Food energy | EPFL Graph Search

Food energy is chemical energy that animals (including humans) derive from their food to sustain their metabolism, including their muscular activity. Most animals derive most of their energy from aerobic respiration, namely combining the carbohydrates, fats, and proteins with oxygen from air or dissolved in water. Other smaller components of the diet, such as organic acids, polyols, and ethanol (drinking alcohol) may contribute to the energy input. Some diet components that provide little or no food energy, such as water, minerals, vitamins, cholesterol, and fiber, may still be necessary to health and survival for other reasons. Some organisms have instead anaerobic respiration, which extracts energy from food by reactions that do not require oxygen. The energy contents of a given mass of food is usually expressed in the metric (SI) unit of energy, the joule (J), and its multiple the kilojoule (kJ); or in the traditional unit of heat energy, the calorie (cal). In nutritional contexts, the latter is often (especially in US) the "large" variant of the unit, also written "Calorie" (with symbol Cal, both with capital "C") or "kilocalorie" (kcal), and equivalent to 4184 J or 4.184 kJ. Thus, for example, fats and ethanol have the greatest amount of food energy per unit mass, , respectively. Proteins and most carbohydrates have about , though there are differences between different kinds. For example, the values for glucose, sucrose, and starch are respectively. The differing energy density of foods (fat, alcohols, carbohydrates and proteins) lies mainly in their varying proportions of carbon, hydrogen, and oxygen atoms. Carbohydrates that are not easily absorbed, such as fibre, or lactose in lactose-intolerant individuals, contribute less food energy. Polyols (including sugar alcohols) and organic acids contribute and respectively. The energy contents of a complex dish or meal can be approximated by adding the energy contents of its components.

Differential Heating Drives Downslope Flows that Accelerate Mixed-LayerWarming in Ice-Covered Waters

Alfred Johny Wüest, Damien Bouffard, Hugo Nicolás Ulloa Sánchez, Kraig Bates Winters

In ice-covered lakes, penetrative radiation warms fluid beneath a diffusive boundary layer, thereby increasing its density and providing energy for convection in a diurnally active, deepening mixed layer. Shallow regions are differentially heated to warmer temperatures, driving turbulent gravity currents that transport warm water downslope and into the basin interior.We examine the energetics of these processes, focusing on the rate at which penetrative radiation supplies energy that is available to drive fluid motion. Using numerical simulations that resolve convective plumes, gravity currents, and the secondary instabilities leading to entrainment, we show that advective fluxes due to differential heating contribute to the evolution of the mixed layer in waterbodies with significant shallow areas. A heat balance is used to assess the relative importance of differential heating to the one-dimensional effects of radiative heating and diffusive cooling at the ice-water interface in lakes of varying morphologies.

2019

The phenotypic impact of naturally occurring genetic and molecular mitochondrial variation in a Drosophila Genetic Reference Population

Roel Paulus Josephus Bevers

Genome-wide association (GWA) studies aim to dissect the relationship between genotype and phenotype. So far, the focus has been on nuclear genetic determinants as variation in the mitochondrial genome is often low in the study cohorts. Despite this observation, mitochondrial genomic variants are increasingly linked to metabolic and neurological disorders. Thus, there is much to gain from studying how mitochondrial variation interacts with nuclear variation and/or environment, and how this subsequently affects phenotypes. In my thesis I address these topics using Drosophila melanogaster as a model system, and specifically the Drosophila Genetic Reference Panel (DGRP). The DGRP consists of 200 sequenced and genetically diverse Drosophila populations and has been extensively used to study a wide-range of quantitative traits. However, in all of these studies, researchers have focussed on the influence of nuclear genetic variants in the absence of a high-resolution map of mitochondrial variants. To address this problem, we have developed a high-throughput method to specifically sequence mitochondrial DNA that enabled us to characterize mitochondrial genomic variation to an unprecedented depth. On average, each DGRP line had 25 mitochondrial variants (1 in 600 bp) and that most of the variants detected were unique for each line. However, we also found that some variants are more prevalent and show they can be used to construct mitochondrial haplotypes. We then used these haplotypes to test whether mitochondrial variation affected previously published phenotypes. We detected significant associations with 12 out of 259 publicly accessible phenotypes and found that these were mostly related to metabolism and responses to environmental cues. We selected one of the significant phenotypes, food intake in males, to verify our findings. We demonstrated the effect of mitochondrial haplotypes on the phenotype by swapping mitochondria from ¿high food intake¿ lines with mitochondria from ¿low food intake¿ lines and vice versa. We observed that, largely independent of the nuclear background, DGRP lines with a ¿high food intake mitochondria¿ consumed more food and concomitantly, DGRP lines with the ¿low food intake mitochondria¿ consumed less food. Furthermore, we investigated the influence of natural genetic variation was on the response to a high-fat diet. We designed a control and a high-fat diet and fed this to >100 DGRP lines and measured the lifespan on each diet. On average, lifespan was decreased by 48% on a high-fat diet, however this ranged from an increase of 2% to a decrease of 60% accentuating the complexity of the underlying genetic architecture. Our dataset was relatively small and limited our genome-wide and mitochondrial haplotype association analyses. Nonetheless, our GWA analysis detected variants related to genes involved in lipid metabolism and mitochondria but we did not detect significant associations with mitochondrial haplotypes. This suggests that while mitochondrial function may be important for the response to a high-fat diet, it is not dependent on the mitochondrial haplotype. Taken together, the work described in my thesis demonstrates the significance of accounting for mitochondrial haplotypes in phenotype association analyses. By doing so, it can open up new insights into genotype-to-phenotype relationships and gene regulation.

EPFL2018

Allometric equations for non-destructive biomass estimation of early stage sugarcane plants – Case study in Pernambuco, northeastern Brazil

Hadrien Baecher

Brazil recently became the 5th world power, and with a tremendous growing of its population and the resulting needs, this country is facing challenges in providing energy to every sector of its socio-economical activity. The actual global warming concern and the inevitable decline of fossil energy resources has lead to the research and development of new renewable energy sources as well as to the improvement of the already existing ones. Historically, sugarcane occupies a prominent place among the agricultural crops in Brazil and is in a period of increasing demand. The importance of this crop for the Brazilian economy makes research and development of new varieties and new agricultural techniques a priority. This study aimed to develop a non-destructive method to assess biomass production of live sugarcane plantations at an early stage of development. It highlighted the more relevant non-destructive parameters at different stages of the crop (60, 90, 120 days after planting) to evaluate above-ground biomass by establishing multiple linear regression models. The relevance of the following parameters were established: the diameter at ground level and the dimensions of the leaf F(0). The study was first carried out considering sugarcane as a species and then by comparing equations for five different sugarcane genotypes (varieties). It also assessed the feasibility of developing allometric equations that would be a useful tool to estimate root biomass from more easily measured above-ground plant parameters.

2013

The phenotypic impact of naturally occurring genetic and molecular mitochondrial variation in a Drosophila Genetic Reference Population

Roel Paulus Josephus Bevers

EPFL2018