Explore chapters and articles related to this topic
Putting a Cell Together
Published in Thomas M. Nordlund, Peter M. Hoffmann, Quantitative Understanding of Biosystems, 2019
Thomas M. Nordlund, Peter M. Hoffmann
Figure 7.11 shows the single mitochondrion from Ostreococcus. The number of mitochondria per cell varies by organism and cell type, ranging from one, like in Ostreococcus, to thousands in large cells. The placement of the mitochondrion, next to the cell nucleus, can be seen in Figure 7.10. The major components of the mitochondrion are the outer membrane, inner membrane, cristae (or internal compartments), and dense granules within the mitochondrial matrix. The spatial slices used in these tomographic images, as well as the scale indicates that major parts of the mitochondrion range from 5 to 50 nm. The overall dimensions of mitochondria in large eukaryotic cells are larger, 1–2 µm, larger than the entire Ostreococcus cell and comparable to many bacterial cells.
Computational modeling of stretch induced calcium signaling at the apical membrane domain in umbrella cells
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Amritanshu Gupta, Rohit Manchanda
To ascertain the effect of [Ca]2+ on the mitochondrial enzyme PDHa and the rate constant governing exocytosis, i.e., Kexo, we varied the Ca2+ input to these processes by altering the stretch inputs to the model. In the simulation outputs from Figure 6, we use two net-stretch levels, i.e., 6 and 3 μm, respectively. We observe that [Ca2+] levels in the cytosol (Figure 6a) and mitochondria (Figure 6b) increase with increasing stretch. The SPMS [Ca2+] profiles have not been shown here as they follow the trend shown in Figure 5a. As mentioned previously, the build-up of Ca2+ in the mitochondrial matrix accelerates metabolic reactions in the mitochondria. In Figure 6c, we see that the fraction of activated PDHa rises with increased mitochondrial [Ca2+] levels. Also, the temporal width varies with the mitochondrial [Ca]2+ profile. The activation of PDHa is essential and necessary for the onset of the tricarboxylic acid (TCA) cycle, which is responsible for ATP synthesis via substrate-level phosphorylation but, more crucially, for the production of the majority of NADH. This electron carrier is a critical factor in ATP synthesis via oxidative phosphorylation (Magnus and Keizer 1998). Therefore, we see that mitochondria not only sequester and buffer Ca2+ present in the surrounding cytosol but equally, this has implications in accelerating mitochondrial metabolism via upregulation in the activation of PDHa.