Sub-lethal damage
Encyclopedia
Cell damage is damage to any of the components of the cell
.
s and organelle
s are removed by a cell stress response and autophagy
with new structural components being synthesized. This is termed sub-lethal cell damage and is associated with recognizable structural changes.
Sub-lethal damage can be identified from microscopic changes in affected cells. The first evidence of such damage is seen ultrastructurally
as swelling of the membrane bound organelles, particularly the endoplasmic reticulum
and the mitochondria
. There is:
If ATP
production is insufficient to maintain function, lethal function is marked by disintegration of other organelles and autolysis
proceeds.
Microscopically, these reversible changes caused by swelling of the organelles is reflected in cellular swelling, paleness of cytoplasm
and development of small intracellular vacuoles, giving rise to the widely used descriptive terms cloudy swelling and hydropic degeneration.
, or the rather more controlled apoptosis
of the cell.
and the cell membrane
.
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
.
Sub-lethal damage
If damage to a cell is minimal, the cell can recover following removal of the damaging stimulus. Damaged proteinProtein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s and organelle
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....
s are removed by a cell stress response and autophagy
Autophagy
In cell biology, autophagy, or autophagocytosis, is a catabolic process involving the degradation of a cell's own components through the lysosomal machinery. It is a tightly regulated process that plays a normal part in cell growth, development, and homeostasis, helping to maintain a balance...
with new structural components being synthesized. This is termed sub-lethal cell damage and is associated with recognizable structural changes.
Sub-lethal damage can be identified from microscopic changes in affected cells. The first evidence of such damage is seen ultrastructurally
Ultrastructure
Ultrastructure is the detailed structure of a biological specimen, such as a cell, tissue, or organ, that can be observed by electron microscopy...
as swelling of the membrane bound organelles, particularly the endoplasmic reticulum
Endoplasmic reticulum
The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...
and the mitochondria
Mitochondrion
In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryotic cells. These organelles range from 0.5 to 1.0 micrometers in diameter...
. There is:
- Loss of some ribosomes
- The mitochondria appear swollen
- The vacuoleVacuoleA vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
s push the cristaCristaCristae are the internal compartments formed by the inner membrane of a mitochondrion. They are studded with proteins, including ATP synthase and a variety of cytochromes. The maximum surface for chemical reactions to occur is within the mitochondria...
e apart - Accumulation of electrolyteElectrolyteIn chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
s and water occurs - There is damage to enzymeEnzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s of the membrane sodium pump
- The vacuole
If ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
production is insufficient to maintain function, lethal function is marked by disintegration of other organelles and autolysis
Autolysis (biology)
In biology, autolysis, more commonly known as self-digestion, refers to the destruction of a cell through the action of its own enzymes. It may also refer to the digestion of an enzyme by another molecule of the same enzyme....
proceeds.
Microscopically, these reversible changes caused by swelling of the organelles is reflected in cellular swelling, paleness of cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
and development of small intracellular vacuoles, giving rise to the widely used descriptive terms cloudy swelling and hydropic degeneration.
Lethal damage
Lethal damage leads either to necrosisNecrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
, or the rather more controlled apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...
of the cell.
Targets
The most notable components of the cell that are targets of cell damage are the DNADNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
and the cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
.
- DNA damage: In human cells, both normal metabolicMetabolismMetabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
activities and environmental factors such as UV light and RadiationRadiationIn physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
can cause DNA damage, resulting in as many as 1 millionMillionOne million or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001. The word is derived from the early Italian millione , from mille, "thousand", plus the augmentative suffix -one.In scientific notation, it is written as or just 106...
individual molecular lesionMolecular lesionA molecular lesion is damage to the structure of a biological molecule such as DNA, enzymes, or proteins that results in reduction or absence of normal function or, in rare cases, the gain of a new function...
s per cell per day. - Membrane damage: Damage to the cell membrane disturbs the state of cell electrolyte, e.g. calciumCalciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, which, when constantly increased, induces apoptosis.