07, 19 April 2024
Line 20:		Line 20:
	\| Shape \|\| Most mitochondria are tubular (cylindrical, with rounded ends). The tubular radius is usually significantly less than half the length, e.g., about 1/4 in one example.<ref name=tubular-radius>{{cite web\|url = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2711342/\|title = Diffusion Restrictions Surrounding Mitochondria: A Mathematical Model of Heart Muscle Fibers}}</ref> Some mitochondria are spherical (globular); the transition to spherical/globular shape generally happens due to unusual circumstances such as the loss of membrane potential.<ref name=spherical-contraction>{{cite web\|url = https://www.nature.com/articles/s41598-017-18582-6\|title = Uncoupled mitochondria quickly shorten along their long axis to form indented spheroids, instead of rings, in a fission-independent manner}}</ref>		\| Shape \|\| Most mitochondria are tubular (cylindrical, with rounded ends). The tubular radius is usually significantly less than half the length, e.g., about 1/4 in one example.<ref name=tubular-radius>{{cite web\|url = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2711342/\|title = Diffusion Restrictions Surrounding Mitochondria: A Mathematical Model of Heart Muscle Fibers}}</ref> Some mitochondria are spherical (globular); the transition to spherical/globular shape generally happens due to unusual circumstances such as the loss of membrane potential.<ref name=spherical-contraction>{{cite web\|url = https://www.nature.com/articles/s41598-017-18582-6\|title = Uncoupled mitochondria quickly shorten along their long axis to form indented spheroids, instead of rings, in a fission-independent manner}}</ref>
	\|-		\|-
	\| Size \|\| <math>0.5 - 3 \mu m</math> ~~diameter per mitochondrion~~. In some cells with significant energy needs (such as human heart cells), they could together take up to 1/4 of the cell volume.		\| Size \|\| <math>0.5 - 1 \mu m</math> tubular radius and <math>1 - 4 \mu m</math> length. In some cells with significant energy needs (such as human heart cells), they could together take up to 1/4 of the cell volume.
	\|-		\|-
	\| Interconnection \|\| Mitochondria are usually networked with each other, forming a [[mitochondrial network]]. The extent to which the mitochondria are fused with each other depends on the relative rates of fission and fusion. The study of the shape of mitochondrial networks is called [[mitochondrial morphology]] and the study of the change in these over time is called [[mitochondrial dynamics]].<ref>{{cite web\|url = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672710/\|title = What is the function of mitochondrial networks? A theoretical assessment of hypotheses and proposal for future research}}</ref><ref>{{cite web\|url = https://bmcbiol.biomedcentral.com/articles/10.1186/1741-7007-11-71\|title = Mitochondrial network morphology: building an integrative, geometrical view}}</ref>		\| Interconnection \|\| Mitochondria are usually networked with each other, forming a [[mitochondrial network]]. The extent to which the mitochondria are fused with each other depends on the relative rates of fission and fusion. The study of the shape of mitochondrial networks is called [[mitochondrial morphology]] and the study of the change in these over time is called [[mitochondrial dynamics]].<ref>{{cite web\|url = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4672710/\|title = What is the function of mitochondrial networks? A theoretical assessment of hypotheses and proposal for future research}}</ref><ref>{{cite web\|url = https://bmcbiol.biomedcentral.com/articles/10.1186/1741-7007-11-71\|title = Mitochondrial network morphology: building an integrative, geometrical view}}</ref>

Vipul: /* Summary */

2024-04-19T09:05:36Z

Summary

← Older revision		Revision as of 09:05, 19 April 2024
Line 18:		Line 18:
	\| Number of mitochondria per cell \|\| 1 to 1000s, depending on the energy needs of the cell		\| Number of mitochondria per cell \|\| 1 to 1000s, depending on the energy needs of the cell
	\|-		\|-
	\| Shape \|\| Most mitochondria are tubular (cylindrical, with rounded ends). The tubular radius is usually significantly less than half the ~~diameter~~, e.g., about 1/4 in one example.<ref name=tubular-radius>{{cite web\|url = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2711342/\|title = Diffusion Restrictions Surrounding Mitochondria: A Mathematical Model of Heart Muscle Fibers}}</ref> Some mitochondria are spherical (globular); the transition to spherical/globular shape generally happens due to unusual circumstances such as the loss of membrane potential.<ref name=spherical-contraction>{{cite web\|url = https://www.nature.com/articles/s41598-017-18582-6\|title = Uncoupled mitochondria quickly shorten along their long axis to form indented spheroids, instead of rings, in a fission-independent manner}}</ref>		\| Shape \|\| Most mitochondria are tubular (cylindrical, with rounded ends). The tubular radius is usually significantly less than half the length, e.g., about 1/4 in one example.<ref name=tubular-radius>{{cite web\|url = https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2711342/\|title = Diffusion Restrictions Surrounding Mitochondria: A Mathematical Model of Heart Muscle Fibers}}</ref> Some mitochondria are spherical (globular); the transition to spherical/globular shape generally happens due to unusual circumstances such as the loss of membrane potential.<ref name=spherical-contraction>{{cite web\|url = https://www.nature.com/articles/s41598-017-18582-6\|title = Uncoupled mitochondria quickly shorten along their long axis to form indented spheroids, instead of rings, in a fission-independent manner}}</ref>
	\|-		\|-
	\| Size \|\| <math>0.5 - 3 \mu m</math> diameter per mitochondrion. In some cells with significant energy needs (such as human heart cells), they could together take up to 1/4 of the cell volume.		\| Size \|\| <math>0.5 - 3 \mu m</math> diameter per mitochondrion. In some cells with significant energy needs (such as human heart cells), they could together take up to 1/4 of the cell volume.

Vipul: /* Summary */

2024-04-19T09:05:03Z

Summary

← Older revision		Revision as of 09:05, 19 April 2024
Line 12:		Line 12:
	! Item !! Value		! Item !! Value
	\|-		\|-
	\| Type of organisms whose cells contain mitochondria \|\| [[Eukaryotic cell]]s ''only'', including [[plant cell]]s, [[animal cell]]s, and the cells of [[protist]]s and [[fungus\|fungi]]; some of the more primitive eukaryotic cells (only in unicellular organisms) lack mitochondria; some of them have other similar (and likely ~~evolutionary~~ related) structures such as [[mitosome]]s or [[hydrogenosome]]s. For more, see [[most eukaryotic organisms have mitochondria in most of their cells]].		\| Type of organisms whose cells contain mitochondria \|\| [[Eukaryotic cell]]s ''only'', including [[plant cell]]s, [[animal cell]]s, and the cells of [[protist]]s and [[fungus\|fungi]]; some of the more primitive eukaryotic cells (only in unicellular organisms) lack mitochondria; some of them have other similar (and likely evolutionarily related) structures such as [[mitosome]]s or [[hydrogenosome]]s. For more, see [[most eukaryotic organisms have mitochondria in most of their cells]].
	\|-		\|-
	\| Type of cells within the organisms that contain mitochondria \|\| All cells except [[red blood cell]]s in [[mammal]]s (other vertebrates ''do'' have mitochondria in their red blood cells). For more, see [[most eukaryotic organisms have mitochondria in most of their cells]].		\| Type of cells within the organisms that contain mitochondria \|\| All cells except [[red blood cell]]s in [[mammal]]s (other vertebrates ''do'' have mitochondria in their red blood cells). For more, see [[most eukaryotic organisms have mitochondria in most of their cells]].

Vipul: /* Mitochondrial networks, fission and fusion */

2024-04-18T05:33:43Z

Mitochondrial networks, fission and fusion

← Older revision		Revision as of 05:33, 18 April 2024
Line 161:		Line 161:
	===Mitochondrial networks, fission and fusion===		===Mitochondrial networks, fission and fusion===

	In most cells, the mitochondria are interconnected as a network called the [[mitochondrial network]]. The mitochondria in the network align along their tubular axis. ~~The~~ network ~~could be a single curve (without branching) or it could~~ have ~~branches, depending on details specific to~~ the ~~cell~~.		In most cells, the mitochondria are interconnected as a network called the [[mitochondrial network]]. The mitochondria in the network align along their tubular axis. In particular, the mitochondria within a network will have fairly similar values of tubular radius that will generally not change much throughout the dynamics of the mitochondrion.

	Mitochondria are constantly undergoing [[mitochondrial fission]] (one mitochondrion splitting into two, that then go on to form adjacent nodes in the mitochondrial network) and [[mitochondrial fusion]] (two adjacent mitochondria in the mitochondrial network fusing into one).		The network could be a single curve (without branching) or it could have branches, depending on details specific to the cell.

			Mitochondria are constantly undergoing [[mitochondrial fission]] (one mitochondrion splitting into two, that then go on to form adjacent nodes in the mitochondrial network) and [[mitochondrial fusion]] (two adjacent mitochondria in the mitochondrial network fusing into one). All these changes happen along the tubular axis, without much change to the tubular radius.

	The relative rates of fission and fusion determine how the mitochondrial network evolves over time.		The relative rates of fission and fusion determine how the mitochondrial network evolves over time.

Vipul: /* Qualia of shape: spherical / globular shape versus the more typical tubular shape */

2024-04-18T05:32:20Z

Qualia of shape: spherical / globular shape versus the more typical tubular shape

← Older revision		Revision as of 05:32, 18 April 2024
Line 69:		Line 69:
	* A ratio greater than 2 indicates a more typical tubular (elongated) mitochondrion shape. A typical ratio is around 4; for instance, that's the ratio seen in cardiac cells in one study.<ref name=tubular-radius/>		* A ratio greater than 2 indicates a more typical tubular (elongated) mitochondrion shape. A typical ratio is around 4; for instance, that's the ratio seen in cardiac cells in one study.<ref name=tubular-radius/>

	The shape of a mitochondrion has significance for its functionality. The tubular shape is tied to maintaining membrane potential, which is a key aspect of mitochondrial function, and a spherical/globular shape is often seen as a result of a loss of membrane potential.<ref name=spherical-contraction/>		The shape of a mitochondrion has significance for its functionality. The tubular shape is tied to maintaining membrane potential, which is a key aspect of mitochondrial function, and a spherical/globular shape is often seen as a result of a loss of membrane potential.<ref name=spherical-contraction/> In general, the tubular radius of a mitochondrion is less subject to change than its length, as most dynamics (such as fission and fusion) happen along the tubular axis.

	===Value ranges for size parameters===		===Value ranges for size parameters===

Vipul: /* Size and shape */

2024-04-18T05:27:03Z

Size and shape

← Older revision		Revision as of 05:27, 18 April 2024
Line 50:		Line 50:

	{{size measures backgrounder}}		{{size measures backgrounder}}

			As discussed in the later section [[#Interconnection, propagation, and dynamics]], mitochondria are in constant flux. The scope of the current section, however, is to describe their general shape patterns rather than dynamics. For simplicity, assume for this section that we have a snapshot of the mitochondrion when it's not in the middle of fission of fusion.

	===Size parameters: length and tubular radius===		===Size parameters: length and tubular radius===

Vipul: /* Comparison with molecules */

2024-04-18T05:14:38Z

Comparison with molecules

← Older revision		Revision as of 05:14, 18 April 2024
Line 135:		Line 135:
	===Comparison with molecules===		===Comparison with molecules===

	A water molecule's size is about <math>2.75 * 10^{-10} m</math>, which is a little under 1/1000 of the low end for the tubular radius of a mitochondrion (0.5 <math>\mu m</math>). Since this is in just one dimension (length) we need to square when thinking about cross-sectional area and cube when thinking about volume. Roughly speaking, a cross section has space for millions of water molecules, and the mitochondrion has space for billions of water molecules.		A water molecule's size is about <math>2.75 * 10^{-10} m</math>, which is a little under 1/1000 of the low end for the tubular radius of a mitochondrion (0.5 <math>\mu m</math>). Since this is in just one dimension (length) we need to square when thinking about cross-sectional area and cube when thinking about volume. Roughly speaking, a cross section has space for the order of millions of water molecules, and the mitochondrion has space for the order of billions of water molecules.

	==Physical structure==		==Physical structure==

Vipul: /* Size and shape */

2024-04-18T05:10:10Z

Size and shape

← Older revision		Revision as of 05:10, 18 April 2024
Line 132:		Line 132:

	Mitochondria are among the bigger of the cellular organelles. The mitochondrion, nucleus, and Golgi bodies are the cellular organelles big enough to be identified using a light microscope, and for that reason are among the oldest organelles to be identified and studied (even prior to the advent of electron microscopes).		Mitochondria are among the bigger of the cellular organelles. The mitochondrion, nucleus, and Golgi bodies are the cellular organelles big enough to be identified using a light microscope, and for that reason are among the oldest organelles to be identified and studied (even prior to the advent of electron microscopes).

			===Comparison with molecules===

			A water molecule's size is about <math>2.75 * 10^{-10} m</math>, which is a little under 1/1000 of the low end for the tubular radius of a mitochondrion (0.5 <math>\mu m</math>). Since this is in just one dimension (length) we need to square when thinking about cross-sectional area and cube when thinking about volume. Roughly speaking, a cross section has space for millions of water molecules, and the mitochondrion has space for billions of water molecules.

	==Physical structure==		==Physical structure==

Vipul: /* Comparison with wavelengths of light and implications for visibility under microscopes */

2024-04-18T05:05:47Z

Comparison with wavelengths of light and implications for visibility under microscopes

← Older revision		Revision as of 05:05, 18 April 2024
Line 127:		Line 127:
	===Comparison with wavelengths of light and implications for visibility under microscopes===		===Comparison with wavelengths of light and implications for visibility under microscopes===

	The wavelength of visible light is in the range <math>0.4-0.7 \mu m</math>, which is at the ~~lower end~~ of the ~~diameter range for mitochondria~~. Thus, mitochondria can be viewed with [[light microscope]]s (whose resolution is limited to <math>0.2 \mu m</math>) but their internal structures cannot be clearly identified. [[Electron microscope]]s (that cannot be used on live cells) need to be used to study the structure of mitochondria well.		The wavelength of visible light is in the range <math>0.4-0.7 \mu m</math>, which is approximately equal to the tubular radius and a little less than the length of the mitochondrion. Thus, mitochondria can be viewed with [[light microscope]]s (whose resolution is limited to <math>0.2 \mu m</math>) but their internal structures cannot be clearly identified. [[Electron microscope]]s (that cannot be used on live cells) need to be used to study the structure of mitochondria well.

	===Comparison with other organelles===		===Comparison with other organelles===

Vipul: /* Comparison with cell sizes */

2024-04-18T05:04:56Z

Comparison with cell sizes

← Older revision		Revision as of 05:04, 18 April 2024
Line 121:		Line 121:
	''Comparison with prokaryotic cells'': The mitochondrion size is roughly the lower end of the size range for [[prokaryotic cell]]s (which is explained by their evolutionary origin; see [[endosymbiotic theory of mitochondrial origin]]).		''Comparison with prokaryotic cells'': The mitochondrion size is roughly the lower end of the size range for [[prokaryotic cell]]s (which is explained by their evolutionary origin; see [[endosymbiotic theory of mitochondrial origin]]).

	''Comparison with eukaryotic cells'': Mitochondria are found in [[eukaryotic cell]]s (''not'' prokaryotic cells) which have a diameter in the <math>10-100 \mu m</math> range. Thus, ~~each~~ mitochondrion ~~has~~ about 1/100 to 1/10 the diameter of the whole cell and hence about 1/10^6 to 1/10^3 the ''volume'' of the whole cell.		''Comparison with eukaryotic cells'': Mitochondria are found in [[eukaryotic cell]]s (''not'' prokaryotic cells) which have a diameter in the <math>10-100 \mu m</math> range. Thus, the dimensions of an individual mitochondrion are about 1/100 to 1/10 the diameter of the whole cell and hence about 1/10^6 to 1/10^3 the ''volume'' of the whole cell.

	The total volume of the mitochondria depends on the number of mitochondria as well. It could be as large as 1/5 (or 20%) of cell volume.		The total volume of the mitochondria depends on the number of mitochondria as well. It could be as large as 1/5 (or 20%) of cell volume.