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Genes and Genomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
The centrosome produces the microtubules of a cell, a key component of the cytoskeleton. It directs the transport through the ER and the Golgi apparatus. Centrosomes are composed of two centrioles, which separate during cell division and help in the formation of the mitotic spindle. A single centrosome is present in animal cells. They are also found in some fungi and algae cells.
Genes and genomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
The centrosome produces the microtubules of a cell—a key component of the cytoskeleton. It directs the transport through the ER and the Golgi apparatus. Centrosomes are composed of two centrioles, which separate during cell division and help in the formation of the mitotic spindle. A single centrosome is present in the animal cells. They are also found in some fungi and algae cells.
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The cell is the basic structural and functional unit of all organisms (Figure 1.3). The protoplasm is the living part of a cell consisting of a nucleus embedded in a membrane-enclosed cytoplasm, is the latter being the protoplasm excluding the nucleus and the membrane. The nucleus, which houses the DNA (deoxyribonucleic acid: the double-stranded, helical molecular chain, carrying genetic information), is contained within a membrane and separated from other cellular structures. Its functions are cell regulation and reproduction. Chromatin consists of masses of DNA and associated proteins. A chromosome is a rod-like structure in the nucleus of the cell that carries the genes (segments of DNA that are the basic units of heredity) of the cells and performs an important role in cell division and transmission of hereditary characters. The nucleus contains a small body, the nucleolus, in which ribosomes, where proteins are assembled, are made out of another nucleic acid (ribosomal ribonucleic acid, rRNA) and ribosomal proteins. Mitochondria provide energy to the cell by carrying out cellular respiration. Lysosomes are dark spherical bodies in the cytoplasm, which contain enzymes that break down complex compounds into simpler subunits. The endoplasmic reticulum (ER) is the site of protein synthesis and transport and lipid metabolism. The Golgi apparatus modifies proteins and lipids and distributes them to the rest of the cell. Plastids are spherical bodies (e.g., leucoplasts store starch, while chloroplasts contain chlorophyll and carry out photosynthesis) specific to plants and photosynthetic microbes. Vacuoles are fluid-filled sacs for storage, which are unique to plant cells. Microtubules are tiny tubes associated with transport inside cells. Centrioles are cylindrical bodies concerned with cell division and movement. Cilia and flagella are motile hairs projecting from cells, and linked to movements of cells and substances. Generalized structure of animal cell. The cell is surrounded by a membrane made up of two fluid layers of fatty molecules. The cytoplasm comprises the total cell contents including the subcellular structures and excluding the nucleus. The nucleus contains the genetic information. Mitochondria release energy in a useful form through cellular respiration. The endoplasmic reticulum is the site of protein and lipid production. The Golgi apparatus modifies proteins and lipids and distributes them to the rest of the cell.
Mathematical modelling of ciliary propulsion of an electrically-conducting Johnson-Segalman physiological fluid in a channel with slip
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
N. Manzoor, O. Anwar Bég, K. Maqbool, S. Shaheen
Cilia are bounded by membrane, centriole-derived projections which extend from the surface of cell. They consist of a microtubule cytoskeleton engulfed by ciliary membrane. Many different types of cilia arise in human biology and their geometric design is critical to sustaining health (Blake 1973; Brennen 1974; Sadiqui et al. 2014; Maqbool et al. 2016). Fluid transport induced by ciliary motion has therefore mobilized significant attention in biofluid dynamics for a number of decades. The initial hydrodynamic study of cilia beating was reported by Sleigh (1962). Numerous physiological processes feature ciliary transport including the ovum movement in fallopian tube (Sturgis 1947), transport of mucus in the respiratory track (Wanner et al. 1996) spermatozoa dynamics in ductus efferent of the male reproductive tract (Lardner and Shack 1972), spherule deposition during otolith formation in inner ear hydrodynamics (Colantonio et al. 2009) and molecular transport in photo-receptors for retinal bio-optics (Horst et al. 1990). Cilia generate fluid transport via synchronized beating. When the cilia move, they transmit the energy to the fluid creating propulsion in the forward direction in the effective stroke. Naturally, the cilia are designed to move in hydrodynamically efficient ways. In the effective stroke cilia face large viscous resistance to generate the maximal thrust and during recovery stroke they returned back to their initial position and cilia face small relative fluid velocities. Cilia groups (up to 200 cilia) exist on a mature ciliated cell, and each cilium has length 1 to 10 μm and diameter about 0.2 μm, and has frequency 12 to 15 per second. The locomotion mechanism involves each cilium continuously moving or beating with a two-stroke motion, as visualized in Figure 1. Interestingly there are analogies between cilia beating and also aerodynamic flapping in small fliers (humming birds, bumble bees etc) which have been studied recently by Anwar Bég (2018). The cilia are closed together in rows and the adjacent cilia beat in a harmonized fashion with negligible phase lag. In this way the tip of cilia are used to form a continuous wave-like motion termed the metachronal wave (Lighthill 1975), similar to how continuous wing flapping in natural fliers generates a continuous lift force with very little energy expenditure. Many researchers (Lardner et al. 1970; Sanderson and Sleigh 1981; Gheber and Priel 1990) studied the effect of cilia beating under various assumptions of hydrodynamics characteristics of fluid dynamics and ciliary activity. In the literature, there are two types of model for the propulsion and to transport fluid include: ‘cilia sublayer models’ or ‘discrete cilia models’ and volume force distribution’ or ‘volume force models’. In discrete cilia model, every cilium is dealt independently, and the contributions of all the cilia are often summed up (Dauptain et al. 2008). In contrast, in volume force models the cilia are modelled through a collective distribution of forces and these forces varying in space and times when cilia start to beat (Bottier et al. 2017). In the present simulation, the envelope model is employed where only the motion of tips of cilia are considered, and the tips are used to generate the so-called metachronal wave.