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Bsc 103, week 3 notes

by: Kierra Thompson

Bsc 103, week 3 notes 103

Kierra Thompson

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Notes cover the exam
Biology & Society
Emily Clark
Class Notes
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This 6 page Class Notes was uploaded by Kierra Thompson on Thursday September 8, 2016. The Class Notes belongs to 103 at University of Southern Mississippi taught by Emily Clark in Fall 2016. Since its upload, it has received 9 views. For similar materials see Biology & Society in Science at University of Southern Mississippi.


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Date Created: 09/08/16
Wk 3 notes Getting energy from food Food provide us the building blocks (organic macromolecules) to replicate our DNA, make cells, build muscles.  What else does food give us? o Energy  The energy “currency” that our bodies use is adenosine triphosphate (ATP).  The process to get this out  Food is broken down into small molecules in your stomach and small intestine  Smaller subunits (fatty acids, amino acids, sugars) are transported to cells via your blood  Once in your cell Aerobic respiration starts  Break bonds holding food molecules together (by enzymes0  Chemical energy stored once in those bonds are converted into chemical bonds that make up ATP Food = Energy  Food contains organic molecules  Broken down into building blocks or subunits  Used to make new molecules and as sources of energy Not all Foods are created equal  Macromolecules contain different amounts of stored energy o Fat 9 C/g o Protein and Carbohydrates 4 C/g o Nucleic acids are not a significant source of stored energy  How we go from monomers of organic macromolecules to ATP? o Through aerobic respiration o Multi stage process  Glycolysis  Citric acid cycle  Electron transport chain Glycolysis  Oxygen and glucose pass from a blood vessel through the cell membrane.  Once in the cytoplasm, glucose undergoes glycolysis splitting in half  Get a bit of ATP, not much.  *Glucose is the most common form of energy in all living organism Citric Acid Cycle nd  2 phase of the aerobic respiration takes place in mitochondria  A series of reactions strips high energy electrons from C-H bonds, picked up by NAD+. o NAD+ + e- NADH  Carbon joins oxygen, resulting in CO2  NADH carries the electrons to the inner membrane of the mitochondria Electron Transport Chain  3 stage of aerobic respiration  where you get the majority of your ATP.  Energetic electrons passed from NADH down a chain of molecules in the inner mitochondrial membrane  ETC fuels ATP production  O2 accepts the Transported electrons and join with hydrogen to form water.  Fats and amino acids can also be used, but have to go through more preprocessing. Fats contain more C-H bonds, so more electrons can be harvested; hence, more energy in fats.  Without oxygen, the process wouldn’t work. To Summarize What happens when oxygen levels are scarce?  Glucose still split into 2 pyruvates  NADH has nowhere to load electrons  Dumps it back on pyruvates  Results in lactate production  Makes cell more acidic, which will result in it slowing down until you get more oxygen! Some organisms only generate oxygen through fermentation  Like yeast whose byproduct is ethanol  fermentation does not make for an efficient break down of sugars…. Food has energy. In our everyday life, we typically refer to this energy as Calories As you consume that “energy”, you might not need to use it all right away  Body stores it as glycogen and triglycerides o Made in your liver by linking glucose molecules back together. o Stored in the liver and muscle tissue (about 4 Calories/gram). o Quick energy source when sugars aren’t available in the bloodstream. Your body only needs so much glycogen (about 1200 – 1600 calories worth).  Energy cannot be destroyed, it can only change form o Once those reserves are full, the liver sends excess dietary energy (from carbs, proteins and fats) to be stored as triglycerides in fat cells. o These are your long-term energy reserves. Triglycerides are lipids that store about 9 Calories/gram. Avoid weight gain  Energy in should match energy out  eating too much and making poor food choices could cause weight gain. Evolution  Humans evolved to crave sugar and fats, to eat it whenever possible, and store it  Brain to blame for preferring these high energy foods o Brain needs energy to work  Evidence that from the smell and taste of a food, brains can sense how dense energy is o Metabolic demands of your brain change through life o Biggest when brain supply is growing o The body reduces production of a o hormone (insulin-like growth factor I) needed to break down fats. This helps maintain fat reserves, which the brain will need, at the expense of growth.  Excess fat leads to o Diabetes o Heart failure o Hypertension o Asthma o Cancer Link between Fats and Type ll diabetes  Begins with insulin resistance  Fat cells can only store so much fat  Once overloaded, start releasing free fatty acids  This creates a toxic environment, negatively affecting insulin receptors  Insulin can’t bind, sugar stays in bloodstream  So the pancreas produces even more insulin, until maybe it can’t anymore.  Without insulin, your liver thinks it needs to release more glucose! Genes play a role in obesity  Monogenic Obesity o spontaneous mutations in single genes which regulate appetite control, food intake and energy homeostasis. This has been documented in 11 genes .  Chromosomes Abnormalities o Obesity associates with chromosomes o Prader-Willi syndrome. Here, individuals are missing genes on chromosome 15. This leads to lack of appetite control. o Usually associated with other deficits, e.g. mental retardation  Common obesity o spontaneous mutations in a number of genes are associated with obesity. o generally, why individuals in a population vary with respect to body fat. Photosynthesis  (Harnessing energy from the sun)  Autotrophs use energy from the sunlight and convert it into chemical energy.  Animals have to eat in order to get energy (defined as the capacity to do work).  Energy is stored as chemical energy in food o Bonds that hold the food molecules together (potential energy) o Break those bonds, you release the potential  Law of conservation of energy o Energy cannot be created or destroyed, only change forms Energy Conservation  Food you eat contain potential energy (chemical energy in the bonds)  Once digested, it releases energy allowing muscles to contract. (chemical energy transformed into kinetic energy) Where do heterotrophs get their energy?  Rely on “self-feeders” called autotrophs  Autotrophs compromise most living things on our planet What happens in during photosynthesis?  Needs chloroplast  Two steps o Light energy is captured in chemical form (photo) o Captured energy is used to generate sugars. Don’t require sunlight (synthesis)  Summarized as o Sunlight + H2O + CO2  O2 + glucose Sunlight  Light energy is the energy of the electromagnetic spectrum of radiation  Wavelengths differ in length and energy.  Light energy is made of particles called photons, or packets of light energy “Photo” reactions  Sun emits photons  Chlorophyll absorbs photons  Chlorophyll electrons engage in reactions that create “ATP”  H2O is split and releases energy. Electrons replace lost ones “Synthesis” reactions  ATP is broken down  Energy is used to fix carbon dioxide into organic sugar molecules (glucose) o Carbon fixation: the conversion of inorganic carbon into organic forms. What does autotrophs do with the sugar?  Use it immediately to power cellular functions  Use it as building blocks, to build proteins, amino acids, and lipids.  Store it for later use, e.g. as oil  Long as there is sun and water, autotrophs could do it  they take up carbon dioxide rather than releasing it! Humans rely primarily on fossil fuels  Those are the carbon-rich energy sources formed from the compressed and heated remains plants and animals.  Disadvantages o When your burn them, carbon dioxide is released a lot U.S. Energy consumption  Petroleum - 36%  Nuclear electric power – 8%  Natural Gas – 25%  Coal – 25%  Renewable energy – 9% What can we learn from photosynthesis, and how can we take advantage of it, to live more sustainably?  Use the sun’s energy to generate electricity  solar energy  Use photo synthesizers to make fuel  biofuels .


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