Search results
Jul 1, 2020 · Policies and ethics. This chapter describes the consequences of cold exposure and ice formation on both the cellular, tissue and the organismal level in cold tolerant ectothermic organisms. This includes the direct implication of cold “per se” on various parameters such as...
- Hans Ramløv, Dennis Steven Friis
- 2020
- Water’s Polarity. One of water’s important properties is that it is composed of polar molecules: the hydrogen and oxygen within water molecules (H2O) form polar covalent bonds.
- Water’s States: Gas, Liquid, and Solid. The formation of hydrogen bonds is an important quality of the liquid water that is crucial to life as we know it.
- Water’s High Heat Capacity. Water’s high heat capacity is a property that hydrogen bonding among water molecules causes. Water has the highest specific heat capacity of any liquid.
- Water’s Heat of Vaporization. Water also has a high heat of vaporization, the amount of energy required to change one gram of a liquid substance to a gas.
People also ask
Can ice kill cells?
How does ice preserve life?
How do organisms control ice formation?
What would happen if ice did not freeze?
Ice has the incredible ability to preserve material from living organisms for long periods of time, even thousands of years. Scientists freeze material like cells, sperm, and embryos to preserve them. This is called cryopreservation. But, ice can also be fatal—after all, organisms can freeze to death.
Jan 16, 2024 · Organisms have evolved various ways to control ice formation as an adaptation to survive in cold environments. That means the most efficient ice-nucleating particles are biological in origin, produced in bacteria, fungi and even insects, but the molecular basis and precise mechanisms of "biological ice nuclei" has not been well understood.
- Overview
- Introduction
- What is mitosis?
- Phases of mitosis
How a cell divides to make two genetically identical cells. Prophase, metaphase, anaphase, and telophase.
What do your intestines, the yeast in bread dough, and a developing frog all have in common? Among other things, they all have cells that carry out mitosis, dividing to produce more cells that are genetically identical to themselves.
Why do these very different organisms and tissues all need mitosis? Intestinal cells have to be replaced as they wear out; yeast cells need to reproduce to keep their population growing; and a tadpole must make new cells as it grows bigger and more complex.
Mitosis is a type of cell division in which one cell (the mother) divides to produce two new cells (the daughters) that are genetically identical to itself. In the context of the cell cycle, mitosis is the part of the division process in which the DNA of the cell's nucleus is split into two equal sets of chromosomes.
The great majority of the cell divisions that happen in your body involve mitosis. During development and growth, mitosis populates an organism’s body with cells, and throughout an organism’s life, it replaces old, worn-out cells with new ones. For single-celled eukaryotes like yeast, mitotic divisions are actually a form of reproduction, adding new individuals to the population.
Mitosis consists of four basic phases: prophase, metaphase, anaphase, and telophase. Some textbooks list five, breaking prophase into an early phase (called prophase) and a late phase (called prometaphase). These phases occur in strict sequential order, and cytokinesis - the process of dividing the cell contents to make two new cells - starts in anaphase or telophase.
You can remember the order of the phases with the famous mnemonic: [Please] Pee on the MAT. But don’t get too hung up on names – what’s most important to understand is what’s happening at each stage, and why it’s important for the division of the chromosomes.
Let’s start by looking at a cell right before it begins mitosis. This cell is in interphase (late G2 phase) and has already copied its DNA, so the chromosomes in the nucleus each consist of two connected copies, called sister chromatids. You can’t see the chromosomes very clearly at this point, because they are still in their long, stringy, decondensed form.
This animal cell has also made a copy of its centrosome, an organelle that will play a key role in orchestrating mitosis, so there are two centrosomes. (Plant cells generally don’t have centrosomes with centrioles, but have a different type of microtubule organizing center that plays a similar role.)
In early prophase, the cell starts to break down some structures and build others up, setting the stage for division of the chromosomes.
•The chromosomes start to condense (making them easier to pull apart later on).
When frozen, ice is less dense than liquid water (the molecules are farther apart). This means that ice floats on the surface of a body of water (Figure 2.8 b ). In lakes, ponds, and oceans, ice will form on the surface of the water, creating an insulating barrier to protect the animal and plant life beneath from freezing in the water.
Fractionation of Cells. Although biochemical analysis requires disruption of the anatomy of the cell, gentle fractionation techniques have been devised to separate the various cell components while preserving their individual functions. Just as a tissue can be separated into its living constituent cell types, so the cell can be separated into ...
